Photochemical reduction of 1-methyl-3-carbamoyl-pyridinium by cyanoborohydride induced by outer-sphere charge transfer excitation

The NAD(+) subunit 1-methyl-3-carbamoyl pyridinium cation (or 1-methyl nico tinamide cation, MNA(+)) forms an ion pair with BH3CN- which shows a new ab sorption (lambda (max) = 453 nm) which is assigned to an outer-sphere charg e transfer (OSCT) transition from BH3CN- to MNA(+). At r.t. this ion pair i s not stable and undergoes a hydride transfer from BH3CN- to MNA(+) with th e formation of MNAH. At -77 degreesC this ion pair is persistent but the hy dride transfer occurs as a photoreaction which is induced by OSCT excitatio n. (C) 2000 Elsevier Science S.A. All rights reserved.