• Velkannan Veerapandian

      Articles written in Journal of Chemical Sciences

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

      Bhyrappa Puttaiah Velkannan Veerapandian

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      series of antipodal 𝛽-trisubstituted meso-tetraphenylporphyrins, H2TPP(R)3 (R = CH3, 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′ > Ph > CH3. Synthesis, characterisation and crystal structure of 2,5,10,12,15,20-hexaphenylporphinato zinc(II) bispyridinate, ZnTPP(Ph)2(Py)2 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)2(Py)2 complex revealed slight wave distortion of the macrocycle.

    • Crystal structures of unsymmetrically mixed β-pyrrole substituted nickel(II)-meso-tetraphenylporphyrins

      BHYRAPPA PUTTAIAH VELKANNAN VEERAPANDIAN SARANGI UJWAL KUMAR

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      Crystal structures of solvated unsymmetrically substituted meso-tetraphenylporphyrins, 2,3,12,13, 17-pentachloro-5,7,8,10,15,18,20-hepta-phenylporphyrin, H₂TPP(Ph)₃(Cl)₅, 1 and its nickel(II), NiTPP(Ph)₃(Cl)₅, 2 were determined by single crystal XRD analysis. In addition, a new unsymmetricallysubstituted porphyrin, 2,3,12,13,17-pentacyano-5,7,8,10,15,18,20-heptaphenyl-porphinato nickel(II) complex, NiTPP(Ph)₃(CN)₅, 3 complex was synthesized and its solvated structure was examined by crystallography. These porphyrins exhibited dramatic nonplanar conformation of the macrocycle as evidenced from the averagedisplacement of the β-pyrrole carbon (±ΔCβ ) from the mean plane of the porphyrin ring and the trend in nonplanarity varies in the order: 2 (1.189(5) Å) > 1 (1.036(6) Å) > 3 (0.895(6) Å). The normal-coordinate structural decomposition analysis of these structures revealed mainly saddle distortion of the macrocycle combined with small degree of ruffled or domed distortions. The Hirshfeld surface analysis of structures 1-3 revealed solvate dependent intermolecular contacts with varying degree of H. . .H (43–49%), C. . .H (17–19%), H. . .Cl (25–30%) and N. . .H (~19%) contact contributions.

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