ELECTRONIC SPECTROSCOPY OF 4 CONFORMATIONS OF JET-COOLED 1,6-DIHYDROXYNAPHTHALENE

The electronic spectroscopy of 1,6-dihydroxynaphthalene (DHN) is investigated in an attempt to identify and characterize the four distinct conformations with respect to orientation of the two hydroxyl groups. Fluorescence excitations, dispersed fluorescence, and ground-state fluorescence depletion experiments are used to unambiguously identify the electronic origins and excited vibronic structure of each rotamer. Comparisons to the well-characterized 1- and 2-naphthol species are used to make a tentative assignment of the absolute conformations of the observed electronic origins. The ground-state conformational stabilities of the disubstituted DHN apparently cannot be inferred by simple comparison to the two singly substituted 1- and 2-naphthol species. The electronic transition energies of each rotamer are well separated (> 100 cm-1), indicating a significant change in conformational stability upon electronic excitation. The relative electronic transition energies also cannot be predicted from the behavior of the singly substituted naphthol compounds.