Biological water splitting occurs at the oxygen-evolving complex (OEC) of photosystem II (PSII). Nowadays the laboratory synthesis of an artificial OEC has been the objective of many synthetic chemists. Particular attention has been given to mixed manganese-calcium compounds aimed to shed light on the tetranuclear arrangement of the manganese centers in the OEC [1]. However, at present, there are only several examples of such clusters that involve both calcium and manganese ions and only some of them have an isolated [Mn4Ca] node. Moreover, by 2013 only two Mn/Ca heteroplynuclear complexes were reported in which the manganese ions are in mixed-valent [MnIVMnIII 10MnII 2] [2] and [MnIII 3MnII] [3] oxidation states. In this communication we present a synthetic route to the mixed-valence Mn-Ca cluster [{Mn3 II,IIIO(CHCl2COO)6(H2O)}Ca(CHCl2COO)2(H2O)4] (1). The cluster was synthesized by the reaction of Mn(II) acetate, dichloroacetic acid, Ca(ClO4)2·4H2O and N-n-Bu4MnO4 in the mixture of ethanol and acetonitrile. It was analysed by X-ray crystallography, IR spectroscopy and cyclic voltammetry methods. The complex crystallizes in the monoclinic space group P21/n. The asymmetric unit of 1, as depicted in Fig. 1, consists of an oxo-centered trinuclear [Mn3(μ3-O)]6+ core and an [Ca(H2O)4]2+ moiety. The manganese ions of the mixed-valent [MnIIMnIII 2O]6+ core are bridged by six dichloroacetate ligands. The [Ca(H2O)4]2+ moiety is bridged by Mn through a dichloroacetate ligand. The cyclic voltammogram of (1) exhibits a reversibe one-electron oxidation wave at vs Ag/AgCl (Fig. 2).