Hybrid density functional calculations have been carried out for Au-13-poly(N-vinyl-2-pyrrolidone), abbreviated as Au-13-PVP, and related model clusters, Au-13-PVP4, Au-13-PVP-O-2 and Au-13-PVP4-O-2, to discuss the variation in the electronic structure of Au-13 clusters by PVP adsorption. The calculations have shown that the charge transfer from the adsorbed PVP to Au-13 produces negatively charged O-2 on Au-13-PVP4. These findings suggest that PVP acts not only as a stabilizer to prevent the aggregation of Au clusters but also as an electron donor to Au clusters. Thus we conclude that the catalytic activities of Au clusters are affected by the adsorbed PVPs. (c) 2008 Elsevier B. V. All rights reserved.