Synthesis and characterization of covalently bound self-assembled 5,10,15,20-Tetra(4- pyridyl)-21H,23H-porphine (TPyP) monolayer superlattices on various oxide surfaces such as fused silica, glass or silicon are described. The monomolecular thin film structures are characterized by UV-visible ((lambda) max equals 447 nm) and FTIR-ATR spectroscopy. In addition, x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS) studies are used to confirm the formation of a self-assembled monolayer on the fused- silica surface. Attractive features in these complexes are their second-order nonlinear optical properties, which are enhanced by the completely delocalized (pi) -electrons. Second harmonic generation measurements have been used to determine the uniformity of the film, the relative and absolute magnitudes of nonzero elements of the nonlinear susceptibility, (Chi) (2), and the average molecular orientation of the chromophores.