Photochemical dimerization of acephenanthrylene and the heavy atom effect
The solution-phase photodimerization of acephenanthrylene (1) in cyclohexane, chloroform, dibromomethane, and ethyl iodide with visible light (lambda = 419 nm) occurs to form cis (2) and trans (3) photodimers in ratios that vary with the solvent and with the presence or absence of oxygen. The photodimerization exhibits a significant heavy atom effect and also is sensitive to selective quenching by dissolved oxygen, in which only cis stereoisomers are produced. Irradiation of the dimers (lambda = 254 nm) shows that the trans dimers cleave more rapidly than the cis dimers. This is attributed to stabilization of the excited state in the cis dimers.
Plummer
BF
Department of Chemistry, Trinity University, San Antonio, Texas 78212-7200, USA.
Moore
MJ
Wright
J