Proton Transfer Salt Research Articles

Spectral & biological characteristics of a novel Uranyl Proton transfer salt

Spectral & biological characteristics of a novel Uranyl Proton transfer salt

A novel proton transfer salt of 2-amino-6-sulfamoylbenzothiazole and its metal complexes: the evaluation of their inhibition effects on human cytosolic carbonic anhydrases

A novel proton transfer compound (SMHABT)+(HDPC)− (1) obtained from 2-amino-6-sulfamoylbenzothiazole (SMABT) and 2,6-pyridinedicarboxylic acid (H2DPC) and its Fe(III), Co(II), Ni(II) complexes (2–4), and Fe(II) complex of SMABT (5) have been prepared and characterized by spectroscopic techniques. Additionally, single crystal X-ray diffraction techniques were applied to complexes (2–4). All complexes (2–4) have distorted octahedral conformations and the structure of 5 might be proposed as octahedral according to spectral and analytical results. All compounds, including acetazolamide (AAZ) as the control compound, were also evaluated for their in vitro inhibition effects on human hCA I and hCA II for their hydratase and esterase activities. The synthesized compounds have remarkable inhibitory activities on hCA I and hCA II. Especially, the inhibition potentials of the salt and the metal complexes (1–5) are comparable with AAZ. Inhibition data have been analyzed by using a one-way analysis of variance for multiple comparisons (p < .0001).

Solution and solid-state studies of a new supramolecular proton transfer salt and its VO2 complex constructed with chelidamic acid and 3,4-diaminopyridine

The proton transfer compound (Hdap)(chelH)·2H2O (1) and its related anionic complex (Hdap) [VO2(chel)] (2), where chelH2 = 4-hydroxypyridine-2,6-dicarboxylic acid (chelidamic acid) and dap = 3,4-diaminopyridine, were synthesized and characterized by elemental analysis, spectroscopy (IR, UV–Vis), thermal (TG/DTG) analysis and single-crystal X-ray diffraction. Compound 1 resulted from proton transfer between chelH2 and dap in aqueous solution. In 1, two carboxylic acids of chelH2 were deprotonated and the protons transferred to the nitrogen atoms of one chelidamate anion and one dap moiety. Compound 2 resulted from complexation of 1 and vanadyl sulfate. In the crystal structure of 2, the metal ion is five coordinated by one tridentate ligand (chel)2− and two O2− anions, with (Hdap)+ as a counter cation. In both structures, a complicated hydrogen-bonding network accompanied with π–π, C–O···π and C–H···π stacking interactions leads to formation of a 3D supramolecular network. In the following, solution studies have been performed by means of pH potentiometric titrations method as a power technique. This method was used for determination of protonation constants of chelH2 and dap in their probable protonated forms and for calculation of equilibrium constants for the chelH2–dap proton transfer system and the stoichiometry and stability constants of binary and ternary complexes of this system with VO2+ ion in aqueous solution. The stoichiometries of the most complex species in solution were compared with the corresponding crystalline complexes in the solid state.

Crystal structure and hydrogen bonding in the water-stabilized proton-transfer salt brucinium 4-amino-phenyl-arsonate tetra-hydrate.

In the structure of the brucinium salt of 4-amino-phenyl-arsonic acid (p-arsanilic acid), systematically 2,3-dimeth-oxy-10-oxostrychnidinium 4-amino-phenyl-ar-son-ate tetra-hydrate, (C23H27N2O4)[As(C6H7N)O2(OH)]·4H2O, the brucinium cations form the characteristic undulating and overlapping head-to-tail layered brucine substructures packed along [010]. The arsanilate anions and the water mol-ecules of solvation are accommodated between the layers and are linked to them through a primary cation N-H⋯O(anion) hydrogen bond, as well as through water O-H⋯O hydrogen bonds to brucinium and arsanilate ions as well as bridging water O-atom acceptors, giving an overall three-dimensional network structure.

Synthesis, crystal structure, spectroscopic, thermal analyses and biological properties of novel F-block coordination polymers containing 2,2′-thiodiacetic acid and piperazine

Three new 1D and 2D coordination polymers, {(pipH2)[Ce2(tda)4(H2O)2]·2H2O}n (1), {[Nd2(tda)3(H2O)2]·H2O}n (2) and {(pipH2) [UO2(tda)2]}n (3), where [tdaH2=2,2′-thiodiacetic acid and pip=piperazine] have been synthesized and characterized by elemental analysis, spectral (IR, NMR, UV–Vis and luminescence), thermal (TGA/DTA) analysis, as well as X-ray single crystal diffraction. Compounds 1 and 3 are proton transfer salts of the piperazindiium cation and metal complex anions that crystallized in a solution from dicarboxylic acid, piperazine and metal nitrates or acetates as starting materials. However compound 2 is an interesting neutral 2D coordination polymer containing just 2,2′-thiodiacetate dianions. The acid is coordinated to metal center in a bidentate fashion in 2 and 3 while in 1, coordinated to metal center as bidentate and tridentate, simultaneously. The coordination polyhedron around metal center in 1, 2 and 3 can be described as distorted tricapped trigonal prismatic and distorted hexagonal bipyramidal, respectively. The complicated hydrogen bonding networks connected the various components of 1–3 into a 3D-supramolecular architecture. The 1–3 compounds, tdaH2, pip and metal salts were additionally tested in vitro against three Gram-positive microorganisms (Staphylococcus aureus, Staphylococcus epidermidis and Bacillus subtilis) and three Gram-negative microorganisms (Escherichia coli, Serratia marcescens, and Pseudomonas aeruginosa) to assess their antibacterial properties. The results of antibacterial assays indicated that compound 1 has higher activity than compounds 2 and 3 against the tested Gram-positive bacteria and also compound 2 has better activity compared to 1 and 3 against the tested Gram-negative bacteria.

A comparison of solution and solid state coordination environments for calcium(II), zirconium(IV), cadmium(II) and mercury(II) complexes with dipicolinic acid and methylimidazole derivatives

Four new supramolecular compounds, (2-mimH)[Ca(pydcH)3][Ca(pydcH2)(pydc)(H2O)2]·4H2O (1), (1-mimH)2[Zr(pydc)3] (2), (2-mimH)2[Cd(pydc)2]·8H2O (3), and (2-mimH)2[Hg(pydc)2]·8H2O (4) [where pydcH2 = pyridine-2,6-dicarboxylic acid (dipicolinic acid), 1-mim = 1-methylimidazole, and 2-mim = 2-methylimidazole], have been synthesized and characterized by elemental analyses, spectroscopic techniques (IR, UV–vis, 1H NMR, and 13C NMR), thermal (TG/DTG/DTA) analysis as well as single-crystal X-ray diffraction. All four compounds are proton-transfer salts of the methylimidazolium cations and metal complex anions that crystallized from a solution of pyridine-2,6-dicarboxylic acid, methylimidazole, metal nitrates or chlorides as starting materials. The coordinating dicarboxylic acid is deprotonated at the carboxyl group and methylimidazole is protonated to balance the charge. In the crystal structures of 1–4, hydrogen bonding and π–π stacking play important roles. Water clusters are formed in 1, 3, and 4. The equilibrium constants of dipicolinic acid (pydc) and methylimidazole derivatives (1-mim and 2-mim), pydc-2-mim, pydc-1-mim proton-transfer systems as well as those of their complexes were investigated by a potentiometric pH titration method. The stoichiometries of most of the complex species in solution were very similar to the cited crystalline metal ion complexes.

Synthesis, characterization and biological activities of metal(II) dipicolinate complexes derived from pyridine-2,6-dicarboxylic acid and 2-(piperazin-1-yl)ethanol

The new water-soluble and air stable compounds (H2ppz)[Co(dipic)2]·6H2O (1), (H2ppz)[Ni(dipic)2]·6H2O (2) and (H2ppz)[Zn(dipic)2]·6H2O (3) were prepared by the reaction of corresponding metal(II) acetates and a proton transfer salt, (H2ppz) (Hdipic)2, (4) of pyridine-2,6-dicarboxylic acid (H2dipic) and 2-(piperazin-1-yl)ethanol (ppz). The compounds 1–3 were characterized by elemental, IR, UV–vis. thermal analyses, magnetic measurement and single crystal X-ray diffraction studies. The molecular structures of the title compounds consist of one 1-(2-hydroxyethyl)piperazine-1,4-diium (H2ppz+2) cation, one bis(pyridine-2,6-dicarboxylate)metal(II) [M(dipic)2]2− anion, and six uncoordinated water molecules. In compounds 1–3 the metal ions coordinate to two oxygen and one nitrogen atoms of two pyridine-2,6-dicarboxylate molecules forming an octahedral environment. Antimicrobial activities against Gram (−) wild type (Escherichia coli and Pseudomonas aeruginosa), Gram (+) wild type (Staphylococcus aureus, Staphylococcus epidermidis, Bacillus cereus and Bacillus subtilis) and clinical isolate (Morganella morganii, Proteus vulgaris and Enterobacter aeruginosa) were also studied. The results were reported, discussed and compared with the corresponding starting materials ((H2ppz) (Hdipic)2 (4), H2dipic and ppz). MIC (Minimal Inhibition Concentration) values of the newly synthesized compounds were determined as 4000 μg/ml (except B. subtilis and clinical isolate E. aeruginosa, >4000 μg/ml).

Crystal structures and hydrogen bonding in the proton-transfer salts of nicotine with 3,5-di-nitro-salicylic acid and 5-sulfosalicylic acid.

The structures of the 1:1 anhydrous salts of nicotine (NIC) with 3,5-di-nitro-salicylic acid (DNSA) and 5-sulfosalicylic acid (5-SSA), namely (1R,2S)-1-methyl-2-(pyridin-3-yl)-1H-pyrrolidin-1-ium 2-carb-oxy-4,6-di-nitro-phenolate, C10H15N2 (+)·C7H3N2O7 (-), (I), and (1R,2S)-1-methyl-2-(pyridin-3-yl)-1H-pyrrolidin-1-ium 3-carb-oxy-4-hy-droxy-benzene-sulfonate, C10H15N2 (+)·C7H5O6S(-), (II), are reported. The asymmetric units of both (I) and (II) comprise two independent nicotinium cations (C and D) and either two DNSA or two 5-SSA anions (A and B), respectively. One of the DNSA anions shows a 25% rotational disorder in the benzene ring system. In the crystal of (I), inter-unit pyrrolidinium N-H⋯Npyridine hydrogen bonds generate zigzag NIC cation chains which extend along a, while the DNSA anions are not involved in any formal inter-species hydrogen bonding but instead form π-π-associated stacks which are parallel to the NIC cation chains along a [ring-centroid separation = 3.857 (2) Å]. Weak C-H⋯O inter-actions between chain substructures give an overall three-dimensional structure. In the crystal of (II), A and B anions form independent zigzag chains with C and D cations, respectively, through carb-oxy-lic acid O-H⋯Npyridine hydrogen bonds. These chains, which extend along b, are pseudocentrosymmetrically related and give π-π inter-actions between the benzene rings of anions A and B and the pyridine rings of the NIC cations C and D, respectively [ring centroid separations = 3.6422 (19) and 3.7117 (19) Å]. Also present are weak C-H⋯O hydrogen-bonding inter-actions between the chains, giving an overall three-dimensional structure.

Synthesis and characterization of complexes of a novel proton transfer salt and their inhibition studies on carbonic anhydrase isoenzymes

A novel proton transfer compound (HClABT)+(HDPC.H2DPC)− (1) and its Fe(III), Co(II), Ni(II) and two different Cu(II) complexes (2–6) have been prepared and characterized by spectroscopic techniques. Additionally, single crystal X-ray diffraction techniques were applied to all complexes. All compounds, including acetazolamide (AAZ) as the control compound, were also evaluated for their in vitro inhibition effects on human hCA I and hCA II for their hydratase and esterase activities. Although there is no inhibition for hydratase activities, all compounds have inhibited the esterase activities of hCA I and II. The comparison of the inhibition studies of 1–6 to parent compounds, ClABT and H2DPC, indicates that 1–6 have superior inhibitory effects. The inhibition effects of 2–6 are also compared to the inhibitory properties of the simple metal complexes of ClABT and H2DPC, revealing an improved transfection profile. Data have been analysed by using a one-way analysis of variance for multiple comparisons.

Synthesis and characterization of some metal complexes of a proton transfer salt, and their inhibition studies on carbonic anhydrase isozymes and the evaluation of the results by statistical analysis

A novel proton transfer compound (HMeOABT) + (HDPC)− (1) and its Fe(III), Co(II), Ni(II) and Cu(II) complexes (2–5) have been prepared and characterized by spectroscopic techniques. Complex 4 has distorted octahedral conformation revealed by single crystal X-ray diffraction method. Structures of the other complexes might be proposed as octahedral according to experimental data. All compounds were also evaluated for their in vitro inhibition effects on hCA I and II for their hydratase and esterase activities. Although there is no inhibition for hydratase activities, all compounds have inhibited the esterase activities of hCA I and II. Data have been analyzed by using a one-way analysis of variance. The comparison of the inhibition studies of 1–5 to parent compounds indicates that 1–5 have superior inhibitory effects. The inhibition effects of 2–5 are also compared to inhibitory properties of the metal complexes of MeOABT and H2DPC, revealing an improved transfection profile.

Proton-Transfer and Non-transfer Compounds of the Multi-purpose Drug Dapsone [4-(4-Aminophenylsulfonyl)aniline] with 3,5-Dinitrosalicylic Acid and 5-Nitroisophthalic Acid

The structures of the compounds from the reaction of the drug dapsone [4-(4-aminophenylsulfonyl)aniline] with 3,5-dinitrosalicylic acid, the salt hydrate [4-(4-aminophenylsulfonyl)anilinium 2-carboxy-4,6-dinitrophenolate monohydrate] (1) and the 1:1 adduct with 5-nitroisophthalic acid [4-(4-aminophenylsulfonyl)aniline 5-nitrobenzene-1,3-dicarboxylic acid] (2) have been determined. Crystals of 1 are triclinic, space group P-1, with unit cell dimensions a = 8.2043(3), b = 11.4000(6), c = 11.8261(6) Å, α = 110.891(5)°, β = 91.927(3)°, γ = 98.590(4)° and Z = 4. Compound 2 is orthorhombic, space group Pbcn, with unit cell dimensions a = 20.2662(6), b = 12.7161(4), c = 15.9423(5) Å and Z = 8. In 1, intermolecular analinium N–H···O and water O–H···O and O–H···N hydrogen-bonding interactions with sulfone, carboxyl, phenolate and nitro O-atom and aniline N-atom acceptors give a two-dimensional layered structure. With 2, the intermolecular interactions involve both aniline N–H···O and carboxylic acid O–H···O and O–H···N hydrogen bonds to sulfone, carboxyl, nitro and aniline acceptors, giving a three-dimensional network structure. In both structures π–π aromatic ring associations are present. The structures of both an uncommon proton-transfer salt of the drug dapsone with 3,5-dinitrosalicylic acid and a molecular adduct with 5-nitroisophthalic acid are reported, together with their hydrogen-bonding patterns.

Three-dimensional hydrogen-bonded structures in the hydrated proton-transfer salts of isonipecotamide with the dicarboxylic oxalic and adipic acid homologues

The structures of the 1:1 hydrated proton-transfer compounds of isonipecotamide (piperidine-4-carboxamide) with oxalic acid, 4-carbamoylpiperidinium hydrogen oxalate dihydrate, C6H13N2O(+)·C2HO4(-)·2H2O, (I), and with adipic acid, bis(4-carbamoylpiperidinium) adipate dihydrate, 2C6H13N2O(+)·C6H8O4(2-)·2H2O, (II), are three-dimensional hydrogen-bonded constructs involving several different types of enlarged water-bridged cyclic associations. In the structure of (I), the oxalate monoanions give head-to-tail carboxylic acid O-H···O(carboxyl) hydrogen-bonding interactions, forming C(5) chain substructures which extend along a. The isonipecotamide cations also give parallel chain substructures through amide N-H···O hydrogen bonds, the chains being linked across b and down c by alternating water bridges involving both carboxyl and amide O-atom acceptors and amide and piperidinium N-H···O(carboxyl) hydrogen bonds, generating cyclic R4(3)(10) and R3(2)(11) motifs. In the structure of (II), the asymmetric unit comprises a piperidinium cation, half an adipate dianion, which lies across a crystallographic inversion centre, and a solvent water molecule. In the crystal structure, the two inversion-related cations are interlinked through the two water molecules, which act as acceptors in dual amide N-H···O(water) hydrogen bonds, to give a cyclic R4(2)(8) association which is conjoined with an R4(4)(12) motif. Further N-H···O(water), water O-H···O(amide) and piperidinium N-H···O(carboxyl) hydrogen bonds give the overall three-dimensional structure. The structures reported here further demonstrate the utility of the isonipecotamide cation as a synthon for the generation of stable hydrogen-bonded structures. The presence of solvent water molecules in these structures is largely responsible for the non-occurrence of the common hydrogen-bonded amide-amide dimer, promoting instead various expanded cyclic hydrogen-bonding motifs.

Synthesis and characterization of a proton transfer salt between 2,6-pyridinedicarboxylic acid and 2-aminobenzothiazole, and its complexes and their inhibition studies on carbonic anhydrase isoenzymes

A novel proton transfer compound (HABT)+(Hdipic)− (1) obtained from ABT and H2dipic and its metal complexes (2–5) have been prepared and characterized by spectroscopic techniques. Single crystal X-ray diffraction method has also been applied to 2 and 5. While complex 2 has a distorted octahedral conformation, 5 exhibits a distorted square pyramidal structure. The structures of 3 and 4 might be proposed as octahedral according to experimental data. All compounds were also evaluated for their in vitro inhibition effects on hCA I and II for their hydratase and esterase activities. Although there is no inhibition for hydratase activities, all compounds have inhibited the esterase activities of hCA I and II. The comparison of the inhibition studies of 1–5 to parent compounds indicates that 1–5 have superior inhibitory effects. The inhibition effects of 2–5 are also compared to inhibitory properties of the metal complexes of ABT and H2dipic, revealing an improved transfection profile.

Synthesis and characterization of a proton transfer salt between dipicolinic acid and 2-amino-6-methylbenzothiazole and its complexes, and their inhibition studies on carbonic anhydrase isoenzymes

A novel proton transfer compound (HMeABT)+(HDPC)−·H2O (1) obtained from 2-amino-6-methylbenzothiazole (MeABT) and dipicolinic acid (H2DPC) and its Fe(III), Fe(II), Co(II), Ni(II) and Cu(II) complexes (2–6) have been prepared and characterized by elemental, spectral (1H NMR, IR and UV–Vis) and thermal analyses, magnetic measurement and molar conductivity. Additionally, single crystal X-ray diffraction techniques were applied to all complexes.All compounds, including acetazolamide (AAZ) as the control compound, were also evaluated for their in vitro inhibition effects on human carbonic anhydrase isoenzymes (hCA I and hCA II) for their hydratase and esterase activities. Although there is no inhibition for hydratase activities, all compounds have inhibited the esterase activities of hCA I and II. The comparison of the inhibition studies of 1–6 to parent compounds, MeABT and H2DPC, indicates that 1–6 have more inhibitory effects. The inhibition effects of 2–6 are also compared to the simple metal complexes of MeABT and H2DPC, and the complexes from proton transfer salt (2–6) have shown better inhibition effects. Nevertheless, all the studied compounds have less inhibition effects than AAZ.

Solution and solid state studies of three new supramolecular compounds of zinc(II), nickel(II) and uranium(VI) with chelidamic acid and 9-aminoacridine

Three new supramolecular compounds, (aacrH)2[Zn(hypydc)2]·4H2O 1, (aacrH)2[UO2(hypydc)2]·2DMSO 2, and (aacrH)2[Ni(hypydc)2]·4H2O 3, [where hypydcH2=4-hydroxypyridine-2,6-dicarboxylic acid (chelidamic acid), aacr=9-aminoacridine and DMSO=dimethyl sulfoxide] have been synthesized and characterized by elemental analysis, spectral (IR, UV–Vis, fluorescence), 1H NMR spectroscopy, thermal (TG/DTG/DTA) analysis and single crystal X-ray diffraction. All three compounds are proton transfer salts of the aminoacridinium cation and transition metal complex anions that crystallized from a solution of the dicarboxylic acid, aminoacridine, and metal nitrates as starting materials. The coordinating dicarboxylic acid is deprotonated at the carboxyl rather than the hydroxyl group, and the aminoacridine is selectively protonated at the pyridyl nitrogen but not at the amino group. In the crystal structures of 1–3 complex hydrogen bonding arrangements and π–π stacking play important roles. Water clusters (H2O)n [n=2–4] are formed in compounds 1 and 3. The complexes are strongly luminescent at room temperature, exhibiting a sharp emission at 400nm. The equilibrium constants of chelidamic acid (hypydc), 9-aminoacridine (aacr), proton transfer system as well as those of the complexes, were investigated by a potentiometric pH titration method.

Proton-transfer compounds with 4-amino-N-(4,6-dimethylpyrimidin-2-yl)benzenesulfonamide (sulfamethazine): the structures and hydrogen bonding in the salts with 5-nitrosalicylic acid and picric acid

The structures of the anhydrous proton-transfer compounds of the sulfa drug sulfamethazine with 5-nitrosalicylic acid and picric acid, namely 2-(4-aminobenzenesulfonamido)-4,6-dimethylpyrimidinium 2-hydroxy-5-nitrobenzoate, C12H15N4O2S(+)·C7H4NO4(-), (I), and 2-(4-aminobenzenesulfonamido)-4,6-dimethylpyrimidinium 2,4,6-trinitrophenolate, C12H15N4O2S(+)·C6H2N3O7(-), (II), respectively, have been determined. In the asymmetric unit of (I), there are two independent but conformationally similar cation-anion heterodimer pairs which are formed through duplex intermolecular N(+)-H···O(carboxylate) and N-H···O(carboxylate) hydrogen-bond pairs, giving a cyclic motif [graph set R2(2)(8)]. These heterodimers form separate and different non-associated substructures through aniline N-H···O hydrogen bonds, one one-dimensional, involving carboxylate O-atom acceptors, the other two-dimensional, involving both carboxylate and hydroxy O-atom acceptors. The overall two-dimensional structure is stabilized by π-π interactions between the pyrimidinium ring and the 5-nitrosalicylate ring in both heterodimers [minimum ring-centroid separation = 3.4580 (8) Å]. For picrate (II), the cation-anion interaction involves a slightly asymmetric chelating N-H···O R2(1)(6) hydrogen-bonding association with the phenolate O atom, together with peripheral conjoint R1(2)(6) interactions between the same N-H groups and O atoms of the ortho-related nitro groups. An inter-unit amine N-H···O(sulfone) hydrogen bond gives one-dimensional chains which extend along a and inter-associate through π-π interactions between the pyrimidinium rings [centroid-centroid separation = 3.4752 (9) Å]. The two structures reported here now bring to a total of four the crystallographically characterized examples of proton-transfer salts of sulfamethazine with strong organic acids.

Structural, thermal, morphological and biological studies of proton-transfer complexes formed from 4-aminoantipyrine with quinol and picric acid

4-Aminoantipyrine (4AAP) is widely used in the pharmaceutical industry, biochemical experiments and environmental monitoring. However, residual amounts of 4AAP in the environment may pose a threat to human health. To provide basic data that can be used to extract or eliminate 4AAP from the environment, the proton-transfer complexes of 4AAP with quinol (QL) and picric acid (PA) were synthesized and spectroscopically investigated. The interactions afforded two new proton-transfer salts named 1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-aminium-4-hydroxyphenolate and 1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-aminium-2,4,6-trinitrophenolate for QL and PA, respectively, via a 1:1 stoichiometry. Elemental analysis (CHN), electronic absorption, spectrophotometric titration, IR, Raman, 1H NMR and X-ray diffraction were used to characterize the new products. The thermal stability of the synthesized CT complexes was investigated using thermogravimetric (TG) analyses, and the morphology and particle size of these complexes were obtained from scanning electron microscopy (SEM). It was found that PA and 4AAP immediately formed a yellow precipitate with a remarkable sponge-like morphology and good thermal stability up to 180°C. Finally, the biological activities of the newly synthesized CT complexes were tested for their antibacterial and antifungal activities. The results indicated that the [(4AAP)(QL)] complex exhibited strong antimicrobial activities against various bacterial and fungal strains compared with standard drugs.

Supramolecular Organic Salts Constructed from 6-Hydroxyquinoline and Nitrobenzoic Acids

The crystal structures of the proton-transfer salts of 6-hydroxyquinoline with 3,5-dinitrobenzoic acid (1) and 4-nitrobenzoic acid (2) have been determined at room temperature. Their comparative structural features and hydrogen-bonding patterns are described here. Compound 1 crystallizes in the monoclinic P21/c space group, while 2 in the triclinic P−1 space group. Unit cell dimensions and contents are: a = 7.6956(15), b = 26.075(5), c = 7.7233(15) A, β = 95.96(3)° for 1; a = 7.7325(15), b = 8.5939(17), c = 12.394(3) A, β = 77.63(3)° for 2. Supramolecular architectures are formed by intermolecular hydrogen bonds in the proton-transfer process. The supramolecular structures are stabilized by N–H···O, O–H···O and C–H···O hydrogen bonds between the two components. Extensive hydrogen-bonding interactions give two-dimensional network structures. In addition, π–π stacking interactions exist in the salt 1 due to the aromatic rings. The crystal structures of the proton-transfer salts of 6-hydroxyquinoline with 3,5-dinitrobenzoic acid (1) and 4-nitrobenzoic acid (2) have been determined at room temperature. The supramolecular structures are stabilized by N–H···O, O–H···O and C–H···O hydrogen bonds between the two components. In addition, π–π stacking interactions exist in the salt 1 due to the aromatic rings.

Synthesis, characterization, and biological evaluation of Cu(II) complexes with the proton transfer salt of 2,6-pyridinedicarboxylic acid and 2-amino-4-methylpyridine

A proton transfer compound, (Hamp)+(Hdipic)− · 1.5H2O (1), and Cu(II) complexes, [Cu(dipic)(amp)(H2O)] · [Cu(dipic)(amp)] · H2O · CH3COOH (2) and [Cu(dipic)(amp)Cu(dipic)(amp)(H2O)Cu(dipic)(amp)(H2O)] · 3H2O (3), have been synthesized from 2,6-pyridinedicarboxylic acid (H2dipic) and 2-amino-4-methylpyridine (amp). They have been characterized by elemental, spectral (1H-NMR, IR, and UV-Vis), and thermal analyses. In addition, magnetic measurements and single crystal X-ray diffraction have been applied to 2 and 3. The crystal structure of 2 consists of two independent and different cationic sites with Cu2+ ions. Cu1 is four-coordinate in a distorted square planar geometry and Cu2 is five-coordinate in a distorted square pyramid. Compound 3 has three independent and different cationic sites of Cu2+ ions. Cu1 is four-coordinate in a distorted square planar geometry and Cu2 and Cu3 have five-coordinate, distorted square-pyramidal sites. Inhibitory effects of 1, 2, and 3 have been studied and compared with starting compounds (amp and H2dipic) on bacterial growth of Staphylococcus aureus and Escherichia coli cultures. Compounds 2 and 3 prevent bacterial growth although 1 has no effect. Compounds 2 and 3 are more effective than amp and H2dipic, at similar concentrations on preventing bacterial growth for both organisms.

Protic ionic liquid and ionic melts prepared from methanesulfonic acid and 1H-1,2,4-triazole as high temperature PEMFC electrolytes

Protic ionic liquid and ionic melts were prepared from the combination of methanesulfonic acid (CH3SO3H) and 1H-1,2,4-triazole (C2H3N3) at various molar ratios. The thermal properties, crystal structure, acid–base interactions, ionic conductivity, proton conduction behavior and electrochemical stability of the system were studied. The equimolar composition, 1,2,4-triazolium methanesulfonate (C2H4N3+·CH3SO3− (1)), was a proton transfer salt with a melting point of around 134 °C. Single crystal and powder XRD data, as well as TGA results, revealed that the base-rich region was a mixture of 1 and 1H-1,2,4-triazole. Infrared analysis and single crystal data suggested that the C2H3N3–CH3SO3H system exists in a strongly hydrogen-bonded network. Systematic investigation of the ionic conductivity showed that the ionic conductivity reached local maxima at the compositions of [C2H3N3]/[CH3SO3H] = 10/90 and 80/20, respectively, while it exhibited a local minimum at the equimolar composition. The temperature dependence of the ionic conductivity was found to obey the Vogel–Fulcher–Tamman (VFT) equation. The fitting of the conductivity data to the VFT equation showed that the carrier ion concentration versus the mole fraction of 1H-1,2,4-triazole exhibited a volcano shape. In addition, the C2H3N3–CH3SO3H system showed adequate electrochemical stability under PEMFC conditions as measured by linear sweep voltammetry. The relatively high ionic conductivity, wide electrochemical window and good thermal stability demonstrated that the C2H3N3–CH3SO3H system is a suitable candidate for high temperature PEMFC electrolytes.