Article pubs.acs.org/Organometallics
Platinum Complexes of Alkynyl-Substituted Dimethyldihydropyrenes Pengrong Zhang, David J. Berg,* Reginald H. Mitchell,* Allen Oliver,† and Brian Patrick‡ Department of Chemistry, University of Victoria, P.O. Box 3065, Victoria, British Columbia, Canada V8W 3V6 S Supporting Information *
ABSTRACT: A series of photochromic dimethyldihydropyrenes (DHP) bearing ethyne substituents in the 4-position (RDHP-CCH; R = H (4), acetyl (5), benzoyl (6), 1naphthoyl (7), benzo[e] (8)) were prepared for use as precursors to ethynyl ligands. Dehydrohalogenation of the adduct of these ethynes with various PtCl2(L)2 complexes afforded a series of cis and trans square-planar bis(DHPethynyl) platinum complexes, (RDHP-CC)2Pt(L)2 (cis, R = H, L2 = PEt3 (9), acetyl, PEt3 (10), benzoyl, PEt3 (11), 1-naphthoyl, PEt3 (12), benzo[e], PEt3 (13), benzoyl, PPh3 (14), benzo[e], PPh3 (15); trans, R = H, L2 = dppe (16), benzo[e], dppe (17), acetyl, bipy (18), 1-naphthoyl, bipy (19), H, phen (20)). The DHP-ethynes bearing acyl and benzo[e] substituents on the DHP (5−8) and their platinum complexes (10−19) are photochromic and undergo ring opening to the related cyclophanediene (CPD) isomer on irradiation with visible light (λ >550 nm). In the case of the benzo[e]DHP 8, adding a 4-ethynyl substituent increases the rate of photo-opening 4-fold; however, in the acylDHP series 5−7, addition of a 4-ethynyl group slows the rate of photo-opening by a factor of about 4. The platinum complexes generally open more slowly than the corresponding alkyne precursors, again by a factor of about 4. The rate of photoopening does not appear to be affected significantly by the nature of the ancillary ligands or the metal geometry, suggesting that there is poor electronic communication between the platinum center and the DHP π system. The thermal back-reaction from the open CPD to closed DHP form is about 50% faster for the metal complexes than for the DHP-ethyne precursor. The platinum complexes and the DHP-ethynes were characterized by NMR and IR spectroscopy and MS and by X-ray crystallography for metal complexes 10, 11, 14, 15, and 17.
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INTRODUCTION Photochromic molecules have been intensively studied due to their potential applications in optical switches and storage devices.1 The diarylethene class of photochromes has been studied by Irie, Branda, and others.2 For many years, we have focused our attention on the dimethyldihydropyrene (DHP)− dimethylmetacyclophanediene (CPD) system, 1c/1o (c = closed; o = open).3−8 Molecules of type 1c exhibit negative photochromism in that the thermally more stable and colored form bleaches to the colorless form 1o on irradiation with orange or red light (λ >550 nm). Irradiation with UV light rapidly converts 1o back to 1c, but the thermal (dark) backreaction also occurs at room temperature. Introduction of organic or organometallic groups on the DHP periphery, or at the internal methyl positions, can dramatically alter the photochromic behavior.3,9,10 In general, introduction of acyl groups or annelation increases the quantum yield of the photoopening reaction and slows down the thermal backreaction.5−7,9,11 One of the better photochromes in this family, the benzo[e] derivative 2c(BDHP)/2o(BCPD), shows 100% conversion between the two photostates. However, even in this case the thermal back-reaction is not fully suppressed. Although a number of organometallic π complexes of DHP derivatives have been prepared,10 no complexes containing a © 2012 American Chemical Society
metal fragment connected to the DHP framework by σ bonds have been reported. DHP-alkynyl complexes of a group 10 metal such as Pt are particularly interesting for a number of reasons. Marder has shown that electronic communication through a −CC−Pt−CC− linkage is only slightly smaller than that through a phenylene −CC−C6H4−CC− Received: July 25, 2012 Published: November 8, 2012 8121
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bridge.12 Metal-connected polyynes have attracted considerable attention as fundamental building blocks in macromolecular wires;13 therefore, the potential to use a DHP-photochrome as an optical switch where the open (CPD) form breaks conjugation and changes the wire conductivity is intriguing. Additionally, metal−alkynyl σ complexes show interesting properties in their own right and have been used in nonlinear optical, light-emitting diode, and luminescent materials.14 The potential to alter these properties by changing the state of the DHP photochrome also exists. We are also interested in possible cooperative behavior between DHP-photochromes in complexes containing two (or more) photochromic units. Platinum complexes containing two DHP-alkynyl ligands provide a good opportunity to observe cooperative behavior. The original hypothesis was that energy transfer between photochromic units through a spacer would accelerate photo-opening. Earlier work on bis(DHP) systems with homoconjugation (−CO− linker), no conjugation (−CH2− linker), and fused conjugation (arene bridge) showed that the DHP units opened and closed independently and multiple states were observed, although no photo-opening rate enhancement was achieved.15 Bandyopadhyay previously synthesized a bis-photochrome having two benzo[e]DHP photochromic units joined by a butadiyne spacer, 3.16 Unfortunately, difficulties in distinguishing the fully closed (3cc) and partially open (3co) states made it impossible to evaluate cooperative effects during the photo-opening process. Insertion of a Pt center between the butadiyne alkynes is expected to provide similar electronic communication to the butadiyne system 3 but also allow tuning of the electronic properties of the Pt spacer by changing the ancillary ligands on the metal.
yield (Φo = 0.0015).6 Therefore, to explore the photo-opening reactions in metal complexes, enhancement of the photoopening quantum yield is critical. Adding one alkyne at the 4position or two alkynes at the 4- and 9-positions of DHP has been shown to decrease the quantum yield relative to 1 by factors of 2.7 and 2.9 times, respectively.6 However, we have previously shown that adding a ketone or aldehyde group at the 2- or 4-position of DHP 1 increases the photo-opening rate and the thermal back-reaction from CPD to DHP (1o → 1c).11b For example, adding a benzoyl group at the 4-position of 1 increased the photo-opening quantum yield by 2.5 times, while increasing the thermal return rate by 1.5 times.6 The fused benzo group in BDHP 2 dramatically increases the quantum yield (Φo = 0.04), and addition of an ethynyl group at the 4position of 2 f urther enhances the photo-opening quantum yields by a factor of ca. 2.7 Given the noted unpredictability of the photochemical properties of DHP-alkynes, we elected to investigate the platinum complexes of several 4-acylDHPethynes (5−7), as well as BDHP-ethyne (8) and the simple DHP-ethyne prototype (4). The various DHP-ethynes used in this work are shown in Chart 1, and the synthetic route to the new 4-acylDHP-ethynes is shown in Scheme 1. Chart 1
The synthesis of the 4-acylDHP-ethynes 5−7 is relatively straightforward starting from the parent DHP 1. Friedel−Crafts Scheme 1. Synthesis of 4-acylDHP-10-ethynesa
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a
Conditions and yields: (a) RC(O)Cl, AlCl3, CH2Cl2, room temperature, yields 36 (CH3), 40 (Ph), 42% (Np); (b) I2, Ag(collidine)+PF6−, CH2Cl2, room temperature, 12 h, yields 75 (CH3), 75 (Ph), 90% (Np); (c) TMS-CCH, Pd(PPh3)2Cl2, CuI, NEt3, room temperature, yields 98 (CH3), 95 (Ph), 95% (Np); (d) K2CO3, THF/CH3OH, yields 100 (CH3), 94 (Ph), 100 (Np). Minor amounts (5−15%) of the 4-acyl-9-ethynyl isomer were isolated in all cases.
RESULTS AND DISCUSSION In order to prepare DHP-alkynyl complexes of Pt2+, we first had to synthesize DHP-alkynes having suitable photochemical properties. The DHP 1 does not open photochemically using low-intensity light sources, due to its intrinsically low quantum 8122
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complexes were purified by recrystallization from hexane and dichloromethane; the major and minor isomers were separated in some cases. The complexes were characterized by 1H, 13C, 31 P, and 195Pt NMR spectroscopy (solubility permitting) as well as by electrospray mass spectrometry, elemental analysis, IR and UV/vis spectroscopy. Significant spectroscopic data for Pt complexes 9−20 as well as for the free parent DHP-alkynes 4− 8 are given in Table 1. In cases where the 10-isomers could not be obtained free from the 9-isomer, the 9:1 isomer ratio allowed easy extraction of data for the 10-isomer; see the Experimental Section for full details. Platinum complexes 9−15 containing monodentate phosphine ligands, PEt3 or PPh3, adopt a trans square-planar geometry, as shown by the triplet (2JPC = 14−29 Hz (cis-P)) for the alkynide α-C in the 13C NMR spectrum. In contrast, complexes 16 and 17, which contain the bidentate dppe ligand, must adopt a cis geometry and show a doublet of doublets pattern for this carbon in the 13C NMR (2JPC = 150 Hz (transP), 14−15 Hz (cis-P)). These geometries were confirmed by Xray crystallography for 10, 11, 14, 15, and 17 (vide infra). Complexes 18−20, containing the chelating amines bipy and phen, can be assumed to adopt a cis geometry due to the constraints of the chelate. Complexes of the type trans-Pt(C CR)2(L)2 are more common in the literature than their cis isomers,18 although Sonogashira has shown that the cis complexes can be isolated if the reactions are carried out at low temperature.19 Similarly, Tykwinski has shown that conversion of the trans to cis isomers occurs readily when a monodentate phosphine such as PPh3 is replaced by a bidentate phosphine such as dppe.20 The IR stretching frequencies of the carbonyl groups in complexes containing the acylDHP unit do not change substantially from the free alkyne to the platinum alkynide complex. The CC stretching frequency of the alkyne itself shows a small decrease in the PEt3 complexes 9−13 ranging
acylation occurs readily at the 4-position of the very electron rich DHP, but care must be taken to avoid excess acid chloride or long reaction times, since this can result in significant double acylation and, in the case of acetyl chloride, replacement of one tert-butyl group by an acetyl function.6,17 Iodination of the 4acylDHPs with iodine and Ag(collidine)+PF6− afforded the major 4,10-isomer shown in Figure 1 in 50−75% yield, but about 10−15% of the minor 4,9-isomer was also formed.6 The structures of the major and minor isomers were established by 2D NMR spectroscopy, and although they were chromatographically separable with some difficulty, we elected to carry the isomeric mixture forward. Sonogashira coupling of the acylDHP iodides with (trimethylsilyl)acetylene followed by removal of the TMS group afforded the desired terminal alkynes 5−7. Only the 10-isomers of 5−7 are shown, but small amounts (5−15%) of the 9-isomers were also obtained (see the Experimental Section for details). Platinum Complexes. The platinum alkynide complexes were prepared by dehydrohalogenation of the adduct between the parent alkyne 4−8 and the appropriate PtCl2(L)2 precursor with diethylamine using CuI as a catalyst (Scheme 2). The Scheme 2a
a
Conditions: (a) CuI, HNEt2, 50 °C.
Table 1. Select Spectroscopic Data for DHP-alkynes and the Corresponding DHP-alkynide Complexes of Platinum, (DHP-C C)2Pt(L)2a geom
δint
δα
δβ
PEt3 PEt3 PEt3 PEt3 PEt3 PPh3 PPh3 dppe
trans trans trans trans trans trans trans cis
−3.64 −3.81 −3.72 −3.70 −1.19 −3.85 −3.74 −3.63 −3.62 −1.03 −3.87 −1.25 −3.41
82.5 82.4 82.4 82.4 82.6 115.1 115.1 n.o. n.o. 115.1 n.o. 118.6 114.2
84.7 84.1 84.1 84.0 84.3 111.0 110.5 110.9 110.4 111.0 115.3 115.8 113.3
−220 −252 −254 −382
2383 2384 2383 2385 2398 2651 2677 2277
BDHP
dppe
cis
−1.07
113.4
112.5
−379
2246
CH3C(O)DHP NpC(O)DHP DHP
bipy bipy phen
cis cis cis
−3.70 −3.58 −3.78
92.3 94.1 n.o.
102.8 102.5 103.8
no.
alkyne/alkynide
4 5 6 7 8 9 10 11 12 13 14 15 16
DHP CH3C(O)DHP PhC(O)DHP NpC(O)DHP BDHP DHP CH3C(O)DHP PhC(O)DHP NpC(O)DHP BDHP PhC(O)DHP BDHP DHP
17 18 19 20
L
δPt
−252
1
JPt−P
2
JP−C
29 29 n.o. n.o. 15 n.o. 15 150b 15c 150b 14c
νCC 2085 2091 2091 2093 2090 2082 2081 2077 2080 2071 2092 2099 2093
νCO 1665 1639 1631
1666 1640 1641 1650
2093 2094
1663
2096
a δint, δα, δβ, and δPt refer to the chemical shifts of the internal methyl protons (average value), terminal alkyne carbon (α), internal alkyne carbon (β), and 195Pt resonances in C6D6, respectively. n.o. indicates the experiment was performed but the resonance was not observed. δ values are given in ppm, J values are given in Hz, and ν values are given in cm−1. bCoupling to the trans-P. cCoupling to the cis-P.
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Table 2. Selected Bond Lengths (Å) and Angles (deg) for trans-(RDHP-CC)2Pt(PR′3)2 (10, R = CH3C(O), R′ = Et; 11, R = PhC(O), R′ = Et; 14, R = PhC(O), R′ = Ph; 15, R = C6H4, R′ = Ph) and cis-(RDHP-CC)2Pt(dppe) (17, R = C6H4)a Pt(1)−C(1) Pt(1)−P(1) C(1)−C(2) C(2)−C(3) DHP C−Cav sum DHP C−C alternationb C(1)−Pt(1)−C(1)′ P(1)−Pt(1)−P(1)′ P(1)−Pt(1)−C(1) P(1)−Pt(1)−C(1)′ Pt(1)−C(1)−C(2) C(1)−C(2)−C(3) DHP-SqP dihedralc DHP-(PhCO) dihedrald
10
11
14
15
17
2.009(6) 2.295(2) 1.196(9) 1.450(8) 1.398 0.19(3) 180(2) 180 90.7(2) 89.3(2) 176.3(5) 173.4(6) 26.4
2.009(7) 2.296(3) 1.191(9) 1.430(9) 1.393 0.15(4) 180 180 94.7(2) 85.3(2) 173.3(7) 176.2(7) 6.7 61.1
1.995(4) 2.3064(9) 1.208(6) 1.431(6) 1.400 0.19(3) 180 180.00(6) 93.23(11) 86.77(11) 174.6(3) 173.1(4) 65.6 56.7
1.996(3) 2.297(8) 1.214(4) 1.429(4) 1.405 0.49(2) 180.0(1) 180 92.93(9) 87.07(9) 173.6(3) 173.4(4) 70.3
1.995(8) 2.261(2) 1.191(11) 1.450(12) 1.398 0.63(4) 89.1(4) 87.01(10) 92.0(2) 177.1(3) 175.9(8) 175.9(10) 32.7
C6H4 = benzo[e]DHP. b∑(|bond length − average bond length|) for the 14 DHP edge bonds; esd values are derived from the individual bond length esd values. cDihedral angle between the PtC2P2 square plane and the mean DHP plane. dDihedral angle between the mean C6 plane of the PhCO substituent and the mean DHP plane. a
from 3 to 19 cm−1. However, the CC stretching frequency shows a very slight increase in trans complexes with PPh3 (14 and 15) and the cis complexes (16−20). These observations would seem to imply that there is relatively little π electronic interaction between the metal and the alkynide or DHP fragments. It has been reported in the literature that changing the donor properties of the phosphine causes changes in the CC stretching frequency in trans-Pt(CCR)2(L)2 (L = PCy3, P(OPh)3) complexes, although the effect appears to be small.21 The internal methyl groups of DHP lie within the strong shielding region of the DHP ring current, and their chemical shifts have been shown by us to be extremely sensitive probes of this ring current.4,10c,22 In the trans complexes containing PEt3 (10−13) and the cis complexes bearing dppe (16 and 17) and bipy (18 and 19) ancillary ligands, the internal methyl groups show a small downfield chemical shift change relative to the free DHP-ethynes ranging from Δδ = +0.06 to +0.30 ppm with a median Δδ = +0.12 ppm. A downfield shift indicates a small reduction in DHP ring current. On the other hand, the trans-PEt3 (9) and trans-PPh3 complexes (14 and 15) and the cis-phen complex (20) show small upfield shifts for the internal methyl groups of Δδ = −0.06 to −0.21 ppm, suggesting a small increase in ring current. However, the magnitude of these shifts are small; therefore, other factors such as shielding or deshielding caused by nearby phenyl groups in complexes containing PPh3 or dppe ligands might be as important as minor changes in ring current. Overall it appears that the effect of the platinum center on the DHP π system is small, consistent with the conclusion drawn from the IR spectra. The average 1JPt−P coupling constant in the cis-dppe complexes 16 and 17 is 2262 Hz, about 300 Hz smaller than might be expected from the trans complexes based on the groups attached to the phosphorus.23,24 The smaller coupling constant clearly indicates that the DHP-alkynide ligand has a greater trans influence than a phosphine, consistent with its greater σ donor character. The stronger trans influence of alkynides compared to that of phosphines has been commented on before in the case of cis- and trans-Pt(CCH)2(PEt3)2.23a Structural Studies. The solid-state structures of five Pt(CC-DHP)2(L)2 complexes were determined by X-ray
crystallography; selected bond distances and angles are given in Table 2. Disorder of the internal methyl groups of the DHP unit is virtually always observed in DHP structures, and that was the case here as well. In addition, the tert-butyl substituents show the typical rotational disorder and further disorder was also observed for the acyl groups in complexes 10, 11, and 14. ORTEP325 plots of complexes 10, 14, and 17 are shown in Figures 1−3, respectively. ORTEP3 plots of 11 and 15 are
Figure 1. ORTEP325 plot of trans-(CH3C(O)DHP-CC)2Pt(PEt3)2 (10; 50% probability ellipsoids). The dichloromethane of solvation has been omitted for clarity, and only one component for the disordered internal methyl groups and acetyl group is shown.
included in the Supporting Information but are generally similar to the plots of 10 and 14, respectively. There are many examples of structurally characterized Pt(CCAr)2 (L) 2 complexes (Ar = aryl; L = PR3, PAr3 or L2 = dppe), and the bond lengths within these complexes show a Gaussian distribution with narrow standard deviations, as summarized for comparison in Table 3. The mean CC triple-bond length is essentially insensitive to changes in the phosphines, alkyne substituents, or geometry, and the DHP-alkynide CC distance in the complexes investigated here fall very close to 8124
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to the conclusion drawn from 1JPt−P coupling constants above. The coupling constant data is almost certainly a more reliable predictor of trans influence, as the percentage variation in the J values is far greater across a broad range of complexes than is the bond length. Nevertheless, the fact that these indicators are in opposition suggests that the trans influences of the alkynide and phosphine are similar. The C−C bond lengths around the periphery of the 14annulene DHP ring in 1c, like those in benzene, are very nearly equal and no significant bond length alternation is observed. Substituents such as the acyl and ethynyl groups in 4−7 are expected to cause some bond length alternation, because the C π orbitals are no longer equal in energy but the effect is relatively small. This alternation is best quantified by taking the sum of the bond length differences between all adjacent C−C bonds. The sums of the bond length alternation for the platinum complexes containing acyl-DHP alkynides range from 0.15(4) to 0.19(3) Å. In contrast, fusing a benzene ring at the [e]-position causes much greater bond length alternation because this ring prefers to remain a 6π aromatic unit rather than participate in a larger π system.4,22b As a result, this causes bond fixation in the 14-annulene periphery and strong bond alternation is observed for 2c. The sums of the bond length alternation for the platinum complexes containing benzo-fused DHP alkynides 15 and 17 are 0.49(2) and 0.63(4) Å, respectively. By comparison, the sum of the bond alternation in 2c is 0.54(2) Å. The sum of the C−C bond length alternation is a measure of ring current, with greater bond length alternation implying a reduced ring current. As discussed above, the chemical shift of the internal methyl groups is a sensitive measure of ring current; thus, as expected, the internal methyls of 2c are not as far upfield as those in 1c (−1.58 vs −4.06 ppm). Interestingly, the bond alternation data for 15 and 17 suggest that there is greater bond fixation in 17 and therefore a lower ring current, which agrees well with the observed internal methyl chemical shifts (δint −1.25 (15), −1.07 (17)). The DHP ring plane is only twisted out of the square plane by 26 and 6° for the PEt3 complexes 10 and 11, respectively. In contrast, the DHP plane is twisted by 66 and 70°, respectively, relative to the square plane in PPh3 complexes 14 and 15; the cis-dppe complex 17 is intermediate with a planar dihedral angle of 33°. Presumably the greater twist observed in the PPh3 complexes is a function of steric crowding caused by the larger phosphine ligands. It is tempting to assert that the near- planar arrangement in 11 represents an electronic preference, but packing effects in the solid state may also be responsible for this orientation. Photochemical Studies. As mentioned earlier, features such as photo-opening rates and thermal closing rates, associated with photoswitchable molecules, are particularly important to their applications. Some of the complexes were selected to investigate the effects caused by changing the ligands and substituents on their photochemical properties. Photochemists have traditionally used quantum yields to compare photoefficiencies. Thus, for the reaction DHP 1c → CPD 1o, Φ was found to be 0.0015, in comparison to 0.006 for the parent 14-annulene without the tert-butyl groups.6 On the other hand, fusing a benzo group in the [e]-position increases Φ by about 7-fold to 0.042 for BDHP 2. However, absolute quantum yields are time consuming to measure and we have found that reliable comparisons can be made by measuring the relative rates of opening for two samples side by side under the
Figure 2. ORTEP325 plot of trans-(PhC(O)DHP-CC)2Pt(PPh3)2 (14; 30% probability ellipsoids). The dichloromethane of solvation has been omitted for clarity, and only one component for the disordered internal methyl groups and benzoyl group is shown.
Figure 3. ORTEP325 plot of cis-(BDHP-CC)2Pt(dppe) (17; 30% probability ellipsoids). Only one component of the disordered internal methyl groups is shown.
Table 3. Summary of Bond Length Data for Various (ArC C)2Pt(L)2 Complexesa distance Pt−C
Pt−P
C1C2
C2−C3
ligand (L)
bond length (Å)
mean length (Å)
std dev
PR3 PAr3 dppe PR3 PAr3 dppe PR3 PAr3 dppe PR3 PAr3 dppe
1.981−2.047 1.981−2.027 1.997−2.031 2.281−2.316 2.286−2.325 2.258−2.289 1.128−1.239 1.152−1.217 1.176−1.211 1.414−1.487 1.434−1.461 1.411−1.452
2.003 2.008 2.018 2.299 2.309 2.270 1.198 1.197 1.190 1.443 1.445 1.437
0.015 0.014 0.012 0.007 0.013 0.003 0.026 0.019 0.012 0.018 0.007 0.012
a
The numbers of reported structures in the Cambridge Structural Database containing PR3, PAr3, and dppe are 29, 13, and 11, respectively, at the time of submission.
the mean values. The Pt−P and Pt−C distances for the DHPalkynide complexes are also similar to those reported, although the Pt−C distance in the cis-dppe complex 17 is at 1.995(8) Å slightly shorter than that in any other cis-Pt(CCAr)2(dppe) complex. One interesting observation from the bond length data in Table 2 is that the Pt−P distance is significantly shorter in the cis-dppe complex 17 than in the trans-alkynide complexes 10, 11, 14, and 15. A shorter Pt−P bond when the phosphine is trans to an alkynide in comparison to when it is trans to a phosphine (cf. 17 vs 15) implies that the trans influence of the alkynide is weaker than that of the phosphine. This is contrary 8125
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sample of the same concentration. A plot of mole fraction remaining of the closed form versus time gives good linear behavior over the first few minutes of irradiation in all cases, confirming that, by the NMR method, zero-order kinetics are obtained (Figure 5). The relative rates of photo-opening,
same conditions of temperature, light source, and solvent. The absolute rates measured are not meaningful, but the rate relative to the standard can be used for comparison. We have made much use of BDHP as a standard previously and, provided that the two samples measured have absorptions in the same region, good comparative results are consistently observed.26 The visible openings were performed using a 500 W tungsten light source fitted with a 550 nm cutoff filter. The photochemical reactions were followed by either UV−vis spectroscopy or NMR spectroscopy. The photochemical reaction rate depends directly on the number of photons and the concentration of the photochrome. When excess photons are provided, the photochemical reaction rate only depends on the concentration of the photochrome, and pseudo-first-order kinetics are observed. In practice, Robinson and Mitchell found that NMR samples follow a pseudo-zero-order rate law, while UV−vis samples follow pseudo-first-order kinetics in the photo-opening process.27 The difference in rate law is due to the different concentrations involved in the two methods and the efficiency of light penetrating through the sample solutions.27 At the much higher photochrome concentrations of the NMR experiment, only photochrome molecules very near the surface of the sample are irradiated by light, and this effectively leads to a condition where the concentration of photochrome is constant while the number of photons is in large excess. However, this is only strictly true at the beginning of the opening processes and, since the open CPD isomer is colorless, light penetrates further into the sample with time, causing a change in rate law toward first order. Initial rates, usually obtained over the first 5−10 min depending on the sample (vide infra), can therefore be accurately obtained using a zero-order treatment. When irradiation is carried out on NMR samples, the platinum complexes open completely. The NMR sample shows a downfield shift of the internal methyl resonances from −1.02 and −1.04 ppm in the fully conjugated closed (DHP) form to 1.52 and 1.53 ppm in the “open” CPD isomer. Gradual reduction of the long-wavelength absorptions in the UV−vis spectrum of 13 can be seen in Figure 4. The photo-opening of the BDHP-ethyne 8 and its platinum complexes 13, 15, and 17 was most conveniently carried out by irradiating NMR samples in d6-benzene alongside a BDHP 2
Figure 5. Zero-order plot for the photo-opening of BDHP 2 (■), BDHP-CCH 8 (●), and the platinum complexes 13 (○), 15 (▲), and 17 (⧫) followed by 1H NMR spectroscopy: mole fraction of the closed isomer versus time for samples irradiated at >550 nm.
Table 4. Relative Photo-Opening Rates of DHP-alkynes, Their Precursors, and Platinum Alkynide Complexes compd
krela
BDHP 2 BDHP-CCH 8 13 15 17 CH3C(O)DHP CH3C(O)DHP-CCH 5 10 NpC(O)DHP NpC(O)DHP-CCH 7 12
1 4 1 1 1 1 0.4 0.1 1 0.25 0.06
a
Relative to the parent DHP: BDHP 2, CH3C(O)DHP, or NpC(O)DHP, respectively
summarized in Table 4, show that BDHP-ethyne 8 opens about 4 times faster than BDHP 2. However, the platinum complexes 13, 15, and 17 all open at about the same rate as BDHP 2, meaning that conversion to the alkynide slows the rate of opening by a factor of about 4. The geometry of the platinum complex and the identity of the ancillary phosphines have no discernible effect on the rate of photo-opening. The photo-opening of the acylDHP-ethynes 5 (acyl = CH3C(O)) and 7 (acyl = NpC(O)) and their respective trans(acylDHP-CC)Pt(PEt3)2 complexes 10 and 12 was followed by UV−vis spectroscopy and showed good first-order kinetics (the plot for 12 and NpC(O)DHP is shown in Figure 6). In this case, the platinum complexes opened between 10 and 17 times slower for 10 and 12, respectively, than for the parent acylDHP and about 4 times slower than for the acylDHP-
Figure 4. Photo-opening of 13 on irradiation at >550 nm: (a) 0 min; (b) 30 min; (c) 60 min; (d) 210 min. 8126
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closing of BDHP-ethyne 8 and its platinum complexes 13, 15, and 17 by 1H NMR spectroscopy. The thermal closing process follows first-order kinetics; the half-life, τ1/2, as well as the enthalpy (ΔH⧧) and entropy (ΔS⧧) of activation obtained from an Eyring plot (not shown) are collected in Table 5. Although Table 5. Thermal Closing Rates of DHP-alkynes, Their Precursors, and Platinum Alkynide Complexes compd
τ1/2a
krelb
ΔH⧧c,e
ΔS⧧d,e
BDHP 2 CH3C(O)DHP 5 8 13 15 17
87 67 62 62 42 38 33
1 1.3 1.4 1.4 2.1 2.3 2.6
100 102 97 109 99 99 96
+16 −7 −13 +15 −13 −15 −22
In h. bRelative to BDHP 2. cIn kJ mol−1, dIn J mol−1 K−1 eTypical errors in ΔH⧧ and ΔS⧧ are ca. 3 kJ mol−1 and 10 J mol−1 K−1, respectively. a
Figure 6. First-order plot for the photo-opening of NpC(O)DHP (●) and trans-[NpC(O)DHP]2Pt[PEt3]2 (12; ■) followed by UV−vis spectroscopy: ln[Aclosed/Atotal] versus time for samples irradiated at >550 nm.
the platinum complexes were not investigated, the acetylDHPethyne 5 and the related 4-acetylDHP are included for comparison. In both the BDHP and 4-acetylDHP series, adding an ethynyl group resulted in slightly faster thermal closure as the half-life decreased from 87 to 62 h on going from 2 to 8 and from 67 to 62 h on going from 4-acetylDHP to 5. In comparison, the half-life decreased ca. 33−50% on going from the free alkyne 8 (62 h) to platinum complexes 13 (42 h), 15 (38 h), and 17 (33 h). The half-life for the ring-closing reaction has previously been shown to decrease significantly on introduction of electron-withdrawing groups such as trifluoroacetyl. It has been suggested that this is due to stabilization of a diradical transition state by electron-withdrawing substituents.7,8,17,28 It is interesting to note therefore that the most electron-rich platinum center is found in complex 13, bearing PEt3 ancillary ligands, and this complex does in fact have the longest half-life. Although the effect is not large, it does suggest that there is a small effect of the metal electronic environment on the thermal closing reaction. As might be anticipated for a reaction involving rigid products and reactants and presumably minor changes in solvation, the entropy of activation is near zero when the large error is taken into account. Concluding Remarks. The introduction of ethynyl groups onto the DHP periphery resulted in a 4-fold decrease in the photo-opening rate for the acyl-substituted compounds 5 and 7 but a 4-fold increase in photo-opening rate for the benzo-fused DHP-ethyne 8. However, in both series, the deprotonation of the DHP-ethyne and formation of the bis(DHP-ethynyl) platinum complexes resulted in another 4-fold decrease in the rate of photo-opening. Crystallographic, IR, and NMR spectroscopic studies suggest that the extent of electronic communication between the DHP π system and the platinum center is quite small. This is reflected in the fact that changes in the ancillary ligands and geometry cause no difference in the rate of photo-opening among 13, 15, and 17. The thermal closing rate from CPD back to the DHP isomer increases by about 40% on introduction of an ethynyl group in 8 relative to BCPD 2o. A further increase in the rate of thermal closing occurs on formation of the platinum complexes 13, 15, and 17. No evidence for cooperative effects during either photoopening or thermal closing was observed.
ethynes (Table 4). Thus, in this case, adding an ethynyl group to an acyl-DHP slows the photo-opening by between ca. 2.5 and 4 times, whereas in the case of the BDHP unit, adding an ethynyl group increased the photo-opening rate 4-fold. In both the BDHP and acylDHP cases, deprotonation to an alkynide and formation of a σ complex with platinum slows the photoopening by a factor of 4. The open CPD isomer normally undergoes rapid and complete ring closure to the DHP form on exposure to UV light (254 nm), as illustrated for BDHP 2 in Figure 7. Past
Figure 7. Photochemical conversion of 2o → 2c on UV irradiation at 254 nm.
experience has shown that the rate of closing with UV light is almost invariant to the substituents on the DHP, but we nevertheless decided to check whether this was true for one of the platinum complexes. Irradiation of 13o (the CPD form of 13) with a small UV light source resulted in the same closing rate as for 2 within experimental error, verifying that the UV closure rate is insensitive to the DHP substituents. In contrast to the UV photochemical closing, thermal closing of the open CPD isomer is generally very sensitive to the substituents on the ring system. We followed the thermal 8127
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A small amount of the 9-acetyl isomer was also present, but it was not separated and fully characterized. 10-Benzoyl-2,7-di-tert-butyl-10c,10d-dimethyl-4-ethynyltrans-10c,10d-dihydropyrene (6a) and the 9-Benzoyl Isomer
EXPERIMENTAL SECTION
All solvents and reagents were purchased from Sigma-Aldrich and used without further purification unless otherwise stated. Acetonitrile and CH2Cl2 were distilled from calcium hydride prior to use. Diethyl ether, benzene, toluene, hexane, and THF-d8 were dried by distillation from sodium and benzophenone. Sodium iodide was dried in an oven at 110 °C for 12 h. Silica gel (Merck, 60−200 mesh) and alumina (Aldrich, activated, neutral, Brockmann I, standard grade, ∼150 mesh) used for chromatography were deactivated with 5% (w/w) of water. The synthesis of BDHP (2),5 4-ethynyl-DHP (4),7 and 4-ethynylbenzo[e]DHP (8, 4-ethynyl-BDHP)7 were carried out according to previously published procedures. The 10-acyl-4-ethynyl-DHP compounds 3 (acyl = CH3CO), 4 (acyl = PhCO), and 5 (acyl = βNaphCO) were prepared by Friedel−Crafts acylation of the parent DHP followed by electrophilic iodination,6,11b introduction of the alkyne functionality by Sonogashira coupling with (trimethylsilyl)acetylene, and subsequent TMS deprotection with K2CO3 in a MeOH−THF mixture (Scheme 1). Full experimental and characterization details for all intermediates and byproducts are given in the Supporting Information. Spectroscopic details for the new alkynes 5− 7 themselves are given below. 1 H NMR spectra were recorded on Bruker Avance 500 or 360 MHz spectrometers; 13C NMR spectra were recorded on these instruments at 125.8 or 90.6 MHz, respectively. 1H and 13C NMR spectra were referenced to residual solvent resonances, while 195Pt and 31P were referenced to external K2PtCl4 and 85% H3PO4, respectively. In 1H NMR assignments, H-1,2 indicates H-1 and H-2 while H-1/2 denotes H-1 or H-2. Infrared spectra were recorded on a Bruker IFS25 FT-IR spectrometer, and only the major peaks are reported. All samples were prepared as potassium bromide disks unless otherwise specified. UV− vis spectra were recorded on a Cary 5 UV−vis−near-IR spectrometer in suitable solvents. Melting points were determined on a Reichert 7905 melting point apparatus with an Omega Engineering Model 199 chromel alumel thermocouple and are not corrected. Elemental analyses were performed by Canadian Microanalytical Services Ltd., Vancouver, B.C., Canada or the Chemistry Department of the University of British Columbia, Vancouver, BC, Canada. Mass spectrometric analyses were carried out at the Department of Chemistry at the University of British Columbia. 10-Acetyl-2,7-di-tert-butyl-10b,10c-dimethyl-4-ethynyltrans-10b,10c-dihydropyrene (5): 1H NMR (500 MHz, CDCl3) δ
(6b). 6a (10-benzoyl isomer): 1H NMR (500 MHz, CDCl3) δ 9.04 (d, J = 1.2 Hz, 1H, H-1), 8.91 (d, J = 1.2 Hz, 1H, H-3), 8.68 (s, 1H, H-5), 8.62 (s, 1H, H-9), 8.57 (s, 1H, H-8), 8.56 (s, 1H, H-6), 7.90−7.88 (m, 2H, H-2′), 7.61 (tt, J = 7.4, 1.3 Hz, 1H, H-4′), 7.51−7.47 (m, 2H, H3′), 3.73 (s, 1H, CCH), 1.64 (s, 9H, 7-C(CH3)3), 1.57 (s, 9H, 2C(CH3)3), −3.71 (s, 3H, 10b/10c-CH3), −3.72 (s, 3H, 10b/10cCH3); 13C{1H} NMR (125 MHz, CDCl3) δ 199.19 (PhCO), 150.38 (C-2), 147.13 (C-7), 140.65 (C-1′), 139.72 (C-3a), 136.99 (C-10a), 135.66 (C-5a/10d), 134.88 (C-5a/10d), 132.73 (C-4′), 130.55 (C-2′), 130.40 (C-10), 128.57 (C-3′), 128.13 (C-5), 125.95 (C-9), 124.69 (C8), 123.46 (C-6), 121.09 (C-1), 120.39 (C-3), 114.01 (C-4), 84.10 (CCH), 82.41 (CCH), 36.80 (2-C(CH3)3), 36.17 (7-C(CH3)3), 32.00 (7-C(CH3)3), 31.87 (2-C(CH3)3), 31.33 (C-10b), 29.34 (C10c), 15.31 (10b/10c-CH3), 15.07 (10b/10c-CH3). 6b (9-benzoyl isomer): 1H NMR (500 MHz, CDCl3) δ 9.07, 8.89, 8.64, 8.60, 8.58, 8.52, 3.75, 1.68, 1.54, −3.71, −3.73 (select resonances listed). Mixed isomers 6a and 6b: mp 155−157 °C; IR (KBr) ν 3293, 3245, 2964, 2924, 2905, 2865, 2091, 1639, 1596, 1476, 1447, 1385, 1362, 1347, 1324, 1267, 1247, 1233, 1210, 1196, 1173, 1023, 941, 901, 872, 804, 729, 697, 681, 669 cm−1; UV−vis (toluene) λmax (εmax, L mol−1 cm−1) 355 (52 700), 406 (26 200), 497 (7500), 671 (2400) nm; EI MS m/z 472 (M+); HRMS calcd for C35H36O 472.2766, found 472.2766. 2,7-Di-tert-butyl-10b,10c-dimethyl-4-ethynyl-10-(1′-naphthoyl)-trans-10b,10c-dihydropyrene (7a) and the 9-naphthoyl
Isomer (7b). 7a (10-naphthoyl isomer): 1H NMR (500 MHz, CDCl3) δ 9.34 (d, J = 0.9 Hz, 1H, H-1), 9.05 (d, J = 0.8 Hz, 1H, H-3), 8.68 (s, 1H, H-5), 8.62 (s, 1H, H-9), 8.54 (s, 1H, H-6), 8.47 (s, 1H, H8), 8.45 (d, J = 7.9 Hz, 1H, H-8′), 8.06 (d, J = 8.3 Hz, 1H, H-4′), 7.98 (d, J = 7.9 Hz, 1H, H-5′), 7.63−7.61 (m, 1H, H-2′), 7.56−7.54 (m, 1H, H-6′), 7.51−7.47 (m, 2H, H-3′,7′), 3.73 (s, 1H, CCH), 1.60 (s, 9H, 7-C(CH3)3), 1.56 (s, 9H, 2-C(CH3)3), −3.69 (s, 3H, 10b-CH3), −3.70 (s, 3H, 10c-CH3); 13C{1H} NMR (125 MHz, CDCl3) δ 200.81 (NpCO), 151.71 (C-2), 146.99 (C-7), 140.48 (C-3a), 139.96 (C-1′), 137.72 (C-10a), 135.57 (C-5a/10d), 134.79 (C-5a/10d), 134.12 (C8′b), 131.71 (C-4′), 131.48 (C-8′), 130.74 (C-10), 129.15 (C-2′), 128.67 (C-5′), 128.55 (C-5), 127.67 (C-9), 127.53 (C-7′), 126.68 (C6′), 126.16 (C-8′), 125.46 (C-8), 124.81 (C-3′), 123.96 (C-6), 121.18 (C-1), 120.45 (C-3), 114.01 (C-4), 84.04 (CC−H), 82.44 (CCH), 36.92 (2-C(CH)3), 36.12 (7-C(CH)3), 31.95 (2/7-C(CH)3), 31.87 (2/7-C(CH)3), 31.66 (C-10b), 29.30 (C-10c), 15.28 (10b/10cCH3), 15.09 (10b/10c-CH3). Mixed isomers 7a and 7b: IR (KBr) ν 3304, 3252, 2962, 2923, 2866, 2093, 1631, 1588, 1462, 1383, 1345, 1277, 1258, 1229, 1198, 1121, 1091, 943, 894, 880, 783, 681, 668 cm−1; UV−vis (toluene) λmax (εmax, L mol−1 cm−1) 355 (41 007), 411 (46 473), 493 (6524), 620 (584), 678 (2499) nm; EI MS m/z 522
9.73 (d, J = 1.2 Hz, 1H, H-1), 9.04 (d, J = 1.1 Hz, 1H, H-3), 8.92 (s, 1H, H-9), 8.65 (s, 1H, H-5), 8.64 (s, 1H, H-8), 8.53 (s, 1H, H-6), 3.72 (s, 1H, CCH), 3.06 (s, 3H, COCH3), 1.70 (s, 9H, 2-C(CH3)3), 1.66 (s, 9H, 7-C(CH3)3), −3.80 (s, 3H, 10c-CH3), −3.81 (s, 3H, 10bCH3); 13C{1H} NMR (125 MHz, CDCl3) δ 202.27 (COCH3), 152.38 (C-2), 146.86 (C-7), 140.69 (C-3a), 136.63 (C-10a), 135.53 (C-5a/ 10d), 135.22 (C-5a/10d), 128.49 (C-5), 125.99 (C-9), 125.21 (C-8), 123.90 (C-6), 121.64 (C-1), 120.44 (C-3), 113.99 (C-4), 84.05 (C CH), 82.40 (CCH), 37.10 (2-C(CH3)3), 36.12 (7-C(CH3)3), 32.06 (2/7-C(CH3 )3 ), 32.00 (2/7-C(CH3 )3 ), 31.47 (C-10b), 31.04 (COCH3), 29.19 (C-10c), 15.21 (10b/10c-CH3), 15.16 (10b/10cCH3); IR (KBr) ν 3309, 3262, 2963, 2925, 2865, 2091, 1665, 1477, 1444, 1383, 1361, 1348, 1242, 1225, 1207, 1153, 928, 889, 679, 665 cm−1; UV−vis (toluene) λmax (εmax, L mol−1 cm−1) 372 (42 800), 405 (52 200), 493 (6500), 557 (552), 618 (571), 681 (2880) nm; EI MS m/z 410 (M+); HRMS calcd for C30H34O 410.2610, found 410.2613. Anal. Calcd for C30H34O: C, 87.76; H, 8.35. Found: C, 86.93; H, 8.48. 8128
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(M+); HRMS calcd for C39H38O 522.2923, found 522.2921. Anal. Calcd for C39H38O: C, 89.61; H, 7.33. Found: C, 86.04; H, 7.39. trans-Bis[2′-(2,7-di-tert-butyl-10b,10c-dimethyl-trans10b,10c-dihydropyren-4-yl)ethynyl]bis(triethylphosphino)-
10 (50 mg, 50% yield). 10a (major isomer, bis-10-acetyl): 1H NMR (500 MHz, CD2Cl2) δ 9.70 (d, J = 1.0 Hz, 2H, H-1), 9.19 (d, J = 1.1 Hz, 2H, H-3), 8.80 (s, 2H, H-9), 8.57 (s, 2H, H-5), 8.54 (s, 2H, H-8), 8.42 (s, 2H, H-6), 3.05 (s, 6H, COCH3), 2.47−2.45 (m, 12H, PCH2CH3), 1.71 (s, 18H, 7-C(CH3)3), 1.67 (s, 18H, 2-C(CH3)3), 1.37 (t, J = 7.6 Hz, 18H, PCH2CH3), −3.72 (s, 6H, 10c-CH3), −3.75 (s, 6H, 10b-CH3); 13C{1H} NMR (125 MHz, CD2Cl2) δ 202.55 (COCH3), 150.43 (C-7), 146.44 (C-2), 139.29 (C-3a), 136.64 (C-5a/ 10d), 136.24 (C-10a), 135.29 (C-5a/10d), 128.90 (C-5), 128.25 (C10), 123.88 (C-9), 122.97 (C-8), 122.79 (C-4), 121.76 (C-6), 121.56 (C-3), 120.62 (C-1), 115.13 (d, 1JPt−C = 29.4 Hz, CC-Pt), 110.46 (CC−Pt), 36.93 (7-C(CH3)3), 36.07 (2-C(CH3)3), 32.21 (7C(CH3)3), 32.10 (2-C(CH3)3), 31.67 (C-10b), 31.13 (COCH3), 29.44 (C-10c), 17.04 (t, J = 17.4 Hz, PCH2CH3), 15.59 (10c-CH3), 15.32 (10b-CH3), 8.89 (PCH2CH3); 31P{1H} NMR (CDCl3, 202 MHz) δ 13.12 (1JPt−P = 2384 Hz); 195Pt NMR (CD2Cl2, 77 MHz) δ −252.22 (1JP−Pt = 2655 Hz); Mixture of isomers 10a and 10b: mp 180−187 °C; IR (KBr) ν 2964, 2784, 2081, 1666, 1459, 1409, 1379, 1348, 1242, 1224, 1207, 1154, 1035, 890, 768, 733 cm−1; UV−vis (cyclohexane) λmax (εmax, L mol−1 cm−1) 279 (7500), 387 (20 200), 429 (29 600), 494 (8000), 697 (3500) nm; ESI MS m/z 1249 (M+ + H); HRMS calcd for C72H96O2P2Pt + H 1249.6591, found 1249.6556. trans-Bis[2″-(9-benzoyl-2,7-di-tert-butyl-10b,10c-dimethyltrans-10b,10c-dihydropyren-4-yl)ethynyl]bis-
platinum(II) (9). DHP-ethyne 4 (84 mg, 0.23 mmol) and transPt(PEt3)2Cl2 (50 mg, 0.10 mmol) were mixed in degassed diethylamine (20 mL) in a Schlenk tube at room temperature. CuI (1.0 mg, 0.0052 mmol) was added, and the reaction mixture was heated to a mild reflux at 50 °C under argon for 12 h. The amine was removed under reduced pressure and the crude residue purified on alumina (deactivated with 5% water) using hexane and dichloromethane as eluant. The DHP-ethyne 4 (5 mg, 69% recovery) was eluted first (using hexane/CH2Cl2 10/1), and complex 9 (100 mg, 95% yield) eluted second with 1/1 hexane/CH2Cl2. Complex 9 was recrystallized from CH2Cl2 and methanol to afford dark green crystals: Mp 166−168 °C; 1H NMR (500 MHz, CD2Cl2) δ 9.130 (s, 1H, H-3), 9.128 (s, 1H, H-3), 8.52 (s, 2H, H-5), 8.51 (s, 2H, H-1), 8.48 (s, 2H, H-8), 8.45 (s, 2H, H-6), 8.40 (AB, J = 7.8 Hz, 2H, H-9), 8.38 (AB, J = 7.8 Hz, 2H, H10), 2.56−2.50 (m, 12H, CH2CH3), 1.73 (s, 18H, 2-C(CH3)3), 1.70 (s, 18H, 7-C(CH3)3), 1.41 (dt, 2JP−H = 16.5 Hz, 3JH−H = 7.7 Hz, 18H, −CH2CH3), −3.83 (s, 6H, 10c-CH3), −3.86 (s, 6H, 10b-CH3); 13 C{1H} NMR (125 MHz, CD2Cl2) δ 146.50 (C-7), 145.75 (C-2), 137.61 (C-10a/10d), 137.58 (C-10a/10d), 137.11 (C-5a), 136.46 (C3a), 127.04 (C-5), 123.43 (C-9/10), 122.82 (C-9/10), 122.17 (C-4), 121.45 (C-1), 121.05 (C-3), 120.77 (C-8), 119.87 (C-6), 115.11 (1JPt−C = 29 Hz, CCPt), 110.95 (CCPt), 36.57 (2-C(CH3)3), 36.38 (7C(CH3)3), 32.46 (2-C(CH3)3), 32.26 (7-C(CH3)3), 30.85 (C-10b), 30.30 (C-10c), 17.36 (t, 1JP−C = 17 Hz, CH2CH3), 15.60 (C-10c), 14.81 (C-10b), 9.10 (CH2CH3); 31P{1H} NMR (202 MHz, CD2Cl2) δ 13.24 (1JPt−P = 2383 Hz); IR (KBr) ν 3034, 2963, 2904, 2872, 2082, 1457, 1379, 1357, 1343, 1254, 1231, 1034, 882, 768, 733, 664 cm−1; UV−vis (cyclohexane) λmax (εmax, L mol−1 cm−1) 366 (97 300), 408 (136 000), 479 (30 200), 504 (32 700), 670 (5370) nm; ESI MS m/z 1164 (M+); HRMS calcd for C68H92P2Pt 1164.6301, found 1164.6389. trans-Bis-[2′-(10-acetyl-2,7-di-tert-butyl-10b,10c-dimethyltrans-10b,10c-dihydropyren-4-yl)ethynyl]bis-
(triethylphosphino)platinum(II) (11a) and the 9-Benzoyl 10Benzoyl Isomer (11b). Using the same procedure described for making 9, an isomeric mixture of benzoylDHP-ethyne 6 (30 mg, 0.063 mmol), Pt(PEt3)2Cl2 (15 mg, 0.030 mmol), and CuI (1.0 mg, 5.3 × 10−3 mmol) was reacted in Et2NH (6 mL) to afford pure 11 as dark red crystals after recrystallization from a mixture of hexane, CH2Cl2, and methanol. In this case, the major isomer was the bis-9-benzoyl isomer, despite the fact that the major isomer of the alkyne was confirmed to be the 10-benzoyl 4-ethynyl DHP. The identity of the major isomer was established by 2D NMR studies. The most probable reason for this difference is that repeated recrystallization of the benzoylDHP-ethyne before reaction with platinum resulted in enrichment of the crystals in the less soluble 9-benzoyl-4-ethynylDHP (14 mg, 35% yield). 11a (major isomer, bis-9-benzoyl): 1H NMR (500 MHz, CDCl3) δ 9.19 (s, 1H, H-3), 8.91 (s, 1H, H-8), 8.55 (s, 1H, H10), 8.53 (s, 1H, H-5), 8.48 (s, 1H, H-1), 8.41 (s, 1H, H-6), 7.93−7.89 (m, 2H, H-2′), 7.60 (t, J = 7.5 Hz, 1H, H-4′), 7.52−7.47 (m, 2H, H3′), 2.54−2.43 (m, 6H, PCH2CH3), 1.68 (s, 9H, 2-C(CH3)3), 1.56 (s, 9H, 2-C(CH3)3), 1.44−1.35 (m, 9H, PCH2CH3), −3.60 (s, 3H, 10bCH3), −3.65 (s, 3H, 10c-CH3); 13C{1H} NMR (125 MHz, CDCl3) δ 199.36 (COPh), 149.35 (C-2), 145.77 (C-2), 141.24 (C-1′), 139.18 (C-5a), 136.66 (C-10a), 136.29 (C-3a), 134.84 (C-10d), 132.33 (C4′), 130.57 (C-2′), 128.45 (C-9), 127.39 (C-5), 125.23 (C-10), 124.08 (C-4), 123.44 (C-1), 123.02 (C-3), 119.90 (C-6,8), 110.86 (CCPt), 36.48 (7-C(CH3)3), 36.28 (2-C(CH3)3), 32.20 (2-C(CH3)3), 31.92 (2C(CH3)3), 31.17 (C-10c), 30.20 (C-10b), 17.05 (t, J = 14 Hz, PCH2CH3), 16.10 (10b-CH3), 15.10 (10c-CH3), 8.91 (PCH2CH3); 31 1 P{ H} NMR (CDCl3, 145 MHz) δ 12.81 (1JPt−P = 2383 Hz); 11b: 1 H NMR (500 MHz, CDCl3) δ 9.18 (s), 8.87 (s), 8.59 (s), 8.50 (s), 8.46 (s), 8.45 (s), 1.66 (s, C(CH3)3), 1.58 (s, C(CH3)3), −3.62 (s, internal CH3), −3.64 (s, internal CH3) these are the only clearly distinguishable resonances for the minor isomer. Mixture of isomers
(triethylphosphino)platinum(II) (10a) and the 9-Acetyl 10Acetyl Isomer (10b). Using the same procedure as for 9, the ethyne 5 (70 mg, 0.17 mmol) and trans-Pt(PEt3)2Cl2 (43 mg, 0.086 mmol) with CuI (2.0 mg, 0.011 mmol) in degassed Et2NH (15 mL) gave complex 10. Chromatography on silica gel using 1/1 hexane/CH2Cl2 followed by recrystallization from CH2Cl2 and methanol afforded pure 8129
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11a and 11b: mp 190−198 °C; IR (KBr) ν 2963, 2904, 2873, 2077, 1640, 1511, 1446, 1379, 1345, 1258, 1245, 1209, 1174, 1035, 1021, 892, 767, 733, 698 cm−1; UV−vis (toluene) λmax (εmax, L mol−1 cm−1) 370 (sh, 50 200), 427 (96 300), 523 (24 300), 621 (770), 681 (1990) nm; ESI MS m/z 1373 (M+); HRMS calcd for C82H100O2P2Pt + H 1373.6904, found 1373.6871. trans-Bis[2″-[10-(1-naphthoyl)-2,7-di-tert-butyl-10b,10c-dimethyl-trans-10b,10c-dihydropyren-4-yl]ethynyl]bis-
C6D6) δ 144.94 (C-7), 144.02 (C-2), 138.40 (C-5a), 137.32 (C-3a), 136.26 (C-12e), 135.91 (C-12b), 130.65 (C-12a), 130.09 (C-12f), 126.89 (C-5), 126.63 (C-11), 126.37 (C-10), 125.46 (C-12) 125.42 (C9), 121.32 (C-4), 120.99 (C-3), 120.20 (C-6), 118.18 (C-1), 117.46 (C-8), 115.05 (t, 2JC−P = 15 Hz, CCPt), 111.00 (CCPt), 37.23 (C-12c), 36.44 (C-12d), 36.18 (2-C(CH3)3), 35.78 (7-C(CH3)3), 31.52 (2-C(CH3)3), 31.05 (7-C(CH3)3), 19.04 (12d-CH3), 18.67 (12cCH3), 17.47 (t, 1JC−P = 17.8 Hz, CH2CH3), 9.10 (CH2CH3); 31P{1H} NMR (145 MHz, C6D6) δ 12.18 (1JPt−P = 2398 Hz); 195Pt NMR (77 MHz, C6D6) δ −219.79 (1JPt−P = 2400 Hz); IR (KBr) ν 2960, 2924, 2862, 2071, 1460, 1365, 1249, 1035, 870, 772, 749, 632 cm−1; UV−vis (cyclohexane) λmax (εmax, L mol−1 cm−1) 341 (34 610), 355 (35 700), 399 (51 400), 418 (73 700), 502 (11 600), 525 (14 100), 553 (12 200), 641 (1050) nm; ESI MS m/z 1264 (M+); HRMS calcd for C76H96P2Pt 1264.6614, found 1264.6599. NMR spectral data in CDCl3: 1H NMR (500 MHz) δ internal methyl protons at −1.46 and −1.49; 31P{1H} NMR (145 MHz) δ 12.2 (d, 1JPt−P = 2395 Hz); 195Pt NMR (77 MHz) δ −212.20 (1JPt−P = 2400 Hz). trans-Bis[2″-(10-benzoyl-2,7-di-tert-butyl-10b,10c-dimethyltrans-10b,10c-dihydropyren-4-yl)ethynyl]bis-
(triethylphosphino)platinum(II) (12a) and the 9-Naphthoyl 10Naphthoyl Isomer (12b). Using the same procedure described for 9, 1′-naphthoyl DHP-ethyne 7 (60 mg, 0.12 mmol), trans-Pt(PEt3)2Cl2 (30 mg, 0.060 mmol), and CuI (1.7 mg, 8.9 × 10−3 mmol) were refluxed in degassed Et2NH (6 mL) for 12 h. Recrystallization of the solid residue from benzene and pentane afforded dark orange crystals of 12 (40 mg, 70% yield). 12a (major isomer, bis-10-naphthoyl): 1H NMR (500 MHz, CDCl3) δ 9.31 (s, 2H, H-1), 9.20 (s, 2H, H-3), 8.60 (s, 2H, H-5), 8.50 (s, 2H, H-9), 8.46 (d, J = 8.4 Hz, 2H, H-8′), 8.43 (s, 2H, H-6), 8.37 (s, 2H, H-8), 8.05 (d, J = 8.3 Hz, 2H, H-4′), 7.98 (d, J = 8.0 Hz, 2H, H-5′), 7.64 (dd, J = 7.0, 1.0 Hz, 2H, H-2′), 7.57−7.52 (m, 2H, H-6′), 7.52−7.44 (m, 4H, H-3′,7′), 2.54−2.42 (m, 12H, PCH2CH3), 1.61 (s, 9H, 7-C(CH3)3), 1.57 (s, 9H, 2-C(CH3)3), 1.43−1.34 (m, 18H, PCH2CH3), −3.62 (s, 6H, 10b,10c-CH3); 13 C{1H} NMR (125 MHz, CDCl3) δ 201.07 (NpCO), 149.73 (C2), 146.54 (C-7), 140.39 (C-1′), 139.13 (C-3a), 137.26 (C-10a), 136.62 (C-5a/10d), 134.80 (C-5a/10d), 134.08 (C-8′b), 131.47 (C8′a), 131.36 (C-4′), 130.05 (C-10), 128.88 (C-5,2′), 128.57 (C-5′), 127.45 (C-7′), 126.54 (C-6′), 126.25 (C-8′), 125.51 (C-9), 124.83 (C3′), 123.29 (C-8), 121.82 (C-6), 121.48 (C-3), 120.27 (C-1), 119.96 (C-10), 110.43 (CCPt), 36.73 (2-C(CH3)3), 36.03 (7-C(CH3)3), 31.98 (2/7-C(CH3)3), 31.97 (2/7-C(CH3)3), 31.86 (C-10b), 29.53 (C10c), 17.00 (t, J = 17 Hz, PCH2CH3), 15.71 (10b-CH3), 15.16 (10bCH3), 8.85 (PCH2CH3); 31P{1H} NMR (CDCl3, 202 MHz) δ 12.89 (1JPt−P = 2383 Hz); 195Pt NMR (CDCl3, 77 MHz) δ −214.77 (1JP−Pt = 2385 Hz). 12b (minor 9-naphthoyl 10-naphthoyl isomer): 1H NMR (500 MHz, CDCl3) δ 9.37, 9.18, 8.54, 8.52, 8.42, 8.40 (d, J = 8.6 Hz), only the clearly discernible resonances for 12b are listed. Mixture of isomers 12a and 12b: mp 207−212 °C; IR (KBr) ν 2963, 2905, 2873, 2080, 1641, 1588, 1508, 1477, 1459, 1381, 1345, 1273, 1243, 1196, 1035, 891, 783, 768 cm−1; UV−vis (toluene) λmax (εmax, L mol−1 cm−1) 371 (70 200), 437 (109 000), 495 (25 600), 633 (2100), 694 (7500) nm; ESI MS m/z 1473 (M+); HRMS calcd for C90H104O2P2Pt + H 1473.7217, found 1473.7190. trans-Bis[2′-(2,7-di-tert-butyl-12c,12d-dimethyl-trans12c,12d-dihydrobenzo[e]pyren-4-yl)ethynyl]bis(triethylphosphino)platinum(II) (13). Complex 13 was prepared using a procedure similar to that for 9, by refluxing ethyne 8 (40 mg, 0.096 mmol), Pt(PEt3)2Cl2 (23 mg, 0.046 mmol), and CuI (1.0 mg, 5.3 × 10−3 mmol) in Et2NH (6 mL) for 2 h. The product was recrystallized from methanol to give dark red crystals of 13 (50 mg, 84% yield): mp 169−170 °C; 1H NMR (500 MHz, C6D6) δ 8.86− 8.83 (m, 2H, H-12), 8.80−8.78 (m, 2H, H-9), 8.58 (d, J = 1.3 Hz, 2H, H-3), 8.49 (d, J = 1.3 Hz, 2H, H-1), 8.381 and 8.379 (s, 2H, H-8), 7.725 and 7.724. (s, 2H, H-5), 7.52 (s, 2H, H-6), 7.53−7.48 (m, 4H, H-10,11), 2.34−2.21 (m, 12H, PCH2CH3), 1.60 (s, 18H, 2-C(CH3)3), 1.42 (s, 18H, 7-C(CH3)3), 1.28−1.18 (m, 18H, PCH2CH3), −1.02 (s, 6H, 12d-CH3), −1.04 (s, 3H, 12c-CH3); 13C{1H} NMR (125 MHz,
(triphenylphosphino)platinum(II) (14a) and the 9-Benzoyl 10Benzoyl Isomer (14b). Complex 14 was prepared using a procedure similar to that for 9, by mixing benzoylDHP-ethyne 6 (70 mg, 0.15 mmol), trans-Pt(PPh3)2Cl2 (50 mg, 0.063 mmol), and CuI (1.0 mg, 0.0053 mmol) in Et2NH (10 mL). In this case, the product precipitated from the mixture and after washing with methanol afforded 30 mg of 14 as dark red crystals (30% yield). 14a (major isomer, bis-10-benzoyl): 1H NMR (500 MHz, CD2Cl2) δ 8.71 (s, 2H, H-1), 8.61 (s, 2H, H-3), 8.44 (s, 2H, H-8), 8.41 (s, 2H, H-9), 8.26 (s, 2H, H-6), 8.07−8.03 (m, 12H, H-2″,6″), 7.86 (d, J = 7.2 Hz, 4H, H2′), 7.64−7.60 (m, 4H, H-9,4′), 7.49 (t, J = 7.7 Hz, 4H, H-3′), 7.24− 7.17 (m, 18H, H-3″,4″,5″), 1.65 (s, 18H, 7-C(CH3)3), 1.34 (s, 18H, 2C(CH3)3), −3.87 (s, 6H, 10c-CH3), −3.88 (s, 6H, 10b-CH3); 13C{1H} NMR (125 MHz, CD2Cl2) δ 199.50 (COPh), 148.49 (C-7), 146.89 (C-2), 141.49 (C-1′), 137.94 (C-3a), 136.63 (C-5a/10d), 136.34 (C10a), 135.92 (t, J = 5.6 Hz, C-2″,6″), 135.18 (C-5a/10d), 132.78 (C4′), 132.36 (t, J = 29.2 Hz, C-1”), 130.91 (C-4″), 130.77 (C-2′), 130.18 (C-10), 128.83 (C-3′), 128.49 (C-9/C-3″,5″), 128.44 (C-9/C-3″,5″), 128.40 (C-5/C-3″,5″), 124.11 (C-9), 123.16 (C-4), 122.72 (C-8), 121.57 (C-3,6), 120.42 (C-1), 115.29 (CCPt), 36.70 (7-C(CH3)3), 36.34 (2-C(CH3)3), 32.21 (2-C(CH3)3), 32.13 (7-C(CH3)3), 31.55 (C-10b), 29.85 (C-10c), 15.58 (10b-CH3), 15.33 (10c-CH3); 31P{1H} 8130
dx.doi.org/10.1021/om3007008 | Organometallics 2012, 31, 8121−8134
Organometallics
Article
NMR (145 MHz, CD2Cl2) δ 18.28 (1JPt−P = 2651 Hz); 195Pt NMR (77 MHz, CD2Cl2) δ −252.22 (JP−Pt = 2655 Hz). Mixture of isomers 14a and 14b: mp 172−180 °C; IR (film) ν 3056, 2963, 2092, 1650, 1595, 1480, 1435, 1246, 1098, 691 cm−1; UV−vis (toluene) λmax (εmax, L mol−1 cm−1) 373 (47 300), 433 (63 100), 493 (17 800), 684 (4600) nm; ESI MS m/z 1661 (M+); HRMS calcd for C106H100O2P2Pt + H 1661.6904, found 1661.6877. trans-Bis[2″-(2,7-di-tert-butyl-12c,12d-dimethyl-trans12c,12d-dihydrobenzo[e]pyren-4-yl)ethynyl]bis-
−3.40 (s, 6H, H-10b), −3.41 (s, 6H, H-10c); 13C{1H} NMR (125 MHz, C6D6) δ 146.31 (C-2), 145.59 (C-7), 138.19 (C-10a/10e), 137.64 (C-3a), 137.04 (C-5a), 134.61−134.50 (meta-C), 131.49 (ortho-C, para-C), 129.35−129.24 (ortho-C, para-C), 128.5 (C-5 partially obscured by the solvent resonance), 123.59 (C-10), 123.18 (C-9), 122.81 (C-4), 122.70 (C-3), 121.80 (C-1), 120.84 (C-8), 120.39 (C-6), 114.16 (dd, 2JP(trans)‑C = 150 Hz, 2JP(cis)‑C = 15 Hz, CCPt), 113.28 (d, 2JP(trans)‑C = 35 Hz, CCPt), 36.50 (2-C(CH3)3), 36.26 (7C(CH3)3), 32.60 (2-C(CH3)3), 32.43 (2-C(CH3)3), 31.34 (C-10b), 30.89 (C-10c), 29.00−28.30 (m, PCH2CH2P), 15.98 (C-10b/10c), 15.60 (C-10b/10c); 31P{1H} NMR (202 MHz, CDCl3) δ 39.57 (1JPt−P = 2277 Hz); 195Pt NMR (77 MHz, CDCl3) δ −381.53 (t, 1JPt−P = 2278 Hz); IR (KBr) ν 2960, 2863, 2093, 1589, 1476, 1459, 1435, 1230, 1103, 881, 704, 690, 531 cm−1; UV−vis (toluene) λmax (εmax, L mol−1 cm−1) 367 (55 200), 405 (54 600), 478 (12 100), 503 (12 100), 669 (2200) nm; ESI MS m/z 1327 (M+); HRMS calcd for C82H86P2Pt + H 1327.5910, found 1327.5889. cis-Bis[2″-(2,7-di-tert-butyl-12c,12d-dimethyl-trans-12c,12ddihydrobenzo[e]pyren-4-yl)ethynyl][bis(diphenylphosphino)-
(triphenylphosphino)platinum(II) (15). Complex 15 was prepared using the same procedure as for 14, by mixing benzo[e]DHP-ethyne 8 (40 mg, 0.095 mmol), trans-Pt(PPh3)2Cl2 (35 mg, 0.045 mmol), and CuI (1.0 mg, 0.0053 mmol) in Et2NH (10 mL). The red solid that precipitated was recrystallized from toluene to give 15 (45 mg, 65% yield). 15: mp 180 °C dec; 1H NMR (500 MHz, C6D6) δ 8.83−8.79 (m, 4H, H-9,12), 8.39 (s, 2H, H-1), 8.37 (d, J = 1.1 Hz, 2H, H-8), 8.19 (m, 12H, H-2′), 7.83 (t, J = 1.1 Hz, 2H, H-3), 7.52−7.47 (m, 4H, H10,11), 7.26 (d, J = 1.0 Hz, 2H, H-6), 7.04 (t, J = 7.4 Hz, 12H, H-3′), 6.93 (t, J = 7.0 Hz, 6H, H-4′), 6.62 (dd, J = 3.9, 0.8 Hz, 2H, H-5), 1.46 (s, 2H, 7-C(CH3)3), 1.35 (s, 2H, 2-C(CH3)3), −1.22 (d, J = 3.3 Hz, 2H, 12d-CH3), −1.27 (d, J = 4.2 Hz, 2H, 12c-CH3); 13C{1H} NMR (125 MHz, C6D6) δ 143.99 (C-7), 143.23 (C-2), 136.96 (C-5a), 136.86 (C-3a), 136.15 (t, 2JC−P = 6 Hz, C-2′), 135.87 (C-12e), 135.43 (C-12b), 132.63 (t, 1JC−P = 29.2 Hz, C-1′), 130.78 (C-4′), 130.61 (C12a), 129.99 (C-12f), 128.44 (t, 3JC−P = 5.5 Hz, C-3′), 127.28 (C-5), 126.16 (C-10,11), 125.41 (C-9 or 12), 125.34 (C-9 or 12), 121.24 (C4), 121.13 (C-3), 120.23 (C-6), 118.60 (t, 2JC−P = 15.1 Hz, CCPt), 118.04 (C-1), 117.29 (C-8), 115.77 (CCPt), 36.77 (C-12c), 36.05 (C-12d), 35.88 (2-C(CH3)3), 35.71 (7-C(CH3)3), 31.38 (2-C(CH3)3), 31.11 (7-C(CH3)3), 18.74 (12c-CH3), 18.65 (12d-CH3); 31P{1H} NMR (202 MHz, C6D6) δ 19.02 (1JPt−P = 2677 Hz); 195Pt NMR (77 MHz, C6D6) δ −253.77 (t, 1JPt−P = 2695 Hz); IR (KBr) ν 3057, 2960, 2922, 2864, 2099, 1476, 1434, 1365, 1254, 1096, 743, 692, 521, 513 cm−1; UV−vis (toluene) λmax (εmax, L mol−1 cm−1) 342 (35 200), 359 (37 000), 423 (78 900), 529 (13 600) nm; ESI MS m/z 1553 (M+ + H); HRMS calcd for C100H96P2Pt + H 1553.6692, found 1553.6676. Open form, 15o: 1H NMR (500 MHz, C6D6) δ 8.17−8.11 (m, 2H), 8.11−8.04 (m, 10H), 7.76−7.69 (m, 4H), 7.22−7.18 (m, 4H), 7.08− 6.96 (m, 24H), 6.77−6.74 (m, 2H), 6.00 (s, 1H), 5.97 (s, 1H), 1.43 (s, 3H), 1.42 (s, 3H), 1.39 (s, 6H), 1.278 (s, 9H), 1.276 (s, 9H), 1.137 (s, 9H), 1.134 (s, 9H). cis-Bis[2″-(2,7-di-tert-butyl-10b,10c-dimethyl-trans-10b,10cdihydropyren-4-yl)ethynyl][bis(diphenylphosphino)ethaneP,P′]platinum(II) (16). Complex 16 was prepared using a similar procedure as for 14, by mixing DHP-ethyne 4 (50 mg, 0.135 mmol), Pt(dppe)Cl2 (44 mg, 0.066 mmol), and CuI (1.6 mg, 0.0084 mmol) in Et2NH (10 mL). The brown precipitate was chromatographed on alumina with hexanes/CH2Cl2 (3/10) as eluent. The dialkyne dimer eluted first (6 mg, 12% yield), followed by 16 as an orange solid after removal of solvent. Washing with methanol afforded pure 16 as orange microcrystals (22 mg, 25% yield). 16: mp 180 °C dec; 1H NMR (500 MHz, C6D6) δ 9.88 and 9.87 (s, 2H, H-3), 8.76 (s, 2H, H-5), 8.57 and 8.56 (s, 2H, H-1), 8.54 (s, 2H, H-8), 8.44 (AB, J = 8.9 Hz, 4H, H9,10), 8.38 (s, 2H, H-6), 8.26−8.16 (m, 4H, meta-H), 7.06−6.92 (m, 6H, ortho- and para-H), 2.08−1.91 (m, 4H, PCH2CH2P), 1.609 and 1.607 (s, 18H, 7-C(CH3)3), 1.435 and 1.424 (s, 18H, 2-C(CH3)3),
ethane-P,P′]platinum(II) (17). Using the procedure for complex 9, DHP-ethyne 8 (40 mg, 0.095 mmol), Pt(dppe)Cl2 (30 mg, 0.046 mmol), and CuI (2.6 mg, 0.013 mmol) in Et2NH (7 mL) gave a red solid. This was chromatographed on alumina with hexanes/CH2Cl2 (1/2) as eluent. The dialkyne dimer (5 mg, 12% yield) eluted first, followed by 17 as a red solid after removal of solvent (16 mg, 25% yield). 17: mp 200 °C dec; 1H NMR (500 MHz, C6D6) δ 8.86 and 8.84 (s, 2H, H-3), 8.82−8.77 (m, 4H, H-9,12), 8.43 (s, 2H, H-1), 8.37 (s, 2H, H-8), 8.14−8.07 (m, 8H, meta-H), 7.50−7.44 (m, 4H, H10,11), 7.41 (s, 2H, H-5), 7.29 (s, 2H, H-6), 7.09−6.94 (m, 12H, ortho- and para-H),1.98−1.81 (m, 4H, PCH2CH2P), 1.42 (s, 18H, 7C(CH3)3), 1.33 (s, 18H, 2-C(CH3)3), −1.06, −1.07, and −1.08 (12c,12d-CH3); 13C{1H} NMR (125 MHz, C6D6) δ 144.56 and 144.52 (C-2), 143.93 (C-7), 138.93 (C-3a), 137.45 and 137.43 (C-5a), 135.95 (C-12b/12e), 135.85 (C-12b/12e), 134.56 and 134.46 and 134.38 (meta-C), 131.46 (para-C), 130.66 (C-12a), 130.09 (C-12f), 129.29 and 129.26 and 129.20 (ortho-C), 127.59 and 127.55 (C-5), 126.37 and 126.10 (C-10,11), 125.50 and 125.32 (C-9,12), 122.09 (C3), 120.80 (C-4), 120.52 (C-6), 118.37 (C-1), 117.33 (C-8), 113.42 (dd, 2JP(trans)‑C = 150 Hz, 2JP(cis)‑C = 14 Hz, CCPt), 112.5 (dd, 2 JP(trans)‑C = 36 Hz, 2JP(cis)‑C = 6 Hz, CCPt), 37.08 (C-12c), 36.33 (C8131
dx.doi.org/10.1021/om3007008 | Organometallics 2012, 31, 8121−8134
Organometallics
Article
12d), 36.09 (2-C(CH3)3), 35.72 (7-C(CH3)3), 31.36 (2-C(CH3)3), 31.13 (7-C(CH3)3), 28.76−28.36 (m, PCH2CH2P), 18.86 and 18.83 and 18.77 and 18.74 (12c,12d-CH3); 31P{1H} NMR (202 MHz, C6D6) δ 40.24 (1JPt−P = 2246 Hz); 195Pt NMR (77 MHz, CD2Cl2) δ −378.8 (1JPt−P = 2268 Hz); IR (KBr) ν 3054, 2961, 2921, 2865, 2093, 1475, 1435, 1366, 1253, 1104, 873, 753, 712, 703, 690, 530; UV−vis (cyclohexane) λmax (εmax, L mol−1 cm−1) 339 (63 600), 356 (70 700), 416 (130 000), 527 (12 200) nm; ESI MS m/z 1427 (M+), MS calcd for C90H90P2Pt + H 1427.6223, found 1427.6248. NMR spectral data in CD2Cl2: 1H NMR (360 MHz) δ 8.75−8.72 (m, 4H), 8.24, 8.23, 8.17−8.09 (m, 4H), 8.07 (t), 7.59−7.55 (m), 7.46−7.41 (m), 7.20, (s), 6.95 (s), 2.57−2.43 (m broad,) 1.47, (s, 18H), 1.269 (s, 9H), 1.266 (s, 9H), −1.539 (12c/12d-CH3), −1.542 (12c/12d-CH3); 31P{1H} NMR (146 MHz) δ 41.41 (1JPt−P= 2268 Hz). Open form 17o: 1H NMR (500 MHz, C6D6) δ 8.03−7.85 (m, 8H), 7.75−7.68 (m, 6H), 7.21−7.17 (m, 4H), 7.07−6.92 (m, 16H), 6.91 (s, 1H), 6.89 (s, 1H), 6.80 (d, J = 2.1 Hz, 1H), 6.78 (d, J = 1.9 Hz, 1H), 2.00−1.64 (m, 8H),); 13C{1H} NMR (125 MHz, C6D6) δ 150.74, 150.04, 145.38, 145.35, 140.77, 140.44, 140.16, 139.91, 139.21, 139.04, 135.25, 135.08, 134.32, 134.14, 131.55, 124.85, 124.80, 123.89, 34.62, 34.48, 31.93, 31.88, 31.43, 31.11, 19.95, 19.42; 31P{1H} NMR (202 MHz, C6D6) δ 40.34 and 40.31 (1JPt−P = 2242 Hz). cis-Bis[2″-(10-acetyl-2,7-di-tert-butyl-10b,10c-dimethyltrans-10b,10c-dihydropyren-4-yl)ethynyl](2,2′-bipyridine-
thoyl Isomer (19b). Complex 19 was prepared according to the same procedure as 9 from 1′-naphthoylDHP-ethyne 7 (100 mg, 0.192 mmol), Pt(bipy)Cl2 (43 mg, 0.096 mmol), and CuI (6.0 mg, 0.032 mmol) in Et2NH (15 mL). The crude product was recrystallized in a mixture of CH2Cl2 and methanol to afford dark red crystals of 19 (10 mg, 7% yield). 19a (major isomer, bis-10-naphthoyl): 1H NMR (500 MHz, CD2Cl2) δ 10.34 (d, J = 5.2 Hz, 2H, H-6′), 9.53 (s, 2H, H-3), 9.28 and 9.27 (two overlapping s, 2H, H-1), 8.88 (s, 2H, H-5), 8.54 (s, 4H, H-6,9), 8.45 (s, 2H, H-8), 8.40 (d, J = 8.5 Hz, 2H, H-8″), 8.31− 8.25 (m, 4H, H-3′,4′), 8.08 (d, J = 8.1 Hz, 2H, H-4″), 8.01 (d, J = 8.3 Hz, 2H, H-5″), 7.78 (t, J = 6.7 Hz, 2H, H-5′), 7.64 (d, J = 7.1 Hz, 2H, H-2″), 7.59−7.45 (m, 6H, H-3″,6″,7″), 1.62 (s, 18H, 7-C(CH3)3), 1.46 (s, 9H, 2-C(CH3)3), 1.45 (s, 9H, 2-C(CH3)3), −3.57 (s, 6H, 10bCH3), −3.59 (s, 6H, 10c-CH3); 13C{1H} NMR (125 MHz, CD2Cl2) δ 200.99 (NpCO), 157.18 (C-2′), 152.28 (C-6′), 150.58 (C-2), 147.01 (C-7), 140.85 (C-1″), 140.36 (C-3a), 139.60 (C-4′), 137.63 (C-10a), 136.80 (C-5a/10d), 135.22 (C-5a/10d), 134.45 (C-8″b), 131.68 (C8″a), 131.55 (C-4″), 130.49 (C-10), 130.08 (C-5), 129.02 (C-2″), 128.93 (C-5″), 128.35 (C-5′), 127.66 (C-7″), 126.87 (C-6″), 126.56 (C-8″), 126.21 (C-9), 125.28 (C-3″), 124.02 (C-8), 123.31 (C-3′), 122.88 (C-6), 121.92 (C-3,4), 120.88 (C-1), 102.52 (CCPt), 94.13 (CCPt), 37.00 (2-C(CH3)3), 36.32 (7-C(CH3)3), 32.22 and 32.21 (2/7-C(CH3)3), 32.17 (C-10b), 32.09 (2/7-C(CH3)3), 29.97 (C-10c), 15.78 (C-10b/10c), 15.36 (C-10b/10c). Mixture of isomers 19a and 19b: mp 260−267 °C; UV−vis (toluene) λmax (εmax, L mol−1 cm−1) 370 (70 600), 430 (93 000), 694 (8600) nm; ESI MS m/z 1394 (M ++H); HRMS calcd for C88 H82 N2 O2 Pt 1393.6081, found 1393.6063. cis-Bis[2″-(2,7-di-tert-butyl-10b,10c-dimethyl-trans-10b,10cdihydropyren-4-yl)ethynyl](1′,10′-phenanthroline-N,N′)-
N,N′)platinum(II) (18a) and the 9-Acetyl 10-Acetyl Isomer (18b). Complex 18 was prepared according to the same procedure as 9, from acetylDHP-ethyne 5 (60 mg, 0.15 mmol), Pt(bipy)Cl2 (30 mg, 0.067 mmol), and CuI (2.0 mg, 10 × 10−3 mmol) in Et2NH (6 mL). Recrystallization of the crude product from a mixture of hexane and CH2Cl2 afforded 18 as dark orange crystals (33 mg, 40% yield). 18a (major isomer, bis-10-acetyl): 1H NMR (500 MHz, CDCl3) δ 10.33 (d, J = 5.3 Hz, 2H, H-6′), 9.70 (d, J = 1.4 Hz, 2H, H-1), 9.58 (d, J = 1.3 Hz, 2H, H-3), 8.87 (s, 2H, H-5), 8.83 (s, 2H, H-9), 8.55 (s, 2H, H-8), 8.46 (s, 2H, H-6), 8.23 (d, J = 1.4 Hz, 2H, H-3′), 8.22 (td, J = 7.9, 1.4 Hz, 2H, H-4′), 7.68 (td, J = 6.0, 2.3 Hz, 1H, H-5′), 3.05 (s, 6H, COCH3), 1.66 (s, 18H, 7-C(CH3)3), 1.60 (s, 9H, 2-C(CH3)3), 1.59 (s, 9H, 2-C(CH3)3), −3.69 (s, 6H, 10c-CH3), −3.714/-3.715 (s, 6H, 10bCH3); 13C{1H} NMR (125 MHz, CDCl3) δ 202.52 (COCH3), 156.67 (C-2′), 152.08 (C-6′), 151.07 (C-2), 146.27 (C-7), 140.39 (C-3a), 138.91 (C-4′), 136.63 (C-10a), 136.61 (C-10a minor isomer), 136.33 (C-5a/10d), 135.17 (C-5a/10d), 130.09 (C-5), 128.09 (C-10), 127.78 (C-5′), 124.29 (C-9), 123.35 (C-8), 122.91 (C-3′), 122.36 (C-6), 122.01 (C-3), 121.72 (C-4), 120.68 (C-1), 120.65 (C-1 minor isomer), 102.77 (CC−Pt), 92.30 (CC-Pt), 36.96 (2-C(CH3)3), 36.95 (2C(CH3)3), 36.07 (7-C(CH3)3), 32.33 (2-C(CH3)3), 32.09 (7C(CH3)3), 31.69 (C-10b), 31.11 (COCH3), 29.51 (C-10c), 15.48 (10b/10c-CH3). Mixture of isomers 18a and 18b: mp 182−190 °C; IR (KBr) ν 2962, 2923, 2905, 2865, 2094, 1663, 1657, 1606, 1585, 1468, 1449, 1422, 1408, 1378, 1348, 1243, 1225, 1207, 1155, 1123, 934, 891, 764, 747, 681, 665 cm−1; UV−vis (toluene) λmax (εmax, L mol−1 cm−1) 390 (78 400), 424 (87 700), 492 (19 600), 695 (8500) nm; ESI MS m/z 1170 (M+ + H); HRMS calcd for C70H74N2O2Pt 1169.5455, found 1169.5481. cis-Bis[2‴-[10-(1-naphthoyl)-2,7-di-tert-butyl-10b,10c-dimethyl-trans-10b,10c-dihydropyren-4-yl]ethynyl](2,2′-bipyridine-N,N′)platinum(II) (19a) and the 9-Naphthoyl 10-Naph-
platinum(II) (20). Complex 20 was prepared according to the same procedure as 9 from DHP-ethyne 4 (50 mg, 0.135 mmol), Pt(phen)Cl2 (29 mg, 0.065 mmol), and CuI (1.5 mg, 0.0079 mmol) in Et2NH (8 mL). Brown, microcrystalline 20 precipitated from the reaction mixture (15 mg, 21% yield). The low solubility of 20 precluded the 2D experiments required to assign all of the 1H and 13C resonances; therefore, these are simply listed without assignment. 1H NMR (500 MHz, CD2Cl2) δ 10.55 (m, 2H, H-2,9), 9.51 (s, 2H), 8.82 (s, 2H), 8.78 (m, 2H), 8.52 (d, J = Hz, 2H), 8.50 (s, 4H), 8.43 (d, J = 1.0 Hz, 2H), 8.40 (d, J = 7.4 Hz, 2H), 8.15 (s, 2H), 8.09 (m, 2H), 1.70, 1.64, 1.62, −3.77 (internal CH3), −3.78 (internal CH3); 13C{1H} 8132
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NMR (125 MHz, C6D6) δ 152.25, 148.69, 146.44, 146.38, 138.57, 138.12, 137.71, 137.54, 136.86, 131.35, 128.15, 127.92, 126.85, 123.33, 123.1, 121.50, 121.31, 121.06, 120.92, 120.45, 103.18, 54.44, 54.22, 54.00, 53.79, 53.57, 42.63, 36.62, 36.40, 32.54, 32.25, 30.91, 30.42, 15.53, 15.01; IR (KBr) ν 3035, 2963, 2867, 2096, 1608, 1520, 1460, 1381, 1358, 1343, 1231, 883 cm−1; ESI MS m/z 1109 (M+). X-ray Crystallographic Studies. Crystals for analysis were grown by slow cooling of saturated solutions in a mixed solvent: dichloromethane/methanol (10, 14), dichloromethane/hexane (11, 17), or toluene/hexane (15). Suitable crystals were selected under a microscope and attached to a glass fiber prior to data collection at low temperature (90 K for 10, 11, 14, and 15; 173 K for 17) using a Bruker/Siemens SMART APEX (10, 11, 14, 15) or a Bruker X8 APEX II (17) instrument (Mo Kα radiation, λ = 0.710 73 Å). Data were measured using ω scans of 0.3° per frame for 10 (11), 20 (15) or 30 s (10, 14), and a full sphere of data was collected; for 17, ω scans of 0.5° per frame for 30 s were collected. Data reduction and correction for Lorentz−polarization and decay were performed using SAINTPlus software.29 Absorption corrections were applied using SADABS.30 The structures were solved by direct methods and refined using least squares on F2 as implemented in the SHELXTL program package.31 All non-hydrogen atoms were refined anisotropically except as noted below. Disorder was observed in all five structures related to the orientation of the central methyl groups. In the structures of 14 and 17, this disorder was modeled straightforwardly using a ratio of 75:25 between the two orientations. Similarly, the structure of 15 was modeled using a ratio of 50:50 between the two orientations. Complexes 14 contained one well-ordered CH2Cl2 of solvation per asymmetric unit, while 15 contained a hexane at 50% occupancy. Complex 17 was determined to contain one very badly disordered toluene molecule per asymmetric unit by using the Platon/Squeeze program32 to generate a “solvent-free” data set. The number of electrons removed by the Squeeze program (53 electrons/asymmetric unit) corresponds to one toluene molecule; therefore, the formula reported includes this solvent, although it was not located or refined in the final least-squares cycle. The disorder models used in treating the structures of 10 and 11 were more complex. In the case of 10, the disorder of the central DHP moiety and the acyl group was refined using a ratio of 83:17 for the two fractions. In addition, a disordered CH2Cl2 of solvation was located and refined with 20% occupancy. For the structure of 11, separate disorder models were used to account for the disorder of different groups: two orientations of the Et groups on PEt3 (ratio 75:25), two orientations of each t-Bu group (ratios 73:27 and 70:30), and two orientations of the PhCO unit (ratio 56:44). No significant decomposition was observed during data collection for any of these complexes. A summary of the data collection and refinement parameters is given in the Supporting Information. Photochemical Studies. The visible openings were performed using a 500 W tungsten light source and a 550 nm cutoff filter. The processes were followed by either UV−vis spectroscopy or NMR spectroscopy. For the NMR experiments, the samples were prepared in an inert-atmosphere glovebox using dry, oxygen-free solvents. In the UV−vis experiments, solutions were prepared in solvents that were previously degassed with argon for 15 min. During irradiation, samples were chilled using an ice bath or cold water recirculating flow system. The photo-opening rates for the complexes were compared with the ligand precursor or other DHP compounds with similar photoopening rates. UV photoclosing experiments were performed using a small UV light; only preliminary tests were performed, because the photoclosing rates were fast in all cases.
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Article
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected] (D.J.B.);
[email protected] (R.H.M.). Present Addresses †
Notre Dame University, Notre Dame, IN. University of British Columbia, Vancouver, BC, Canada.
‡
Notes
The authors declare no competing financial interest.
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ASSOCIATED CONTENT
S Supporting Information *
Text, tables, figures, and CIF files giving additional synthetic details, characterization data, and crystallographic data for the crystal structure studies in this paper. This material is available free of charge via the Internet at http://pubs.acs.org. 8133
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