Photochemical reduction of 1-methyl-3-carbamoyl-pyridinium by hexacyanoferrate(II) 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 [Fe(CN)(6)](4-) which shows a new absorption (lambda(max) = 392 nm) in the electronic spectrum. This b and is assigned to an outer-sphere charge transfer (OSCT) transition from [ Fe(CN)(6)](4-) to MNA(+). In aqueous solution OSCT excitation leads to a ph otoredox reaction with the formation of [Fe(CN)(6)](3-) and the radical MNA (.) which undergoes a dimerization or, more likely, a further reduction to MNAH. (C) 2000 Elsevier Science S.A. All rights reserved.