EVALUATION OF THE SEMIEMPIRICAL PM3(TM) METHOD FOR MODELING HIGH-SPINAND LOW-SPIN NICKEL(II) COMPLEXES OF AN EXTENDED SERIES OF TETRAAZA MACROCYCLES

The semiempirical PM3(tm) program, employing the recently released par ametrization for high- and low-spin nickel(II), has been evaluated for modeling the structures of both high- and low-spin nickel(II) complex es of an extended series of tetraaza macrocyclic ligands. The results obtained were compared with those available from our previous parallel studies using the molecular mechanics procedure based on an extended MM2 force field. In general terms, the semiempirical method was found to be clearly less effective, using the available parametrization, tha n the molecular mechanics studies for modeling the structures of the a bove categories of nickel complexes.