ARTICLE pubs.acs.org/Organometallics
Electronically Coupled Tetrathiafulvalene Electrophores across a Non-innocent AcetylideRuthenium Bridge Antoine Vacher,† Frederic Barriere,† Thierry Roisnel,† Lidia Piekara-Sady,‡ and Dominique Lorcy*,† †
Sciences Chimiques de Rennes, UMR 6226 CNRS-Universite de Rennes 1, Campus de Beaulieu, B^atiment 10A, 35042 Rennes Cedex, France ‡ Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznan, Poland
bS Supporting Information ABSTRACT:
The synthesis and structural characterization of trans-[Ru(CtCMe3TTF)2(dppe)2] (HCtCMe3TTF = 4-ethynyl-40 ,5,50 trimethyltetrathiafulvalene) are described together with the X-ray crystal structures of the organic pro-ligands. Cyclic voltammetry experiments show sequential oxidation of the neutral compound with five one-electron processes up to the corresponding pentacation, trans-[Ru(III)(CtCMe3TTF)2(dppe)2]5þ, evidencing electronic interactions among the three coupled electrophores, the two TTFs and the Ru(II) center. A strong effect of the supporting electrolyte in dichloromethane was observed on the ΔE values especially between the second and third oxidation steps and between the third and fourth one, when [NBu4][PF6] was substituted for Na[B(C6H4(CF3)2)4]. This indicates the appreciable role ion-pairing interactions play in stabilizing these higher charge states, although solvation factors have been shown to be less significant in this case. The separation of the first two redox events was essentially independent of medium effects, indicating a more significant, inherent intramolecular electronic effect. The combined spectroscopic and computational investigations have evidenced that (i) the organic and the metal-based electroactive sites are strongly electronically coupled and (ii) the bisacetylideruthenium linker efficiently mediates electronic coupling between the two tetrathiafulvalenes.
’ INTRODUCTION Electronic interactions between two organic electrophores such as tetrathiafulvalene (TTF), through covalent1,2 or noncovalent attachment,3 have stimulated the imagination and the skill of the chemists involved in this research area. A range of TTF dimers linked by one or two covalent bonds have been synthesized for that purpose with the aim of creating mixed valence states.1 The interplay between two redox-active TTF generates a multistage redox behavior affected by the type of linker. The typical redox behavior of an isolated single TTF unit consists of the sequential reversible oxidation of the neutral species into the radical cation and the dication. For dimeric structures, however, where through-bond and/or through-space interactions exist, four or five redox states are observed rather than three as expected for an isolated TTF. In the rare situation of TTF dimers linked through a rigid organic bridge involving two monatomic connections such as benzo-,4 1,4-dithiine-,5 pyrazine-,6 or 1,4-diphosphinine-fused,7 1,4 disylil or digermanyl8 r 2011 American Chemical Society
bisTTFs (Chart 1, a), the stepwise electrochemical generation of the radical cation, dication, trication, and tetracation is observed. In most cases however, where two TTFs are connected either directly or through a single heteroatom (Chart 1, b), only three redox steps corresponding to the sequential formation of the cation radical, biscation radical, and finally the tetracation are electrochemically detected.9,10 The common feature of all these dimers is the close proximity of the TTFs cores, as the linker is only one atom long. A sizable interaction between two TTF ligands was also observed in the case of dimeric TTFs, where the linker involves a metal(II) center chelated by two TTF-acac units (Chart 1, c).11 Interestingly, no interplay has been electrochemically detected so far within TTF dimers or between TTF and a FeCp*(dppe) group, where the two redox active moieties are connected by a linker involving an organometallic fragment.12 Nevertheless, it has been shown that Received: March 25, 2011 Published: June 13, 2011 3570
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Chart 1. Selected TTF Dimers
Chart 2. TTF Organometallic Complexes
Scheme 1. Synthesis of 3: trans-[Ru(acetylideTTF)2(dppe)2]
within trans-bis(acetylideferrocenyl) ruthenium complexes, the two Fe redox systems interact along the bisacetylide ruthenium linker.13 We recently reported the synthesis of a rutheniumacetylideTTF complex, trans-[RuCl(CtCMe3TTF)(dppe)2], where the TTF and the ruthenium center are shown to be strongly electronically coupled (Chart 2, left).14 Actually such strong mutual electronic interactions within hybrid organicinorganic building blocks involving TTF are unique.15 With this in mind, we investigated the synthesis of an original metalTTF complex where the ruthenium was linked to two TTF units via an alkynyl linkage, trans-[Ru(CtCMe3TTF)2(dppe)2], 3, and studied the electronic interaction between its three redox active units, i.e., the Ru(II) center and the two TTF moieties. Herein we present the synthesis and the structural properties of an original bis(TTF-acetylide) ruthenium complex, 3 (Chart 2). We also report the electrochemical and spectroscopic investigations (UVvisNIR and EPR) of this complex. These experimental data together with DFT and TD-DFT calculations are used to get
Figure 1. ORTEP drawings of TTFs 1 (top) and 2 (bottom). Ellipsoids are drawn at 50% probability.
insight on the nature of the electronic interactions among the three coupled electrophores of this original organometallic complex.
’ RESULTS AND DISCUSSION Synthesis and Crystal Structures. The synthesis of TTF alkyne 2 was carried out starting from the trimethylsilylprotected TTF pro-ligand 1, according to the synthetic pathway described in Scheme 1.14 Deprotection of 1 with KF in MeOH afforded TTF alkyne 2 in quantitative yield. Orange crystals, amenable to single-crystal X-ray diffraction, were obtained for both TTF derivatives 1 and 2, and the molecular structures are shown in Figure 1. The target molecule was synthesized by the reaction of TTF alkyne 2 with cis-Cl2Ru(dppe)2 in the presence of NaPF6 and NEt3 in dichloromethane at room temperature and under an inert atmosphere. 3571
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Figure 3. Cyclic voltammogram of 3 in CH2Cl2-[NBu4][PF6] 0.2 M. E in V vs FeCp*2þ/FeCp*2, ν = 100 mV s1. Figure 2. ORTEP drawing of the molecular structure of 3 (top) and side view (bottom). H atoms are omitted for clarity. Ellipsoids are drawn at 50% probability.
The reaction was monitored by 31P NMR spectroscopy. The phosphorus atoms of the starting material cis-Cl2Ru(dppe)2 resonate at 37.8 and 45.1 ppm, and during the course of the reaction the decrease of this set of signals is concomitant with the growth of a new signal at 49.9 ppm assigned to complex 3 (Scheme 1). The presence of this single signal indicates the equivalence of the four phosphorus atoms and therefore a trans arrangement of the alkynyl ligands around the metallic center. The IR vibration of the acetylide bond in 3, νCtC = 2033 cm1, is found at a lower energy than in the starting alkyne TTF 2, νCtC = 2140 cm1. This νCtC stretching frequency in 3 is close to that observed for the TTF-acetylide-Ru complex (2029 cm1) reported previously14 and, hence, belongs to the lowest νCtC frequencies observed for documented Ru(II) acetylide complexes.16 This indicates a high degree of conjugation in 3. Single crystals of complex 3 were grown by slow diffusion of pentane into a concentrated solution of 3 in dichloromethane under an inert atmosphere. The molecular structure of 3 (Figure 2) shows that the ruthenium center is chelated by two dppe units and that two TTF acetylide ligands are coordinated to the ruthenium center in a trans arrangement. The CβtCRRuCRtCβ spacer is almost linear, with angles at CRRuCR, RuCRtCβ, and CRt CβCTTF of 180.00°, 173.91(16)°, and 173.59(19)°, respectively. The RuC distance of 2.0691(18) Å and the CtC bond length of 1.203(3) Å lie in the typical range observed for other trans ruthenium coordinated bisacetylide ligands.13 It is worth noting that the alkyne bond in TTF 2 amounts to 1.152(8) Å, much shorter than in the ruthenium complex 3. Actually, the acetylide CtC distance in 3 is comparable with that of the trimethylsilyl-protected pro-ligand, TTF 1 (1.209(3) Å). Both Me3TTF-CtC-SiMe3 1 and Me3TTF-CtCH 214 exhibit a planar structure, without distorsions of the dithiole rings, Figure 1. The TTF units in 3 adopt a boat conformation with the dithiole rings folded along the S 3 3 3 S axis with values of 15.5(1)° and 12.2(1)° and a central CdC bond length of 1.344(3) Å typical for neutral TTF and similar to that observed for TTF 2, where C5C6 amounts to 1.348(7) Å. The wave shape of 3 seen in Figure 2 (right) is reminiscent of that previously reported for other dimeric TTFs with a rigid bridge involving two connections.7 Electrochemical Studies. The cyclic voltammogram (CV) of complex 3 in CH2Cl2 using [NBu4][PF6] as supporting
electrolyte is shown in Figure 3. The CV displays three main reversible systems, the two first ones being actually split into two closely spaced reversible oxidation waves, indicating the stepwise formation of six oxidation states from the neutral to the fully oxidized species 35þ (E11/2 = 0.05 V; E21/2 = 0.16 V; E31/2 = 0.58 V; E41/2 = 0.69 V; E51/2 = 1.33 V, vs SCE, E11/2 = 0.14 V; E21/2 = 0.25 V; E31/2 = 0.67 V; E41/2 = 0.78 V; E51/2 = 1.42 V, vs FeCp*2þ/FeCp*2). The first two redox systems are observed at less anodic potentials compared with TTFs 1 and 2 (E11/2 = 0.35 and E11/2 = 0.38 V vs SCE, respectively) or with the mononuclear ruthenium complex congener trans-[ClRu(CtCPh)(dppe)2] (E = 0.55 V vs Ag/AgCl).17 This result is reminiscent of what was previously observed for the complex trans-[RuCl(CtCMe3TTF)(dppe)2] (E11/2 = 0.07 V vs SCE).14 In this latter case, the first oxidation process was assigned to the oxidation of the TTF core into the cation radical species and rationalized by the increase of the electron density on the TTF from the metal fragment, efficiently transmitted by the acetylide linker. Similarly, the first oxidation of 3 is assigned to the oxidation of one TTF core, strongly affected by the electronrich Ru(II) acetylide linkage. The splitting of the first system indicates that each TTF unit in 3 is oxidized into the cation radical species sequentially, with a potential difference (ΔE) of 110 mV between the two successive oxidation processes. At more anodic potentials, each TTF cation radical oxidizes successively into the dication species with a ΔE between the third and the fourth oxidation processes amounting again to 110 mV. Consistent with the sequence described in Scheme 2, the fifth oxidation process at E1/2 = 1.33 V is then logically viewed as involving the RuII/RuIII couple. The RuII oxidation process is anodically shifted compared to trans-[RuCl(CtC-Me3TTF)(dppe)2] (E1/2 = 1.07 V vs SCE) due to the presence of a total of four positive charges in the immediate vicinity of the Ru(II) metal center. The splitting of the first two oxidation systems is independent of the concentration of 3 (between 106 and 103 M). This suggests intramolecular interactions between the two TTF units through the bisacetylide CtCRu(II)CtC linkage. Such splitting of the two redox systems due to throughbond interactions is rare. It is generally observed for rigid molecules where the two TTF moieties are connected with two short organic linkages such as benzo-,4 1,4-dithiine-,5 pyrazine-,6 and 1,4-diphosphinine-fused,7 inducing a close proximity of the donor cores. The present example is original in that the dimer in which the two TTFs are separated by ca. 9.372(11) Å 3572
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Scheme 2. Sequential Oxidation of 3
Chart 3.
19
(CTTF 3 3 3 CTTF), by the bis(acetylide) ruthenium organometallic fragment, exhibits such a splitting of the two redox systems. It is known that trans-bis(acetylide)ruthenium systems efficiently mediate interaction between ferrocenyl centers. For example, the two ferrocenyl units of differocenylacetylene (Fc-CtC-Fc) are oxidized successively with a potential difference of 130 mV in CH2Cl2-[NBu4][BF4],18 whereas ΔE is 205 mV in Fc-CtCRu(dppe)2-CtC-Fc (CH2Cl2-[NBu4][PF6]).13c It should also be stressed that no splitting of the redox waves was obtained for dimers where the TTF moieties are directly linked with one acetylenic bridge (Chart 3). We note however that the electrochemical properties of these species were recorded in rather polar electrolytes, respectively C6H5CN or DMF-[NBu4][ClO4].19 Although many factors are known to affect the magnitude of ΔE,20 the present results evidence a stabilization of the cation radical intermediates 3þ• and 33þ• with respect to disproportionation, possibly due, at least in part, by delocalization of the charge in the mixed valence states. To get insights on the electrostatic contributions to the ΔE values, we investigated the redox behavior of 3 in the weakly coordinating electrolyte CH2Cl2-Na[B(C6H4(CF3)2)4].21 As observed in Figure 4, the splitting of the first two oxidation systems is barely affected by the nature of the supporting electrolyte (ΔE = 130 mV). This may indicate a significant contribution to the ΔE value of electronic delocalization in the mixed valence state. Considering that in 32þ both TTF moieties are positively charged, the large anodic potential shift between the second and third electron transfer is easily rationalized by simple electrostatic repulsion between like charges. The extent of ΔE separating the third and fourth redox system is strongly modified in the presence of the CH2Cl2-Na[B(C6H4(CF3)2)4] electrolyte. Indeed, the third and fourth redox waves are anodically shifted by þ280 and þ460 mV, respectively, leading to the larger ΔE value of 290 mV between these two redox processes. This shows that the electrostatic tuning of the potential difference (ΔE) is larger in the case of the oxidation of the TTF
Figure 4. Cyclic voltammograms of 3 in 0.2 M CH2Cl2-[NBu4][PF6] (red) and in 0.2 M CH2Cl2-Na[B(C6H4(CF3)2)4] (black). E in V vs FeCp*2þ/FeCp*2, ν = 100 mV s1.
moieties in their dicationic state. The increase in the ΔE values, when the supporting electrolyte in CH2Cl2 is changed from [NBu4][PF6] to Na[B(C6H4(CF3)2)4], can be explained by the very low ion-pairing properties of [B(C6H4(CF3)2)4] in dichloromethane.21 Different solvation energies of the multicharged species as a function of charge delocalization may also play a significant role in the magnitude of ΔE values.22 Here, addition of acetonitrile in the dichloromethane-[NBu4][PF6] electrolyte (up to 1:1 v/v) had no effect on the cyclic voltammogram of 3 and hence on ΔE values. This hints to a limited effect of solvation on the extent of the ΔE values. We note that the electrochemistry of the related Cr(III) bis(acetylide)-TTF complex recently reported in acetonitrile-[NBu4][ClO4] shows no splitting of the redox waves.12 Finally, due to the large potential separation and anodic shifts of the first four sequential redox processes of 3, the oxidation of the Ru(II) metallic center is shifted outside of the electrolyte potential window. The splitting of the redox waves discussed above hints at a possible contribution of electronic delocalization in the 3þ• and 33þ• mixed valence states and also at a different extent of electronic coupling in these species. To probe these effects further, spectroelectrochemical and EPR spectroscopy studies were undertaken together with molecular modeling, as discussed next. 3573
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Figure 5. UVvisNIR monitoring of the first (left) and the second (right) electrochemical oxidation of 3 in 0.2 M CH2Cl2-[NBu4][PF6].
Figure 6. UVvisNIR monitoring of the third (left) and fourth (right) electrochemical oxidation of 3 in 0.2 M CH2Cl2-[NBu4][PF6].
UVVisNIR Spectroelectrochemical Investigations. In order to get more insight into the formation of the various oxidized species, UVvisNIR spectroelectrochemical investigations were carried out on a dichloromethane solution of 3 (c = 1.6 104 M). The neutral complex exhibits absorption bands in the visible range at λmax = 215 nm (ε = 51 000 L mol1 cm1) and 326 nm (ε = 21 600 L mol1 cm1), close to that observed for the mono-TTF-substituted ruthenium derivative.14 The latter band is ascribed to a metal-to-ligand charge transfer (MLCT) transition and is located at a lower energy than in the trans-[RuCl(CtCMe3TTF)(dppe)2] complex (317 nm). The assignment is consistent with the result of TD-DFT calculations, with two main transitions found to contribute in the lowest energy transition involving occupied orbitals with a strong metal acetylide character to unoccupied orbitals with ligand character (TTF and dppe). Upon gradual oxidation to the mono-oxidized species 3þ• (Figure 5 left), two new absorption bands centered at λmax = 460 and 1360 nm grow, the latter being a broad absorption band (ε = 3100 L mol1 cm1),23 concomitant with the decrease of the band centered at 326 nm (ε = 16 125 L mol1 cm1).23 The broad band centered at 1360 nm is assigned to a SOMO LUMO transition, as indicated by TD-DFT calculations (vide infra for the calculated nature of the 3þ• frontier orbitals). The presence of this band, in the near IR spectrum of 3þ•, confirms the electronic delocalization and demonstrates the electronic coupling between the two organic redox centers across the bisacetylide ruthenium linker, as shown below with the calculated spin density of 3þ. (vide infra). It is worth mentioning that UVvisNIR studies carried out on mono-oxidized dimeric TTF exhibit similar low-energy
Figure 7. UVvisNIR spectra recorded full range in 0.2 M CH2Cl2[NBu4][PF6].
transitions that have been assigned to intervalence charge transfer bands.6 Then, upon oxidation to the biscation radical species 32(þ•), the absorption band centered at 326 nm continually decreases, whereas the 460 nm one continually increases. Interestingly, upon oxidation, the broad absorption band centered at 1360 nm increases, is shifted toward higher energy at λmax = 1200 nm, and takes a Gaussian shape (Figure 5 right). This band is assigned to a SOMOLUMO transition, which is consistent with the result of TD-DFT calculations for the triplet 3574
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Figure 8. X-band EPR spectra of 3þ• (left) and trans-[RuCtC(Me3TTF)Cl(dppe)2] (right) in CH2Cl2 at room temperature (blue lines), frozen solution (black lines), and simulation (red lines).
state of 32(þ•). The nature of the SOMO is found to be fully delocalized across the TTF-acetylide-Ru-acetylide-TTF framework, while the LUMO has a similar nature with, however, no contribution from the metal. In purely organic dimeric-TTF derivatives,6 the near-infrared bands are not observed in the dicationic state. The present result highlights the non-innocence of the metalacetylide linkage between the TTF moieties. Upon gradual oxidation to the third (Figure 6, left) and to the fourth (Figure 6, right) oxidation processes, similar trends can be observed on the spectra. Indeed the broad absorption band centered at 1164 nm increases and shifts to higher energy (1085 nm) together with the increase of the one at 460 nm, while the band at 326 nm continually decreases. Interestingly if we summarize the overall process (Figure 7), upon gradual oxidation of 3, the intensity of the lowest energy band gradually increases and is shifted toward higher energy with a bandwidth narrowing. The nature of this low-energy band is different depending on the oxidation state. According to TDDFT calculations, in 3þ, the SOMOLUMO transition involves a charge transfer from the TTF to the metalacetylide, while in 32þ, it involves a delocalized SOMO with a strong metallic character and a TTF-based LUMO. No calculations were attempted on higher oxidation states. EPR Measurements. The mono-oxidized species was obtained by adding to a solution of 3 in CH2Cl2 one equivalent of NOPF6. At room temperature, the solution EPR spectrum displays a single line at giso = 2.013 with no hyperfine coupling resolved and the line width of ΔHpp = 7.5 G. The value of the giso for 3þ• is close to the one observed for the mono-oxidized ruthenium-substituted derivative we reported previously,14 trans-[RuCl(CtC-Me3TTF)(dppe)2]þ• (giso = 2.015). The absence of hyperfine coupling for 3þ• could be due to the broader individual line width from the slower tumbling rate of a bigger molecule or results from a conjugation between two TTF moieties. The frozen solution EPR spectrum for 3þ• (Figure 8 left) is almost axial, with g1 = 2.004, g2 = 2.012, g3 = 2.014, and Δg = gmax gmin = 0.010, which is remarkably different in symmetry, i.e., rhombic in trans-[RuCl(CtC-Me3TTF)(dppe)2]þ• (Figure 8 right). The simulated gi values give Δg = gmax gmin = 0.018. As compared to 3þ• there is an increase in g tensor anisotropy. Therefore, 3þ• exhibits smaller anisotropy measured by Δg = gmax gmin, by 0.008, and slightly lower giso (0.002) than trans-[RuCl(CtC-Me3TTF)(dppe)2]þ•, which is consistent with the lighter weight of ruthenium in the
Figure 9. HOMO and LUMO of 3 (left) and SOMO and LUMO of 3þ• (right) shown with a cutoff of 0.05 [e/bohr3]1/2.
SOMO of 3þ•. The spin density of 3þ• is calculated to be fully delocalized (vide infra). Theoretical Calculations. DFT calculations [Gaussian03, B3LYP/LanL2DZ] were performed on 3, 3þ•, and 32þ. Full geometry optimizations led to the molecular structure depicted in Figure 9. The optimized geometry of 3 is in good agreement regarding bond angles and bond lengths with that obtained by X-ray diffraction (Figure 2). In the optimized geometry of 3þ•, it can be noticed that compared with 3 the RuCR and the CβCTTF bond lengths are shortened, while the CRtCβ is slightly lengthened, and the bond angles of the linker between the TTF and the Ru atom are not modified. The calculated central CdC bond length of each TTF is lengthened compared to that in the neutral species, in accordance with the presence of partially oxidized TTF species in 3þ•. The HOMO of 3 is delocalized across the whole molecule with, however, a poor contribution on the carbon atoms of the distal dithiole rings. There is also a significant metal and acetylide contribution in the HOMO of 3, so that the assignment of the primary oxidation as a pure TTFs-based electron transfer is, like in [RuCl(CtCMe3TTF)(dppe)2], not possible. The calculated spin density in the mono-oxidized species 3þ• is symmetrically spread out from one TTF to the other across the bisacetylideruthenium linker with a lesser delocalization on the TTF carbon atoms at the outer limits of the molecule and with a strong contribution of the metal and acetylide tethers 3575
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Table 1. Crystallographic Data 1
2
3
formula
C14H18S4Si
C11H10S4
fw (g mol1)
342.61
270.43
1436.7
cryst syst
monoclinic
monoclinic
triclinic
space group
P21
P21/n
P1
a (Å)
6.6734(2)
7.6755(6)
11.2985(4)
b (Å)
5.9293(2)
7.6302(6)
13.1056(5)
c (Å)
22.1276(7)
20.4398(15)
13.6310(5)
Figure 10. Spin density of 3þ• shown with a cutoff of 0.02 e/bohr3.
R (deg) β (deg)
90 95.854(3)
90 91.350(5)
105.621(2) 90.910(2)
(Figure 10). However, since DFT is notorious for overemphasising electronic delocalization, we attempted geometry optimization at the HartreeFock level. The failure of the self-consistentfield procedure at this level of theory hints that the solution might indeed be delocalized. In any case, the system is found delocalized at the time scale of the EPR experiment.
γ (deg)
90
90
114.311(2)
V (Å3)
870.99(5)
1196.74(16)
1752.90(11)
’ CONCLUSION In conclusion we have reported here the synthesis of an original electroactive rutheniumbis(acetylide-TTF) complex and showed through experimental investigations strong electronic coupling between the three covalently linked electrophores. Electrochemical, spectroscopic, and theoretical investigations have evidenced not only electronic interactions between the TTF and the Ru atom but also intramolecular interactions between the two TTF cores of the complex. This result indicates that the organometallic bridge, acetylideRuacetylide, is a useful building block for facilitating the formation of mixed valence states in TTF radical dimers. This molecule also represents an example of a non-innocent organometallic bridge linking two equivalent organic electrophores, mirroring the well-documented opposite case of non-innocent conjugated organic bridges linking two equivalent metal-based electrophores.24 ’ EXPERIMENTAL SECTION General Procedures. All the reactions were performed under an argon atmosphere using standard Schlenk techniques. The solvents were purified and dried by standard methods. The cis-RuCl2(dppe)225 and TTF 114 were synthesized according to literature procedures. Sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate was purchased from Aldrich. NMR spectra were recorded on a Bruker AV300III spectrometer. Chemical shifts are reported in ppm referenced to TMS for 1H NMR and 13 C NMR and to H3PO4 for 31P NMR. Mass spectra were recorded with a Varian MAT 311 instrument by the Centre Regional de Mesures Physiques de l'Ouest, Rennes. Cyclic voltammetry was carried out on a 103 M solution of 3 derivatives in CH2Cl2, containing 0.2 M [NBu4][PF6] as supporting electrolyte. Voltammograms were recorded at 0.1 V s1 on a platinum disk electrode (A = 1 mm2). The potentials were measured versus saturated calomel electrode. The spectroelectrochemical setup was realized versus SCE in 0.2 M CH2Cl2-[NBu4][PF6]. A Cary 5 spectrophotometer was employed to record the UVvisNIR spectra. The EPR measurements were performed on a Bruker ESP-300E X-band spectrometer. The EPR study was carried out on a CH2Cl2 solution of 3 with one equivalent of the oxidizing agent NOPF6. Synthesis of trans-[Ru(CtCMe3TTF)2(dppe)2] (3). To a solution of trimethylsilylacetylenetrimethyl TTF (1 mmol; 270 mg), cis-RuCl2(dppe)2 (0.40 mmol; 386 mg), and NaPF6 (2 mmol, 336 mg) in CH2Cl2 (40 mL) was added freshly distilled Et3N (1 mL), and the solution was stirred at room temperature for 4048 h. This reaction was
C74H66P4RuS8
T (K)
120(2)
120(2)
100(2)
Z
2
4
1
Dcalc (g cm3)
1.306
1.501
1.361
μ (mm1)
0.599
0.756
0.595
total reflns abs corr
8113 multiscan
16 839 multiscan
22 425 multiscan
2724 (0.0883)
7796 (0.0304)
uniq reflns (Rint)
3098 (0.0302)
uniq reflns
2852 (I > 2σ(I)) 2112 (I > 2σ(I)) 6816 (I > 2σ(I))
R1, wR2
0.0255, 0.0633
R1, wR2 (all data) 0.0297, 0.0649 Flack param
0.02(8)
GoF
1.071
0.0795, 0.2195
0.0300, 0.0753
0.097, 0.2322
0.035, 0.0784
1.064
1.055
monitored by 31P NMR until all starting product was used. The solution was filtered and evaporated under vacuum. The crude was dissolved with CH2Cl2 (30 mL), washed with distilled water several times, dried on Na2SO4, filtered, and evaporated in vacuo. A brown-orange powder was obtained after washing with pentane (30 mL). The product was purified by precipitation in CH2Cl2 (30 mL) and pentane (100 mL). A yellow-orange powder was obtained in good yield (65%): 1H NMR (CDCl3) δ 7.357.00 (m, 40H, Ar), 2.67 (m, 8H, dppe), 1.981.97 (s, 18H, MeTTF); 31P NMR (CDCl3) δ 49.93 (s, 4P); 13C NMR (CD2Cl2) δ 139.47139.07 (CR), 135.92135.38 (Cipso Ph dppe), 133.00 (CH Ph dppe), 127.98 (CH Ph dppe), 126.22 (CH Ph dppe), 121.89 (TTF), 121.49 (TTF), 114.68 (Cβ), 108.82 (TTF), 106.24 (TTF), 104.20 (TTF), 30.5729.93 (CH2 dppe, |1JPCþ3JPC| = 24.6 Hz), 24.59 (TTF), 13.29 (MeTTF), 12.82 (MeTTF), 12.79 (MeTTF); IR (KBr) 2028 cm1 (s, νCtC); HRMS (EI) m/z calcd for C74H66P4RuS8 1436.09243, found 1436.0936. Crystallography. Crystals were picked up with a cryo-loop and then frozen at T = 120 K for compounds 1 and 2 and at T = 100 K for compound 3 under a stream of dry N2 on a APEX II Bruker AXS diffractometer for X-ray data collection (Mo KR radiation, λ = 0.71073 Å). The structures were solved by direct methods using the SIR97 program26 and then refined with full-matrix least-squares methods based on F2 (SHELX-97)27 with the aid of the WINGX28 program. For complex 3, the contribution of the disordered solvents to the calculated structure factors was estimated following the BYPASS algorithm,29 implemented as the SQUEEZE option in PLATON.30 A new data set, free of solvent contributions, was then used in the final refinement. All non-hydrogen atoms were refined with anisotropic atomic displacement parameters. H atoms were finally included in their calculated positions. Details of the final refinements are given in Table 1 for all compounds.
’ COMPUTATIONAL DETAILS Full geometry optimization of models of 3 and 3þ• with density functional theory31 and time-dependent density functional theory 3576
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Organometallics calculations was performed with the hybrid Becke-3 parameter exchange functional32 and the LeeYangParr nonlocal correlation functional33 (B3LYP) implemented in the Gaussian 03 (revision D.02) program suite34 using the LANL2DZ basis set35 with the default convergence criteria implemented in the program. The figures were generated with Molekel 4.3.36 The method and results of DFT and TD-DFT calculations are detailed in the Supporting Information.
’ ASSOCIATED CONTENT
bS Supporting Information. X-ray crystallographic files in CIF format. This material is available free of charge via the Internet at http://pubs.acs.org. ’ AUTHOR INFORMATION Corresponding Author
*Fax: (þ33)-2-23-23-67-38. E-mail:
[email protected].
’ ACKNOWLEDGMENT The authors thank the CINES (Montpellier, France) for allocation of computing time, and colleagues in Rennes for useful discussions. This work was supported by the French-Polish bilateral program Polonium 20092010 contract no. 20083YF. ’ REFERENCES (1) Iyoda, M.; Hasegawa, M.; Miyake, Y. Chem. Rev. 2004, 104, 5085–5113. (2) Jeppesen, J. O.; Nielsen, M. B.; Becher, J. Chem. Rev. 2004, 104, 5115–5131. (3) (a) Coskun, A.; Spruell, J. M.; Barin, G.; Fahrenbach, A. C.; Forgan, R. S.; Colvin, M. T.; Carmieli, R.; Benitez, D.; Tkatchouk, E.; Friedman, D. C.; Sarjeant, A. A.; Wasielewski, M. R.; Goddard, W. A.; Stoddart, J. F. J. Am. Chem. Soc. 2011, 133, 4538–4547. (b) Saad, A.; Barriere, F.; Levillain, E.; Vanthuyne, N.; Jeannin, O.; Fourmigue, M. Chem.—Eur. J. 2010, 16, 8020–8028. (c) Chiang, P.-T.; Chen, N.-C.; Lai, C.-C.; Chiu, S.-H. Chem.—Eur. J. 2008, 14, 6546–6552. (d) Yoshizawa, M.; Kumazawa, K.; Fujita, M. J. Am. Chem. Soc. 2005, 127, 13456–13457. (e) Ziganshina, A. Y.; Ko, Y. H.; Jeon, W. S.; Kim, K. Chem. Commun. 2004, 806–807. (4) Adam, M.; M€ullen, K. Adv. Mater. 1994, 6, 439–459. (5) Aqad, E.; Becker, J. Y.; Bernstein, J.; Ellern, A.; Khodorkovsky, V.; Shapiro, L. J. Chem. Soc., Chem. Commun. 1994, 2775–2776. (6) (a) Lahlil, K.; Moradpour, A.; Merienne, C.; Bowlas, C. J. Org. Chem. 1994, 59, 8030–8033. (b) Lahlil, K.; Moradpour, A.; Bowlas, C.; Menou, F.; Cassoux, P.; Bonvoisin, J.; Launay, J.-P.; Dive, G.; Dehareng, D. J. Am. Chem. Soc. 1995, 117, 9995–10002. (7) Danila, I.; Biaso, F.; Sidorenkova, H.; Geoffroy, M.; Fourmigue, M.; Levillain, E.; Avarvari, N. Organometallics 2009, 28, 3691–3699. Avarvari, N.; Fourmigue, M. Chem. Commun. 2004, 2794–2795. (8) Biaso, F.; Geoffroy, M.; Canadell, E.; Auban-Senzier, P.; Levillain, E.; Fourmigue, M.; Avarvari, N. Chem. —Eur. J. 2007, 13, 5394–5400. (9) (a) Kreicberga, J.; Edzina, A.; Kampare, R.; Neiland, O. Y. Zh. Org. Khim. 1989, 25, 1456–1462. (b) Tatemitsu, H.; Nishikawa, E.; Sakata, Y.; Misumi, S. Synth. Met. 1987, 19, 565–568. (c) John, D. E.; Moore, A. J.; Bryce, M. R.; Batsanov, A. S.; Howard, J. A. K. J. Mater. Chem. 2000, 1273–1279. (d) Iyoda, M.; Hara, K.; Ogura, E.; Takano, T.; Hasegawa, M.; Yoshida, M.; Kuwatani, Y.; Nishikawa, H.; Kikuchi, K.; Ikemoto, I.; Mori, T. J. Solid State Chem. 2002, 168, 597–607. (10) (a) Bryce, M. R.; Cooke, G.; Dhindsa, A. S.; Ando, D. J.; Hursthouse, M. B. Tetrahedron Lett. 1992, 33, 1783–1786. (b) Khodorkovsky, V. Y.; Becker, J. Y.; Bernstein, J. Synth. Met. 1993, 56, 1931–1935. (c) Becker, J. Y.; Bernstein, J.; Bittner, S.; Sarma, J. A.
ARTICLE
R. P.; Shahal, L. Tetrahedron Lett. 1988, 29, 6177–6180. (d) Fourmigue, M.; Huang, Y. S. Organometallics 1993, 12, 797–802. (11) (a) Massue, J.; Bellec, N.; Chopin, S.; Levillain, E.; Roisnel, T.; Clerac, R.; Lorcy, D. Inorg. Chem. 2005, 44, 8740–8748. (b) Bellec, N.; Massue, J.; Roisnel, T.; Lorcy, D. Inorg. Chem. Commun. 2007, 10, 1172–1176. (12) (a) Nishijo, J.; Judai, K.; Nishi, N. Inorg. Chem. 2011, 50, 3464–3470. (b) Miyazaki, A.; Ogyu, Y.; Justaud, F.; Ouahab, L.; Cauchy, T.; Halet, J.-F.; Lapinte, C. Organometallics 2010, 29, 4628–4638. (13) (a) Colbert, M. C. B.; Lewis, J.; Long, N. J.; Raithby, P. R.; White, A. J. P.; Williams, D. J. J. Chem. Soc., Dalton Trans. 1997, 99–104. (b) Jones, N. D.; Wolf, M. O.; Giaquinta, D. M. Organometallics 1997, 16, 1352–1354. (c) Lebreton, C.; Touchard, D.; Le Pichon, L.; Daridor, A.; Toupet, L.; Dixneuf, P. H. Inorg. Chim. Acta 1998, 272, 188–196. (14) Vacher, A.; Barriere, F.; Roisnel, T.; Lorcy, D. Chem. Commun. 2009, 7200–7202. (15) Lorcy, D.; Bellec, N.; Fourmigue, M.; Avarvari, N. Coord. Chem. Rev. 2009, 253, 1398–1438. (16) Younus, M.; Long, N. J.; Raithby, P. R.; Lewis, J.; Page, N. A.; White, A. J. P.; Williams, D. J.; Colbert, M. C. B.; Hodge, A. J.; Khan, M. S.; Parker, D. G. J. Organomet. Chem. 1999, 578, 198–209. (17) Powell, C. E.; Cifuentes, M. P.; Morrall, J. P.; Stranger, R.; Humphrey, M. G.; Samoc, M.; Luther-Davies, B.; Heath, G. A. J. Am. Chem. Soc. 2003, 125, 602–610. (18) Levanda, C.; Bechgaard, K.; Cowan, D. O. J. Org. Chem. 1976, 41, 2700–2704. (19) (a) Otsubo, T.; Kochi, Y.; Bitoh, A.; Ogura, F. Chem. Lett. 1994, 23, 2045–2050. (b) Iyoda, M.; Hasegawa, M.; Takano, J.-I.; Hara, K.; Kuwatani, Y. Chem. Lett. 2002, 31, 590–591. (20) Lapinte, C. J. Organomet. Chem. 2008, 693, 793–801. (21) (a) Barriere, F.; Geiger, W. E. J. Am. Chem. Soc. 2006, 128, 3980–3989. (b) Geiger, W. E; Barriere, F. Acc. Chem. Res. 2010, 43, 1030–1039.(c) Barriere, F.; LeSuer, R. J.; Geiger, W. E. “Electrochemical advances using fluoroarylborate anion supporting electrolytes. In Trends in Molecular Electrochemistry; Pombeiro, A. J. L.; Amatore, C., Eds.; Fontis Media, Marcel Dekker, 2004; Chapter 13, pp 413444. (22) Hapiot, P.; Kispert, L. D.; Konovalov, V. V.; Saveant, J.-M. J. Am. Chem. Soc. 2001, 123, 6669–6677. (23) ε calculated assuming quantitative oxidation of the neutral species. (24) (a) Fox, M. A.; Farmer, J. D.; Roberts, R. L.; Humphrey, M. G.; Low, P. J. Organometallics 2009, 28, 5266–5269. (b) Costuas, K.; Rigaut, S. Dalton Trans. 2011, 40, 5643–5658. (25) Chaudret, B.; Commenges, G.; Poilblanc, R. J. Chem. Soc., Dalton Trans. 1984, 1635–1639. (26) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna, R. J. Appl. Crystallogr. 1999, 32, 115–119. (27) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112–122. (28) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837–838. (29) van der Sluis, P.; Spek, A. L. Acta Crystallogr. 1990, A46, 194–201. (30) Spek, A. L. Acta Crystallogr. 2009, D65, 148–155. (31) (a) Hohenberg, P.; Kohn, W. Phys. Rev. 1964, 136, B864. (b) Parr, R. G.; Yang, W. Density-Functional Theory of Atoms and Molecules; Oxford University Press: Oxford, U.K., 1989. (32) (a) Becke, A. D. Phys. Rev. A 1988, 38, 3098. (b) Becke, A. D. J. Chem. Phys. 1993, 98, 1372. (c) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (33) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785. (34) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin, K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken, V.; 3577
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Organometallics
ARTICLE
Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J., Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian 03, Revision D.02; Gaussian, Inc.: Wallingford, CT, 2004. (35) (a) Wadt, W. R.; Hay, P. J. J. Chem. Phys. 1985, 82, 284. (b) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 299. (36) Fl€ukiger, P.; L€uthi, H. P.; Portmann, S.; Weber, J. MOLEKEL 4.3; Swiss Center for Scientific Computing: Manno (Switzerland), 20002002.
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