LASING ACTION IN A FAMILY OF PERYLENE DERIVATIVES - SINGLET ABSORPTION AND EMISSION-SPECTRA, TRIPLET ABSORPTION AND OXYGEN QUENCHING CONSTANTS, AND MOLECULAR MECHANICS AND SEMIEMPIRICAL MOLECULAR-ORBITAL CALCULATIONS

We present experimental and computational determinations of the excited-state properties in several perylene dyestuffs that are potential candidates for use as laser dyes. Attention is focused on the following species derived from 3,4,9,10-perylenetetracarboxylic acid dianhydride: the bis((2,6-dimethylphenyl)imide) (1b, DXP); the bis(methylimide) (1c, DMP); both 1,6,7,12-tetrachloro- (1d, Cl4DMP) and 1,2,5,6,7,8,11,12-octachloro- (1e, Cl8DMP) derivatives. Soluble derivatives of seven-ringed or larger aromatic systems are produced by the introduction of relatively rigid out-of-plane substituents that prevent intermolecular close packing. Chiral distortions in ring-chlorinated perylene derivatives significantly alter the shape of the absorption bands, a consequence of symmetry breaking. Triplet-triplet absorptions and oxygen-quenching rates are observed under the conditions found in a dye laser cavity. Semiempirical molecular orbital calculations (INDO/S) provide detailed mapping of the singlet and triplet excited state manifolds of DMP, Cl4DMP, and Cl8DMP. Computed transition energies and intensities are used in the interpretation of the spectral features, in particular the observed T1 --> T(n) and potential S1 --> S(n) absorptions. We conclude that perylene-3,4,9,10-tetracarboxylic acid diimide chromophores may be solubilized and utilized in laser materials exhibiting superior performance in terms of power output, tuning range, and light stability.