Hydrogen-Bonding Stabilized Self-Assembled Monolayer Film of a Functionalized Diacid, Protoporphyrin IX Zinc(II), onto a Gold Surface

Formation of a stable self-assembled monolayer film of a functionalized diacid, protoporphyrin IX Zn(II), on Au surface is reported. On the basis of UV−vis and infrared data, it is concluded that the porphyrin is chemically bound to the Au surface via one of the two COOH groups. The other COOH group remains unbound to the surface but forms a hydrogen bond with COOH group(s) of adjacent porphyrin molecule(s). In addition, the chromophore−chromorphore interactions are weak in the porphyrin SAM.