The synthesis, X-ray structure analysis, and photophysical characterization of 3,3&; prime; -diacetylstilbene

3,3\'-Diacetylstilbene was produced in modest yield (26%) from a palladium(II) acetate-catalyzed coupling reaction between triethoxyvinylsilane and the triazene 1-{3-[(E)-morpholin-4-yldiazenyl]phenyl}ethanone. X-ray analysis of crystals of 3,3\'-diacetylstilbene revealed a nearly planar molecule (average deviation 0.037 a) on a crystallographic inversion center. Its crystal packing was found to be composed of sheets of individual molecules of the stilbene interacting through C---H times times times O hydrogen bonds with the sheets in turn participating in two types of weak C---H times times times pi aromatic interactions. The room-temperature absorption spectra of 3,3\'-diacetylstilbene in propanenitrile and chloroform featured two pi arrow right pi super(*) transitions with maxima at approximately 250 and 300 nm. 3,3\'-Diacetylstilbene was observed to be luminescent in room-temperature solution, in propanenitrile glass at 77 K, and in the solid state with maxima in the range 385-470 nm. The broadness of the emission spectra qualitatively indicated the degree that 3,3\'-diacetylstilbene aggregated in solution. Quantum yields of 2 in propanenitrile and chloroform solution indicated that it had a higher fluorescence efficiency than 4,4\'-diacetylstilbene.