Effect of platinum on the photophysical properties of a series of phenyl-ethynyl oligomers

In this work we detail the photophysical properties of a series of butadiynes having the formula H - (C6H4 - C equivalent to C)(n)-(C equivalent to C-C6H4)(n)-H, n= 1-3 and ligands H-(C6H4-C equivalent to C)(n)-H, n= 1-3 and compare these to previous work done on a complimentary series of platinum-containing complexes having the formula trans-Pt[(PC4H9)(3)](2)[(C equivalent to C-C(6)H(4)d)(n)-H](2), n= 1-3. We are interested in understanding the role of the platinum in the photophysical properties. We found that there is conjugation through the platinum in the singlet states, but the triplet states show more complex behavior. The T-1 exciton, having metal-to-ligand charge-transfer character, is most likely confined to one ligand but the T-n exciton appears to have ligand-to-metal charge-transfer character. The platinum effect was largest when n= 1. When n= 2-3, the S-0-S-1, S-1-S-0, T-1-S-0, and T-1-T-n spectral properties of the platinum complex are less influenced by the metal, becoming equivalent to those of the corresponding butadiynes. When n= 1, platinum decreases the triplet state lifetime, but its effect diminishes as n increases to 2. (c) 2005 American Institute of Physics.