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  • 1
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: In the title compound, [Ni(C6H4NO2)(C16H36N4)]ClO4, the macrocyclic unit adopts a folded conformation, allowing the two carboxyl O atoms to occupy two neighbouring coordination sites and thus form an additional four-membered chelate ring. The less crowded side of the macrocycle (that with the two asymmetric C—H groups) is directed towards the nicotinate anion and the asymmetric C—CH3 groups are directed away from it. The macrocyclic NH groups neighbouring the C—CH3 groups are also directed away from the nicotinate anion, while those NH groups which are near to the geminal methyl groups are directed towards the nicotinate anion. Although the complex does not include water molecules, three types of hydrogen bond were found, involving NH groups of the macrocyclic ligand, pyridine N atoms and O atoms of the perchlorate anions.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. 598-599 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The title compound, C12H19N3O2, is an unusual product of silica-catalyzed intermolecular condensation of α-aminoisobutyric acid. The molecule has three types of C—N bonds: a double bond, a cis-amide bond and single bonds, two of which are typical and two having intermediate lengths due to π-electron delocalization between C=N and C=O groups. The cis-amide moieties interact to form dimers via hydrogen bonds which stack in parallel layers.
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  • 3
    ISSN: 1572-8854
    Keywords: 1,4,8,11-tetraazacyclotetradecane ; cyclam ; anthraflavic acid ; water ; supramolecular network
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A 1:1:2 complex of 1,4,8,11-tetraazacyclotetradecane (cyclam), anthraflavic acid, and water has been obtained and characterized by X-ray diffraction. C24H36N4O6, monoclinic, P21/c, a = 11.966(1) Å, b = 11.570(1) Å, c = 9.604(1) Å, β = 107.16(1)°,V = 1270.5(2) Å3, Z = 2. Two of the four N atoms of the macrocyclic ring are protonated, and the corresponding anthraflavic acid exists as a dianion. The following types of H-bonding have been found in this complex: (1) between protonated NH groups of the macrocycle and O atoms of the ionized anthraflavic hydroxyls; (2) between protonated and nonprotonated NH groups of the macrocycle; (3) between the water molecules and O atoms of the ionized anthraflavic hydroxyls. The above interactions give rise to the formation of a 2D-supramolecular network in the cyclam complex; however, the major difference from the azamacrocyclic anthraflavates studied previously is that there is no direct interaction between the anthraflavic anions.
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  • 4
    ISSN: 1572-8854
    Keywords: 1,4,10,13-Tetraoxa-7,16-diazacyclooctadecane ; 2,5-pyridinedicarboxylic acid ; 2,2′-dithiosalicylic acid ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A 1:2:2 complex of 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane with 2,5-pyridinedicarboxylic acid and water (1) and its 1:1:1.75 complex with 2,2′-dithiosalicylic acid and water (2) have been obtained and characterized by x-ray diffraction. C26H40N4O14 (1), triclinic, $$P\bar 1$$ , a = 9.574(1) Å, b = 9.632(1) Å, c = 9.723(1) Å, α = 112.70(1)°, β = 91.07(1)°, γ = 115.45(1)°, V = 728.35(13) Å3, Z = 1. C26H39.5N2O9.75S2 (2), M = 600.22, triclinic, $$P\bar 1$$ , a = 10.492(1) Å, b = 10.945(1) Å, c = 14.535(2) Å, α = 102.74(1)°, β = 109.08(1)°, γ = 90.68(1)°, V = 1532.2(3) Å3, Z = 2. In complex 1, both N-atoms of the macrocyclic ring are protonated. The following types of H-bonding have been found: (1) between protonated aza groups of the macrocycle and ionized carboxylic groups; (2) between the protonated aza groups and N-atoms of the pyridine nuclei (D–A distance slightly exceeds 3 Å); (3) between water molecules and C=O groups of the non-ionized carboxylic groups; and (4) between the nonionized and ionized groups of the carboxylic acid. The above interactions give rise to the formation of a developed supramolecular network in the crystals of 1. In complex 2, despite the presence of several types of hydrogen bonds involving the aza crown, 2,2′-dithiosalicylic acid and water, the aromatic anions are H-bound only to the two other components, and not to each other. The H-bonds found in complex 2 are between (1) one of the protonated aza groups and water, (2) protonated aza groups and O-atoms of the ionized carboxylic groups, (3) water molecule and carboxylic O-atom, (4) water molecule and sulfur atom, and (5) water molecule and O-atom of diaza-18-crown-6.
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  • 5
    ISSN: 1572-8854
    Keywords: 5,7-Dioxo-1,4,8,11-tetraazacyclotetradecane ; 2,6-dihydoxyanthraquinone ; hydrogen bonding ; supramolecular network
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A complex of 5,7-dioxo-1,4,8,11-tetraazacyclotetradecane (dioxocyclam) and 2,6-dihydoxyanthraquinone (anthraflavic acid) has been obtained. The complex (crystals grown from water-ethanol solution) has a stoichiometry dioxocyclam-anthraflavic acid 1:1:5. C31H32N4O8, chemical formula weight 588.61, triclinic, P − 1, a = 10.542(3) Å, b = 11.936(2) Å, c = 12.206(2) Å, α = 104.00(1)°, β = 92.68(2)°, γ = 103.64(2)°, V = 1439.4 (5) Å3, Z = 2, Dx = 1.358 g cm−3. Only one of the two amine N-atoms of the macrocycle is protonated due to very weak acidic properties of 2,6-dihydoxyanthraquinone. Due to the rather poor quality of the crystals and structure refinement, reliable determination of H-bonds is complicated. Nevertheless, several types of H-bonding responsible for the formation of a developed supramolecular network can be suggested: between the protonated amino groups and macrocycle's C=O moieties; between non-protonated amino groups and macrocycle's C=O moieties; between protonated and non-protonated amino groups; between the amide NH and C=O groups of anthraflavic acid; and between protonated and deprotonated hydroxy groups of the acid. Two types of anthraflavic components can be distinguished in the lattice: those having a parallel orientation with respect to the macrocyclic fragments and forming hydrogen bonds with the latter, and those lying in an approximately perpendicular plane and not involved in H-bonding with the macrocycles.
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  • 6
    ISSN: 1572-8854
    Keywords: 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane ; 2,6-dihydroxyanthraquinone ; hydrogen bonding ; ribbon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A 1:2:2 complex of diaza crown ether 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane, anthraflavic acid (2,6-dihydroxyanthraquinone) and water has been synthesized. The crystal is triclinic, P1, with a = 7.705(2), b = 10.871(2), c = 11.540(2) Å, α = 100.40(2), β = 91.38(2), γ = 98.01(2)°, Z = 1, and Dcalc = 1.375 mg m−3. The main feature of the crystal structure is the formation of a supramolecular sheet by hydrogen bonding of the anthraflavic monoanions, not only head-to-tail through the hydroxyl oxygens, but sideways through the quinone oxygens. This complex represents an intermediate case between total transfer of protons of a hydroxy-guest to crown N-atoms, and no transfer.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Origins of life and evolution of the biospheres 28 (1998), S. 167-193 
    ISSN: 1573-0875
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract To evaluate the types of amino acid thermal transformations caused by silicate materials, we studied the volatilization products of Aib, L-Ala, L-Val and L-Leu under temperatures of up to 270 °C in the presence of silica gel as a model catalyst and pulverized basaltic lava samples. It was found that silica gel catalyzes nearly quantitative condensation of amino acids, where piperazinediones are the major products, whereas lava samples have much lower catalytic efficiency. In addition bicyclic and tricyclic amidines and several products of their subsequent thermal decomposition have been identified using the coupled technique of GC-FTIR-MS and HPLC-PB-MS, with auxiliary computer simulation of IR spectra and NMR spectroscopy. The decomposition is due to dehydrogenation, elimination of the alkyl substituents and dehydration as well as cleavage of the bicyclic ring system. The imidazole ring appears to be more resistant to thermal decomposition as compared to the pyperazine moiety, giving rise to the formation of different substituted imidazolones. The amidines were found to hydrolyze under treatment with concentrated HCl, releasing the starting amino acids and thus behaving as amino acid anhydrides. The thermal transformations cause significant racemization of amino acid residues. Based on our observations, the formation of amidine-type products is suggested to be rather common in the high-temperature experiments on amino acid condensation.
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  • 8
    ISSN: 1573-1111
    Keywords: [Ni(rac-Me6[14]aneN4)] ; 2,5-pyridinedicarboxylate ; preparation ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A bridged high-spin complex,bis-[Ni(II)(rac-5,5,7,l2,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane)]-2,5-pyridinedicarboxylate diperchlorate monohydrate has been obtained by reaction of [Ni(II)(rac-5,5,7, 12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane)](ClO4)2 and 2,5-pyridinedicarboxylic acid in aqueousalkaline (NH4OH) medium. C39H77Cl2N9Ni2O13, chemical formula weight 1068.42, orthorhombic, P212121, a = 11 .423(3) Å,b = 14.770(6) Å, c = 31.608(7) Å,α = β = γ =90.00°, V = 5333(3) Å3, Z = 4, Dcalc = 1.331 g cm-3, μcalc = 0.869 mm-1, F(000) = 2272, T = 293(2), R = 0.0870 for 2686 observed reflections [I 〉 2σ(I)]. The complexincludes two folded [Ni(rac- Me6[14]aneN4)]2+ units havingopposite diastereomeric configuration. They are bridged through a dianion of2,5-pyridinedicarboxylic acid, with one Ni-atom coordinated to the O-atom ofthe 2-carboxylic group and the pyridine N-atom (forming a 5-membered chelatering), and with the second Ni-atom coordinated to both O-atoms of the 5-carboxylic group (forming a 4-membered chelate ring). Hydrogen bonding involving macrocyclic NH groups, both 2- and 5-carboxylic groups, perchlorate anions and water molecules gives rise to the formation of an infinite supramolecular network in the title compound's crystals.
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  • 9
    Publication Date: 2004-05-01
    Print ISSN: 1530-6984
    Electronic ISSN: 1530-6992
    Topics: Chemistry and Pharmacology , Physics
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  • 10
    Publication Date: 2020-01-23
    Print ISSN: 0022-2461
    Electronic ISSN: 1573-4803
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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