Optical, magnetic, and electronic properties of peripherally fused macrocycles: Molybdocene porphyrazines

Metal-free and copper porphyrazines, [H(2)pz] and [Cu pz], have been fused at the periphery with molybdocene dithiolene, [Cp2Mo]. The optical, magneti c, and electronic properties of the resulting neutral and cationic complexe s are studied, using first-principles density functional theory implemented by the discrete variational method. Analysis of the charge and spin distri bution shows that the porphyrazine core is strongly coupled with the periph eral complex. The calculated optical absorption is found to be in reasonabl e agreement with experimental spectra, lending support to our theoretical m odel. Under appropriate circumstances one observes interaction of unpaired spins localized in the vicinity of both metal sites. The calculated spin di stribution shows that [Cp2Mo][Cu pz] and [Cp2Mo][H(2)pz](+) have a magnetic moment of 1 mu (B) while [Cp2Mo][Cu pz](+) and [Cp2Mo][H(2)pz] have no mom ent, in good agreement with the results of X-band EPR spectra. The Cu-Mo ma gnetic interaction is antiferromagnetic, being mediated by pyrrol nitrogens , meso nitrogens, carbons, and sulfurs.