The low-temperature luminescence of benzamide and six additional N-arylbenzamides has been investigated
in a methyltetrahydrofuran glass. The luminescence of microcrystalline benzamide has also been studied.
Assignments of the fluorescence and phosphorescence have been made on the basis of comparisons with the
spectra of benzamide and the six aminoarenes and with the results of semiempirical ZINDO calculations for
the amines and amides. This information was used to construct state-energy diagrams for the six amides. The
430 nm fluorescence of benzanilide and the amides derived from 4-aminobiphenyl and 4-aminodiphenylacetylene is assigned to a n,π* state having a relaxed geometry and localized on the benzoyl group. The
structured fluorescence of the amides derived from 4-aminostilbene and 2-aminoanthracene is attributed to a
delocalized π,π* singlet state. The amide derived from 2-aminophenanthrene displays dual fluorescence. The
amides derived from 4-aminostilbene and 2-aminoanthracene are nonphosphorescent. The structured
phosphorescence of the amides derived from the other aminoarenes is assigned to a π,π* triplet state similar
to that for the aminoarene. These results serve to further elucidate the unusual luminescence properties of the
benzamides in solution as well as in low-temperature glasses.