Photophysical characteristics of directly linked pyrene-dimethylaniline derivatives

Experimental and theoretical investigations of the spectroscopic properties have been carried out on three charge-transfer model systems, covalently l inked donor-acceptor compounds of the type pyrene and derivatives of N,N-di methylaniline (dimethyl(4-pyren-1-ylphenyl)amine (PyDMA), dimethyl(3-methyl -4-pyren-1-ylphenyl)amine (PyMDMA), and (3,5-dimethyl-4-pyren-1-ylphenyl)di methylamine (PyDMDMA)). Comparing stationary absorption and emission spectr a as well as fluorescence lifetimes in different solvents, one can show tha t small chemical changes such as substitution of ortho-hydrogens by methyl groups on the DMA moiety introduces dramatic effects in spectroscopic and k inetic behavior. On the basis of infrared measurements and quantum chemical calculations, the experiments are interpreted within a statistical framewo rk, with particular emphasis on the discussion of preferred large amplitude motion (twist angle) and pyrene-specific vibronic coupling.