The electronic absorption spectrum of ferrocene has been investigated in the vapor, in liquid solutions, and in glassy matrices. Temperatures used ranged from 420° to 77°K. The absorption spectrum contains at least 11 distinct electronic absorption bands. Three of these appear to be triplet←singlet in nature, and to be made allowed by spin—vibronic perturbations (i.e., spin—orbit coupling of the triplet manifold with vibronically coupled singlets). It is shown that a spin—orbit coupling factor 300≤ζ≤400 cm−1 can account for the observed intercombination intensities. The singlet←singlet absorption spectrum is dominated by one allowed transition at ∼50 000 cm−1 with f∼0.69. It is possible that all other electronic transitions, the 53 000-cm−1 band excepted, are dipole forbidden and obtain intensity by first-order vibronic stealing from the ∼50 000-cm−1 band. The higher-energy absorption bands show vibrational structure, and this structure is analyzed herein; unfortunately, the resolution is restricted by ``molecular'' reasons associated with vibrational ``richness,'' hindered rotations, and vibrational ``hot bands.'' The higher-energy absorption bands are heavily localized on the aromatic rings in contrast to the three low-energy diffuse electronic systems in Regions IV, V, and VI which contain much d-orbital and intramolecular charge-transfer character. No phosphorescence emission of ferrocene has been observed here.

The emission spectrum of the anthracene-sym-trinitrobenzene complex has been investigated in a solid solution in a diethylether-isopentane (EP) glass at 77°K. The observed luminescence consists of two distinct electronic transitions: one transition is the reverse of the charge-transfer E←N absorption of the complex; the other transition is a phosphorescence very similar to the T→S emission of anthracene in EP, but blurred somewhat in vibrational structure, blue shifted by 113 cm—1, decreased in lifetime by a factor of about 2 and showing decreases in the ground state vibrational frequencies of a few percent. These results, as opposed to previous conclusions (vide infra), would suggest that the phosphorescence is truly a T→S process of the complex which is largely localized on the anthracene component. Vibrational analyses of T→S spectra of anthracene in EPA and in EP and of the T→S and E→N spectra of the complex in EP at 77°K are given.