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The quasibinary section of the intermetallic phases MAl4 and MGa4 with M=Sr and Ba have been characterised by means of X-ray diffraction (XRD) studies and differential thermal analysis. The binary phases show complete miscibility and form solid solutions M(Al1− xGa x)4 with M=Sr and Ba. These structures crystallise in the BaAl4 structure type with four- and five-bonded Al and/or Ga atoms (denoted as Al(4b), Al(5b), Ga(4b), and Ga(5b), respectively) that form a polyanionic Al/Ga sublattice. Solid state 27Al NMR spectroscopic analysis and quantum mechanical (QM) calculations were applied to study the bonding of the Al centres and the influence of Al/Ga substitution, especially in the regimes with low degrees of substitution. M(Al1− xGa x)4 with M=Sr and Ba and 0.925≤ x≤0.975 can be described as a matrix of the binary majority compound in which a low amount of the Ga atoms has been substituted by Al atoms. In good agreement with the QM calculations, 27Al NMR investigations and single crystal XRD studies prove a preferred occupancy of Al(4b) for these substitution regimes. Furthermore, two different local Al environments were found, namely isolated Al(4b1) atoms and Al(4b2), due to the formation of Al(4b)-Al(4b) pairs besides isolated Al(4b) atoms within the polyanionic sublattice. QM calculations of the electric field gradient (EFG) using superlattice structures under periodic boundary conditions are in good agreement with the NMR spectroscopic results. [ABSTRACT FROM AUTHOR]

Complete miscibility of the intermetallic phases (IPs) SrGa2 and BaGa2 forming the solid solution Sr1− xBa xGa2 is shown by means of X-ray diffraction, thermoanalytical and metallographic studies. Regarding the distances of Sr/Ba sites versus substitution degree, a model of isolated substitution centres (ISC) for up to 10 % cation substitution is explored to study the influence on the Ga bonding situation. A combined application of NMR spectroscopy and quantum mechanical (QM) calculations proves the electric field gradient (EFG) to be a sensitive measure of different bonding situations. The experimental resolution is boosted by orientation-dependent NMR on magnetically aligned powder samples, revealing in first approximation two different Ga species in the ISC regimes. EFG calculations using superlattice structures within periodic boundary conditions are in fair agreement with the NMR spectroscopy data and are discussed in detail regarding their application on disordered IPs. [ABSTRACT FROM AUTHOR]

In catena-poly[copper(II)-di-μ-chlorido-μ-proline-κ2 O: O′], [CuCl2(C5H9NO2)] n, two symmetry-independent metal cations adopt distorted octahedral coordination, typical for d9 Jahn-Teller systems. Each chloride bridge is involved in both a short and a very long interaction with a CuII centre. The centrosymmetric crystal structure contains homochiral chains of opposite handedness which extend along the shortest lattice parameter ( i.e. a). The O: O′-bridging coordination mode of proline, although a common motif for such complexes in general, is remarkable for CuII; the vast majority of amino acid derivatives of this cation are characterized by N, O-chelation. [ABSTRACT FROM AUTHOR]

In catena-poly[copper(II)-di-μ-chlorido-μ-proline-κ2 O: O′], [CuCl2(C5H9NO2)] n, two symmetry-independent metal cations adopt distorted octahedral coordination, typical for d9 Jahn-Teller systems. Each chloride bridge is involved in both a short and a very long interaction with a CuII centre. The centrosymmetric crystal structure contains homochiral chains of opposite handedness which extend along the shortest lattice parameter ( i.e. a). The O: O′-bridging coordination mode of proline, although a common motif for such complexes in general, is remarkable for CuII; the vast majority of amino acid derivatives of this cation are characterized by N, O-chelation. [ABSTRACT FROM AUTHOR]

Four new structures based on CaCl2 and proline are reported, all with an unusual Cl-Ca-Cl moiety. Depending on the stoichiometry and the chirality of the amino acid, this metal dihalide fragment represents the core of a mononuclear Ca complex or may be linked by the carboxylate to form extended structures. A cisoid coordination of the halide atoms at the calcium cation is encountered in a chain polymer. In the 2D structures, CaCl2 dumbbells act as nodes and are crosslinked by either enantiomerically pure or racemic proline to form square lattice nets. Extensive database searches and topology tests prove that this structure type is rare for MCl2 dumbbells in general and unprecedented for Ca compounds. [ABSTRACT FROM AUTHOR]

Reactions of manganese(II) chloride, bromide and iodide with proline as an enantiopure and racemic ligand result in six crystalline solids for which diffraction experiments have been performed at 100 K. For two of these compounds, crystal structures at ambient temperature had been reported previously. The most surprising outcome of our systematic comparison lies in the role of chirality: with enantiopure proline three different coordination polymers have been obtained, whereas racemic proline yields isomorphous mononuclear complexes under the same reaction conditions. [ABSTRACT FROM AUTHOR]

The quasibinary section of the intermetallic phases MAl 4 and MGa 4 with M=Sr and Ba have been characterised by means of X-ray diffraction (XRD) studies and differential thermal analysis. The binary phases show complete miscibility and form solid solutions M(Al 1-x Ga x ) 4 with M=Sr and Ba. These structures crystallise in the BaAl 4 structure type with four- and five-bonded Al and/or Ga atoms (denoted as Al(4b), Al(5b), Ga(4b), and Ga(5b), respectively) that form a polyanionic Al/Ga sublattice. Solid state 27 Al NMR spectroscopic analysis and quantum mechanical (QM) calculations were applied to study the bonding of the Al centres and the influence of Al/Ga substitution, especially in the regimes with low degrees of substitution. M(Al 1-x Ga x ) 4 with M=Sr and Ba and 0.925≤x≤0.975 can be described as a matrix of the binary majority compound in which a low amount of the Ga atoms has been substituted by Al atoms. In good agreement with the QM calculations, 27 Al NMR investigations and single crystal XRD studies prove a preferred occupancy of Al(4b) for these substitution regimes. Furthermore, two different local Al environments were found, namely isolated Al(4b1) atoms and Al(4b2), due to the formation of Al(4b)-Al(4b) pairs besides isolated Al(4b) atoms within the polyanionic sublattice. QM calculations of the electric field gradient (EFG) using superlattice structures under periodic boundary conditions are in good agreement with the NMR spectroscopic results., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Complete miscibility of the intermetallic phases (IPs) SrGa2 and BaGa2 forming the solid solution Sr(1-x)Ba(x)Ga2 is shown by means of X-ray diffraction, thermoanalytical and metallographic studies. Regarding the distances of Sr/Ba sites versus substitution degree, a model of isolated substitution centres (ISC) for up to 10% cation substitution is explored to study the influence on the Ga bonding situation. A combined application of NMR spectroscopy and quantum mechanical (QM) calculations proves the electric field gradient (EFG) to be a sensitive measure of different bonding situations. The experimental resolution is boosted by orientation-dependent NMR on magnetically aligned powder samples, revealing in first approximation two different Ga species in the ISC regimes. EFG calculations using superlattice structures within periodic boundary conditions are in fair agreement with the NMR spectroscopy data and are discussed in detail regarding their application on disordered IPs., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Completing our reports concerning the reaction products from calcium halides and the amino acid proline, two different solids were found for the reaction of l- and dl-proline with CaI2. The enanti-opure amino acid yields the one-dimensional coordination polymer catena-poly[[aqua-μ3-l-proline-tetra-μ2-l-proline-dicalcium] tetra-iodide 1.7-hydrate], {[Ca2(C5H9NO2)5(H2O)]I4·1.7H2O} n , (1), with two independent Ca(2+) cations in characteristic seven- and eightfold coordination. Five symmetry-independent zwitterionic l-proline mol-ecules bridge the metal sites into a cationic polymer. Racemic proline forms with Ca(2+) cations heterochiral chains of the one-dimensional polymer catena-poly[[di-aquadi-μ2-dl-proline-calcium] diiodide], {[Ca(C5H9NO2)2(H2O)2]I2} n , (2). The centrosymmetric structure is built by one Ca(2+) cation that is bridged towards its symmetry equivalents by two zwitterionic proline mol-ecules. In both structures, the iodide ions remain non-coordinating and hydrogen bonds are formed between these counter-anions, the amino groups, coordinating and co-crystallized water mol-ecules. While the overall composition of (1) and (2) is in line with other structures from calcium halides and amino acids, the diversity of the carboxyl-ate coordination geometry is quite surprising.

Reactions of manganese(II) chloride, bromide and iodide with proline as an enantiopure and racemic ligand result in six crystalline solids for which diffraction experiments have been performed at 100 K. For two of these compounds, crystal structures at ambient temperature had been reported previously. The most surprising outcome of our systematic comparison lies in the role of chirality: with enantiopure proline three different coordination polymers have been obtained, whereas racemic proline yields isomorphous mononuclear complexes under the same reaction conditions.