Two-Dimensional Lattice of Out-of-Plane Dinuclear Iron Centers Exhibiting Kondo Resonance

We present an investigation of two-dimensional coordination networks formed by 5,10,15,20-tetra(4-pyridyl)porphyrin and iron atoms on a Au(111) surface. The coordination bonds are very robust as evidenced by STM manipulated lateral displacement of an entire network of islands consisting of hundreds of molecules and atoms. We also applied vertical manipulation to detach and attach single Fe atoms at the coordination sites. Moreover, low-temperature tunneling spectroscopy reveals a Kondo resonance at the Fe coordination center. These findings evidence that the network structure is stabilized by a coordination motif in which a pair of vertically aligned Fe atoms is ligated by four equatorial pyridyl groups. Such out-of-plane dinuclear coordination centers provide potential functions, such as catalytic, adsorption, and template for growing three-dimensional framework architectures.