Resonance Raman studies and vibrational analysis of Ni(II) porphyrins

A local coordinate scheme has been established for a 37-atom metalloporphyrin skeleton, which takes into account the phasing of adjacent bond stretches within the pyrrole ring and at the methine bridges. A consistent valence force field has been developed for Ni porpine (NiP), Ni tetraphenylporphine (NiTPP), and Ni octaethylporphyrin (NiOEP) by fitting the observed Raman and IR band frequencies and the 15N, 13C, and 2H isotope shifts with the aid of bond length-force constant relationships. NiP and its isotopomers deuterated at meso (d4), pyrrole (d8), and meso + pyrrole (d12) carbon atoms have been studied by RR and IR spectroscopies. NiTPP and its 15N4 (pyrrole), 13C4 (methine bridge), d8 (pyrrole), and d20 (phenyl) isotopomers have been investigated by RR spectroscopy with variable wavelength excitations in both crystalline and solution phases. NiOEP and its 15N4 (pyrrole), d4 (meso), d16 (methylene group) isotopomers, as well as d4 + 15N4, and d4 + 62Ni double isotopomers have been systematically studied in solution and in three different crystalline forms by RR spectroscopy with variable wavelength excitations. IR spectra for NiOEP and its NiOEP-d16 isotopomer are reported