Electronic spectra of azanaphthalenes: Solid state spectra of cinnoline and quinazoline

The first electronic absorption region ($\text{π}{}^1\text{← n}$) of cinnoline has been measured in durene and naphthalene as host crystals at 4 K and of quinazoline likewise in durene, naphthalene, and the pure crystal. The $\text{π}{}^1\text{← n}$ region is analyzed as a single transition in both cases in agreement with prior vapor studies, but all the spectra are complicated by the presence of at least two inequivalent sites with site splittings as large as 450 cm^?1. In one instance (quinazoline in naphthalene) polarization ratios permit the conclusion that the two observed site spectra correspond to the two alternative placements of the guest molecule in a vacancy in the host lattice. Site and host dependent effects are documented on phonon activity, vibrational frequencies, polarization ratios, and the incidence of vibronic (Herzberg-Teller) activity.The salient properties of the first $\text{π}{}^1\text{← π}$ absorptions of both molecules and of the $\text{π}{}^1\text{→ π}$ phosphorescence of quinazoline are briefly noted.