Single-electron transfer (SET) between donor-acceptor complex PTZ-TCBQ (phe nothiazine : tetrachloro-p-benzoquinone = 1/1) and thiol-stabilized gold nanoclusters Au-25(SC2H4Ph)(18)(-)TOA(+) (abbreviated as Au-25(-)) is firstly researched here. Cyclic voltammetry (CV), UV-vis spectroscopy, electron spin resonance (ESR) and nuclear magnetic resonance (NMR) are utilized to study their electron transfer reaction. The characteristic results show only one-electron transfer from Au-25(-) to the complex, and the excess amount of PTZ-TCBQ complex cannot oxidate Au-25(0) further as (HNMR)-H-1 observed. So those results indicate that this well defined gold nanoclusters with a molecular-like redox behavior as an electron donor can be applied as a solar photocatalytic nanomaterial, SET catalyst and so on. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.