title: Photoisomerization of cis-1,2-di(1-Methyl-2-naphthyl)ethene at 77 K in Glassy Media.
abstract: cis-1,2-Di(1-methyl-2-naphthyl)ethene, c-1,1, undergoes photoisomerization in methylcyclohexane, isopentane and diethyl ether/isopentane/ethanol glasses at 77 K. On 313 nm excitation the fluorescence of c-1,1 is replaced by fluorescence from t-1,1. Singular value decomposition reveals that the spectral matrices behave as two component systems suggesting conversion of a stable c-1,1 conformer to a stable t-1,1 conformer. However, the fluorescence spectra are λexc dependent. Analysis of global spectral matrices shows that c-1,1 is a mixture of two conformers, each of which gives one of four known t-1,1 conformers. The λexc dependence of the c-1,1 fluorescence spectrum is barely discernible. Structure assignments to the resolved fluorescence spectra are based on the principle of least motion and on calculated geometries, energy differences and spectra of the conformers. The relative shift of the c-1,1 conformer spectra is consistent with the shift of the calculated absorption spectra. The calculated structure of the most stable conformer of c-1,1 agrees well with the X-ray crystal structure. Due to large deviations of the naphthyl groups from the ethenic plane in the conformers of both c- and t-1,1 isomers, minimal motion of these bulky substituents accomplishes cis → trans interconversion by rotation about the central bond.
authors.affiliation: Department of Chemistry and Biochemistry, The Florida State University, Tallahassee, FL.
authors.forename: Christopher
authors.initials: C
authors.lastname: Redwood
authors.forename: V K
authors.initials: VK
authors.lastname: Ratheesh Kumar
authors.forename: Stuart
authors.initials: S
authors.lastname: Hutchinson
authors.forename: Frank B
authors.initials: FB
authors.lastname: Mallory
authors.forename: Clelia W
authors.initials: CW
authors.lastname: Mallory
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Clark
authors.forename: Olga
authors.initials: O
authors.lastname: Dmitrenko
authors.forename: Jack
authors.initials: J
authors.lastname: Saltiel