Nicole Pienack

In-situ monitoring of the formation of crystalline solids.

The processes occurring during the early stages of the formation of crystalline solids are not well understood thus preventing the rational synthesis of new solids. The investigation of the structure-forming processes is an enormous challenge for both analytical and theoretical methods because very small particles or aggregates with different chemical composition and different sizes must be probed, both before and during nucleation. Furthermore, these precursors are present in a complex and dynamic equilibrium. This Review gives a survey of the in-situ methods available for the study of the early stages of crystallization of solids and how they can help in the synthesis of metastable polymorphs, of transient intermediates, and/or precursors displaying new or improved properties. Examples of actual research demonstrate the necessity and potentials but also the limitations of in-situ monitoring of the formation of crystalline solids.

Review. Synthesis of Inorganic-Organic Hybrid Thiometallate Materials with a Special Focus on Thioantimonates and Thiostannates and in situ X-Ray Scattering Studies of their Formation

A rich variety of inorganic-organic hybrid thioantimonates and thiostannates were prepared during the last few years under solvothermal conditions applying organic amine molecules or transition metal complexes as structure directors. In this review synthetic approaches to and structural features of these thiometallates are discussed. For thioantimonates(III) the structures range from well isolated thioanions to three-dimensional networks, whereas the structural chemistry of thiostannates(IV) is strongly dominated by the [Sn2S6]4− anion, and no three-dimensional thiostannate has been reported so far. In the structures of thioantimonates(III) several primary building units like the [SbS3] trigonal pyramid, the [SbS4] unit or even the [SbS5] moiety are joined by vertex- and/or edge-linkages to form building blocks of higher structural hierarchy like [Sb3S4] semi-cubes or SbxSx heterocycles. A pronounced difference between thioantimonate and thiostannate chemistry is the tendency of Sb(III) to enhance the coordination geometry via so-called secondary bonds. In most cases the environment of Sb(III) is better described as a 3+n polyhedron with n = 1 - 3. The thioantimonate(V) structural chemistry is less rich than that of thioantimonates(III), and the [SbS4]3− anion shows no tendency for further condensation. By applying suitable multidentate amine molecules, transition metal cations which normally prefer bonding to the N atoms of the amines can be incorporated into the thiometallate frameworks Graphical Abstract Review. Synthesis of Inorganic-Organic Hybrid Thiometallate Materials with a Special Focus on Thioantimonates and Thiostannates and in situ X-Ray Scattering Studies of their Formation

The Layered Thiostannate (dienH2)Cu2Sn2S6: a Photoconductive Inorganic−Organic Hybrid Compound

The new inorganic-organic hybrid compound (dienH2)Cu2Sn2S6 (dien = diethylenetriamine) was synthesized under solvothermal conditions. It crystallizes in the tetragonal space group I4m2 with a = 7.8793(3) A, c = 24.9955(15) A, and V = 1551.80(13) A(3). The structure consists of anionic [Cu2Sn2S6](2-) layers extending in the (001) plane and protonated amine molecules as charge compensating ions sandwiched between the layers. The layered [Cu2Sn2S6](2-) anion is composed of a single layer of edge-sharing CuS4 tetrahedra which is joined above and below to straight chains constructed by corner-sharing SnS4 tetrahedra. The material is a semiconductor with an optical band gap of 1.51 eV. More interestingly, preliminary results demonstrate that the compound exhibits photoconductive properties with an increase of the conductivity by a factor of 3 when irradiated with UV light. Upon heating in an inert atmosphere the compound starts to decompose at about 256 degrees C.

The Interplay of Crystallization Kinetics and Morphology in Nanostructured W/Mo Oxide Formation: An in situ Diffraction Study†

The controlled and facile preparation of transition-metal oxide (TMO)nanomaterials is a challenging research topic of general interest, because the extraordinarily wide range of TMO applications needs to be opened up for nanotechnology. As hydrothermalmethodshavebeenprovena straightforward and technically flexible approach for the production of TMOs in general, they will play a major role in these technological trends. Despite their preparative elegance, hydrothermal processes are still difficult to control with respect to nanomaterials design, and this holds especially for the synthesis of ternary and higher functional oxides for the following reasons. Firstly, the prediction of hydrothermal products is often impossible due to a lack of general theoretical models and secondly, the structural and redox chemistry of higher-oxide systems is usually complicated, offering a wide variety of potential products. This renders the mechanistic investigation of hydrothermal reactions a key task of modern materials research. Therefore, wepresent kinetic hydrothermal studies on an important oxide model system. The additive-assisted morphology control of W/Mo hexagonal tungsten bronzes (HTBs) was monitored by in situ energy-dispersive X-ray diffraction (EDXRD) investigations to track down their formationmechanisms through a detailed study of the reaction kinetics. As the number of detailed mechanistic studies on hydrothermal oxide synthesis is still quite limited, getting new insights into such reactions is vital for the advanced development of hydrothermal processing.

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.

The Influence of the Amine Concentration onto Product Formation: Crystal Structures, Thermal Stability and Spectroscopic Properties of Two New Manganese Thiostannates Obtained under Solvothermal Conditions

Abstract Two new thiostannates with Mn2+ ions were obtained under solvothermal conditions applying different amine concentrations. [Mn(C6H14N2)2(H2O)]2Sn2S6 (1) (C6H14N2 = 1,2-diaminocyclohexane, 1,2-dach) crystallizes in the monoclinic space group C2/c (with a = 23.7500(18), b = 15.5655(16), c = 12.1072(9) Å , β = 113.532(8)°, Z = 8). The second compound, [Mn(C6H14N2)2]- Sn2S6 ・2 C6H15N2 (2), crystallizes in the triclinic space group P¯1 with a = 7.3019(6), b = 11.1798(9), c = 13.2837(11) Å , α = 76.877(10), β = 74.719(9), γ = 82.972(10)°, Z = 1. Both structures feature [Sn2S6]4− anions acting as bidentate ligands and joining the octahedrally coordinated Mn2+ cations, but in 1 a molecular complex is formed, whereas in 2 a one-dimensional coordination polymer is observed. In 1 the Mn2+ cation has bonds to four N atoms of two 1,2-dach ligands, to one H2O molecule, and to one S atom of the [Sn2S6]4− anion. The [Sn2S6]4− anion is located on a center of inversion joining two symmetry related complexes. In 2 Mn2+ is surrounded by four N atoms of two 1,2-dach ligands and by two S atoms of two neighboring [Sn2S6]4− anions. In contrast to 1 a negatively charged coordination polymer is formed with [Sn2S6]4− anions acting as linkers and the Mn2+ centered complexes being the nodes. The co-crystallized 1,2-dach molecules are protonated, and they are located between the chains. The first compound was obtained from diluted aqueous solutions of 1,2-dach, and 2 crystallized from solutions containing < 25% H2O. In both compounds several short S···H distances indicate weak hydrogen bonding interactions. Compound 1 is stable up to 121 °C and 2 up to 220 °C. In the Raman spectra of 1 and 2 resonances which are typical for [Sn2S6]4− units could be observed. The band gaps are found to be 2.6 eV (477 nm) and 3.1 eV (400 nm) for 1 and 2, respectively.