The triplet-state photophysical behaviors of three trans-1,2-diarylethylenes with a phenyl, 2-naphtyl, or 2-thienyl group as one substituent and a 2-anthryl as the other have been studied by laser flash photolysis and pulse radiolysis. The triplets have been generated by energy transfer under sensitized conditions, direct intersystem crossing (in bromobenzene), and assisted intersystem crossing in the presence of such singlet quenchers as oxygen, ethyl iodide (EtI), di-tert-butyl nitroxide (DTBN), and N,N-dimethylaniline (DMA). The absorption spectra of the triplets are sharp, intense, and well resolved and display two major band systems at 400-500 and 550-650 nm, respectively. The observed triplet lifetimes (tau/sub T/) are in the range 15-120 ..mu..s. On the basis of the data concerning triplet-triplet (T-T) spectra, tau/sub T/'s, triplet quenching by azulene and di-tert-butyl nitroxide, and Stern-Volmer behavior for triplet formation via exciplexes with N,N-dimethylaniline, the triplets are assignable to predominantly one conformeric species, or multiple species with indistinguishable spectral and kinetic behaviors, with the excitation energy in either case being localized primarily on the anthracene moiety. In the case of 1-(2-thienyl)-2-(2-anthryl)ethylene, triplet-related formation and decay processes with associated lifetimes 100-120 ns are observed at the initial stage following the laser excitation; these are tentatively attributed to intramolecular relaxationmore » in the initially formed triplet conformers in the form of rotation of aryl groups about quasi-single bonds. 5 figures, 3 tables.« less