On the nature of the charge-transfer transient in photocatalysis by the decatungstate anion

The decatungstate anion [W10O32](4-) is an efficient catalyst in the photooxidation of alkanes. Laser flash photolysis studies suggested that after photoexcitation the decatungstate anion relaxes to an intermediate with an electronic distribution similar to that of the singly reduced cluster. Using vibronic theory of mixed-valence compounds, we study possible electronic distributions of decatungstate with one excess electron in the LUMO. Under some conditions this electron can be delocalized over a part of equatorial tungsten centres. In some cases this delocalized electronic distribution can coexist with the electron localization at one tungsten site. The intermediate form in the photocatalytic reaction could be assigned to the partly delocalized state which can be attained from an initially localized photoexcited state. (C) 1998 Elsevier Science B.V. All rights reserved.