The electronic spectra of the group IV tetraphenyls

The absorption and emission spectra of carbon, silicon, germanium, tin, and lead tetraphenyl are reported in their entirety. The two electronic transitions observed in absorption are shown to be analogous to those of benzene and benzene derivatives. Vibrational structure is analyzed and correlated for all five tetraphenyls. Two electronic transitions are observed in emission. The emitting levels are the lowest members of the singlet and triplet systems. The effect of atomic number of the central atom on the rate of intersystem crossing is a corollary of the usual atomic number effect on the radiative lifetime of the triplet state.