SPECTROSCOPIC AND KINETIC-STUDY OF THE MOLECULAR ASSOCIATION BETWEEN PYRENE AND BENZYL VIOLOGEN

The molecular interaction of pyrene with benzyl viologen in methanol h as been studied by electronic absorption, NMR H-1, and time resolved a nd stationary emission spectroscopies. The system forms a charge trans fer complex characterized by an electronic absorption band centered on 480 mm. The association constant of the complex calculated at differe nt temperatures is within the range of 6.5-12.3 1 mol(-1) in the tempe rature interval of 303-273 K, and the enthalpy change of the associati on process is - 3.4 kcal mol(-1). The complex is less stable in the ex cited state, and subject to dissociation upon excitation as indicated by potential energy curve, obtained from semi-empirical quantum molecu lar calculation and time resolved emission decay and quenching data. ( C) 1998 Elsevier Science B.V. All rights reserved.