4,4'-Diphenyltetrathiafulvalene (DPTTF) capped gold nanoparticles of 3- to 5-nm diameter have been prepared and their thermal stability has been investigated by variable temperature FT-IR spectroscopy. The DPTTF molecules at the cluster surface undergo charge-transfer complexation with C-60 to form Au/ DPTTF.C-60. Direct evidence of complexation is observed in the x-ray photoelectron and infrared spectra of the clusters. The orientational ordering transition of C-60 in Au/DPTTF.C-60 clusters occur at a higher temperature than pure C-60 indicating increased resistance to orientational disorder due to charge transfer. Variable-temperature infrared spectroscopic studies yield complementary information. Both FT-IR and mass spectra show that some of the sites on the gold surface are occupied by the phase-transfer reagent used in the cluster preparation.