Intramolecular charge transfer and thermal exciplex dissociation with p-aminobenzonitriles in toluene

摘要: The rate constants of the reversible intramolecular excited-state charge-transfer (CT) reaction 4-(dimethylamino)benzonitrile (DMABN;I) in toluene were determined as a function temperature, from double-exponential fluorescence decays measured by time-correlated single-photon counting. same decay times found for locally excited (LE) and CT state, shown global analysis. For stabilization enthalpy {Delta}H ({minus}6 kJ mol{sup {minus}1}) change entropy {Delta}S ({minus}24 J K{sup {minus}1} M{sup determined. A correlation time DMABN with longitudinal dielectric relaxation was not observed. presence dimers or solute/solvent complexes ground state excluded {sup 1}H NMR experiments. to occur planar molecules 1-methyl-5-cyanoindoline (NMCI; II) 1-methyl-6-cyano-1,2,3,4-tetrahydroquinoline (NMCQ;III) well 3,5-dimethyl-4-(dimethylamino)benzonitrile (DMADBN;IV), based on wavelength dependence decays. Such N-methyl-4-aminobenzonitrile (MABN; IH), 4-aminobenzonitrile (ABN; IHH), 3,5-dimethyl-4-aminobenzonitrile (ADBN; IVHH), which is attributed an increase energy relative LE these secondary primary aromatic amines.