Triplet States of Naphthalene Derivatives. I. 1,4-Dibromonaphthalene

A doublet structure is observed in the T1←S0, T2←S0, and S1←S0 spectra of single crystals of 1,4-dibromonaphthalene. The crystal structure is known to contain asymmetric units, and the spectral band doubling is attributed to the difference in dispersion interactions at the two sites. The observed asymmetric site splittings are 52 cm−1(T1), 103 cm−1(T2), and 85 cm−1(S1). Each of these values is in reasonable accord with expectations for certain diagonal Coulomb terms in the exciton matrix. The vibrational analyses of the T1, T2, and S1 states are presented. These states are located at 20 197 cm−1(T1), 29 783 cm−1(T2), and 30 357 cm−1(S1). The triplet spectra are briefly discussed with reference to the polarization of the vibronic bands.