Conformational study of porphyrin-based molecules using non-contact atomic forcemicroscopy

Abstract

To control the interaction between tetrakis(3,5 di-t-butylphenyl)porphyrin (TBPP) moleculesand substrates, 5-(4-methylthiophenyl)-10,15,20-tris(3,5-di-t-butylphenyl)porphyrin(MSTBPP) molecules were tailored; one of the four di-t-butylphenyl groups of TBPPmolecules was replaced by a methylthiophenyl group. By means of non-contactatomic force microscopy (NC-AFM) operated in the force feedback control mode,the conformation of MSTBPP molecules deposited on an Au(111) substrate wasinvestigated. It was found that the methylthiophenyl group introduced into theTBPP molecules enhanced the attractive interaction between the molecule and thesubstrate. This interaction seems to improve the spatial resolution of NC-AFM.