It has recently been proposed that disulfide/thiolate interconversion supported by transition-metal ions is involved in several relevant biological processes. In this context, the present contribution represents a unique investigation of the effect of the coordinated metal (M) on the M(n+)-disulfide/M((n+1)+)-thiolate switch properties. Like its isostructural Co(II)-based parent compound, Co(II)2SS (Angew. Chem. Int. Ed.- 2014, 53, 5318), the new dinuclear disulfide-bridged Mn(II) complex Mn(II)2SS can undergo an M(II)-disulfide/M(III)-thiolate interconversion, which leads to the first disulfide/thiolate switch based on Mn. The coordination of iodide to the metal ion stabilizes the oxidized form, as the disulfide is reduced to the thiolate. The reverse process, which involves the reduction of M(III) to M(II) with the concomitant oxidation of the thiolates, requires the release of iodide. The Mn(II)2SS complex slowly reacts with Bu4NI in CH2Cl2 to afford the mononuclear Mn(III)-thiolate complex Mn(III)I. The process is much slower (ca. 16 h) and much less efficient (ca. 30% yield) with respect to the instantaneous and quantitative conversion of Co(II)2SS into Co(III)I under similar conditions. This distinctive behavior can be rationalized by considering the different electrochemical properties of the involved Co and Mn complexes and the DFT-calculated driving force of the disulfide/thiolate conversion. For both Mn and Co systems, M(II)-disulfide/M(III)-thiolate interconversion is reversible. However, when the iodide is removed with Ag(+), the M(II)2SS complexes are regenerated, albeit much slower for Mn than for Co systems.

What is the most significant result of this study? We report on the experimental and theoretical investigation of the magnetic behavior for as eries of Co III complexes displaying an intermediate S = 1s pin state. The magnetic anisotropy of these complexes , the zero-field splitting parameter (D), shows ad ependence on the nature of the halide:t he largest D value was obtained for the chloride compound and the smallest for the iodide one. Examples of such reported behavior are still very limited and in most of studies, it was observed that the D value increases from the chloride to the iodide metal complexes. By using quantum chemical methods (DFT and CASSCF calculations), we were able to predict and rationalize both the sign and magnitude of D for the three complexes. The DFT method appears as the most appropriate method if one wants to obtain structure-property relationships. No general rule can be extrapolated from the present study and magneto-structural correlations can only be defined though benchmark studies using ac ombination of experimental and theoretical approaches.

What is the most significant result of this study?We report on the experimental and theoretical investigation of the magnetic behavior for as eries of Co III complexes displaying an intermediate S = 1s pin state. The magnetic anisotropy of these complexes, the zero-field splitting parameter (D), shows ad ependence on the nature of the halide:t he largest D value was obtained for the chloride compound and the smallest for the iodide one. Examples of such reported behavior are still very limited and in most of studies, it was observed that the D value increases from the chloride to the iodide metal complexes. By using quantum chemical methods (DFT and CASSCF calculations), we were able to predict and rationalize both the sign and magnitude of D for the three complexes. The DFT method appears as the most appropriate method if one wants to obtain structure-property relationships. No general rule can be extrapolated from the present study and magneto-structural correlations can only be defined though benchmark studies using ac ombination of experimental and theoretical approaches.

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