New insight into the fluorescence properties of 1,2,-bis(9-anthryl) ethanes: Temperature dependence and conformational effects in dilute methylcyclohexane solutions

Unimolecular photochemistry of anthracenes

“…312,313 In several electron spectroscopic studies on l,2-di(9anthryl)ethanes, evidence has been obtained for more than one excimer geometry, and for the existence of anti and gauche conformers. 286,314,326,330,331 Geometrically different excimers also have been detected spectroscopically for photoexcited l,2-di(l-anthryl)ethane which undergoes intramolecular 4x + 4x cycloaddition involving the 9,10 positions of both anthracene moieties. 285 The polar character of the excimer state of dianthrylethanes is borne out in the dependence of its electronic structure on solvent polarity.325 Moreover, results obtained by time-resolved picosecond laser spectroscopy indicate the formation of a common intermediate in the photochemical cycloaddition and cycloreversion, and it has been established spectroscopically that intramolecular electron transfer between the two aromatic moieties is involved in both the cycloaddition and cycloreversion process.315,344 C. Dimethylsllyl-Linked Bichromophoric Anthracenes…”

“…311 In line with earlier observations on a series of a,«-dipyrenyl alkanes, quantum yields of excimer luminescence vary with the length of the alkane chain.324 For l,2-di(9-anthryl)ethane and l,3-di(9-anthryl)propane, the question of excimer formation continues to be of interest, although excimer emission has been detectable only under special environmental conditions. [326][327][328][329][330][331] In a recent emission spectroscopic investigation of a,<i)-di(9-anthryl)alkanes of varying chain length (C3, C5, C7, C10, C12, C14, and Cjg), picosecond time-resolved measurements have revealed intramolecular "excitation hopping" for photoexcited l,7-di(9-anthryl)heptane and its higher homologues. 332 It should be pointed out that the quantum yields of disappearance of a,«-di(9-anthryl)alkanes are not to be considered quantum yields of isomerization, because intermolecular cycloaddition may become an important competing reaction if intramolecular cycloaddition proceeds with low quantum yield.…”