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Leibniz Institute for Science and Mathematics Education, Kiel

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  • Articles  (47)
  • 1
    Publication Date: 2018-03-09
    Description: Due to their rich structural chemistry and wide variety of applications, borate materials have provided a rich area of research. In a continuation of this research, diethylammonium bis(2-oxidobenzoato-κ 2 O 1 , O 2 )borate, C 4 H 12 N + ·BO 4 (C 7 H 4 O) 2 − , (1), and propylammonium bis(2-oxidobenzoato-κ 2 O 1 , O 2 )borate, C 3 H 10 N + ·BO 4 (C 7 H 4 O) 2 − , (2), have been synthesized by the reaction of boric acid with salicylic acid under ambient conditions. In both structures, the B atom exhibits a slightly distorted tetrahedral environment formed by the bidentate coordination of two salicylate anions via the O atoms of the central carboxylate and oxide groups. In the crystals of salts (1) and (2), mixed cation–anion layers lying parallel to the (101) plane are formed through N—H…O, C—H…O and C—H…π/N—H…O hydrogen-bonding interactions, resulting, in each case, in a two-dimensional supramolecular architecture in the solid state. The photoluminescence properties of the salts were studied using the as-synthesized samples and reveal that salts (1) and (2) both display a strong blue-light emission, with maxima at 489 and 491 nm, respectively. In DFT/TD–DFT (time-dependent density functional theory) studies, the blue emission appears to be derived from an intramolecular charge transfer (ICT) excited state. In addition, IR and UV–Vis spectroscopies were used to investigate the title salts. The synthesis and structural determination of the diethylammonium and propylammonium salts of bis(salicylato)borate are reported. The crystal structures are stabilized by N—H…O, C—H…O and C—H…π/N—H…O hydrogen bonds. The salts displays a strong blue-light emission with maxima around 490 nm which appears to be derived from the intramolecular charge transfer (ICT) excited state.
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  • 2
    Publication Date: 2018-03-09
    Description: A detailed structural analysis of the benzimidazole nitroarenes 1-(4-nitrophenyl)-1 H -1,3-benzimidazole, C 13 H 9 N 3 O 2 , (I), 1-(4-nitrophenyl)-2-phenyl-1 H -1,3-benzimidazole, C 19 H 13 N 3 O 2 , (II), and 2-(3-methylphenyl)-1-(4-nitrophenyl)-1 H -1,3-benzimidazole, C 20 H 15 N 3 O 2 , (III), has been performed. They are nonplanar structures whose crystal arrangement is governed by C sp 2 —H… A ( A = NO 2 , N py and π) hydrogen bonding. The inherent complexity of the supramolecular arrangements of compounds (I) ( Z ′ = 2) and (II) ( Z ′ = 4) into tapes, helices and sheets is the result of the additional participation of π– and n –π* ( n = O and N py ; π* = C sp 2 and ) interactions that contribute to the stabilization of the equi-energetic conformations adopted by each of the independent molecules in the asymmetric unit. In contrast, compound (III) ( Z ′ = 1) is self-paired, probably due to the effect of the steric demand of the methyl group on the crystal packing. Theoretical ab initio calculations confirmed that the presence of the arene ring at the benzimidazole 2-position increases the rotational barrier of the nitrobenzene ring and also supports the electrostatic nature of the orthogonal ONO…C sp 2 and N py …NO 2 interactions. Participation of π– and n –π* ( n = O and N py ; π* = C sp 2 and ) interactions in the equi-energetic conformations of 1-(4-nitrophenyl)-1 H -1,3-benzimidazoles.
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  • 3
    Publication Date: 2018-03-09
    Description: During our studies of urea and thiourea adducts, we noticed that no adducts with unsubstituted pyridine had been structurally investigated. The 1:1 adduct of pyridine and urea, C 5 H 5 N·CH 4 N 2 O, crystallizes in the P 2 1 / c space group with Z  = 4. The structure is of a standard type for urea adducts, whereby the urea molecules form a ribbon, parallel to the a axis, consisting of linked R 2 2 (8) rings, and the pyridine molecules are attached to the periphery of the ribbon by bifurcated (N—H…) 2 N hydrogen bonds. The 1:1 adduct of pyridine and thiourea, C 5 H 5 N·CH 4 N 2 S, crystallizes in the P 2 1 / n space group, with Z = 32 ( Z ′ = 8). The structure displays similar ribbons to those of the urea adduct. There are two independent ribbons parallel to the b axis at z ≃ 0 and , and three at z ≃ and ; the latter are crosslinked to form a layer structure by additional long N—H…S interactions, which each formally replace one branch of a bifurcated hydrogen-bond system. The 1:1 adduct of pyridine and urea crystallizes in the P 2 1 / c space group with Z = 4 ( Z ′ = 1). The structure is of a standard type for urea adducts, whereby the urea molecules form a ribbon consisting of linked (8) rings and the pyridine molecules are attached to the periphery of the ribbon by bifurcated (N—H…) 2 N hydrogen bonds. The 1:1 adduct of pyridine and thiourea crystallizes in the P 2 1 / n space group with Z = 32 ( Z ′ = 8). The structure displays similar ribbons to those of the urea adduct.
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  • 4
    Publication Date: 2018-03-09
    Description: The design and synthesis of coordination polymers (CPs) have attracted much interest due to the intriguing diversity of their architectures and topologies. The functional solid catena -poly[μ 2 -aqua-triaqua{μ 4 -5-[4-carboxyphenoxy)methyl]benzene-1,3-dicarboxylato}{μ 3 -5-[4-carboxyphenoxy)methyl]benzene-1,3-dicarboxylato}dicobalt(II)], [Co 2 (C 16 H 10 O 7 ) 2 (H 2 O) 4 ] n or [Co 2 (H L ) 2 (μ 2 -H 2 O)(H 2 O) 3 ] n , was synthesized successfully by self-assembly of Co II ions with 5-[(4-carboxyphenoxy)methyl]isophthalic acid (H 3 L ). The title compound was obtained under hydrothermal conditions and exhibits a twofold interpenetrated three-dimensional skeleton with hms 3,5-conn topology according to the cluster representation for valence-bonded metal–organic frameworks (MOFs). It has been characterized by single-crystal X-ray diffraction, IR spectroscopy, powder X-ray diffraction (PXRD), thermogravimetric analysis and susceptibility measurements. The antiferromagnetic coupling between adjacent Co II centres occurs via superexchange through the ligands. A novel Co II -containing twofold interpenetrated coordination polymer was assembled with the flexible ligand 5-[(4-carboxyphenoxy)methyl]isophthalic acid. The polymer adopts a (3,5)-connected topology and shows antiferromagnetic interactions between the two Co II cations in the asymmetric unit.
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  • 5
    Publication Date: 2018-03-09
    Description: Hydrazones and their derivatives are closely related to imine compounds and are potential antimicrobial agents. They have also found application in supramolecular chemistry as multitopic ligands to link multiple metal centres for the design of hybrid molecular frameworks. The molecule of the title compound, C 6 H 8 N 4 , consists of an imine linkage with an N—N bond length of 1.3540 (14) Å. This asymmetric compound is nearly planar and adopts an E configuration about the azomethine C=N double bond. In the solid state, there are two intermolecular N—H…N interactions that interconnect the molecules into a two-dimensional network. The three-dimensional arrangement of the crystal packing is further stabilized by intermolecular π–π interactions interconnecting the centroids of the heterocyclic rings. The molecule [1-(pyrazin-2-yl)ethylidene]hydrazine consists of an imine linkage with an N—N bond length of 1.3540 (14) Å. This asymmetric compound is nearly planar and adopts an E configuration about the azomethine C=N double bond. In the solid state, there are two intermolecular N—H…N interactions that interconnect the molecules into a two-dimensional network.
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  • 6
    Publication Date: 2018-02-28
    Description: The search for new tuberculostatics is an important issue due to the increasing resistance of Mycobacterium tuberculosis to existing agents and the resulting spread of the pathogen. Heteroaryldithiocarbazic acid derivatives have shown potential tuberculostatic activity and investigations of the structural aspects of these compounds are thus of interest. Three new examples have been synthesized. The structure of methyl 2-[amino(pyridin-3-yl)methylidene]hydrazinecarbodithioate, C 8 H 10 N 4 S 2 , at 293 K has monoclinic ( P 2 1 / n ) symmetry. It is of interest with respect to antibacterial properties. The structure displays N—H…N and N—H…S hydrogen bonding. The structure of N ′-(pyrrolidine-1-carbonothioyl)picolinohydrazonamide, C 11 H 15 N 5 S, at 100 K has monoclinic ( P 2 1 / n ) symmetry and is also of interest with respect to antibacterial properties. The structure displays N—H…S hydrogen bonding. The structure of ( Z )-methyl 2-[amino(pyridin-2-yl)methylidene]-1-methylhydrazinecarbodithioate, C 9 H 13 N 4 S 2 , has triclinic ( P ) symmetry. The structure displays N—H…S hydrogen bonding. The structures of three new potentially tuberculostatic compounds were determined by X-ray diffraction. Their activities against other Gram-positive bacteria were also determined.
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  • 7
    Publication Date: 2018-02-28
    Description: Magnesium alloys are the basis for the creation of light and ultra-light alloys. They have attracted attention as potential materials for the accumulation and storage of hydrogen, as well as electrode materials in metal-hydride and magnesium-ion batteries. The search for new metal hydrides has involved magnesium alloys with rare-earth transition metals and doped by p - or s -elements. The synthesis and characterization of a new quaternary carbide, namely dimagnesium lithium aluminium carbide, Mg 1.52 Li 0.24 Al 0.24 C 0.86 , belonging to the family of hexagonal close-packed (hcp) structures, are reported. The title compound crystallizes with hexagonal symmetry (space group P m 2), where two sites with m 2 symmetry and one site with 3 m . symmetry are occupied by an Mg/Li statistical mixture (in Wyckoff position 1 a ), an Mg/Al statistical mixture (in position 1 d ) and C atoms (2 i ). The cuboctahedral coordination is typical for Mg/Li and Mg/Al, and the C atom is enclosed in an octahedron. Electronic structure calculations were used for elucidation of the ability of lithium or aluminium to substitute magnesium, and evaluation of the nature of the bonding between atoms. The presence of carbon in the carbide phase improves the corrosion resistance of the Mg 1.52 Li 0.24 Al 0.24 C 0.86 alloy compared to the ternary Mg 1.52 Li 0.24 Al 0.24 alloy and Mg. The crystal structure of the new hexgonal quaternary carbide Mg 1.52 Li 0.24 Al 0.24 C 0.86 has been determined by single-crystal X-ray diffraction and represents the stucture family based on hexagonal close-packed structures.
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  • 8
    Publication Date: 2018-02-28
    Description: The nucleoside analogue entecavir {systematic name: 2-amino-9-[(1 S ,3 R ,4 S )-4-hydroxy-3-hydroxymethyl-2-methylenecyclopentyl]-1,9-dihydro-6 H -purin-6-one}, C 12 H 15 N 5 O 3 , is an antihepatitis B virus drug that has been approved in the US, EU and several countries worldwide. We report here the single-crystal structure of the anhydrous form and compare it with that of the previously reported monohydrate form [Jiang & Liu (2009). Acta Cryst. E 65 , o2232]. Hirshfeld surface analysis has been employed to understand and visualize the subtle packing differences between the two crystalline forms. The results show that, compared to the previously reported hydrated form, the anhydrous crystal has significantly different intermolecular interactions and packing patterns. The single-crystal structure for the anhydrous crystalline form of the anti-HBV drug entecavir is reported for the first time. It presents significantly different hydrogen-bonding and packing patterns to the hydrated form.
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  • 9
    Publication Date: 2018-02-28
    Description: Two new two-dimensional lanthanide coordination polymers, namely poly[[tetra-μ 2 -acetato-tetraaquabis(μ 4 -biphenyl-3,3′,5,5′-tetracarboxylato)tetrakis(dimethylacetamide)tetraterbium(III)] pentahydrate], {[Tb 4 (C 16 H 6 O 8 ) 2 (C 2 H 3 O 2 ) 4 (C 4 H 9 NO) 4 (H 2 O) 4 ]·5H 2 O} n , (1), and poly[[tetra-μ 2 -acetato-tetraaquabis(μ 5 -biphenyl-3,3′,5,5′-tetracarboxylato)tetrakis(dimethylacetamide)tetraeuropium(III)] tetrahydrate], {[Eu 4 (C 16 H 6 O 8 ) 2 (C 2 H 3 O 2 ) 4 (C 4 H 9 NO) 4 (H 2 O) 4 ]·4H 2 O} n , (2), have been synthesized from biphenyl-3,3′,5,5′-tetracarboxylic acid (H 4 bpt) and Ln(NO 3 ) 3 ·6H 2 O (Ln = Tb and Eu) under solvothermal conditions. Single-crystal X-ray structure analysis shows that the two compounds are isostructural and crystallize in the monoclinic P 2 1 / n space group. The crystal structures are constructed from bpt 4− ligands (as linkers) and {Ln 2 (μ 2 -CH 3 COO) 2 } building units (as nodes), which topological analysis shows to be a (4,6)-connected network with sql topology. Compounds (1) and (2) have been characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA) and fluorescence analysis in the solid state. In addition, a magnetic investigation shows the presence of antiferromagnetic interactions in compound (1). Two new two-dimensional lanthanide coordination polymers have been synthesized under solvothermal conditions from biphenyl-3,3′,5,5′-tetracarboxylic acid (H 4 bpt) and Ln(NO 3 ) 3 ·6H 2 O (Ln = Tb and Eu). Topological analysis shows that the bpt 4− ligand and the {Ln 2 (μ 2 -CH 3 COO) 2 } building unit could be considered as a (4,6)-connected network with sql topology. A magnetic investigation shows the presence of antiferromagnetic interactions in the Tb compound.
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  • 10
    Publication Date: 2018-02-28
    Description: The crystal structure of 6-chloro-2,4-dihydro-1 H -3,1-benzoxazine-2,4-dione (5-chloroisatoic anhydride), C 8 H 4 ClNO 3 , has been determined and analysed in terms of connectivity and packing patterns. The compound crystallizes in the noncentrosymmetric space group Pna 2 1 with one molecule in the asymmetric unit. The role of different weak interactions is discussed with respect to three-dimensional network organization. Molecules are extended into one-dimensional helical arrangements, making use of N—H…O hydrogen bonds and π–π interactions. The helices are further organized into monolayers via weak C—H…O and lone pair–π interactions, and the monolayers are packed into a noncentrosymmetric three-dimensional architecture by C—Cl…π interactions and C—H…Cl and Cl…Cl contacts. A Hirshfeld surface (HS) analysis was carried out and two-dimensional (2D) fingerprint plots were generated to visualize the intermolecular interactions and to provide quantitative data for their relative contributions. In addition, tests of the antimicrobial activity and in vitro cytotoxity effects against fitoblast L929 were performed and are discussed. The crystal structure of 5-chloroisatoic anhydride has been determined and analysed with respect to connectivity and packing patterns. The role of weak and nonspecific intermolecular interactions is elucidated.
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