Spectroscopy and Photochemistry of a Derivative of an Anthracene-Naphthalene Phane

Article abstract of DOI:10.1021/ja00293a011

The effects of interchromophore interaction on the energy levels of two different polyacene chromophores (anthracene and naphthalene) have been determined.Two new coupled-chromophore compounds were used for the study, 1,2,3,4-tetrahydro-<2.3>(9,10)-anthracenophane (V) and 1-(9-anthryl)-3-(1',2',3',4'-tetrahydro-9'-anthryl)propane (III).Polarized absorption spectra of V and III, the latter obtained in a face-to-face conformation by photocleavage of its photoisomer, were observed as guests in the single crystal host material 1,3-di(9-anthryl)propane photoisomer (cycloadduct, DAPC).V was also studied by fluorescence polarization methods in a rigid hydrocarbon glass.These measurements have unambiguously detected the presence of two interchromophore charge-transfer bands at 33000 and 37000 cm^-1, the lower of which is likely to be from anthracene to naphthalene.The ¹L_a and ¹L_b states of each chromophore are appreciably shifted to low energy by the face-to-face interaction between the two ?-electron systems, but the two ¹B states are merged into one state in the phane.The spectrum of V does not require consideration of "through-bond" interactions between the two chromophores, and the important interactions are "through-space" in nature.Fluorescence is observed from V at low temperatures, but this is quenched at room temperature with the formation of the photoisomer.Ultraviolet irradation of the latter gives rise to electronically excited product fluorescence identical with that from V.Fluorescence from V has been assigned to a mixture of localized ¹L_a and ¹L_b states of the anthracene chromophore.