Condensed Aromatics. Part XX. Coronene

Abstract

Abstract The molecular vibrations of coronene, both in-plane and out-of-plane, are studied. The simple Hückel molecular orbitals are derived and the CC bond Oiders calculated. The bond orders are used to fix the CC stretching force constants. A complete set of independent symmetry coordinates is constructed. The in-plane vibrational frequencies are calculated by (a) the five-parameter approximation and (b) the Califano-Neto method; those of the out-of-plane vibrations only by the five-parameter approximation. The calculated frequencies are compared with observed values and previous calculations. A few new Raman bands are reported along with the presumably most complete set of infrared frequencies reported so far. A complete assignment of the infrared- active (E1u and A2u) fundamentals is proposed. A majority of the Raman-active frequencies (A1g, E1g and E2g) are also assigned, using Raman, fluorescence and phosphorescence spectra.