Structure-Dependent Reactions of Tetraphenylporphyrin with Cu(111)

Abstract

Tetraphenylporphyrin (2HTPP) undergoes several distinct, structure-dependent reactions on Cu(111): Firstly metalation, forming copper(II)tetraphenylporphyrin (CuTPP), and subsequently dehydrogenation. Dehydrogenation takes places in two steps. In the first step the phenyl rings fuse with the pyrrole rings, flattening the molecule on the surface, and in the last step the remaining hydrogen atoms are lost producing an ill-defined, interlinked, nitrogen-doped carbon network on the surface. The rate of metalation and dehydrogenation depends strongly on coverage, with an abrupt change as the coverage is increased and the structure of the adsorbed 2HTPP layer changes. Using ultrahigh vacuum, XPS, STM and TPD (of both deuterated and undeuterated molecules) the reaction rates and the different intermediates on the surface have been investigated in the temperature range from 200-1000 K as a function of the structure of the initial 2HTPP layer.