A boron dipyrrin (BODIPY) dye was designed as a molecular single-component electrophore for redox flow batteries. All positions of the BODIPY core were assessed on the basis of literature data, in particular cyclic voltammetry and density functional calculations, and a minimum required substitution pattern was designed to provide solubility, aggregation, radical cation and anion stabilities, a large potential window, and synthetic accessibility. In-depth electrochemical and physical studies of this electrophore revealed suitable cathodic behavior and stability of the radical anion but rapid anodic decomposition of the radical cation. The three products that formed under the conditions of controlled oxidative electrolysis were isolated, and their structures were determined by spectroscopy and comparison with a synthetic model compound. From these structures, a benzylic radical reactivity, initiated by one-electron oxidation, was concluded to play the major role in this unexpected decomposition.

A single-substance redox-flow battery (RFB) based on the iodide/triiodide and triiodide/iodine redox couples has been investigated. Stable charge-discharge curves were recorded under ambient air in a stirred PTFE batch cell. Current efficiencies were > 90 %. Current densities were kept low (33 µA cm -2 ) due to high resistance (5.8 kΩ cm 2 ) of the cation exchange membrane used. It is shown theoretically, that the open voltage potential of redox flow batteries with complex stoichiometry is concentration dependent. For comproportionation electrolytes, the increases with bulk concentration, which is proved experimentally for the system. The open cell voltage ranged from 0.36 V to 0.58 V for 1-80 mM solutions. The formal potential difference was determined by cyclic voltammetry (0.655 V) and open cell voltages (0.69 V), respectively. Interestingly, the calculation of required the evaluation of the open cell voltage at a state of charge of the inverse of the golden number. This is a consequence of the "golden" stoichiometric factors of the iodide/iodine comproportionation. To the authors' knowledge, this is the first report of a non-aqueous redox-flow battery utilizing an anionic catholyte and thus also the first where only anionic or neutral redox active species are employed.

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