The electrostatic association between mercaptosuccinic acid-coated gold clusters, about 2 nm in diameter, and amine silane derivatized silicon was examined, Relatively good coverage takes place in the pH range between 5 and 6 that coincides with the dissociation of the acid coating on the. gold clusters. The latter was established by IR spectroscopy taking advantage of the typical carboxylate vibrations that differ from the protonated species. The pK(a) value of the gold-bound acid was estimated to be 1.3 units higher than that on the free acid. Such displacements are anticipated for monolayers of bases or acids, but it is smaller in the spherical cluster than on flat surfaces. The microstructure of the films may be manipulated through control of pH, contact time, and the nature of the crystalline substrate.