AN AB-INITIO ANALYSIS OF THE ELECTRONIC-STRUCTURE AND HARMONIC FREQUENCIES OF NICKEL PORPHYRIN

Ab initio calculations are performed to understand the geometry, elect ronic structure, and vibrational frequencies of nickel porphyrin (NIP) . Hartree-Fock (HF) and second-order perturbation (MP2) theories are a pplied with polarized basis sets. The calculated geometrical parameter s are in very good agreement with the crystal structure determination. The electronic structure and bonding are analyzed in terms of complex ation and correlation effects. Not unexpectedly, the HF depiction of t he metal-porphyrin interaction is rather ionic while ligand sigma dona tion is dominant at the MP2 level. Scaled HF frequencies of NIP and it s isotopomers are in very good agreement with observed infrared and re sonance Raman data.