Henning Lühmann

Unprecedented layered inorganic-organic hybrid compound Mn(3)Sb(2)S(6)(C(6)H(18)N(4)) composed of Mn(4)Sb(2)S(6) double-cubane units showing magnetic long-range order and frustration.

The title compound Mn(3)Sb(2)S(6)(C(6)H(18)N(4)) (C(6)H(18)N(4) = triethylenetetramine) was obtained under solvothermal conditions by reacting Mn, Sb, S, and the amine at 140 degrees C for 7 days. The compound crystallizes in the triclinic space group P1 with a = 6.645(1) A, b = 8.667(1) A, c = 9.660(1) A, alpha = 90.82(2) degrees , beta = 109.70(2) degrees , gamma = 110.68(2) degrees , Z = 1, and V = 484.4(1) A(3). The Mn(4)Sb(2)S(6) double-heterocubane unit is the main motif in the structure of the title compound, which results from the interconnection of two SbS(3) trigonal pyramids, two MnS(6) octahedra, and two MnS(4)N(2) octahedra. The two N atoms completing the environment of the latter Mn(2+) ions belong to the tetradentate amine; i.e., the amine acts in a bidentate manner. The Mn(4)Sb(2)S(6) groups are joined by corner sharing of the MnS(6) octahedra, yielding one-dimensional linear Mn(3)Sb(2)S(6) rods along [100]. The two other N atoms of the amine molecule act in a bidentate manner to Mn(2+) ions of neighboring rods, thus producing layers within the (010) plane. Within the rods, the arrangement of the Mn(2+) ions in triangles leads to a chain of Mn(2+) diamonds connected via opposite corners. For the magnetic properties, each edge connecting the Mn(2+) ions represents a superexchange path due to coupling of the Mn(2+) centers via S bridges. The resulting Mn(2+) triangles give rise to substantial competing interaction and magnetic frustration. Below about 100 K, a gradual buildup of short-range antiferromagnetic correlations is observed. At lower temperatures, long-range antiferromagnetic interactions occur with T(N) = 2.90 K, as indicated by a lambda-type anomaly in the heat capacity curve. The analysis of the magnetic and heat capacity data evidences that the magnetic properties are essentially determined by the one-dimensional character of the Mn(3)Sb(2)S(6) chain. In addition, significant magnetic frustration due to the arrangement of the Mn(2+) ions in a triangular configuration cannot be neglected.

New Thiostannates Synthesized Under Solvothermal Conditions: Crystal Structures of (trenH)2Sn3S7 and {(Mn(tren))2Sn2S6}

The two new thiostannate compounds (trenH)2Sn3S7 (1) and {[Mn(tren)]2Sn2S6} (2) (tren=tris-2-aminoethylamine) were obtained under solvothermal conditions. Compound 1 crystallizes in the hexagonal space group P63/mmc with a=13.2642(19), c=19.078(3) Å, V =2906.9(7) Å3. The layered [Sn3S7]2- anion is constructed by Sn3S4 semi-cubes sharing common edges. The layers are characterized by large hexagonal pores with dimensions of about 11×11 Å2. Compound 2 crystallizes in the triclinic space group P1̄ with lattice parameters a=7.6485(7), b=8.1062(7), c=12.1805(11) Å, α =97.367(11), β =103.995(11), γ = 108:762(10)°, V =676.17(10) Å3. The [Sn2S6]4- anion is composed of two edge-sharing SnS4 tetrahedra and joins two Mn2+-centered complexes by Mn-S bond formation. The Mn2+ cation is in a trigonal-bipyramidal environment of four N atoms of the tren ligand and one S atom of the thiostannate anion. Both compounds are semiconductors with a band gap of 2:96 eV for 1 and of 2:75 eV for 2. Graphical Abstract New Thiostannates Synthesized Under Solvothermal Conditions: Crystal Structures of (trenH)2Sn3S7 and {[Mn(tren)]2Sn2S6}

Two Pseudopolymorphic Star-Shaped Tetranuclear Co3+ Compounds with Disulfide Anions Exhibiting Two Different Connection Modes and Promising Photocatalytic Properties

The compound [Co4(C6H14N2)4(μ4-S2)2(μ2-S2)4] (I) and the pseudo-polymorph [Co4(C6H14N2)4(μ4-S2)2(μ2-S2)4]⋅4 H2O (II) were obtained under solvothermal conditions (C6H14N2=trans-1,2-diaminocyclohexane). The structures feature S2(2-) ions exhibiting two different coordination modes. Terminal S2(2-) entities join two Co(3+) centres in a μ2 fashion, whereas the central S2(2-) groups connect four Co(3+) cations in a μ4-coordination mode. Compound II can be transformed into compound I by heat and storage over P2O5 and storing compound I in humid air yields in the formation of compound II. The intermolecular interactions investigated through Hirshfeld surface analysis reveal that besides S⋅⋅⋅H bonding close contacts are associated with relatively weak H⋅⋅⋅H interactions. A detailed DFT analysis of the bonding situation explains the long S-S bonds in the μ4-bridging S2(2-) units and the short bonds for the S2(2-) moieties in the μ2-connecting mode. Photocatalytic hydrogen evolution experiments demonstrate the potential of compound II as catalyst.