Spectra and conformation of α-naphthil

Abstract

From spectroscopic studies of α-naphthil in its ground state, three conformers in isopropanol and two conformers in methyl cyclohexane have been identified. In methyl cyclohexane, one conformer shows green phosphorescence with a lifetime of 60 ms at 77 K, and band maxima at 519, 530 and 561 nm. The excitation peak of this conformer appears at 346 nm. The other conformer emits yellow phosphorescence with a lifetime of 2.2 ms at 77 K and a major peak at 566 nm. This conformer has an excitation peak at 368 nm. In isopropanol glass at 77 K, the compound has one more conformer, as well as the two found methyl cyclohexane. This third conformer in isopropanol has a phosphorescence spectrum with peaks at 502 and 536 nm, a lifetime of 2.85 ms at 77 K and an excitation peak at 383 nm. The fluorescence spectra and fluorescence kinetic studies of α-naphthil corroborate the presence of three different conformers in isopropanol. The green phosphorescent conformer fluoresces at 414 nm with a lifetime of 7.0 ns, the yellow phosphorescent conformer fluoresces with a band maximum at 425 nm and a lifetime of 1.5 ns, while the third conformer, which phosphoresces at 502 and 536 nm, fluoresces at 455 nm and has a lifetime of 3.5 ns. The absorption studies at different temperatures also confirm the presence of three different conformers of the compound in isopropanol.