610322-34-4Relevant academic research and scientific papers
Excited states of bromine-substituted distyrylbenzenes: Models for conjugated polymer emission
Sarker, Ananda M.,Kaneko, Yuji,Lahti, Paul M.,Karasz, Frank E.
, p. 6533 - 6537 (2003)
Model 1,4-bis(styryl)benzene derivatives 1a,b related to poly(2-bromo-5-methoxy-1,4-phenylenevinylene) were synthesized to probe the effect of bromination on excited-state behavior of conjugated phenylenevinylene analogues. They showed solution absorption maxima at about 385 nm, without evidence of excimer formation up to 100μM. Their fluorescence spectra showed overlapping bands at 435 and 460 nm, with quantum yields in tetrahydrofuran of 0.16 and 0.21 for 1a and 1b, respectively. Excited-state transients were monitored by time-resolved laser flash spectroscopy at room temperature. The triplet states were characterized by absorption maxima at about 520-530 nm with lifetimes of about 0.6 μs, much longer than would be observed for prompt fluorescence states. The quantum yields of singlet to triplet-state intersystem crossing were determined to be 0.45 and 0.28 for 1a and 1b, respectively. The acceleration of triplet transient decay rates under increased oxygen pressure according to the Stern-Volmer law further supports the triplet-state assignments. The relatively high yields of intersystem crossing and low yields of fluorescence are attributed to a bromine-modulated heavy atom effect that enhances intersystem crossing between excited singlet and triplet states.
