Molecules Porphyrins Self assembled monolayers 6-Mercaptopurine Aliphatic thiols Carboxylate groups Carboxylation Chemical reactions Covalent anchoring Electronic structure Elevated temperature Exposed to Free base porphyrins Hydroxyl groups Interfaces (materials) Lower temperatures Metals Molecular dipole Molecular domains Molecular state Monolayers Negative charge Oxide minerals Phase interfaces Porphyrin molecules Positive charges Protoporphyrin IX Rectangular lattices Rutile TiO2 Scannning tunneling microscopies