Quinolinium Cations Research Articles

Haloantimonate(III) complexes with halogen-substituted quinolinium cations: Structural features of non-covalent interactions in solid state

Reactions between the halometalate-containing solutions (Sb2O3 in HCl or HBr) and halide salts of halogen-substituted quinolinium cations resulted in a series of haloantimonate complexes: (3-BrQuinH)4[Sb2X10] (X = Cl (1), Br (2)), (5-BrQuinH)2{[SbBr5]} (3), (1-Me-3-BrQuin)2[Sb2Cl8] (4) and (1-Me-3-BrQuin)3[Sb3Br12] (5). Their structures were determined using X-ray diffractometry; analysis of non-covalent interactions in crystalline state was performed by theoretical methods.

Molecular versus ionic liquids: Development of a thermodynamic framework for predicting vaporization thermodynamics

Ionic liquids based on the pyridinium and quinolinium cations show good result in desulfurization of fuels. The knowledge of their vaporisation thermodynamics is of practical importance. The standard molar enthalpies of vaporization of pyridinium based ionic liquids were derived from the vapor pressure temperature dependences measured by the quartz-crystal microbalance method. We have collected available primary experimental results on vapour pressures, and enthalpies of phase transitions (solid-solid, crystal-gas, and liquid-gas) of analogous molecular species – substituted pyridines and quinolines. These data were evaluated using the structure-property correlations. The consistent sets of evaluated thermodynamic data on the molecular and ionic liquids were used to develop the “centerpiece” based group-additivity method for predicting enthalpies of vaporization of molecular and ionic compounds. The general transferability of the contributions to the enthalpy of vaporization from the molecular liquids to the ionic liquid has been established.

Chiral Memory in Silyl-Pyridinium and Quinolinium Cations.

Pyridine- and quinoline-stabilized silyl cations have been prepared, and their structure in condensed phases unambiguously assigned using 1H, 13C, 15N, 29Si, and 1H DOSY NMR as well as X-ray diffraction studies. Solid state structures thus show in both cases a stabilization of the cationic silicon center through an N-Si interaction and formation of a highly strained four-membered ring system. Chiral memory at the silicon atom in these heterocycle-stabilized silyl cations was also established, leading to various levels of selectivity depending on the nature of the heterocycle. Lowest energy conformations of the starting silanes obtained through DFT calculations, along with the isolation and characterization of the Si-centered chiral silyl cation intermediates, finally allowed to propose a plausible hypothesis as to the configurational stability of these silyl cations.

Bis(quinolinium) tetrabromidomanganate(II)

The title compound, (C9H8N)2[MnBr4], consists of two quinolinium cations and a [MnBr4]2− anion. The manganese(II) atom, which lies on a twofold rotation axis, is coordinated by four bromide ligands and exhibits a tetrahedral coordination geometry. The [MnBr4]2− anion and the quinolinium cations are linked by N—H...Br hydrogen bonds. π–π stacking interactions are observed between the quinolinium cations.

New Stationary Ionic Liquid Phases with Quinolinium Cations for Capillary Gas Chromatography

The work provides the study of quinolinium ionic liquids (ILs)—a new class of stationary phases for capillary gas chromatography (GC). Quinolinium ILs were shown to have new attractive properties. They are not only highly polar, but also very selective for aromatic compounds and oxygenates. Depending on the substituents in the quinolinium ring, the studied ILs possess polarity numbers from 64 to 99, so they are polar and strongly polar. By the variation of the substituent and its position, changes in the prevailing types of interactions with analytes are observed. It is worth noting that Abraham’s constants for the quinolinium phases are significantly different from the previously known imidazolium and pyridinium ionic liquids (ILs) that cause significant variations in their selectivity. The most significant differences are observed in the π–π interactions and hydrogen bond acidity parameters. The investigation of background mass spectra for quinolinium ILs showed the most intense signals related to peaks at m/z 69 and 143 belonging to [CF3]+ and quinolinium ring fragments. The most thermostable ILs are N-propyl-6-methylqionoinium and bis(6-methylquinolinium)hexane that are stable up to 300 °C. With regard to the possible use of quinolinium ILs, apart from the separation of polar substances, it is expected that they will find applications in two-dimensional chromatography for the separation of complex mixtures compose of compounds that differ substantially in their properties. The applications of the columns for the determination of aromatic hydrocarbons in gasoline and phenolic compounds in pyrolysis biodiesel are demonstrated.

Transition metal salts of quinoline: synthesis, structure and magnetic behavior of (QuinH)2[MX4]·2H2O [Quin = quinoline; M = Mn, Co, Cu, Zn], (QuinH)2[MnBr2(H2O)2](Br)2 and (QuinH)[Cu(Quin)Br3

A family of compounds of general formula (QuinH)2MX4·2H2O has been prepared and characterized [Quin = quinoline; M, X = Co,Cl (1); M, X = Co,Br (2); M, X = Zn,Br (3); M, X = Mn,Cl (4)]. The complexes crystallize in the monoclinic space group C2/c as well-isolated layers containing the MX4−2 anions and water molecules, separated by the quinolinium cations. The bromide analogue of 4, compound 5 (QuinH)2[MnBr2(H2O)2](Br)2, also crystallizes in the C2/c space group, but comprises a co-crystal of manganese bromide dihydrate and quinolinium bromide. The temperature dependent magnetic properties of the complexes are described, along with the tetrachlorocuprate analogue (7). All compounds show weak antiferromagnetic interactions (J/kB ∼ 0.06–1.4 K) and good one- or two-dimensional isolation. In addition, the crystal structure of the mixed quinoline/quinolinium complex (QuinH)[Cu(Quin)Br3] (triclinic, P-1) is reported.

Mesomeric betaines constructed of quinolinium cations and carboxylate anions separated by thiophene-ethynyl spacers as fluorescent dipoles

4- and 5-((1-Methylquinolinium-3-yl)ethynyl)thiophene-2-carboxylates were prepared starting from 3-ethynylquinoline which was subjected to a Sonogashira-Hagihara coupling with ethyl 4- and 5-bromothiophenecarboxylates, respectively. Methylation to give the corresponding quinolinium salts, saponification under basic conditions, acidification to give the carboxylic acids, and basification finally yielded the title compounds. Calculations of the frontier orbital profiles confirm the classification of these mesomeric betaines as cross-conjugated systems, as the HOMO is essentially located in the carboxylate group which is connected to the spacer by a nodal position. Fluorescence spectroscopic investigations were performed.

Understanding the interplay between the solvent and nuclear rearrangements in the negative solvatochromism of a push-pull flexible quinolinium cation.

A detailed computational characterization of the one-photon absorption spectrum of a 2-((E)-2-[2,2']-bithiophenyl-5-yl-vinyl)-1-methyl-quinolinium cation in acetonitrile solution is presented. The main physico-chemical effects (solvation, vibronic progression) affecting the band position and shape are progressively introduced in the computational model, highlighting their relative role in the spectral profile. The reported results underline how an accurate reproduction of the experimental spectrum can only be obtained by going beyond oversimplified methods. Moreover, the deep interplay between the solvent effects and nuclear rearrangements permits the negative solvatochromism exhibited by hypsochromic molecules to be explained. This illustrates the potential of the computational investigation, which can shed light on the information hidden in experimental spectra.

Selective Inhibition of the Mitochondrial Permeability Transition Pore Protects against Neurodegeneration in Experimental Multiple Sclerosis

The mitochondrial permeability transition pore is a recognized drug target for neurodegenerative conditions such as multiple sclerosis and for ischemia-reperfusion injury in the brain and heart. The peptidylprolyl isomerase, cyclophilin D (CypD, PPIF), is a positive regulator of the pore, and genetic down-regulation or knock-out improves outcomes in disease models. Current inhibitors of peptidylprolyl isomerases show no selectivity between the tightly conserved cyclophilin paralogs and exhibit significant off-target effects, immunosuppression, and toxicity. We therefore designed and synthesized a new mitochondrially targeted CypD inhibitor, JW47, using a quinolinium cation tethered to cyclosporine. X-ray analysis was used to validate the design concept, and biological evaluation revealed selective cellular inhibition of CypD and the permeability transition pore with reduced cellular toxicity compared with cyclosporine. In an experimental autoimmune encephalomyelitis disease model of neurodegeneration in multiple sclerosis, JW47 demonstrated significant protection of axons and improved motor assessments with minimal immunosuppression. These findings suggest that selective CypD inhibition may represent a viable therapeutic strategy for MS and identify quinolinium as a mitochondrial targeting group for in vivo use.

Crystal structure of bis-(quinolin-1-ium) tetra-chlorido-ferrate(III) chloride.

The asymmetric unit of the title hybrid compound, (C9H8N)[FeCl4]Cl, comprises a tetra­hedral tetra­chlorido­ferrate(III) anion, [FeCl4]−, a Cl− anion and two quinolinium cations. There are N—H⋯Cl hydrogen-bonding inter­actions between the protonated N atoms of the quinolinium cations and the chloride anion, which together with π–π stacking between adjacent quinolinium rings [centroid-to-centroid distances between C6 and C5N rings in adjacent stacked quinolinium cations of 3.609 (2) and 3.802 (2) Å] serve to hold the structure together.

Synthesis and structure of interaction products of quinoline-2(1H)-thione with molecular iodine

The behavior of quinoline-2(1H)-thione, which is a potential antithyroid drug toward molecular iodine, was investigated. The ability of quinoline-2(1H)-thione to form the outer-sphere charge-transfer complex C9H7NS·I2 with iodine molecular in dilute chloroform solution has been studied by UV–vis spectroscopy (lgβ=3.85). The crystal structure of the new salt 2-(quinoline-2-yldisulfanyl)quinolinium triiodide – product of irreversible oxidation of quinoline-2(1H)-thione was determined by X-ray diffraction. The 2-(quinoline-2-yldisulfanyl)quinolinium cations form dimers through π–π–stacking interaction between quinoline rings. Strong intramolecular interactions are observed between iodine – sulfur atoms and iodine – hydrogen atoms with shortened contacts (less of sum of van der Waals contacts). It is noteworthy that two perfectly centrosymmetrical anions I3− form a very short contact I(3)⋯I(3′) 3.7550(5) so we can state the formation of the dianion I62−. Therefore the formation and topology of polyiodide species depend on the characteristics, such as shape, size and charge, etc., of the counter cation, 2-(quinoline-2-yldisulfanyl)quinolinium, which is considered as templating agent.

Crystal Engineering of Acentric Styryl Quinolinium Crystals with Strongly Hydrogen-Bonded Phenolic Anions

We report on new acentric styryl quinolinium crystals with phenolic sulfonate counteranions and investigate their supramolecular interactions that affect their quadratic nonlinear optical properties. The phenolic group acting as an electron-donor as well as hydrogen-bond donor site is located at one end of the anion, while the sulfonate group acting as an electron-acceptor as well as hydrogen-bond acceptor site is located at the opposite end of the anion. New styryl quinolinium crystals with 4-hydroxybenzenesulfonate and 6-hydroxynaphthalene-2-sulfonate counteranions exhibit a large macroscopic optical nonlinearity with very efficient second harmonic generation (SHG) efficiency. In styryl quinolinium 4-hydroxybenzenesulfonate crystals, the styryl quinolinium cation chromophores exhibit an acentric ordering with a high order parameter close to 1.0, which is optimal for electro-optic applications or THz-wave generation. The 4-hydroxybenzenesulfonate counteranions form strong head-to-tail hydrogen bonds, and...

Hydrothermal Synthesis, Crystal Structure, and Luminescent Properties of One New Inorganic-organic Hybrid Compound (ClBzQl)3[PMo12O40] (ClBzQl = 1- (4′-Cl-benzyl)quinolinium cation)

A new polyoxometalate-based inorganic-organic hybrid compound (ClBzQl)3[PMo12O40] 1 (ClBzQl = 1-(4′-Cl-benzyl)quinoli- nium cation) has been synthesized by hydrothermal method and characterized by IR, elemental analysis, and X-ray crystallography. Analysis of the crystal structure of 1 suggests that there are multiform intermolecular C−H···O hydrogen bonds between polyoxoanions and organic cations and obvious face-to-face π−π interactions involving quinoline rings of adjacent cations. The luminescent properties of the compound 1 in the solid state at room temperature were investigated.

Spectroscopic and structural investigation of interaction product of 8-mercaptoquinoline with molecular iodine

The behavior of 8-mercaptoquinoline, which is a potential antithyroid drug toward molecular iodine was investigated. The ability of 8-mercaptoquinoline to form the outer-sphere charge-transfer complex C9H7NS·I2 with iodine molecular in dilute chloroform solution has been studied by UV/vis spectroscopy (lgβ=3.14). The crystal structure of the new salt 8-(quinoline-8-yldisulfonyl)quinolinium triiodide – product of irreversible oxidation of 8-mercaptoquinoline was determined by X-ray diffraction. Intramolecular hydrogen bond of N–H⋯N type is presented in the organic cation. The triiodide ion is the nearly centrosymmetrical anion. The 8-(quinoline-8-yldisulfanyl)quinolinium cations form dimers through π–π-stacking interaction between quinolinium rings. The reduced intramolecular interactions are observed between iodine – sulfur atoms and iodine–hydrogen atoms with shortened contacts (less of sum of van-der-waals contacts).

Cation exchange, solvent free synthesis and packing patterns of quinolinium nickel(II) dipicolinates

Nickel dipicolinate complexes (HQ)2[NiL2]·5H2O (1) and (H5AQ)2[NiL2]·4H2O (2) (where L=pyridine-2,6-dicarboxylate anion, Q=quinoline, 5AQ=5-aminoquinoline) are synthesized in solution and also through solvent free cation exchange reactions of H2[NiL2]·3H2O. The crystal structures of the complexes 1 and 2 are determined. The strong π–π interactions between the quinolinium cations disrupt the conventional π-stacking interactions of the nickel–dipicolinate anions. The quinolinium cations of these complexes exchanges with alkali metal cations in basic medium and only at an extreme acidic condition the pyridine-2,6-dicarboxylate can be replaced from these complexes by halide ions.

Quinolinium 8-hy-droxy-7-iodo-quinoline-5-sulfonate 0.8-hydrate.

In the crystal structure of the title hydrated quinolinium salt of ferron (8-hy­droxy-7-iodo­quinoline-5-sulfonic acid), C9H7N+·C9H5INO4S−·0.8H2O, the quinolinium cation is fully disordered over two sites (occupancy factors fixed at 0.63 and 0.37) lying essentially within a common plane and with the ferron anions forming π–π-associated stacks down the b axis [minimum ring centroid separation = 3.462 (6) Å]. The cations and anions are linked into chains extending along c through hy­droxy O—H⋯O and quinolinium N—H⋯O hydrogen bonds to sulfonate O-atom acceptors which are also involved in water O—H⋯O hydrogen-bonding inter­actions along b, giving a two-dimensional network.

Electron Transfer Triggers Fast Dimer/Monomer Switching of Pyridinium and Quinolinium Cations

N-Heteroaromatic cations with quaternary pyridine-type nitrogen atoms have a rich application potential due to their bioactivity, fluorescence, and redox properties. Reactivityof radicals formed by reduction of such compounds is of key importance. We report the electron transfer mechanismof four novel compounds containing pyridinium, quinolinium, and benzothiazolium moiety. The reduction of pyridinium and quinolinium derivatives by one electron yields radicals that very rapidly form σ-dimers. Dimers can be converted to parent cations by oxidation, which proceeds at considerably higher potentials. Hence the dimerization can be reversibly switched by application of the appropriate electrode potential. In contrast, in benzothiazolium derivative the electron transfer yields a stable radical in which the follow-up dimerization reaction is completely blocked. Analysis of experimental data as well as theoretical models led to the identification of dimerization sites in reduced pyridinium and quinolinium species....

Quinolinium and isoquinolinium ionic liquid crystals

Ionic liquid crystals based on quinolinium and isoquinolinium salts were prepared by quaternization of quinoline and isoquinoline, respectively. In the first place the influence of the alkyl chain on the thermal behaviour was investigated. Two types of (iso)quinolinium salts were synthesized. Long-chained (iso)quinolinium cations (with chain lengths varying from C12H25 to C22H45), with the inclusion of the odd homologues C17H35 and C19H39, were combined with the spherical anions bromide, tetrafluoroborate (BF4−) and hexafluorophosphate (PF6−). Dodecyl sulfate, dioctyl-, dihexyl- and dicyclohexylsulfosuccinate anions allowed the introduction of anions with (long) alkyl chains. It is shown that a subtle balance between strong electrostatic forces and the degree of disorder originating from molten alkyl chains is crucial for mesophase formation. The influence of the anion size on the mesophase behaviour was studied. Smectic A phases were observed for the long chain analogues of the bromide, tetrafluoroborate and hexafluorophosphate salts. The minimum alkyl chain length needed to induce mesomorphism increases when the bromide is exchanged by more voluminous anions, while the transition temperatures are lowered. The introduction of an alkyl chain in the anionic part drastically changes the thermal behaviour. The dodecyl sulfate salts show smectic A phases for cations with much shorter chain lengths than the other anions. For the dioctylsulfosuccinate salts this trend is even more pronounced, as the N-methyl(iso)quinolinium dioctylsulfosuccinate salts exhibited enantiotropic smectic A phases at ambient temperature. Structural models for the packing of the quinolinium and isoquinolinium salts in the liquid-crystalline state are presented, as well as the crystal structures of N-octylquinolinium dodecyl sulfate and N-octylisoquinolinium bromide.

Catena-Poly[1-[(2-fluorobenzylidene)amino]quinolinium [plumbate(II)-tri-μ-iodido

The title complex, {(C16H12FN2)[PbI3]}n, consists of 1-[(2-fluoro­benzyl­idene)amino]­quinolinium cations and a polymeric PbI3 − anion formed by face-sharing PbI6 octa­hedra. These octa­hedra form straight and regular infinite chains along the b axis. In the asymmetric unit, one cation and one anionic [PbI3]− fragment are observed in general positions. Polymeric chains are produced by the glide plane perpendicular to the a axis.

Two cadmium–thiocyanate coordination polymers with organic cations: Synthesis, crystal structures and luminescent properties

Two new inorganic–organic hybrid polymers [ClBzQl] 2[Cd(SCN) 3.5Br 0.5]·0.25H 2O ( 1) and [ClBzMePy][Cd(SCN) 3] ( 2) (ClBzQl = 1-(4′-Cl-benzyl)quinolinium cation and ClBzMePy = 1-(4′-Cl-benzyl)-2-methylpyridinium cation) have been synthesized and characterized by IR, UV, elemental analysis and X-ray crystallography. Crystal structure analyses show that two polymers belong to the monoclinic space group P2/ n ( 1) and P2 1/ c ( 2) with a = 18.548(2) Å, b = 9.526(1) Å, c = 20.689(2) Å, β = 94.008(1)°, V = 3646.6(5) Å 3 for 1, and a = 11.195(2) Å, b = 16.415(3) Å, c = 10.751(2) Å, β = 102.930(3)°, V = 1925.7(7) Å 3 for 2. The Cd atom exhibits a distorted octahedral coordination geometry for 1 and 2. For 1, a pair of 1,1- μ-SCN − anions and a pair of 1,3- μ-SCN − anions are alternately bridge adjacent Cd centers to form infinite polymeric chains. For 2, adjacent Cd atoms are linked by three 1,3- μ-SCN − anions to form infinite [Cd(SCN) 3 −] ∞ polymeric chains. The luminescent properties of the two polymers in the solid state at room temperature were investigated.