Magnetic field effect on exciplex-forming organic acceptor/donor system: a powerful tool for understanding preferential salvation

Abstract

Many acceptor/donor systems can form excited-state charge-transfer complexes (exciplexes) in photo-induced electron transfer reactions. Exciplex can be detected by their luminescence. In addition, the exciplex luminescence is magneto-sensitive. Here, we employ an approach based on the magnetic field effect on the exciplex of 9,10-dimethylanthracene/N,N-dimethylaniline pair in micro-homogeneous and micro-heterogeneous binary solvents to investigate the effects of the preferential solvation processes on solute molecules in solutions. Micro-homogeneous solvent mixtures of propyl acetate (PA)/butyronitrile (BN) allow for a systematic variation of the static dielectric constants, e_s , in the range from 6.0 to 24.6. The mixtures of toluene (TO)/dimethylsulfoxide (DMSO) with varying the e_s values in the range from 4.3 to 15.5 are used as micro-heterogeneous binary solvents. In micro-heterogeneous environment, DMSO molecules get preferentially favoured in the solvation shell, forming micro-clusters surrounding the solute molecules. This solvation effect is reflected in the altered magnetic field effects, lifetimes and dissociation rate constants of the exciplexes.