Browsing by Author "Pavithra Jayachandran"

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    QUANTUM CHEMICAL STUDY ON THE STRUCTURE AND ENERGETICS OF BINARY IONIC PORPHYRIN COMPLEXES
    (Wiley Online Library, 2018-02-02) Pavithra Jayachandran; Abiram Angamuthu; Praveena Gopalan
    We study the structural and energetic properties of binary ionic porphyrin molecular complexes [H4TPPS4]2−∙∙∙SnTP using quantum chemical techniques. As the axial ligands and the protonation of pyridine sites highly influence the structure and coordination of metal‐containing porphyrin, various structures of SnTP in the presence and absence of axial ligands and pyridine protons were considered. The constructed porphyrins were then made to interact face to face, and the formed complexes were optimized at the HF/STO‐3G level of theory. The stability and stack‐like interaction of the complexes were analyzed through interplanar spacing, planar angle, and edge‐to‐edge distance. The structural parameters emphasize the importance of axial ligands for the formation of stack‐like structures. The complex that contains axial ligands with pyridine protons, namely [H4TPPS4]2−∙∙∙[X'SnXTPH]4+, shows a perfectly stacked layer with a reasonable interplanar distance, which is confirmed from the calculated counterpoise interaction and deformation energies. The energetic parameters were found to correlate well with the obtained geometries. The molecular electrostatic potential (MEP) maps were obtained to infer the presence of nonbonded interaction between the binary ionic porphyrins.
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    UV-VIS ABSORPTION SPECTRA OF SN(IV)TETRAKIS(4-PYRIDYL) PORPHYRINS ON THE BASIS OF AXIAL LIGATION AND PYRIDINE PROTONATION
    (SPRINGER, 2019-09-02) Pavithra Jayachandran; Abiram Angamuthu; Praveena Gopalan
    The present study highlights the structural and electronic spectra of Sn(IV)tetrakis(4-pyridyl) porphyrins (SnTP) using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The impact of axial ligands (OH− , Cl− , and H2O) and protonation at pyridine sites on the excitation properties of SnTP is also explored. The considered SnTPs were optimized at B3LYP/6-31+G* level of theory with LANL2DZ basis set for Sn metal. The effects of tetrahydrofuran (THF) and dimethylformamide (DMF) solvents were also assessed employing conductor-like polarizable continuum (C-PCM) model. The observed structural effects correlate well with the experimental data and clearly depict the impact of axial ligands on the SnTP ring. The absorption spectra along with the frontier orbitals in all three phases show noticeable dependence of axial ligation on the photophysical properties of SnTPs. The transition character of molecular orbitals and their respective density of states (DOS) were explored to infer the orbitals involved in electronic transitions.