Electrochemically initiated (retro)electrocyclization reactions have received much less attention compared to its photochemical equivalent. The few existing reports on electrochromic diarylethenes motivated us to investigate the redox properties of ()-1a and ()-1b. We hypothesized that their corresponding radical anions or dianions should undergo ring-opening as the product would gain substantial stabilization due to aromatization compared to their closed forms. The cyclovoltammogram (CV) of diketone ()-1a-C shows a reversible reduction at Ered,1 = -2.00 V (vs. Fc/Fc + , scan rate: 1 V s -1 ) and a second irreversible reduction at Ered,2 = -2.28 V. An additional anodic product peak at a potential of -0.7 V is observed after sweeping towards a positive potential (Figure ). We followed these electrochemical processes using in situ UV/Vis spectroscopy (scan rate: 10 mV s -1 ). Upon sweeping to the first reduction potential Ered,1, the absorption profile changes with defined isosbestic points and a new absorption band arises between 700-900 nm (Figure ). This band can be assigned to the radical anion ()-1a-C •-, which is continuously produced and exists prior to the subsequent second reduction to give the open form dianion ()-1a-O 2-with a new absorption maximum at 460 nm (for the detailed electrochemical mechanism, see the Supporting Information Schemes S1, S2). This is further supported by the comparison of the experimentally observed UV/Vis absorption spectrum of the reduced dianion and the spectra obtained from TD-DFT calculations for 1a-O 2-(Figure ). Upon inverting the potential in CV, the dianion ()-1a-O 2-is stable up to an onset potential of -1.0 V vs. Fc/Fc + where an anodic current is observed and the intermediate is reoxidized to regain the closed form ()-1a-C (Figure ). Bis(dicyanomethylidene) ()-1b-C shows an equivalent electrochemicaly induced switching. The CV trace shows one irreversible reduction wave at Ered,1 = -1.32 V vs. Fc/Fc + exclusively (scan rate: 1 V s -1 ), which we assign to a twoelectron transfer and the direct formation of the open dianion ()-1b-O 2-(Figure ), again supported by the calculated TD-DFT spectra (Figure ). Here, the radical anion spontaneously opens to 1b-O ⋅-and the second reduction, confirmed by quantitative electrolysis, occurs instantly under potential inversion conditions. The open dianion is stable up to an anodic onset potential of -0.4 V, where back-oxidation leads to electrocyclization reforming the neutral closed ()-1b-C. This is in accordance with our observation in spectroelectrochemistry (scan rate: 10 mV s - 1 ) where no absorption of a transient radical anion species arises above 550 nm upon reduction (Figure ). Analogous to the diketone, the absorption spectrum of the closed form ()-1b-C is fully recovered after anodic oxidation (Figure ). We further discuss the detailed mechanisms of the ongoing electrochemical processes at different sweep rates in the Supporting Information (Section S9). Finally, we aimed for an unambiguous structural proof for the electrochemical retroelectrocyclization product under quantitative electrolysis. Coulometric reduction and subsequent oxidation in combination with HPLC analysis allowed us to determine the structure of the electrochemically generated open intermediate and the reoxidized closed form (Figure ). The gross charge of the reductive coulometric process was determined as a twoelectron process for both, (±)-1a-C and (±)-1b-C, with a quantified 78% and 72% reoxidation, respectively. Taking aliquots of the intermediate quantitative reduction product for subsequent HPLC analysis with a protic mobile phase confirmed the formation of the open form (±)-1b-O-H2 by comparison with the analytical data of an authentic isolated sample obtained from the stepwise synthesis towards (±)-1b-C (HPLC retention time, see Figure , and UV/Vis absorption spectra, Figures ). The oxidative coulometric recovery of (±)-1b-C was again confirmed using the same methods. For the reduction of diketone (±)-1a-C, no open intermediate could be trapped due to the spontaneous occurrence of electrocyclization analogously to Scheme 1. Nevertheless, full reversibility of the coulometric reduction and reoxidation to (±)-1a-C was confirmed by HPLC analysis (Figure ). In both coulometric experiments with (±)-1a-C and (±)-1b-C, no significant sideproducts were observed. We demonstrated the concept of photochemical spin state switching between a diamagnetic EPR silent and a paramagnetic EPR active form of a dimethyl [5] during a quantitative electrolysis experiment. Our findings are supported by CASSCF calculations that revealed the energetic level and the diracaloid character indices of the closed-and open-shell states of each form participating in the switching. This system establishes the concept of photoswitching between different bistable spin states through chemical reactivity -unrelated to conformational stabilization-induced by light and thermal energy. We envision that the presented 4,11-substitution pattern of radical-stabilizing groups in conjunction with the 1,14dimethyl groups at the [5]helicene core has the potential for tuning various parameters of this spin state switch system through a wide range of future derivatizations. Towards this end, our laboratory will further report on substituent effects in various patterns and their influence towards favored spin states, suppressing the thermal back reaction and increasing the temperature of bistable operation in due course. The enantiopure intermediates (M/P)-2 afford synthetic access to exploit future chiroptical spin state switching and chiral recognition for sensing applications with an additional information bit. The presented concept of induced spin state switching through bond breaking and making could serve the future demand on single-molecule magnets for applications in spintronics, data storage devices, and quantum computing. The Supporting Information is available via ChemRxiv. N.G. was supported by a doctoral fellowship of the Fonds der Chemischen Industrie (FCI) and O.D. thanks the FCI for a generous Liebig scholarship. This work was supported by a Joint Seed Fund between the Humboldt-Universität zu Berlin and the Universität Zürich, Switzerland.