Symmetry reduction of metal phthalocyanines on metals

Abstract

The temperature-dependent adsorption behavior of fourfold symmetric metal phthalocyanines $(M\text{Pcs})$ on metals with commensurate and incommensurate symmetries was investigated by scanning tunneling microscopy. On the fourfold symmetric Cu(100) surface, planar and fourfold molecular structures in two equivalent orientations were found for $M\text{Pcs}$ when prepared at room temperature. In addition, two metastable orientations were identified when prepared at low temperature, which can be depopulated upon annealing. $M\text{Pcs}$ adsorbed on the sixfold symmetric Cu(111) surface showed a disturbed molecular appearance. The symmetry of molecular structures changed from fourfold to twofold, which is discussed in terms of molecule-substrate interaction.