Intriguing Physical and Chemical Properties of ... - ACS Publications

Article pubs.acs.org/IC

Intriguing Physical and Chemical Properties of Phosphorus Corroles Jenya Vestfrid,† Rashmi Kothari,† Arseni Kostenko,† Israel Goldberg,*,‡ Boris Tumanskii,† and Zeev Gross*,† †

Schulich Faculty of Chemistry, Technion−Israel Institute of Technology, Haifa 32000, Israel School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel

‡

S Supporting Information *

ABSTRACT: The fluorescence intensity of phosphorus corroles increases upon meso-aryl C−F/C−H and P−OH/ P−F substitutions, the latter affects corrole-centered redox processes more than C−H/C−F substitution on the corrole’s skeleton, and the presence of F atoms allows for the first experimental insight into the electronic structures of oxidized corroles. Experimental and theoretical methodologies reveal that mono- but not bis-chlorosulfonation of the corrole skeleton is under kinetic control. Selective introduction of heavy atoms leads to complexes that are phosphorescent at room temperature.

■

INTRODUCTION The outstanding spectroscopic,1 photophysical,2 and redox properties3 of corroles led to intensive research toward their utilization as catalysts,4 dyes,5 imaging probes,6 singlet oxygen generating agents,7 and drug candidates.8 The most prominent physical feature of post-transition metal complexes of corroles is their fluorescence, whose intensity is generally much larger than that of porphyrins and other related macrocycles.2 Nontransition metal complexes are also ideal for looking into the fundamental properties of corroles through investigations that are not affected by metal-centered redox processes.9 Phosphorus as chelated element is particularly well suited for the above-mentioned tasks, as (a) it is not expected to quench the intense corrole fluorescence; (b) it can be utilized in both NMR and EPR spectroscopy due to the I = 1/2 spin of its exclusive 31P isotope; and (c) its two available axial coordination sites may be used for property tuning. Porphyrins with phosphorus as the chelated element have been known for almost 40 years;10 and the most prominent approach for their utilization in various applications is taking advantage of the two axial bonds to the central phosphorus atom.11 Phosphorus chelates of octa-alkylated corroles were first reported by Paolesse in 199812a and by Kadish in 2000;12b one year later our group reported the first phosphorus(V) complex of a mesotriaryl corrole,12c and electrophilic substitution reactions thereof were just reported.12f Recently published research on phosphorus corroles further raised the interest, due to their very useful utility as bioimaging probes6b and photosensitizers.5b,7c−e The most stable corrole reported so far is H3(tpfc) (1, Scheme 1),13 which contains three C6F5 groups on the mesopositions of the corrole skeleton. These meso-substituents are © XXXX American Chemical Society

apparently also responsible for the very high selectivity obtained during electrophilic substitutions on the macrocycle,14,15 for reasons that have not being fully addressed so far. One limitation of these complexes is that the C6F5 groups induce relatively high oxidation potentials, a feature that could be either advantageous or a drawback depending on the particular application. We have hence decided to prepare the phosphorus chelates with a corrole that has only two fluorine atoms in the ortho-position of the aryls, H3(tdfc) (2), anticipating to maintain the selectivity and stability while achieving more electrochemical versatility. One focus of this study was to determine how this relatively small change affects the following parameters: (a) fluorescence quantum yield; (b) redox potentials; and (c) the frontier molecular orbitals. Investigation of the effect of hydroxides vs fluorides as axial ligands on the structural and redox properties of the corresponding complexes also led to a novel experimental insight about the electronic structure of corrole radical ions. Electrophilic substitution of phosphorus corroles was addressed for two different purposes: chlorosulfonation with emphasis on understanding the origin of its regioselectivity with the aid of density functional theory (DFT) calculations and selective iodination for inducing room temperature (RT) phosphorescence.

■

RESULTS AND DISCUSSION Synthesis. The insertion of phosphorus into electron deficient porphyrins and corroles, by using either POCl3 or PCl3, was reported in the literature to take place in pyridine at Received: March 9, 2016

A

DOI: 10.1021/acs.inorgchem.6b00544 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry Scheme 1. Synthesis and Ligand Exchange for P(corrole) Complexes, and the 19F (a) and 31P (b) NMR Spectra of 6

reflux under inert atmosphere.6b,12c,d We have introduced a much simpler methology,7b,e by adding small portions of PCl3 to the corrole solution over a period of time, at RT under air. Standard workup and column chromatography afforded the bishydroxo-phosphorus(V) complexes 3 and 4 (Scheme 1) in high yields, for both corroles. Attempted exchange of the axial hydroxides in 3 and 4 by chlorides were not successful,12c but their treatment with aqueous HF led to the bis-fluoridecoordinated complexes 5 and 6 in quantitative yields (Scheme 1). This transformation resulted in very significant and enlightening changes in the NMR spectra; disappearance of the 1H resonances corresponding to the hydroxyl groups (Figure S1); appearance of new 19F signals that are well separated from those of the C6F5 and C6H3F2 groups present in 5 and 6, respectively (Scheme 1a); and 31P resonances with chemical shifts characteristic of 6-coordinated phosphorus (Scheme 1b).12 Another prominent feature is the J = 810 Hz splitting coupling constant between the axial fluorides (appear as doublet) and phosphorus (appears as triplet). X-ray Crystallography. X-ray quality crystals were obtained from CH2Cl2:hexane solvent mixtures for compounds 2 and 4−6, and their structures were fully analyzed. Only one tautomer was observed for the free base corrole 2 (Figure S3), the same one as that obtained earlier for H3(tpfc) (1),16 suggesting it to be the most stable form. The phosphorus chelated complexes of corroles 4−6 are six-coordinate with the central phosphorus located in the plane of the flat corrole macrocycles (Figure 1), with only minor distortions from planarity (rather than the ruffled derivatives obtained upon βpyrrole-substitution of phosphorus corroles).12d The binding environments around the central phosphorus represent distorted octahedra, with axial P−O bonds that are considerably shorter (1.66 Å) than the equatorial P−N bonds (1.82−1.85 Å) for 4. The equatorial P−N bonds (1.80−1.83 Å) in 5 and 6 are similar to those in 4, while the axial P−F bonds

(1.61−1.63 Å) are shorter than the P−O bonds in 4 as expected (Table 1). Table 1. Selected Structural Data for the Phosphorus Corrole Complexes complex

P−N bond length range [Å]

4

1.821(3)−1.847(3)

6 5

1.802(2)−1.818(2) 1.796(1)−1.828(1)

P−O bond length range [Å] 1.658(2)−1.664(2) P−F bond length range [Å] 1.614(1)−1.633(1) 1.619(1)−1.625(1)

Both bond types are still much longer than in pure inorganic compound like POF3 or H3PO4, indicative of only weak dπ−pπ bonding interactions between the phosphorus and the F/O atoms. This is apparently due to significant d(P)−π(corrole) interactions, which is also reflected in the 450 mV more positive redox potentials of 3 relative to the analogous Al corrole.3b The strong electron withdrawing effect of the axial Fsubstituents in 5 and 6 (as compared with the OH-ligands in 4) pulls the pyrrole N atoms toward the central-P, causing a slight shortening of the P−N bonds (Table 1). Photophysical Characterization. The electronic spectra of phosphorus corroles 3−6 consist of typical near-UV (Soret) band and visible (Q) bands: the Soret bands are slightly blueshifted relative to other post-transition metallocorroles and the ε values are very large (Table S1). The identity of the meso-aryl substituents, C6F5 vs C6H3F2, has practically no effect on the Soret and Q-band’s λmax values, while the spectra of the fluoride-ligated complexes are 8−10 nm blue-shifted relative to the hydroxide-coordinated ones. The emission spectra recorded in toluene exhibit characteristic double peak structures, without an additional shoulder that was reported for a series of phosphorus meso-triaryl corroles in coordinating solvents (THF and MeOH).12d The emission intensity (i.e., the fluorescence quantum yield) was larger for P(tdfc)L2 (3, 5) relative to analogous P(tpfc)L2 (4, 6) complexes (Table 2, a 10% increase for L = F and 35% for L = OH). Apparently, despite of the fact that fluoride is generally not considered to display a large “heavy atom effect”,17,18 it still comes into play in that the difluorophenyl groups (in 3 and 5) induce less nonradiative decay than the pentafluorophenyl groups in 4 and 6. Redox Potentials. Cyclic voltammetry (CV) examinations revealed HOMO−LUMO gaps of about 2.18 V for the bishydroxide and about 2.25 V for the bis-fluoride complexes (Table 2), within the range reported for other metalloporphyrinoids.3,12d,19 The data further allows for the deduction of how F atoms affect redox potentials as a function of their positioning. Previous studies have uncovered that the contribution of each halogen atom in the β-pyrrole position is

Figure 1. Side views of the X-ray structures of the phosphorus corroles complexes: 4 (a), 6 (b), and 5 (c). B

DOI: 10.1021/acs.inorgchem.6b00544 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry Table 2. Photophysical and Electrochemical Data for the Phosphorus Corrole Complexesa comp 3 5 4 6

emission [nm] 592, 577, 593, 579,

648 631 650 633

Φf (%)

first ox [E1/2, V]

first red [E1/2, V]

ΔE [V]

31 42 47 52

1.00 1.30 0.87 1.19

−1.17 −0.95 −1.31 −1.05

2.17 2.25 2.18 2.24

a

Emission quantum yields were measured in toluene, relative to the quantum yield of 0.13 for tetraphenylporphyrin (TPP). Redox potentials, vs Ag/AgCl, were determined for 1 mM substrate in 0.1 M TBAP/CH3CN. The redox potential of ferrocene under identical conditions was 0.42 V.

about 55 mV/halogen, and the main conclusion was that the identity of the halogen has no influence on the redox potential of the complex.2d Changing the corrole ligand from 1 with its 15 F atoms to 2 with only 6 C−F bonds induces an about 120 mV negative shift in the oxidation and reduction potentials, which may be presented as a 13 mV shift for each fluorine atom on the meso-aryl groups (ignoring the relative position on the aryl group). The effect of axial fluorides is much larger: a 150− 160 mV/F shift in the oxidation potential and about 110−130 mV/F in the reduction potential. The conclusion is that despite of the fact that both redox processes are corrole-centered, the introduction of the electron-withdrawing F atoms is most influential when bound to the central element (consistent with the structural observations above), followed by C−F vs C−H on the β-pyrroles on the corrole’s skeleton, and smallest for the meso-aryl positions. Electronic Structure of Oxidized Corroles. In all previous work on post-transition metallocorroles, the EPR of both oxidized and reduced derivatives did not disclose coupling with the central element and the splitting from the N atoms could not be resolved.12c,20 Close examination of the 1-electron oxidized bis-hydroxy complexes ([3]+ and [4]+, obtained via treatment with tris(4-bromophenyl)aminium hexachloroantimonate) show splitting to a doublet due to the I = 1/2 31P nucleus, with aP = 5.7 and 6.1 G, respectively. Moreover, additional splitting from the two axial fluorides with aF(219F) = 15.8 G (triplet of doublets) was detected for the oxidation product of 6 (Figure 2). The oxidation of 5 was not possible under similar conditions, consistent with the very positive half wave potential seen in its CV. The experimental hyperfine coupling constants of the P and F atoms in 3, 4, and 6 were accurately reproduced by DFT,21 via calculations at the BP8622D323/def2-TZVP(-f)24//BP86-D3/def2-TZVP(-f) level of theory (Table S2), using the ORCA 3.0.225 electronic structure software package. The calculated hyperfine coupling constants of the corrole’s nitrogen atoms were only about 1 G, which explains why they could not be experimentally observed. Also calculated were the frontier molecular orbitals of the phosphorus corroles 3, 4, and 6, which disclosed high similarity to those of previously reported Ga(tpfc):20 The b1(C2v) is the HOMO and the a2(C2v) is the HOMO − 1, corresponding to the a2u(D4h) and a1u(D4h) orbitals of metalloporphyrins (Figure S4). Most of the electron density in the b1(C2v) and a2(C2v) orbitals resides on the meso-carbon and β-pyrrole-carbon atoms, respectively. The tpfc ligand lowers the HOMO and HOMO − 1 energies and the energetic gap between them, as concluded from the comparison between 3 vs 4 and 5 vs 6 (Table S3). Regioselectivity of the Chlorosulfonation Reaction. The first selective electrophilic substitutions reported for

Figure 2. Experimental (blue) and simulated (red) EPR spectra of the 1 − e− oxidized phosphorus corroles [4]+ and [6]+, in CH2Cl2 at RT.

corroles was chlorosulfonation,14a which is of large utility since it allows for further functionalization by either hydrolysis or reaction with amines,14d and the metal of choice is inserted latest. The reaction proceeds with high selectivity for free base H3(tpfc), while mixture of products were obtained for the free base corrole 2 and the Ga complexes of those corroles.14b Later investigation suggested that in order to preserve high selectivity of the reaction two of the aryl groups on the corrole macrocycle should remain pentafluorophenyl.14c Mixture of products were obtained for nonfluorinated corroles, which is also true for nitration and bromination of the phosphorus complex of 5,10,15-tritolylcorrole.26,12f We now tested the selectivity of chlorosulfonation on the phosphorus corroles 3 and 4. Complex 3 yielded only one product, with no need of any purification procedure. The identity of the product as the 3,18bis-chlorosulfonyl phosphorus corrole (Scheme 2) was deduced from NMR spectroscopy:27 there are two high field 1H resonances that display splitting only from the P nucleus and no vicinal 3JH−H coupling and three triplets for the para-F atoms in the 19F-NMR, consistent with the low-symmetry isomer (Figure S2a). Complex 4 also provided the analogous compound as the major product, but with much lower selectivity, as may be appreciated from the corresponding 1H and 19F NMR spectra (Figure S2b). The selectivity issue was addressed by DFT calculations, by looking at the electron density of the relevant β-pyrrole carbon atoms: C2, C3, C7, and C8 (Figure 3). This revealed that the main reactivity trend for the phosphorus corroles is identical to that reported for the analogous gallium complex: C3 > C8 ≫ C7 > C2.15 This suggests that the first substitution should occur on C3, true for both 3 and 4. The calculations on the 3-SO2Clsubstituted derivatives revealed that the pattern of electron density is C17 ≫ C12 ≥ C3 ≫ all other C atoms. The clear conclusion is that the DFT-predicted product should be the C

DOI: 10.1021/acs.inorgchem.6b00544 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry Scheme 2. Plausible Reaction Pathway for the Second Chlorosulfonation Leading to the Two Isomeric Corroles

the directly joined pyrrole rings.2c,d We have now treated the more fluorescent derivative 4 with N-iodosuccinimide (NIS) for 1 h in acetonitrile (ACN) at room temperature in the dark, which yielded the 2,3,17,18-tetra-iodinated derivative (4-I4) as the main product (Scheme S2). Since purification of 4-I4 was troublesome, 4 was treated with 1,3-diiodo-5,5-dimethylhydantoin (DIH)2c instead of NIS, which led to the 2,3,18tris-iodinated derivative (4-I3) as the main product without any problems. The electronic spectrum of 4-I3 revealed a split Soret-band characteristic of lower symmetry corroles2f and expected red shifts due to the addition of halogen atoms onto the β-pyrrole positions2d,f (Table S2). The RT emission spectrum of 4-I3 disclosed two components derived from the radiative decays of short- and long-lived excited states (Figure 4). The maximum at 608 nm with a 662 nm shoulder Figure 3. Mulliken population analysis of the HOMO of 3, 4, and their 3-SO2Cl substituted derivatives, at the BP86-D3/def2-TZVP(-f) level of theory.

high symmetry 3,17- and not the lower symmetry 3,18-bissubstituted isomer, which is not the case however. Having deduced that selectivity for the second substitution is not predicted correctly by considering the nucleophilicity of the reactant’s carbon atoms, the focus was turned to the thermodynamic stabilities of the isomeric products and of the positively charged intermediates leading to them (Scheme 2). The calculated energy of [3,17]+ was found to be 4.7−4.8 kcal/ mol lower than that of [3,18]+ (Scheme 2, Scheme S1) for both examined corroles, suggesting again that the higher symmetry complex should be formed with preference. The clue for resolving the puzzle came from calculating the energy of the products obtained from 3 and 4: the neutral [3,18] isomers are 3−4 kcal/mol more stable than the [3,17] isomers. This suggests that all processes involved in the reaction pathway to final products are in equilibrium, i.e., that the reaction might actually be under thermodynamic control. The origin of the larger experimental selectivity in chlorosulfonation of 3 compared to 4 could not be resolved, however, since the differences in the stabilities of the isomers formed from either 3 or 4 were too small. DFT calculations were carried out as to account for the solvation effect, by using the conductor like screening model (COSMO), but only insignificant differences were obtained (full data in the SI). Selective Iodination of Phosphorus Corroles. The other selective electrophilic substitution of corroles (reported for the Ga and Al complexes) is iodination, occurring only on

Figure 4. Room temperature steady-state emission spectrum of 4-I3, in DMSO under N2.

corresponds to fluorescence, whose intensity (Φf = 1.44%) is more than 1 order of magnitude lower than that of the parent corrole 4. The second emission appears in the near-infrared (NIR) region (λmax = 825 nm) with a long lifetime (232 μs), due to phosphorescence (Φph = 0.35%).28

■

CONCLUSIONS A series of phosphorus corrole complexes that differ in the identity of the aryls, the axial ligands and substituents on the βpyrrole positions was investigated. The derivatives with 2,6difluorophenyl groups on the meso-carbon atoms and with fluoride as axial ligands displayed the highest fluorescence quantum yield: 52%. The redox potentials were varied by almost 0.5 V by relatively small changes without inducing D

DOI: 10.1021/acs.inorgchem.6b00544 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

Synthetic Methods. The free base corroles H3tpfc (1) and H3(tdfc) (2) were synthesized as previously reported.32 Crystal data for H3(tdfc) (2) C37H20F6N4, Mr = 634.57, monoclinic, space group P21/c, a = 16.2749(6), b = 13.4409(6), c = 13.0094(4) Å, β = 95.628(2)°, V = 2832.1(2) Å3, T = 110 K, Z = 4, μ(Mo Kα) = 0.117 mm−1, ρ(calcd) = 1.488 g·cm−3, 25 428 reflections measured to θ = 28.30°, of which 7004 were unique (Rint = 0.039) and 5148 with I > 2σ(I). Final R1 = 0.044 (wR2 = 0.094) for the 5148 data above the intensity threshold, and R1 = 0.068 (wR2 = 0.106) for all unique data. CCDC 1426111. Synthesis of P(tdfc) (OH)2 (4). A sample of a free base (50 mg, 79.2 μmoL) was added to 10 mL of pyridine and was stirred vigorously. This was followed by the addition of 300 μL of PCl3 over 30 min (100 μL every 10 min). Then the reaction was stirred for another 10 min followed by addition of water. The product was extracted using CH2Cl2. The reaction mixture was evaporated to dryness and chromatographed (silica, CH2Cl2:hexanes, 1:1) to afford pure 4 (46 mg, 83%). 1H NMR (400.4 MHz, CDCl3): δ = 9.30 (dd, J = 2.44, 1.76, 2H), 8.95 (broad s, 2H), 8.90 (t, J = 3.64, 3.56, 2H), 8.77 (broad s, 2H), 7.77 (unresolved m, J = 6.29, 6.33, 3H), 7.39 (unresolved m, J = 6.77, 8.17, 6.47, 6H), −4.60 (d, J = 7.54, 2H). 19F NMR: −108.12 (unresolved t, J = 6.29, 6.55, 6F). 31P NMR: −191.44 (s, 1P). UV−vis (toluene) λmax (ε) [nm (× 104 cm−1 M−1)]: 394 (3.4), 414 (14.9), 563 (1.2), 588 (2.0). Crystal data for C37H19F6N4O2P·CH2Cl2, Mr = 781.46, monoclinic, space group P21/c, a = 19.6670(14), b = 12.4500(10), c = 13.7064(9) Å, β = 106.074(3)°, V = 3224.9(4) Å3, T = 110 K, Z = 4, μ(Mo Kα) = 0.331 mm−1, ρ(calcd) = 1.610 g·cm−3, 18 263 reflections measured to θ = 25.08°, of which 5695 were unique (Rint = 0.033) and 4344 with I > 2σ(I). Final R1 = 0.051 (wR2 = 0.131) for the 4344 data above the intensity threshold, and R1 = 0.072 (wR2 = 0.142) for all unique data. CCDC 1426112. Synthesis of P(tpfc)F2 (5). A sample of P(tpfc) (OH)2 (3) (20 mg, 23 μmol) was dissolved in 5 mL CH2Cl2 in a small plastic flask. A 2 mL portion of 40% HF was added and the mixture was stirred overnight. After standard workup complex 5 was obtained in quantitative yield. 1H NMR (400.4 MHz, CDCl3): δ = 9.51 (dd, J = 3.24, 1.20, 2H), 9.09 (t, J = 4.76, 2H), 9.04 (dd, J = 4.41, 4.36 2H), 8.91 (dd, J = 4.08, 4.56, 2H). 19F NMR: −37.36 (d, J = 818.50, 2F), −136.18 (dt, J = 6.59, 22.57, 6F; ortho-F), −151.05 (t, J = 20.97, 2F; para-F), −151.24 (t, J = 21.03, 1F; para-F), −160.75 (dt, J = 5.65, 21.02, 4F; meta-F), −160.92 (dt, J = 5.83, 21.12, 2F; meta-F). 31P NMR: −182.44 (t, J = 819.29, 1P). HRMS+ (APPI, positive mode) for C37H8F17N4P: m/z = 862.0210 (calculated), 862.0678 (observed). UV−vis (toluene) λmax (ε) [nm (× 104 cm−1 M−1)]: 385 (6.8), 406 (48.7), 558 (2.3), 574 (2.5). Crystal data for C37H8F17N4P·CH2Cl2, Mr = 947.46, monoclinic, space group P21/c, a = 16.3119(4), b = 15.6400(4), c = 13.7885(3) Å, β = 95.900(10)°, V = 3499.1(2) Å3, T = 110 K, Z = 4, μ(Mo Kα) = 0.362 mm−1, ρ(calcd) = 1.798 g·cm−3, 34 380 reflections measured to θ = 28.34°, of which 8725 were unique (Rint = 0.028) and 7192 with I > 2σ(I). Final R1 = 0.055 (wR2 = 0.129) for the 7192 data above the intensity threshold, and R1 = 0.062 (wR2 = 0.143) for all unique data. CCDC 1426113. Synthesis of P(tdfc)F2 (6). The procedure for axial ligand substitution was performed on complex 4, in the same fashion as for complex 3. 1H NMR (400.4 MHz, CDCl3): δ = 9.36 (t, J = 3.40, 3.32, 2H), 9.03 (t, J = 4.77, 4.73, 2H), 8.97 (t, J = 4.40, 4.36, 2H), 8.84 (t, J = 4.20, 4.48, 2H), 7.77 (unresolved m, 3H), 7.38 (unresolved m, J = 7.09, 8.33, 6.97, 6H). 19F NMR: −38.10 (d, J = 810.92, 2F), −108.12 (unresolved m, J = 7.08, 7.12, 6.52, 6F). 31P NMR: −181.98 (t, J = 800.04, 1P). HRMS− (APPI, negative mode) for C37H17F8N4P: m/z = 700.1058 (calculated), 700.2096 (observed). UV−vis (toluene) λmax (ε) [nm (× 104 cm−1 M−1)]: 385 (4.5), 406 (32.4), 558 (1.6), 576 (2.2). Crystal data for C37H17F8N4P·CH2Cl2, Mr = 785.44, monoclinic, space group P21/n, a = 15.8026(7), b = 12.6026(5), c = 16.4580(7) Å, β = 101.942(2)°, V = 3206.7(2) Å3, T = 110 K, Z = 4, μ(Mo Kα) = 0.337 mm−1, ρ(calcd) = 1.627 g·cm−3, 31 478 reflections measured to θ = 28.34°, of which 7966 were unique (Rint = 0.037) and 6282 with I

structural modifications. The chelated P element attracts much electron density from the macrocycle, which is reflected by its effect on redox potentials and the EPR spectra of the singly oxidized products. Monochlorosulfonation occurs with large selectivity on the most electron-rich carbon atom (i.e., proceeds under kinetic control), while bis-chlorosulfonation leads to the lowest energy product (consistent with thermodynamic control). Iodination proceeds with selectivity on the directly joined pyrrole moieties and converts the complexes into products that display NIR phosphorescence at ambient temperatures.33 The facile synthetic transformations that change the compounds from lipophilic to amphipolar and from fluorescent to phosphorescent, together with a delicate control of redox potentials by a proper choice of axial ligands, highlight the utility of phosphorus corroles in a large diversity of potential applications.

■

EXPERIMENTAL SECTION

Materials. Reagents (Aldrich) and solvents were used without further purification. Silica gel 60 (230−400 mesh) was used for column chromatography. Physical Methods. 1H, 19F, and 31P NMR spectra were recorded on a Bruker Avance III 400 spectrometer equipped with a 5 mm, automated tuning, and matching broad band probe (BBFO) with zgradients, operating at 400.4 MHz for 1H, 376.7 MHz for 19F, and 162.08 MHz for 31P, respectively. Chemical shifts are reported in ppm relative to the residual hydrogen atoms in the deuterated solvent CDCl3 (δ = 7.26). Absorption spectra of the samples were measured on an HP 8453 diode array spectrophotometer. High-resolution mass spectra for the noniodinated compounds were performed on a Bruker Maxis Impact mass spectrometer, using APPI (atmospheric pressure photoionization) direct probe in either positive or negative mode. High-resolution mass spectra for the iodinated compound was performed on a Waters LCT Premier mass spectrometer, using TOF electron spray positive mode in CH3CN/water 70:30, flow 0.25. Crystal Structure Determination. The X-ray measurements (ApexDuo, Bruker-AXS, Mo Kα radiation) for the analyzed compounds 2, 4, 5, and 6 were carried out at ca. 110(2) K on crystals coated with a thin layer of amorphous oil to minimize crystal deterioration, possible structural disorder and related thermal motion effects, and to optimize the precision of the structural results. The structures were solved by direct methods and refined smoothly by fullmatrix least-squares (SHELXTL-2014 and SHELXL-2014). Structures 4−6 were found to contain molecules of the CH2Cl2 crystallization solvent within the intralattice voids. Spectroscopy. Steady-state short-lived and long-lived emission spectra were recorded on a Cary Eclipse fluorometer, at room temperature, under nitrogen. For the calculation of quantum yields (QY) of emission, steady-state emission spectra were recorded on a Fluorolog-3 spectrofluorometer (model FL3-11; HORIBA Jobin Yvon Inc., Edison, NJ) equipped with a Xenon-arc lamp. The data were recorded at room temperature, under nitrogen. Toluene was used as the solvent for the noniodinated derivatives, and DMSO, for the iodinated derivative. Standards used for calculations QY: tetraphenylporphyrin (TPP) for emission at 600 nm [Φtol = 0.13,29 ΦDMSO = 0.2230], and indocyanine green (IR-125) at 800 nm [ΦDMSO = 0.13].31 Electrochemistry. The cyclic voltammograms (CV) were obtained utilizing a WaveNow USB potentiostat/galvanostat (Pine Research Instrumentation), using the Pine AfterMath Data Organizer software. A three electrode system was used, consisting of a mini glassy carbon electrode (diameter of the active zone: 2.8 mm; Metrohm) working electrode, a platinum wire as the counter electrode, and an Ag/AgCl reference electrode. The CV measurements were performed in acetonitrile solutions (HPLC grade), 0.1 M in tetrabutylammonium perchlorate (TBAP, Fluka, recrystallized twice from methanol), and 1 mM substrate at ambient temperature. Scan rates of 100 mV/s were applied. The E1/2 value for the ferrocene/ferrocenium couple under these conditions was 0.42 V. E

DOI: 10.1021/acs.inorgchem.6b00544 Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry

■

> 2σ(I). Final R1 = 0.040 (wR2 = 0.091) for the 6282 data above the intensity threshold, and R1 = 0.056 (wR2 = 0.100) for all unique data. CCDC 1426114. Chlorosulfonation on Corroles 3 and 4. The reaction was performed in complete analogy with the procedure reported for the free base corrole 1,14a on the phosphorus corroles 3 and 4. This led to the 2,17-bis-chlorosulfonated derivative of 3 without any need for separation of further purification, while a mixture of products was obtained for complex 4, whose separation was not completed. Iodination of 4Synthesis of 4-I3. A sample of 4 (20 mg, 29 μmol) and 10 eq. of DIH (100 mg) were dissolved in acetonitrle (7 mL) and stirred for 1 h at room temperature in the dark. The reaction mixture solution was washed with 10% Na2S2O3 and water, dried over Na2SO4, and evaporated. The purple solid material was crystallized in hexanes/acetonitrle = 5:1. 1H NMR (400.4 MHz, CDCl3): δ = 9.95 (d, 3J = 2.70, 1H), 8.85 (t, J = 3.08, 2.15, 2H), 8.67 (t, J = 4.92, 2.77, 2H), 7.81 (unresolved m, 3H), 7.37 (t, J = 6.12, 8.72, 6H), −4.11 (broad s, 2H). 19F NMR: −108.19 (t, J = 6.63, 2F), −108.29 (dt, J = 6.63, 7.23, 4F). 31P NMR: −187.71 (s, 1P). HRMS+ (TOF, ESI+) for C37H16 N4 O2F6 I3P: m/z = 1096.7947 (calculated), 1096.7946 (observed). UV−vis (toluene) λmax (ε) [nm (× 104 cm−1 M−1)]: 419 (17.0), 427 (18.7), 578 (2.9), 600 (4.8). Synthesis of 4-I4. A sample of 4 (20 mg, 29 μmol) and 30 equiv of NIS (190 mg) were dissolved in acetonitrile (7 mL) and stirred for 1 h at room temperature in the dark. The reaction mixture solution was washed with 10% Na2S2O3 and water, dried over Na2SO4, and evaporated. The purple solid material was crystallized in hexanes/ CH2Cl2 = 5:1, and then recrystallized from hexanes/acetonitrile = 5:1. HRMS+ (TOF, ESI+) for C37H15N4O2F6I4P: m/z = 1199.7016 (calculated), 1199.7010 (observed). UV−vis (toluene) λmax (ε) [nm (× 104 cm−1 M−1)]: 398 (4.0), 422 (34.5), 576 (2.1), 595 (3.5). The 1 H, 19F, and 31P NMR spectra indicated the presence of more than one product, of which the data for the major product is as follows: 1H NMR (400.4 MHz, CDCl3): δ = 8.84 (broad s, 2H), 8.68 (broad s, 2H), 7.79 (unresolved m, 3H), 7.37 (unresolved m, 6H), −4.16 (broad s, 2H). 19F NMR: −108.23 (t, J = 6.79, 4F), −108.67 (t, J = 6.79, 2F). 31P NMR: −187.27 (s, 1P).

■

REFERENCES

(1) (a) Aviv-Harel, I.; Gross, Z. Chem. - Eur. J. 2009, 15, 8382−8394. (b) Aviv-Harel, I.; Gross, Z. Coord. Chem. Rev. 2011, 255, 717−736. (2) (a) Shi, L.; Liu, H.; Shen, H.; Hu, J.; Zhang, G. L.; Wang, H.; Ji, L. N.; Chang, C. K.; Jiang, H. F. J. Porphyrins Phthalocyanines 2009, 13, 1221−1226. (b) Rabinovich, E.; Goldberg, I.; Gross, Z. Chem. - Eur. J. 2011, 17, 12294−12301. (c) Vestfrid, J.; Botoshansky, M.; Palmer, J. H.; Durrell, A. C.; Gray, H. B.; Gross, Z. J. Am. Chem. Soc. 2011, 133, 12899−12901. (d) Vestfrid, J.; Goldberg, I.; Gross, Z. Inorg. Chem. 2014, 53, 10536−10542. (e) Zhang, L.; Liu, Z. Y.; Zhan, X.; Wang, L. L.; Wang, H.; Liu, H. Y. Photochem. Photobiol. Sci. 2015, 14, 953−962. (f) Lemon, C. M.; Halbach, R. L.; Huynh, M.; Nocera, D. G. Inorg. Chem. 2015, 54, 2713−2725. (3) (a) Shen, J.; Shao, J.; Ou, Z.; Wenbo, E.; Koszarna, B.; Gryko, D. T.; Kadish, K. M. Inorg. Chem. 2006, 45, 2251−2265. (b) Mahammed, A.; Tumanskii, B.; Gross, Z. J. Porphyrins Phthalocyanines 2011, 15, 1275−1286. (c) Sudhakar, K.; Velkannan, V.; Giribabu, L. Tetrahedron Lett. 2012, 53, 991−993. (4) Aviv, I.; Gross, Z. Chem. Commun. 2007, 1987−1999. (5) (a) Walker, D. C.; Chappel, S.; Mahammed, A.; Brunschwig, B. S.; Winkler, J. R.; Gray, H. B.; Zaban, A.; Gross, Z. J. Porphyrins Phthalocyanines 2006, 10, 1259−1262. (b) Brennan, B. J.; Lam, Y. C.; Kim, P. M.; Zhang, X.; Brudvig, G. H. ACS Appl. Mater. Interfaces 2015, 7, 16124−16130. (6) (a) Hwang, J. Y.; Agadjanian, H.; Medina-Kauwe, L. K.; Gross, Z.; Gray, H. B.; Sorasaenee, K.; Farkas, D. L. Proc. SPIE 2008, 6859, 68590G-1−68590G-7. (b) Liang, X.; Mack, J.; Zheng, L. M.; Shen, Z.; Kobayashi, N. Inorg. Chem. 2014, 53, 2797−2802. (7) (a) Ventura, B.; Degli Esposti, A.; Koszarna, B.; Gryko, D. T.; Flamigni, L. New J. Chem. 2005, 29, 1559−1566. (b) Shao, W.; Wang, H.; He, S.; Shi, L.; Peng, K.; Lin, Y.; Zhang, L.; Ji, L.; Liu, H. J. Phys. Chem. B 2012, 116, 14228−34. (c) Pohl, J.; Saltsman, I.; Mahammed, A.; Gross, Z.; Röder, B. J. Appl. Microbiol. 2015, 118, 305−312. (d) Preuss, A.; Saltsman, I.; Mahammed, A.; Pfitzner, M.; Goldberg, I.; Gross, Z.; Röder, B. J. Photochem. Photobiol., B 2014, 133, 39−46. (e) Mahammed, A.; Gross, Z. Angew. Chem., Int. Ed. 2015, 54, 12370− 12373. (f) Sinha, W.; Ravotto, L.; Ceroni, P.; Kar, S. Dalton Trans. 2015, 44, 17767−17773. (8) (a) Kupershmidt, L.; Okun, Z.; Amit, T.; Mandel, S.; Saltsman, I.; Mahammed, A.; Bar-Am, O.; Gross, Z.; Youdim, M. B. H. J. Neurochem. 2010, 113, 363−373. (b) Mahammed, A.; Gross, Z. Catal. Sci. Technol. 2011, 1, 535−540. (c) Haber, A.; Angel, I.; Mahammed, A.; Gross, Z. J. Diabetes Complications 2013, 27, 316− 321. (9) (a) Barzilay, C. M.; Sibilia, S. A.; Spiro, T. G.; Gross, Z. Chem. Eur. J. 1995, 1, 222−231. (b) Ehlinger, N.; Scheidt, W. R. Inorg. Chem. 1999, 38, 1316. (10) (a) Carrano, C. J.; Tsutsui, M. J. Coord. Chem. 1977, 7, 79−83. (b) Sayer, P.; Gouterman, M.; Connell, C. R. J. Am. Chem. Soc. 1977, 99, 1082−1087. (11) (a) Kunimoto, K.; Segawa, H.; Shimidzu, T. Tetrahedron Lett. 1992, 33, 6327−6330. (b) Zhan, Y.; Cao, K.; Wang, C.; Jia, J.; Xue, P.; Liu, X.; Duan, X.; Lu, R. Org. Biomol. Chem. 2012, 10, 8701. (c) Poddutoori, P. K.; Thomsen, J. M.; Milot, R. L.; Sheehan, S. W.; Negre, C. F. A.; Garapati, V. K. R.; Schmuttenmaer, C. A.; Batista, V. S.; Brudvig, G. W.; van der Est, A. J. Mater. Chem. A 2015, 3, 3868− 3879. (12) (a) Paolesse, R.; Boschi, T.; Licoccia, S.; Khoury, R. G.; Smith, K. M. Chem. Commun. 1998, 1119−1120. (b) Kadish, K. M.; Ou, Z.; Adamian, V. A.; Guilard, R.; Gros, C. P.; Erben, X.; Will, S.; Vogel, E. Inorg. Chem. 2000, 39, 5675−5682. (c) Simkhovich, L.; Mahammed, A.; Goldberg, I.; Gross, Z. Chem. - Eur. J. 2001, 7, 1041−1055. (d) Ghosh, A.; Ravikanth, M. Chem. - Eur. J. 2012, 18, 6386−6396. (e) Giribabu, L.; Kandhadi, J.; Kanaparthi, R. K. J. Fluoresc. 2014, 24, 569−577. (f) Pomarico, G.; Tortora, L.; Fronczek, F. R.; Smith, K. M.; Paolesse, R. J. Inorg. Biochem. 2016, DOI: 10.1016/j.jinorgbio.2016.02.005. (13) (a) Geier, G. R.; Chick, J. F. B.; Callinan, J. B.; Reid, C. G.; Auguscinski, W. P. J. Org. Chem. 2004, 69, 4159−4169. (b) Barata, J. F.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.6b00544. Full spectral data and computational data. (PDF) Crystallographic data (including reflection and refinement data) for compound 4, deposited in the Cambridge Crystallographic Data Center as CCDC-1426112 (CIF) Crystallographic data (including reflection and refinement data) for compound 6, deposited in the Cambridge Crystallographic Data Center as CCDC-1426114 (CIF) Crystallographic data (including reflection and refinement data) for compound 2, deposited in the Cambridge Crystallographic Data Center as CCDC-1426111 (CIF) Crystallographic data (including reflection and refinement data) for compound 5, deposited in the Cambridge Crystallographic Data Center as CCDC-1426113 (CIF)

■

Article

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. Funding

This research was supported by the Israel Science Foundation. Notes

The authors declare no competing financial interest. F

DOI: 10.1021/acs.inorgchem.6b00544 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

(31) Benson, R. C.; Kues, H. A. J. Chem. Eng. Data 1977, 22, 379− 383. (32) (a) Gross, Z.; Galili, N.; Saltsman, I. Angew. Chem., Int. Ed. 1999, 38, 1427−1429. (b) Gross, Z.; Galili, N.; Simkhovich, L.; Saltsman, I.; Botoshansky, M.; Blaser, D.; Boese, R.; Goldberg, I. Org. Lett. 1999, 1, 599−602. (33) For a detailed account on the phosphorescence of free base corroles with halo-aryl substituents at 77 K, see: Knyukshto, V.; Ngo, T.; Dehaen, W.; Maes, W.; Kruk, M. M. RSC Adv. 2016, 6, 43911.

B.; Neves, M. G. P. M. S.; Tome, A. C.; Faustino, M. A. F.; Silva, A. M. S.; Cavaleiro, J. A. S. Tetrahedron Lett. 2010, 51, 1537−1540. (c) Blumenfeld, C.; Fisher, K. J.; Henling, L. M.; Grubbs, R. H.; Gray, H. B.; Virgil, S. C. Eur. J. Org. Chem. 2015, 2015, 3022−3025. (14) (a) Mahammed, A.; Goldberg, I.; Gross, Z. Org. Lett. 2001, 3, 3443−3446. (b) Saltsman, I.; Mahammed, A.; Goldberg, I.; Tkachenko, E.; Botoshansky, M.; Gross, Z. J. Am. Chem. Soc. 2002, 124, 7411−7420. (c) Nigel-Etinger, I.; Mahammed, A.; Gross, Z. Catal. Sci. Technol. 2011, 1, 578−581. (d) Mahammed, A.; Gross, Z. J. Porphyrins Phthalocyanines 2010, 14, 911−923. (15) (a) Gross, Z.; Mahammed, A. J. Porphyrins Phthalocyanines 2002, 6, 553−555. (b) Balazs, Y. S.; Saltsman, I.; Mahammed, A.; Tkachenko, E.; Golubkov, G.; Levine, J.; Gross, Z. Magn. Reson. Chem. 2004, 42, 624−635. (16) (a) Gross, Z.; Galili, N.; Simkhovich, L.; Saltsman, I.; Botoshansky, M.; Bläser, D.; Boese, R.; Goldberg, I. Org. Lett. 1999, 1, 599−602. (b) Ding, T.; Harvey, J. D.; Ziegler, C. J. J. Porphyrins Phthalocyanines 2005, 9, 22−27. (17) (a) O’Sullivan, M.; Testa, A. C. J. Am. Chem. Soc. 1970, 92, 258−261. (b) Deng, F.; Kubin, J.; Testa, A. C. J. Photochem. Photobiol., A 1997, 104, 65−67. (18) (a) Zenkevich, E.; Sagun, E.; Knyukshto, V.; Shulga, A.; Mironov, A.; Efremova, O.; Bonnett, R.; Songca, S. P.; Kassem, M. J. Photochem. Photobiol., B 1996, 33, 171−180. (b) Cavaleiro, J. A. S.; Görner, H.; Lacerda, P. S. S.; MacDonald, J. G.; Mark, G.; Neves, M. G. P. M. S.; Nohr, R. S.; Schuchmann, H. P.; von Sonntag, C.; Tomé, A. C. J. Photochem. Photobiol., A 2001, 144, 131−140. (c) Pandey, S. K.; Gryshuk, A. L.; Graham, A.; Ohkubo, K.; Fukuzumi, S.; Dobhal, M. P.; Zheng, G.; Ou, Z.; Zhan, R.; Kadish, K. M.; Oseroff, A.; Ramaprasad, S.; Pandey, R. K. Tetrahedron 2003, 59, 10059−10073. (19) (a) Kadish, K. M. Prog. Inorg. Chem. 1986, 34, 435−605. (b) Kadish, K. M.; Will, S.; Adamian, V. A.; Walther, B.; Erben, C.; Ou, Z.; Vogel, E.; Guo, N. Inorg. Chem. 1998, 37, 4573−4577. (c) Johansen, I.; Norheim, H.-K.; Larsen, S.; Alemayehu, A. B.; Conradie, J.; Ghosh, A. J. Porphyrins Phthalocyanines 2011, 15, 1335− 1344. (20) (a) Bendix, J.; Dmochowski, I. J.; Gray, H. B.; Mahammed, A.; Simkhovich, L.; Gross, Z. Angew. Chem., Int. Ed. 2000, 39, 4048−4051. (b) Wagnert, L.; Berg, A.; Stavitski, E.; Berthold, T.; Kothe, G.; Goldberg, I.; Mahammed, A.; Simkhovich, L.; Gross, Z.; Levanon, H. Appl. Magn. Reson. 2006, 30 (3−4), 591−604. (21) Parr, R. G.; Yang, W. Density-Functional Theory of Atoms and Molecules; Oxford University Press: New York, 1989. (22) (a) Becke, A. D. Phys. Rev. A: At., Mol., Opt. Phys. 1988, 38, 3098−3100. (b) Perdew, J. P. Phys. Rev. B: Condens. Matter Mater. Phys. 1986, 33, 8822−8824. (c) Perdew, J. P. Phys. Rev. B: Condens. Matter Mater. Phys. 1986, 34, 7406. (23) (a) Grimme, S.; Antony, J.; Ehrlich, S.; Krieg, H. J. Chem. Phys. 2010, 132, 154104. (b) Grimme, S.; Ehrlich, S.; Goerigk, L. J. Comput. Chem. 2011, 32, 1456−1465. (24) (a) Schaefer, A.; Horn, H.; Ahlrichs, R. J. Chem. Phys. 1992, 97, 2571−2577. (b) Weigend, F.; Ahlrichs, R. Phys. Chem. Chem. Phys. 2005, 7, 3297−3305. (25) Neese, F. WIREs Comput. Mol. Sci. 2012, 2, 73−78. (26) Naitana, M. L.; Nardis, S.; Lentini, S.; Cicero, D.; Paolesse, R. J. Porphyrins Phthalocyanines 2015, 19, 735−744. (27) While the accurate nomenclature is 2,17-bis chlorosulfonyl, 3,18-bis chlorosulfonyl is used herein because the proper name of the monosubstituted derivative is 3-chlorosulfonyl and the purpose is to indicate the positioning of the next substitution. (28) The quantum yields of the short- and long-lived emissions were determined in DMSO, relative to tetraphenylporphyrin (TPP) and indocyanine green (IR-125), respectively (full details in the SI). (29) Dolphin, D. The Porphyrins; Academic Press: New York, 1978; Vol. III. (30) The QY of TPP in DMSO was obtained by comparing two identical solutions of TPP in DMSO and toluene and relying on the QY = 0.13 for TPP in toluene. G

DOI: 10.1021/acs.inorgchem.6b00544 Inorg. Chem. XXXX, XXX, XXX−XXX