Fluorescence studies on some anthryl compounds

Abstract

The fluorescence properties of 9-anthraldehyde (1) and 3-methyl-5-(9-anthryl)-2E,4E-pentadienal (2) in organic (n-hexane, tetrahydrofuran, n-butanol) and micellar (Triton-X-100 in water) environments are described. The fluorescence efficiency φ_f of 1 (0.38) is approximately ten times larger than that of 2 (0.035). Fluorescence quenching of 1 and 2 with N,N-dimethylaniline (DMA) was also studied. Compound 1 exhibits exciplex formation with DMA in organic solvents. Exciplex formation between compound 2 and DMA is only seen in non-polar solvents. The fluorescence lifetime τ of 2 is very similar in different media. Thus the lifetime τ of compound 2 in n-butanol (14.78 ns) is similar to that in Triton-X-100 (14.45 ns). Stern-Volmer analyses of quenching data indicate a dynamic quenching mechanism with a quenching rate constant of 1.23×10⁹ M⁻¹ s⁻¹. The fluorophores are likely to have a polar, viscous micro-environment.