Effects of chemical modifications on photophysics and exciton dynamics of pi-conjugation attenuated and metal-chelated photoconducting polymers

Effects of two types of chemical modifications on photoconducting polymers consisting of polyphenylene vinylene (PPV) derivatives are studied by stati c and ultrafast transient optical spectroscopy as well as semi-empirical ZI NDD calculations. The first type of modification inserts 2,2'-bipyridyl-5-v inylene (bpyV) units in the PPV backbone, and the second type involves meta l-chelation with the bpy sites. Photoluminescence (PL) and exciton dynamics of polymers 1 and 2 with PV:bpyV ratios of I and 3 were examined in soluti on, and compared with those of the homo-polymer, poly(2,5-bis(2'-ethylhexyl oxy)-1,4-phenylene vinylene) (BEH-PPV). Similar studies were carried out fo r several metal-chelated polymers. These results can be explained by change s in pi -conjugation throughout the polymer backbone. The attenuation in pi -conjugation by the chemical modifications transforms a conducting polymer from one-dimensional semiconductor to molecular aggregates. (C) 2001 Elsev ier Science B.V. All rights reserved.