In the crystal structure of the title compound, C48H38N4, the molecule is positioned on a center of symmetry and the porphyrin ring shows a nearly planar geometry in spite of the presence of four bulky methyl groups at the anti-podal Β-pyrrole positions. © International Union of Crystallography 2007.

Puttaiah Bhyrappa

Department Of Chemistry

Karuppaiah Karunanithi

Babu Varghese

Tetra

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IIT Madras

2,3,12,13‐Tetramethyl‐5,10,15,20‐tetraphenylporphyrin

Acta Crystallographica Section E: Structure Reports Online

A series of electron-deficient porphyrin/fullerene solvated cocrystallates, β-tetracyano/tetrabromo-meso-tetraphenylporphyrin/Cn (n = 60 or 70) [(H2TPP(CN)4)3·C60, 1; (CuTPP(CN)4)3·C60, 2; (H2TPP(CN)4)·C70, 3; (H2TPPBr4)·(C60)2, 4] were examined by single crystal XRD analysis. Cocrystallates 1 and 2 showed hexagonal honeycomb layer-like structure while 3 and 4 revealed one-dimensional linear/zigzag chain structure. Porphyrin ring in the cocrystallates, 1-3 revealed enhanced distortion (r.m.s. &gt; 0.245(6) Å) than that of a nearly planar parent H2TPP(CN)4 (0.046(3) Å) structure. The supramolecular interactions in the cocrystallates, 1-4 revealed shortest (por)C...C(C70) = 3.165 Å, (C60)C...Npor = 3.034 Å and (C60)C...C(C60) = 2.992 Å close contact distances. The normal-coordinate structural decomposition analysis of the macrocycle in 1-3 revealed mainly saddling (∼71%) with minimal domed (10-15%) distortions. The nonplanar distortion in these cocrystallates has been ascribed to intermolecular interactions/crystal packing forces. © 2014 Published by Elsevier B.V.

Inorganica Chimica Acta

Structural elucidation of a few electron-deficient porphyrin/fullerene cocrystallates: Effect of fullerene on the porphyrin ring conformation

Synthesis of two new classes of mixed β-pyrrole substituted tetraphenylporphyrins, H2TPP(Ph)4(R)4 (R = 2-thienyl and phenylethynyl, PE) and H2TPP(CH3)4(R)4 (R = 2-thienyl and PE) and their metal complexes have been reported. These porphyrins showed dramatic red-shift in electronic absorption bands relative to their corresponding MTPP(R)4 derivatives. Crystal structures of H2TPP(R)4(2-thienyl)4 (R = Ph and CH3) and MTPP(CH3)4(PE)4 (M = Zn(II) and Cu(II)) derivatives are highly nonplanar as evidenced from the mean displacement of β-pyrrole carbon (ΔCb) in the range ±(0.33-1.07) Å. Normal-coordinate structural decomposition analysis of the 24-atom core in these crystal structures revealed largely saddle (73-93%) combined with different degree of ruffled, domed and wave distortions. Electrochemical redox properties of these porphyrins exhibited interesting trend in redox potentials relative to their corresponding H2TPP(R)4s. The tunable trend in redox potentials and electronic absorption bands of mixed substituted porphyrins suggests the role of nonplanarity of macrocycle and electronic effects of the substituents. © 2014 Elsevier B.V. All rights reserved.

Mixed β-pyrrole substituted meso-tetraphenylporphyrins and their metal complexes: Synthesis, structures and electrochemical redox properties

A series of planar and nonplanar free-base b-pyrrole substituted meso-tetraarylporphyrins were characterized by electrochemistry, spectroelectrochemistry, and protonation or deprotonation reactions in neutral, acidic, and basic solutions of CH2Cl2. The neutral compounds are represented as H2(P), in which P represents a porphyrin dianion with one of several different sets of electron-withdrawing or -donating substituents at the messo and/or b-pyrrole positions of the macrocycle. The conversion of H2(P) to [H4(P)]2+ in CH2Cl2 was accomplished by titration of the neutral porphyrin with trifluoroacetic acid (TFA) while the progress of the protonation was monitored by UV/Vis spectroscopy, which was also used to calculate logb2 for proton addition to the core nitrogen atoms of the macrocycle. Cyclic voltammetry was performed after each addition of TFA or TBAOH to CH2Cl2 solutions of the porphyrin and half-wave potentials for reduction were evaluated as a function of the added acid or base concentration. Thin-layer spectroelectrochemistry was used to obtain UV/Vis spectra of the neutral and protonated or deprotonated porphyrins under the application of an applied reducing potential. The magnitude of the protonation constants, the positions of λmax in the UV/Vis spectra and the half-wave or peak potentials for reduction are then related to the electronic properties of the porphyrin and the data evaluated as a function of the planarity or nonplanarity of the porphyrin macrocycle. Surprisingly, the electroreduction of the diprotonated nonplanar porphyrins in acid media leads to H2(P), whereas the nonplanar H2(P) derivatives are reduced to [(P)]2- in CH2Cl2 containing 0.1m tetra-n-butylammonium perchlorate (TBAP). Thus, in both cases an electrochemically initiated deprotonation is observed. © 2014 Wiley-VCH Verlag GmbH&amp; Co. KGaA, Weinheim.

Chemistry - A European Journal

Planar and nonplanar free-base tetraarylporphyrins: β-Pyrrole substituents and geometric effects on electrochemistry, spectroelectrochemistry, and protonation/deprotonation reactions in nonaqueous media

Crystal structures of a series of 2,3,5,10,12,13,15,20-octaphenylporphinato zinc(II) complexes with varying axial ligands have been examined to elucidate the role of fifth ligand on the stereochemistry of the porphyrin macrocycle. The nonplanarity of the macrocycle varies in the order, ZnOPP &lt; ZnOPP(pyridine) &lt; ZnOPP(H2O). The electron deficient porphyrin complex of five-coordinated Zn(II), ZnTPP(CN)4(CH3OH) showed enhanced nonplanarity of the macrocycle and it is less than that of ZnOPP(H 2O)·TCE complex. Normal coordinate structure decomposition analysis of the out-of-plane displacement of the porphyrin ring in these structures revealed negligible wave distortion in planar four-coordinated ZnOPP and saddle, ruffled and domed distortions in other five-coordinated Zn(II)-porphyrins. The pronounced distortion of the macrocyclic ring in these structures is possibly due to the axial ligand, solvate and/or intermolecular interactions compared to steric crowding of the peripheral substituents. © 2011 Elsevier B.V. All rights reserved.

Synthesis and crystal structures of five-coordinated β-pyrrole tetra(phenyl/cyano) substituted zinc(II)-tetraphenylporphyrins

Nonmesogenic 2,3,12,13-tetra-bromo-5,10,15,20-tetra-kis(4-butoxy-phenyl)- porphyrin crystallizes as the title 1,2-dichloro-ethane solvate, C60H58Br4N4O4·C2H4Cl2. The porphyrin ring shows a nonplanar conformation, with an average mean plane displacement of the Β-pyrrole C atoms from the 24-atom (C20N4) core of ±0.50 (3) Å. The 1,2-dichloro-ethane solvent is incorporated between the porphyrin units and induces the formation of one-dimensional chains via inter-halogen Cl⋯Br and butyl-aryl C - H⋯π inter-actions. These chains are oriented along the unit-cell a axis, with the macrocyclic ring planes lying almost parallel to the (010) plane. The chains are arranged in an offset fashion by aligning the butoxy chains approximately above or below the faces of the adjacent porphyrin core, resulting in decreased inter-porphyrin π-π inter-actions, and they are held together by weak inter-molecular (C - Br⋯π, C - H⋯π and C - H⋯Br) inter-actions. The nonplanar geometry of the macrocyclic ring is probably due to the weak inter-porphyrin inter-actions induced by the solvent mol-ecule and the peripheral butoxy groups. The nonplanarity of the mesogens could influence the mesogenic behaviour differently relative to planar porphyrin mesogens. © 2008 International Union of Crystallography.

Acta Crystallographica Section C: Crystal Structure Communications

2,3,12,13-Tetra-bromo-5,10,15,20-tetra-kis(4-butoxy-phen-yl)porphyrin 1,2-dichloro-ethane solvate

To examine the influence of mixed substituents on the structural, electrochemical redox behavior of porphyrins, two new classes of β-pyrrole mixed substituted free-base tetraphenylporphyrins H2(TPP(Ph) 4X4) (X = CH3, H, Br, Cl, CN) and H 2(TPP(CH3)4X4) (X = H, Ph, Br, CN) and their metal (M = Ni(II), Cu(II), and Zn(II)) complexes have been synthesized effectively using the modified Suzuki cross-coupling reactions. Optical absorption spectra of these porphyrins showed significant red-shift with the variation of X in H2(TPPR4X4), and they induce a 20-30 nm shift in the B band and a 25-100 nm shift in the longest wavelength band [Qx(0,0)] relative to the corresponding H2TPPR 4 (R = CH3, Ph) derivatives. Crystal structure of a highly sterically crowded Cu(TPP(Ph)4(CH3)4) ·2CHCl3 complex shows a combination of ruffling and saddling of the porphyrin core while the Zn(TPP(Ph)4Br4(CH 3OH))· CH3OH structure exhibits predominantly saddling of the macrocycle. Further, the six-coordinated Ni(TPP(Ph) 4(CN)4-(Py)2)·2(Py) structure shows nearly planar geometry of the porphyrin ring with the expansion of the core. Electrochemical redox behavior of the MTPPR4X4 compounds exhibit dramatic cathodic shift in first ring oxidation potentials (300-500 mV) while the reduction potentials are marginally cathodic in contrast to their corresponding MTPPX4 (X = Br, CN) derivatives. The redox potentials were analyzed using Hammett plots, and the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap decreases with an increase in the Hammett parameter of the substituents. Electronic absorption spectral bands of H2TPPR4X4 are unique that their energy lies intermediate to their corresponding data for the H 2(TPPX8) (X = CH3, Ph, Br, Cl) derivatives. The dramatic variation in redox potentials and large red-shift in the absorption bands in mixed substituted porphyrins have been explained on the basis of the nonplanarity of the macrocycle and substituent effects. © 2006 American Chemical Society.

Journal	Acta Crystallographica Section E: Structure Reports Online
ISSN	16005368
Open Access	No