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9. Co-crystals of zwitterionic GABA API's pregabalin and phenibut: properties and application.

Author

Komisarek, Daniel, Haj Hassani Sohi, Takin, and Vasylyeva, Vera

Subjects
ZWITTERIONS, PREGABALIN, CRYSTAL structure
Abstract

We present several multicomponent crystalline species formed by zwitterionic GABA analogues pregabalin and phenibut. These compounds are evaluated based on their crystal structure in congruence with properties such as melting behaviour, solubility, and lattice energies. Furthermore, it is discussed how major property distinctions between a homo- and heterochiral co-crystalline system enable enantiopurification of pregabalin. [ABSTRACT FROM AUTHOR]

Published
2022
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18. In-Situ Crystal Growth and Properties of the Magnetic Ionic Liquid [C2mim][FeCl4]

Author

Bäcker, Tobias, Breunig, Oliver, Valldor, Martin, Merz, Klaus, Vasylyeva, Vera, and Mudring, Anja-Verena

Abstract

[C2mim][FeCl4] behaves like a paramagnetic liquid at room temperature. Specific heat measurements indicate that there is a magnetic ordering below 3.8 K. The released entropy is far from the expected value for a J= 5/2 system, implying that the magnetic state is partly disordered. Full magnetic polarization was reached in fields above 4 T, and the anomaly in the magnetic susceptibility can be fully suppressed in higher B fields. Hence, the suggested magnetic ground state is superparamagnetic. In order to better understand the magnetic nature of this compound, structural investigations were carried out. Raman and IR-spectroscopy as well as UV–vis absorption measurements reveal the features characteristic for isolated [FeCl4]−anions in the liquid and solid state. The formation of dimeric [Fe2Cl7]−units could be not be evidenced. Thermal investigations show that the compound melts at 283 K. A solid–solid phase transition is observed at 261 K. [C2mim][FeCl4] decomposes above 623 K. By in situ crystal growth, it was possible to trap the two solid polymorphs of [C2mim][FeCl4]. The high temperature form of [C2mim][FeCl4] (1) crystallizes in the centric, monoclinic space group P21/c(No. 14) (a= 9.4124(19) Å, b= 14.645(3) Å, c= 12.444(4) Å, β = 129.841(18)°, V= 1317.1(6) Å3, Z= 4, ρ = 1.557 mg/m3), and the low temperature modification (2) in the non-centrosymmetric, monoclinic space group P21(No. 4) (a= 6.1337(12) Å, b= 14.362(3) Å, c= 7.1111(14) Å, β = 91.33(3)°, V= 626.3(2) Å3, Z= 2, ρ = 1.638 mg/m3). Both polymorphs show the characteristic structural features of the [C2mim]+cation and isolated complex [FeCl4]−anions. However, they deviate in the conformation of the ethyl-chain of the cation and more importantly the relative arrangements of cation and anion. Interestingly, the low temperature modification shows only weak hydrogen bonds, whereas the high temperature modification shows an extended hydrogen-bonding network.

Published
2024
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24. Spontaneous resolution of a Δ/Λ-chiral-at-metal pseudo-tetrahedral Schiff-base zinc complex to a racemic conglomerate with C–H…O organized 41- and 43-helices.

Author

Enamullah, Mohammed, Vasylyeva, Vera, Quddus, Mohammad Abdul, Islam, Mohammad Khairul, Höfert, Simon-Patrick, and Janiak, Christoph

Subjects
*CHIRALITY, *SCHIFF bases, *ISOMORPHOUS structures
Abstract

The Schiff-base ligand N-2-(pyridyl)salicylaldimine (HL) reacts with zinc(ii) acetate or nitrate to obtain the enantiomorphous chiral-at-metal compound Δ/Λ-bis[N-2-(pyridyl)salicylaldiminato-κ2N,O]zinc(ii), [Zn(L)2] (1), which crystallizes as a racemic conglomerate via spontaneous resolution. Two deprotonated N,O-chelate ligands form a pseudo-tetrahedral N2O2-coordination sphere with a Δ/Λ-configured zinc atom. The Δ- and Λ-configured molecular complexes in 1 assemble in P (right)- and M (left)-handed 41- and 43-helical chains in the chiral space groups P41212 and P43212, respectively, through weak C–H…O hydrogen bonding between neighbouring molecules along the chain axis. Only molecules of the same Δ- or Λ-configuration combine into a helical chain and only chains of the same P- or M-handedness combine to form homochiral crystals. According to the analyses of intermolecular interactions with the Hirshfeld surface, the supramolecular packing features C–H…O bonding as the most apparent significant contribution. This is a rare example of solely weak C–H…O hydrogen bonding interaction leading to spontaneous resolution to a racemic conglomerate. This case also supports the notion of less repulsive packing interactions between homochiral molecules because of spin polarization. Optimized structures and excited state properties by DFT/TD-DFT calculations are comparable to experimental results. [ABSTRACT FROM AUTHOR]

Published
2018
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28. α-Aminoxy Peptoids: A Unique Peptoid Backbone with a Preference for cis-Amide Bonds.

Author

Krieger, Viktoria, Ciglia, Emanuele, Thoma, Roland, Vasylyeva, Vera, Frieg, Benedikt, de Sousa Amadeu, Nader, Kurz, Thomas, Janiak, Christoph, Gohlke, Holger, and Hansen, Finn K.

Subjects
CHEMICAL synthesis, AMINO acid neurotransmitters, AMIDE synthesis, ACETIC acid, SPECTRUM analysis, MOLECULAR dynamics
Abstract

α-Peptoids, or N-substituted glycine oligomers, are an important class of peptidomimetic foldamers with proteolytic stability. Nevertheless, the presence of cis/ trans-amide bond conformers, which contribute to the high flexibility of α-peptoids, is considered as a major drawback. A modified peptoid backbone with an improved control of the amide bond geometry could therefore help to overcome this limitation. Herein, we have performed the first thorough analysis of the folding propensities of α-aminoxy peptoids (or N-substituted 2-aminoxyacetic acid oligomers). To this end, the amide bond geometry and the conformational properties of a series of model α-aminoxy peptoids were investigated by using 1D and 2D NMR experiments, X-ray crystallography, natural bond orbital (NBO) analysis, circular dichroism (CD) spectroscopy, and molecular dynamics (MD) simulations revealing a unique preference for cis-amide bonds even in the absence of cis-directing side chains. The conformational analysis based on the MD simulations revealed that α-aminoxy peptoids can adopt helical conformations that can mimic the spatial arrangement of peptide side chains in a canonical α-helix. Given their ease of synthesis and conformational properties, α-aminoxy peptoids represent a new member of the peptoid family capable of controlling the amide isomerism while maintaining the potential for side-chain diversity. [ABSTRACT FROM AUTHOR]

Published
2017
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29. Natural Abundance 15N and 13C Solid-State NMR Chemical Shifts: High Sensitivity Probes of the Halogen Bond Geometry.

Author

Cerreia Vioglio, Paolo, Catalano, Luca, Vasylyeva, Vera, Nervi, Carlo, Chierotti, Michele R., Resnati, Giuseppe, Gobetto, Roberto, and Metrangolo, Pierangelo

Subjects
CHEMICAL shift (Nuclear magnetic resonance), HALOGENS, BIPYRIDINE, DENSITY functional theory, NUCLEOPHILIC reactions, PHOSPHONIUM compounds
Abstract

Solid-state nuclear magnetic resonance (SSNMR) spectroscopy is a versatile characterization technique that can provide a plethora of information complementary to single crystal X-ray diffraction (SCXRD) analysis. Herein, we present an experimental and computational investigation of the relationship between the geometry of a halogen bond (XB) and the SSNMR chemical shifts of the non-quadrupolar nuclei either directly involved in the interaction (15N) or covalently bonded to the halogen atom (13C). We have prepared two series of X-bonded co-crystals based upon two different dipyridyl modules, and several halobenzenes and diiodoalkanes, as XB-donors. SCXRD structures of three novel co-crystals between 1,2-bis(4-pyridyl)ethane, and 1,4-diiodobenzene, 1,6-diiodododecafluorohexane, and 1,8-diiodohexadecafluorooctane were obtained. For the first time, the change in the 15N SSNMR chemical shifts upon XB formation is shown to experimentally correlate with the normalized distance parameter of the XB. The same overall trend is confirmed by density functional theory (DFT) calculations of the chemical shifts. 13C NQS experiments show a positive, linear correlation between the chemical shifts and the C−I elongation, which is an indirect probe of the strength of the XB. These correlations can be of general utility to estimate the strength of the XB occurring in diverse adducts by using affordable SSNMR analysis. [ABSTRACT FROM AUTHOR]

Published
2016
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33. Induced chirality-at-metal and diastereoselectivity at Δ/Λ-configured distorted square-planar copper complexes by enantiopure Schiff base ligands: combined circular dichroism, DFT and X-ray structural studies

Author

Enamullah, Mohammed, primary, Uddin, A. K. M. Royhan, additional, Pescitelli, Gennaro, additional, Berardozzi, Roberto, additional, Makhloufi, Gamall, additional, Vasylyeva, Vera, additional, Chamayou, Anne-Christine, additional, and Janiak, Christoph, additional

Published
2014
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34. Pro-Apoptotic and Immunostimulatory Tetrahydroxanthone Dimers from the Endophytic Fungus Phomopsis longicolla

Author

Rönsberg, David, primary, Debbab, Abdessamad, additional, Mándi, Attila, additional, Vasylyeva, Vera, additional, Böhler, Philip, additional, Stork, Björn, additional, Engelke, Laura, additional, Hamacher, Alexandra, additional, Sawadogo, Richard, additional, Diederich, Marc, additional, Wray, Victor, additional, Lin, WenHan, additional, Kassack, Matthias U., additional, Janiak, Christoph, additional, Scheu, Stefanie, additional, Wesselborg, Sebastian, additional, Kurtán, Tibor, additional, Aly, Amal H., additional, and Proksch, Peter, additional

Published
2013
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42. Synthesis, characterization and antimicrobial studies of mixed ligand silver(I) complexes of triphenylphosphine and heterocyclic thiones: Crystal structure of bis[{(μ2-diazinane-2-thione)(diazinane-2-thione)(triphenylphosphine)silver(I) nitrate}]

Author

Nawaz, Sidra, primary, Isab, Anvarhusein A., additional, Merz, Klaus, additional, Vasylyeva, Vera, additional, Metzler-Nolte, Nils, additional, Saleem, Muhammad, additional, and Ahmad, Saeed, additional

Published
2011
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50. Bifunctional pyrazolate–carboxylate ligands for isoreticular cobalt and zinc MOF-5 analogs with magnetic analysis of the {Co4(μ4-O)} node.

Author

Heering, Christian, Boldog, Ishtvan, Vasylyeva, Vera, Sanchiz, Joaquín, and Janiak, Christoph

Subjects
PYRAZOLATES, CARBOXYLATES, COBALT, ZINC, SOLVENTS, SORPTION
Abstract

The ditopic ligands 3,5-dimethyl-pyrazolate-4-carboxylate, –Me2pzCO2–, and 4-(3,5-dimethyl-1H-pyrazol-4-yl)benzoate, –Me2pzC6H4CO2–, combine a pyrazolate and carboxylate functionality in axial orientation and lead to porous cobalt or zinc azolate–carboxylate frameworks that have the same cubic pcu-a topology and {M4(μ4-O)} nodes (M = Co, Zn) as MOF-5 and other IRMOFs. The microporous networks [M4(μ4-O)(Me2pzCO2)3] (M = Co, Zn) with the short linker exhibit a solvent-induced gate effect, evidenced by gas desorption hysteresis due to small pore apertures of 2.8 Å diameter together with small amounts of high-boiling solvent remaining in the activated samples. For [Co4(μ4-O)(Me2pzCO2)3], the low-pressure H2 storage capacity (1.7 wt%, 1 bar , 77 K) is higher than for MOF-5, and the CO2 uptake of 20.8 wt% puts it among the top MOFs for low-pressure CO2 sorption even though the BET surface is less than 1000 m2 g−1. The analysis of the magnetic properties of [Co4(μ4-O)(Me2pzCO2)3] takes into account the distribution of tetrahedra resulting from the disorder of the pyrazolate–carboxylate linker. An antiferromagnetic coupling observed for [Co4(μ4-O)(Me2pzCO2)3] arises from the interactions of the cobalt(ii) ions through the combined μ4-O + syn–syn carboxylate and μ4-O + pyrazolate bridges. [ABSTRACT FROM AUTHOR]

Published
2013
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