Effects of Acceptor Structure on Charge-Transfer Complexation in Aqueous Polyelectrolyte Solution

Charge-transfer (CT) complexation between 1-pyrenesulfonate (PyS−) (donor) and 9,10-anthraquinone-1-sulfonate (1-AQS−) (acceptor), and between PyS− and 9,10-anthraquinone-2-sulfonate (2-AQS−) (acceptor) in the solution of poly(1,1-dimethyl-3,5-dimethylenepiperidinium chloride) (PDDP+Cl−) was investigated by absorption spectroscopy, viscosity and solubility measurements, and molecular orbital calculation. New broad UV bands corresponding to CT complexation between PyS− and 1- or 2-AQS− were observed only when the polycation was present in the system. A continuous variation method for both systems showed the stoichiometries of the CT complexes were both 1:1 in donor:acceptor composition. Reduced viscosity measurements showed to ηsp/c of PDDP+Cl− in Na+PyS−/Na+2-AQS− solutions decrease more rapidly than in Na+PyS−/Na+1-AQS− solutions as the salt concentration increase. Solubility measurements suggested that the polymer precipitated more easily in Na+PyS−/Na+2-AQS− than in Na+PyS−/Na+1-AQS− solution. These results suggest that interactions between the polycation and the CT complex for Na+PyS−/Na+2-AQS− are stronger than that for Na+PyS−/Na+1-AQS−. Plausible structures of the CT complexes are discussed on the basis of the HOMO and LUMO energies and molecular orbital symmetry obtained by the MOPAC semi-empirical molecular orbital calculation program.