Electronic spectra of azanaphthalenes: Mixed crystal spectra of quinoxaline and quinoxaline- d6

Abstract

The following spectra have been measured at 4 K, in three polarizations: 1B 1(n,π ∗) ← 1A 1 absorption of quinoxaline in durene, durene- d 14, naphthalene and naphthalene- d 10, and of quinoxaline- d 6 in durene and naphthalene. The polarized phosphorescence of quinoxaline- d 6 in durene is also recorded. The analyses permit unusually extensive assignments of excited state vibrational frequencies. Also noted are various crystal effects: isotope shifts, modification of molecular frequencies, prominence of Herzberg-Teller origins, site splittings, effects of perdeuterated hosts, and polarization ratios. An unusual line-splitting seen in durene is analyzed as a resonance between coincident a 1 and b 1 vibrations of the quinoxaline molecule, coupled through the exciton bands of the host.