Biomedical subjects
Publications and source records attributed to Wolfgang Bensch.
The structures of the novel compounds K3Ln(AsS4)2 (Ln = Nd, Sm, Gd) contain infinite straight (1)infinity[Ln(AsS4)2]3- anionic chains which are composed of interconnected LnS8 polyhedra and AsS4 tetrahedra. The compounds were synthesized via reactions of Ln metals with in-situ-formed potassium polythioarsenate fluxes.
The intercalation reaction between Cr(4)TiSe(8) and Li was investigated from a kinetic and an electrochemical perspective. The structural phase transition from monoclinic to trigonal symmetry was probed by in situ energy-dispersive X-ray diffraction (in situ EDXRD) for chemical intercalation with butyllithium (BuLi). A change in the kinetic mechanism was detected for the reaction at room temperature; this was interpreted in terms of a trend from phase boundary control to diffusion control. A single diffusion-controlled mechanism is obeyed at 60 degrees C. The electrochemical measurements and the corresponding in situ X-ray diffraction (in situ XRD) data revealed that the monoclinic host is intercalated up to the composition Li(x approximately 0.1)Cr(4)TiSe(8) before the characteristic phase transition starts. The monoclinic phase undergoes complex structural changes in the following two-phase regime. Owing to the co-existence of two phases, the cell potential is constant for 0.1<x<0.7 and 0.9<x<3.0. The subsequent intercalation into the trigonal phase leads to a pronounced increase in the cell volume of the trigonal phase that stops at x approximately 0.8. At this point, the complete reduction of Ti(IV) gives rise to a voltage drop of the cell potential. XANES measurements revealed that the reduction of Ti(IV) occurs prior to the reduction of Cr(III).
The two novel compounds, [Mn(tren)]Sb2S4 (1 and 2), were obtained by the reaction of elemental Mn, Sb, and S in aqueous solutions of tren (tren = tris(2-aminoethyl)amine, C6H18N4) after different reaction times. Compound 1 is formed up to a reaction time of 13 d, and an extension of the reaction time leads to the formation of 2. Both compounds crystallize in monoclinic space groups (1, P2(1)/c; 2, C2/c). In 1, the two unique SbS3 trigonal pyramids share a common S atom to form a Sb2S5 unit. Two S atoms of this group have a bond to Mn2+ yielding a MnSb2S3 heteroring in the boat conformation. The Sb2S5 moieties are joined via common corners into the final undulated [Sb2S4]2- anion which is directed along [001]. The structure of 2 contains the [Mn(tren)]2+ ion, one SbS3 pyramid, and a SbS4 unit. Two symmetry-related SbS4 groups share an edge, forming a Sb2S6 group containing a Sb2S2 ring. This group is joined via corners to two SbS3 pyramids on both sides producing a Sb4S4 ring. The Sb2S2 and Sb4S4 rings are condensed into the final [Sb2S4]2- anion which runs along [010]. The [Mn(tren)] groups are bound to the thioantimonate(III) backbone on opposite sides of the Sb4S4 ring, and a small MnSbS2 ring is formed. In both structures, weak S...H bonds are found which may contribute to the stability of the materials. The two compounds decompose in one step upon heating, and only MnS and Sb2S3 could be identified as the crystalline part of the decomposition products. Both compounds can also be prepared under solvothermal conditions using MnSb2S4 as starting material. Compounds 1 and 2 are obtained from this ternary material in a high yield.
The reaction of Cr/Se multilayers when they are annealed occurs in two steps: interdiffusion of the single layers to an amorphous Cr-Se alloy and crystallization of Cr3Se4. Both reaction steps were characterized using various techniques. At approximately 300 degrees C the layers have interdiffused completely to form a homogeneous amorphous Cr-Se alloy. Short-range order in the alloy was probed with X-ray absorption spectroscopy (XAS) and, according to the results of this, is already very similar to Cr3Se4, which crystallizes around 500 degrees C. Crystallization occurs at a well-defined temperature, whereas crystallite growth proceeds in the whole temperature interval above the crystallization temperature and is not finished at 660 degrees C. The reaction yields a polycrystalline thin film of Cr3Se4 in a preferred orientation exhibiting a (00l) texture. In Cr-rich samples amorphous Cr is present as a by-product. A Cr-Se/Se multilayer was observed as an intermediate in the interdiffusion of some Cr-rich samples which is stable between 200 and 250 degrees C.
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The structures of the title complexes, (C6H15N2)2[MoS4], (I), and (C6H16N2)[MoS4], (II), can be described as consisting of discrete tetrahedral [MoS4]2- dianions that are linked to the organic ammonium cations via weak hydrogen-bonding interactions. The asymmetric unit of (I) consists of a single (+/-)-trans-2-aminocyclohexylammonium cation in a general position and an [MoS4]2- anion located on a twofold axis, while in (II), two crystallographically independent trans-cyclohexane-1,4-diammonium cations located on centres of inversion and one [MoS4]2- anion in a general position are found. The differing dispositions of the amine functionalities in the organic cations in the title complexes lead to different crystal packing arrangements in (I) and (II).
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Two new neutral thioantimonates(III) were first prepared by the reaction of elemental manganese, antimony, and sulfur in tren (tren = tris(2-aminoethyl)amine, C6H18N4) at 140 degrees C. In the amine-rich compound [Mn(tren)]2Sb2S5 (1) the trigonal SbS3 pyramids are connected via common corners (S(3)) into the tetradentate [Sb2S4]4- anion. Four S atoms have bonds to the manganese atoms of the [Mn(tren)2+] cations. A special structural feature is the large Sb-S(3)-Sb(a) angle of 134 degrees. Density functional calculations clearly demonstrate that this large angle results from the steric interactions between the two Mn(tren) subunits. In the crystal structure of the amine-poorer compound [Mn(tren)]2Mn2Sb4S10 (2), MnS4 tetrahedra and SbS3 pyramids are linked via common corners and edges to form a new heterometallic [Mn2Sb4S10] core. The [Mn(C6H18N4)2+] cations are located at the periphery of the core and are bound to the [Mn2Sb4S10] unit via two S atoms. The thermal behavior of both compounds was investigated using simultaneous thermogravimetry (TG), differential thermoanalysis, and mass spectroscopy. The amine-richer compound 1 decomposes in three steps upon heating. After the first TG step an intermediate phase is formed, which was identified as the amine-poorer compound 2 by X-ray diffraction. Reaction of compound 2 at 140 degrees C with an excess of tren forms the amine-rich compound 1.
The reaction of Ta with an in situ formed polythiophosphate melt of Cs2S3, P2S5, and S yields the two new quaternary tantalum thiophosphates Cs2Ta2P2S12 (I) and Cs4Ta4P4S24 (II). Both compounds were obtained with the same stoichiometric ratio but at different reaction temperatures. Compound I was prepared at 873 K and crystallizes in the monoclinic space group P2(1)/c (No. 14) with a = 8.862(2) A, b = 12.500(3) A, c = 17.408(4) A, beta = 99.23(3) degrees, and Z = 4. Compound II was prepared at 773 K and crystallizes in the monoclinic space group P2(1)/n (No. 14) with a = 14.298(3) A, b = 17.730(4) A, c = 16.058(3) A, beta = 106.19(3) degrees, and Z = 4. The two structures are closely related and exhibit two-dimensional anionic layers consisting of dimeric [Ta2S11] units which are linked by two tetradentate and two tridentate [PS4] tetrahedra. The significant difference between these two compounds is the orientation of the [Ta2S11] units in infinite [Ta2S4(PS4)]x chains which are subunits of both structures. The specific orientation of the [Ta2S11] blocks in compound I leads to the formation of one cavity in the 2(infinity)[Ta2P2S12]2- layers, whereas in compound II two types of cavities are observed in the 2(infinity)[Ta4P4S24]4- layers. The Cs+ ions are located between the layers above and below the cavities. The compounds were characterized with infrared spectroscopy in the MIR region, Raman spectroscopy, and UV/Vis diffuse reflectance spectroscopy. When Cs4Ta4P4S24 (II) is heated at the synthesis temperature of compound I it is fully converted into compound I.
The new quaternary group V thiophosphate K(4)VP(2)S(9) (tetrapotassium vanadium diphosphorus nonasulfide) was prepared by reacting a mixture of K(2)S(3), VP, P(4)S(3) and S. The crystal structure consists of discrete [VS(PS(4))(2)](4-) anions and K(+) cations. The V(4+) cation is in a fivefold coordination of S atoms which form a square-pyramidal environment. Each VS(5) group shares a common edge with two bidentate [PS(4)] tetrahedra, yielding the complete anion. The anions are stacked in the direction of the crystallographic b axis and are separated by the K(+) ions.
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The title complexes, (C(3)H(12)N(2))[WS(4)] and (C(6)H(18)N(2))[WS(4)], contain tetrahedral [WS(4)](2-) dianions, which accept a complex series of hydrogen bonds from the organic dications. The strength and number of these hydrogen bonds affect the W-S distances.
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Turquoise crystals of the title salt, propylammonium di-mu-thio-1:2 kappa(4)S-dithio-2 kappa(2)S-tris(2-aminoethyl)amine-1 kappa(4)N-antimony(V)nickel(II), (C(3)H(10)N)[NiSbS(4)(C(6)H(18)N(4))] or [PAH][Ni(tren)SbS(4)] [where tren is tris(2-aminoethyl)amine and PA is propylamine], were synthesized under solvothermal conditions by reacting [Ni(tren)(2)]Cl(2), Sb and S in a solution of PA. The Ni(II) ion is octahedrally surrounded by four N atoms of the tetradentate tren molecule and by two S atoms of the tetrahedral [Sb(V)S(4)](3-) anion, thus forming the anionic [Ni(tren)SbS(4)](-) part of the compound. Charge balance is achieved through the PAH(+) cation. An extended intermolecular hydrogen-bonding network is observed between the anion and the cation.
In the crystal structure of the title compound, [Ni(2)(C(4)H(4)O(6))(2)(H(2)O)(2)].3H(2)O, two nickel cations, two tartrate anions and two water molecules form the dimeric complex. Each nickel cation is in a distorted octahedral environment composed of four O atoms of two crystallographically independent tartrate anions, one water molecule and one O atom of a symmetry-equivalent tartrate anion. The asymmetric unit contains three additional water molecules which are connected via hydrogen bonding.
Both title compounds, bis[tris(2-aminoethyl)amine]nickel(II) dichloride, [Ni(tren)(2)]Cl(2), (I), and bis[tris(2-aminoethyl)amine]nickel(II) tetrathiotungstate, [Ni(tren)(2)]WS(4), (II), contain the [Ni(tren)(2)](2+) cation [tren is tris(2-aminoethyl)amine, C(6)H(18)N(4)]. The tren molecule acts as a tridentate ligand around the central Ni atom, with the remaining primary amine group not bound to the central atom. In (I), Ni(2+) is located on a centre of inversion surrounded by one crystallographically independent tren molecule. In the [Ni(tren)(2)](2+) cation of (II), the Ni atom is bound to two crystallographically independent tren molecules. The Ni atoms in the [Ni(tren)(2)](2+) complexes are in a distorted octahedral environment consisting of six N atoms from the chelating tren molecules. The counter-ions are chloride anions in (I) and the tetrahedral [WS(4)](2-) anion in (II). Hydrogen bonding is observed in both compounds.
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