Coadsorption of ZnTPP and 2HMCTPP on Rutile TiO₂(110)

Abstract

Pure zinc tetraphenylporphyrin (ZnTPP) adsorbs on rutile TiO2(110) as flat‐lying molecules, mostly interacting with the surface through weak van‐der‐Waals interactions. Pure monocarboxyphenyl triphenylporphyrin (2HMCTPP) forms a covalent bond to the rutile TiO2(110) surface through the carboxylic acid group, yielding densely‐packed layers of upright‐standing molecules. If given the chance, 2HMCTPP could therefore be expected to displace the weaker‐bonding ZnTPP molecules. However, if 2HMCTPP is deposited on top of a ZnTPP layer, a coadsorption structure instead forms, with the carboxylic‐acid groups of the 2HCMTPP molecules bonding to titanium atoms of the surface exposed by gaps between the molecules in the flat‐lying ZnTPP adsorption structure.