PROPERTIES OF METAL PHTHALOCYANINES AND METAL PORPHYRINS AS CATALYSTS FOR O//2 REDUCTION FROM PREDICTIVE MOLECULAR ORBITAL THEORY.

Several transition metal macrocycles have been studied as catalysts for the reduction of O//2. In contrast to the fairly extensive literature dealing with experimental studies aimed primarily at elucidating reaction pathways and evaluating rate parameters, the efforts devoted to develop a theoretical framework, which may provide insight into the factors involved in the activation and further reduction of O//2, have been sparse. The use of simpler, semi-empirical approaches is desirable as a first step in understanding the bonding and electronic properties which are expected to play key roles in the macrocycle-mediated O//2 reduction. This paper will apply the principles of molecular orbital theory to the analysis of the electronic properties of primitive macrocycle fragments as calculated using a semiempirical method. The calculations employ the semiempirical atom superposition electron delocalization theory.