Prediction and interpretation of electronic spectra of transition metal complexes via the combination of molecular mechanics and angular overlap model calculations

The combination of molecular mechanics (MM) and angular overlap model (AOM) calculations has been applied in the prediction of the d-d electronic spectra of a variety of hexaamine complexes of Co(III), Cr(III), and Ni(II). Assuming that the e(sigma) parameters (equatable with Dq) are directly proportional to r-6, where r is the M-N bond length, a proportionality constant, C, was determined for each type of M-N bond, i.e. M-NH3, M-NH2R, M-NHR2, and M-NR3. The C parameters were found to increase with the addition of each alkyl group for all three systems.