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.