A study has presented combined optical and structural in study of (sub) organic monolayers on an inorganic substrate, and also analyzed surprisingly sharp optical transitions recorded at room temperature. Special commensurate square lattice explained the unusually narrow optical spectra at room temperature that demonstrates strong structure-property dependence, and also observed that the commensurate growth minimizes the inhomogeneous broadening in displayed optical spectra, and the Coulomb interaction and the van der Waals-bonding between inorganic substrate and molecules results in an unexpected formation of a quadratic structure for the first monolayer, which could not be directly visualized by noncontact atomic force microscopy (AFM). The molecules rearrange and form islands that exhibit the structure of the bulk single crystals. The study also demonstrates the significant impact of the physical structure on the resulting physicochemical properties of molecular layers.