Thermal Transition from a Disordered, 2D Network to a Regular, 1D, Fe(II)–DCNQI Coordination Network

We report the formation of an Fe–DCNQI (DCNQI = dicyano-p-quinodiimine) coordination network on the Ag(111) surface, where the Fe atoms are 4-fold coordinated in a square-planar geometry with the N atoms of the cyano groups. Depending on the formation temperature, the coordination network can be a two-dimensional arrangement of Fe atoms in a hexagonal lattice joined by DCNQI molecules in an apparent random way, or a set of 1D chains bound together by hydrogen bonds, but with the Fe atoms maintaining the same hexagonal lattice. The electronic structure of this network is studied by a combination of photoemission spectroscopy and theoretical calculations based on the density functional theory. In particular, we show that the oxidation state of the Fe atoms in this 1D arrangement is +2, which has been compared with the atomic charges values obtained from first-principles calculations.