Effect of substituent position on molecular assembly: Hydrogen-bonded arrangement of aminobenzoates adsorbed on Cu(110)

The growth and assembly of the aminobenzoate (NH₂C ₆H₄COO^-) isomers, ortho-aminobenzoate (OAB), meta-aminobenzoate (MAB), and para-aminobenzoate (PAB), on Cu(110) have been investigated by low-temperature scanning tunneling microscopy (STM). In the submonolayer regions, OAB and PAB formed well-ordered islands, whereas MAB produced disordering when dosed at room temperature. We found that the growth of the OAB and PAB layers proceeds in a different manner. The OAB islands developed from the step site to the terrace, while the nucleation and growth of the PAB islands occurred at the terrace. An increase in the surface coverage resulted in further growth of the islands for the OAB and PAB layers, which ended with the formation of ordered monolayers with (4×3) and (3×4) superstructures, respectively. In contrast, MAB showed a complex self-assembly on the Cu(110) surface. Our STM study clearly demonstrates that the substituent position in the aminobenzoate affects not only the monolayer structure but also the growth process.