An unusual self-assembly of a deuteroporphyrin 4-aminothiophenol derivative on Au(111) surfaces

An unexpected ruthenium(ii)-deuteroporphyrin 4-aminothiophenol (4-ATP) thiolester derivative (Ru-4ATPP) was obtained by the condensation of 4-ATP with carbonyl[13,17-bis(propanoic acid)-2,7,12,18-tetramethylporphyrinato] ruthenium(ii). Ru-4ATPP was self-assembled on Au(111) surfaces through the terminal amino groups, as shown by cyclic voltammetry (CV) and confirmed by X-ray photoelectron spectroscopy (XPS). A slow and incomplete isomerisation process of the self-assembled 4-RuATPP thiolester to its amido analogue was observed, due to the catalytic effect of the gold surface. Consequently, the formed amido isomer of Ru-4ATPP became self-assembled on Au(111) through the resulting terminal thiolate groups, a condition characterized by CV reductive desorption (peak at ca. -0.7 eV) and XPS (S2p peaks at 162.1 and 163.3 eV).