Vapour phase exciplex emission in 9-cyanoanthracene + amine mixtures

Abstract

Exciplex emission has been observed in the gas phase for the 9-cyanoanthracene + triethylamine (9-CNA + TEA)(171°C) and 9-cyanoanthracene + dimethylaniline (9-CNA + DNA)(231°C) systems with emission maxima at 515 and 490 nm, respectively.The excitation spectra of these exciplex emissions are in good agreement with the absorption spectrum of 9-CNA in the gas phase. There was no evidence in absorption of significant ground state 9-CNA + amine interactions. In solution, no exciplex emission is detected for the 9-CNA + TEA system, while for the 9-CNA + DMA system, exciplex emission is also observed in cyclo-hexane with its maximum at 530 nm. In both phases, decay characteristics of total fluorescence from the 9-CNA + DMA system are dual-exponential with a long lived component attributed to the exciplex with decay times of 27.5 and 60.2 ns in the gas phase and in cyclohexane solution respectively. Quenching of monomer fluorescence was less efficient in the vapour phase than in solution, and the nature of the charge-transfer process in the vapour phase was discussed with reference to these observations.