Interaction between Electrolyte and Charge-Transfer States: Evidence for Complex Formation

The effects of tetraalkylammonium salts on intramolecular charge-transfer absorption and emission spectra in solution are measured. Addition of tetrabutylammonium hexafluorophosphate (TBAPF 6 ) to methylene chloride solutions of the donor-spacer-acceptor compound 2 reduces the intensity of the charge-transfer emission band and red shifts the emission maximum. The band maximum (cm -1 ) and width of the lowest-energy, charge-transfer absorption transition in 1 increase upon addition of salts. The observed shift and broadening are strongly dependent on the structure of the salt cation, being larger for tributylmethylammonium (TBMPF 6 ) than for tetrabutylammonium (TBAPF 6 ) salts, but are independent of the salt anion