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.

Puttaiah Bhyrappa

Department Of Chemistry

Karuppaiah Karunanithi

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Inorganica Chimica Acta

A series of antipodal β-trisubstituted meso-tetraphenylporphyrins, H<inf>2</inf>TPP(R)<inf>3</inf> (R = CH<inf>3</inf>, Ph, PE, and 2′-thienyl) derivatives and their metal (Cu(II) and Zn(II)) complexes were synthesised and characterised by electronic absorption, 1H NMR spectroscopy and mass spectrometry. The magnitude of the red-shift in absorption bands in these free-base porphyrins depend on the nature of the substituent and follow the general trend: PE >2′-thienyl > Br > Ph > CH<inf>3</inf>. Synthesis, characterisation and crystal structure of 2,5,10,12,15,20-hexaphenylporphinato zinc(II) bispyridinate, ZnTPP(Ph)<inf>2</inf>(Py)<inf>2</inf> complex is also reported. It shows planar geometry of the porphyrin ring with two β-phenyls located at the antipodal 2,12-pyrrole positions. The two axially coordinated pyridine ring planes are oriented almost parallel to each other and they are in staggered conformation relative to opposite pyrrolic nitrogens. The normal-coordinate structural decomposition analysis of the ZnTPP(Ph)<inf>2</inf>(Py)<inf>2</inf> complex revealed slight wave distortion of the macrocycle. [Figure not available: see fulltext.] © 2015 Indian Academy of Sciences.

Fulltext

Journal of Chemical Sciences

Synthesis of antipodal β-trisubstituted meso-tetraphenylporphyrins and the crystal structure of hexaphenylporphinatozinc(II) bispyridinate complex

Bromination of meso-tetraphenylporphyrin, H2TPP with controlled amounts of N-bromosuccinimide at ambient conditions in CHCl3 produced β-dibromo and tribromotetraphenylporphyrins. The regiochemistry of the ZnTPPR3 (R = Br, Ph) complexes indicate the antipodal substitution at the β-pyrrole positions. © 2009.

Tetrahedron Letters

Synthesis of β-di and tribromoporphyrins and the crystal structures of antipodal tri-substituted Zn(II)-porphyrins

To examine the influence of fullerene on the macrocyclic ring conformation, crystal structures of a series of cocrystals of 2,3,5,10,12,13,15,20- octaphenylporphyrin, M(TPP)(Ph)4 (M = 2H, Co(II), Cu(II)), and 2,312,13-tetramethyl-5,7,8,10,15,17,18,20-octaphenyl-porphinato copper(II), CuTPP(Ph)4(CH3)4, derivatives with fullerene, C60, were elucidated. Furthermore, crystal structures of the parent porphyrins, M(TPP)(Ph)4 (M = Co(II), Cu(II)) complexes, were also determined. All the cocrystals revealed one-to-one stoichiometry between the porphyrin and C60 and were free of lattice solvates. Porphyrin rings in M(TPP)(Ph)4·C60 cocrystals revealed significant distortion with the root-mean-square (rms) value as high as 0.265(2) Å which is the average deviation of the 24 atoms core from the least-squares plane. Crystal structures of the parent M(TPP)(Ph)4 (M = Co(II), Cu(II)) complexes indicated near planarity of the 24-atom core with the root-mean-square deviation value of 0.016(2) Å. Molecular packing in the M(TPP)(Ph)4·C60 cocrystals showed essentially one-dimensional chains interconnected by weak interporphyrin and porphyrin-fullerene close contacts. The Nporphyrin⋯C(C 60) shortest distances between the H2(TPP)(Ph)4 (M = 2H, Co(II), Cu(II)) and fullerene in the cocrystals are 3.031(5) Å, 3.062(4) Å, and 3.059(3) Å, respectively. Similarly, close contact M⋯C distances in the M(TPP)(Ph)4·C60 (M = Co(II), Cu(II)) are 2.761(6) Å and 2.886(3) Å, respectively. In the Cu(TPP)(Ph)4(CH3)4·C60 cocrystal, the shift of macrocyclic ring toward planarity was evidenced from the rms value of 0.236(2) Å relative to that observed in CuTPP(Ph) 4(CH3)4·CHCl3 (0.391(2) Å). The distortion of the macrocyclic ring in M(TPP)(Ph) 4·C60 complexes was examined by normal-coordinate-structure decomposition (NSD) analyses. Their out-of-plane displacement of the core atoms revealed predominant contribution being saddle (∼95-96%) and gentle domed distortions (3-4%). In the case of M(TPP)(Ph)4(CH3)4·C60 cocrystal, it showed mainly saddled (∼83%), minimal ruffled (8%) and domed (8%) distortions of the macrocyclic ring. In-plane displacement on the 24-atom core of the porphyrin in these cocrystallates features generally a varying degree of N-str (B1g) and bre (A1g) distortions. © 2010 American Chemical Society.

Inorganic Chemistry

Porphyrin-fullerene, C60, cocrystallates: Influence of C 60 on the porphyrin ring conformation

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.

Acta Crystallographica Section E: Structure Reports Online

2,3,12,13-Tetra-methyl-5,10,15,20-tetra-phenyl-porphyrin

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.

Mixed substituted porphyrins: Structural and electrochemical redox properties

This work reports an improved protocol for the regioselective synthesis of 2,3,12,13-tetrabromo-5,10,15,20-tetraphenylporphyrin (H2TPPBr4) and the crystal structure of its Zn(II) complex which shows saddle shaped geometry. © 2003 Elsevier Science Ltd. All rights reserved.

Journal	Inorganica Chimica Acta
ISSN	00201693
Open Access	No