Electronic interactions in metal complexed photoconducting polymers: a ZINDO study

Semi-empirical (INDO/s) calculations have been conducted on molecular fragments with zero to three phenylenevinylene (PV) units attached to 4 and 4′ positions of a 2,2′-bipyridine (bpy) group, with and without chelated metal ions, mimicking metal-free and metal-chelated photoconducting polymers 1 and 2 [Chen et al., J. Phys. Chem. B 104 (2000) 1950]. The calculations suggest that: (1) a global lowering of the molecular orbital energy levels due to metal-chelation is responsible for the observed red-shift in the lowest energy transitions; and (2) metal chelation attenuates π-electron delocalization. The relevance of these effects to photoluminescence of metal-chelated polymers is also discussed.