Effect of Oligomer Length on Photophysical Properties of Platinum Acetylide Donor-Acceptor-Donor Oligomers.
We report a systematic study that explores how the triplet excited state is influenced by conjugation length in a series of benzothiadiazole units containing donor-acceptor-donor (DAD)-type platinum acetylide oligomers and polymer. The singlet and triplet excited states for the series were characterized by an array of photophysical methods including steady-state luminescence spectroscopy and femtosecond-nanosecond transient absorption spectroscopy. In addition to the experimental work, a computational study using density functional theory was conducted to gain more information about the structure, composition, and energies of the frontier molecular orbitals. It is observed that both the singlet and triplet excited states are mainly localized on a single donor-acceptor-donor unit in the oligomers. Interestingly, it is discovered that the intersystem crossing efficiency increases dramatically in the longer oligomers. The effect is attributed to an enhanced contribution of the heavy metal platinum in the frontier orbitals (HOMO and LUMO), an effect that leads to enhanced spin-orbit coupling.
Department of Chemistry and Center for Macromolecular Science and Engineering, University of Florida , Gainesville, Florida 32611-7200, United States.
Seda
S
Cekli
Department of Chemistry and Center for Macromolecular Science and Engineering, University of Florida , Gainesville, Florida 32611-7200, United States.
Russell W
RW
Winkel
Department of Chemistry and Center for Macromolecular Science and Engineering, University of Florida , Gainesville, Florida 32611-7200, United States.
Kirk S
KS
Schanze