Cover Picture: [Fe(H2O)5(NO)]2+, the “Brown‐Ring” Chromophore (Angew. Chem. Int. Ed. 25/2019)

Over 100 years after a suggestion of how the chromophore of the brown ring known from analysis, the ion [Fe(H2O)5(NO)]2+, can be crystallized, this has finally been achieved. In their Communication on page 8566 ff., P. Klüfers et al. analyze the crystal structure and the bonding situation of the complex. The Fe−NO bond can be described by two long spin-polarized π interactions and challenges the concept of oxidation state. Over 100 years after a suggestion of how the chromophore of the brown ring known from analysis, the ion [Fe(H2O)5(NO)]2+, can be crystallized, this has finally been achieved. In their Communication on page 8566 ff., P. Klüfers et al. analyze the crystal structure and the bonding situation of the complex. The Fe−NO bond can be described by two long spin-polarized π interactions and challenges the concept of oxidation state. Oxygen Evolution Reaction Ionic Liquids Surface Self-Assembly