Time-resolved fluorescence and solvatochromy of directly linked pyrene-DMA derivatives in alcoholic solution

Picosecond transient absorption spectroscopy and picosecond spectro-streak fluorescence measurements have been carried out in order to understand the complex photophysical dynamics of directly linked donor-acceptor systems and the solvation dynamics in longer-chain alcohols. With these techniques, the fast solvent response to optically generated charge transfer (CT) species can be followed. Studies were performed on covalently linked donor-acceptor systems of the type pyrene with derivatives of N,N-dimethylaniline: dimethyl-(4-pyren-1-yl-phenyl)-amine, dimethyl-(3-methyl-4-pyren-1-yl-phenyl)-amine and (3,5-dimethyl-4-pyren-1-yl-phenyl)-dimethylamine. The results are interpreted with particular emphasis on solvation dependent electronic restructuring of the CT species. We suggest a mechanism where the adiabatic electronic restructuring coincides with the coupling to the torsional degrees of freedom of the solvent.