Surface assisted intermolecular interactions in self-assembled coumarin submonolayers

Spectroscopic characterization of chemically immobilized coumarin molecules on a silica surface at different concentrations and in a variety of solvents is presented. The characterization involves surface concentration and orientation of coumarin molecules with different linkers. Due to high surface concentration (up to 10¹⁴ cm^-2), the immobilized molecules exhibit intermolecular interactions, which compete with solvation. The molecular orientation with respect to the surface and intermolecular interaction varies with the solvent, the linker, and the surface concentration of coumarin, but as a first approximation the data can be simplified as nearly random molecule orientation with respect to the surface.