Low dimensional solids based on Mo-6 cluster cyanides and Mn2+, Mn3+ or Cd2+ metal ions crystal chemistry, magnetic and optical properties

International audienceFive new cluster compounds based on [Mo6Br8i(CN)(a)(6)](2-) and [Mo(6)Br(6)(i)Q(2)(i)(CN)(a)(6)](n-) (Q = S, Se, n = 3, 4) cluster units have been synthesized and characterized. Structures were determined by X-ray single crystal diffraction techniques and measurements of relevant magnetic susceptibility and optical properties were carried out. [trans-Mn(H2O)(2)][Mo6Br8(CN)(6)] (1) crystallizes in the orthorhombic system (Imma space group) and contains 2D square-net-layers built-up from [Mo6Br8i(CN)(a)(6)](2-) and [trans-M(H2O)(2)](2+) moieties. Cs-x[trans-((MnxMn1-xIII)-Mn-II)(H2O)(2)][Mo(6)Br(6)Q(2)(CN)(6)] (Q = S (2) and Se (3)) crystallize in the Imma space group as well; their structures are strongly related to that of 1 with a 2D square net of cluster units and transition metals. They are based on [Mo(6)Br(6)(i)Q(2)(i)(CN)(a)(6)](3-) (Q = S, Se) cluster units whose charge is counter balanced by Cs+ as well as Mn2+ and Mn3+ in high spin states. It is evidenced that the x content of the Cs+ counter-cation is equal to that of Mn2+ in order to maintain - along with (1 - x) Mn3+ - 23 valence electrons per cluster and a 3- charge for the cluster unit. The two oxidation states Mn2+ and Mn3+ were confirmed by electron energy loss spectroscopy (EELS) measurements. (H3O)H[cis-Cd(H2O)(2)][Mo(6)Br(6)Q(2)(CN)(6)]-H2O (Q = S (4) and Se (5)) crystallize in the trigonal system (P3(1)21 space group) and are based on [Mo(6)Br(6)(i)Q(2)(i)(CN)(a)(6)](4-) (Q = S, Se) cluster units. In contrast to compounds 1-3, owing to the cis-position of the two water molecules around the transition metal, 4 and 5 exhibit a close-packed 3D structure based on an interpenetrated framework of cluster-based chains. In particular, it contains infinite chains alternating [Mo(6)Br(6)(i)Q(2)(i)(CN)(a)(6)](4-) and H+ protons as linkers. Magnetic and optical properties are also reported as well as theoretical calculations to support the structural analysis and physical properties. Structural analogies with [Re(6)Q(8)(i)(CN)(a)(6)](4-) based compounds are discussed