Direct observation of copper-induced metalation of 5,15-diphenylporphyrin on Au(111) by scanning tunneling microscopy

In-situ metalation process of porphyrin molecules has been investigated by introducing guest copper atoms into porphyrins on the gold substrate in various ways. Scanning tunneling microscopy observations unambiguously demonstrate that the copper atoms aggregate to form islands directly on the gold surface at room temperature regardless of whether this gold surface is covered by the molecular layer or not. Under thermal activation of 363 K, these introduced copper atoms at the gold surface can be incorporated into the macrocycles of the molecules. Based on such experimental observations, a pathway for copper induced metalation is proposed: a copper atom prefers to enter the porphyrin macrocycles from the bottom of the molecule.