Spectroscopic and structural elucidation of 4-dimethylaminopyridine and its hydrogensquarate

Investigation of hydrogen bonds in proton transfer complexes derived from the reaction of 2- and 4-(N,N-dimethylamino)pyridines with chloranilic acid

New complexes of 2-(N,N-dimethylamino)pyridine with chloranilic acid (2-DMAP + CLA) and 4-(N,N-dimethylamino)pyridine with chloranilic acid (4-DMAP + CLA) were synthesized and characterized by single crystal X-ray diffraction, infrared spectroscopy, thermal analysis methods and 1H, 13C and 15N NMR spectroscopy. The NMR spectroscopies were carried out in both, DMSO solution and in the solid state (CPMAS NMR). The 2-DMAP + CLA and 4-DMAP + CLA complexes crystallize in centrosymmetric P-1 and P21/c space group, respectively. In both complexes, the phenomenon of proton transfer is observed, which results in the formation of strong N+-H···O- hydrogen bonds. Thermal decompositions of 2-DMAP + CLA and 4-DMAP + CLA complexes were studied by thermogravimetric analysis. Temperature dependent IR spectra revealed that methyl groups of 4-DMAP + CLA perform fast stochastic reorientational motion at room temperature which is slowed on cooling while in 2-DMAP + CLA reonrientational motion of CH3 groups is much slower due to steric effects.

From Solid-State Cluster Compounds to Functional PMMA-Based Composites with UV and NIR Blocking Properties, and Tuned Hues

New nanocomposite materials with UV-NIR blocking properties and hues ranging from green to brown were prepared by integrating inorganic tantalum octahedral cluster building blocks prepared via solid-state chemistry in a PMMA matrix. After the synthesis by the solid-state chemical reaction of the K₄[{Ta₆Brⁱ₁₂}Br^a₆] ternary halide, built-up from [{Ta₆Brⁱ₁₂}Br^a₆]^4- anionic building blocks, and potassium cations, the potassium cations were replaced by functional organic cations (Kat⁺) bearing a methacrylate function. The resulting intermediate, (Kat)₂[{Ta₆Brⁱ₁₂}Br^a₆], was then incorporated homogeneously by copolymerization with MMA into transparent PMMA matrices to form a brown transparent hybrid composite Ta@PMMA_brown. The color of the composites was tuned by controlling the charge and consequently the oxidation state of the cluster building block. Ta@PMMA_green was obtained through the two-electron reduction of the [{Ta₆Brⁱ₁₂}Br^a₆]^2- building blocks from Ta@PMMA_brown in solution. Indeed, the control of the oxidation state of the Ta₆ cluster inorganic building blocks occurred inside the copolymer, which not only allowed the tuning of the optical properties of the composite in the visible region but also allowed the tuning of its UV and NIR blocking properties.

A New Cu(II) Metal Complex Template with 4–Tert–Butyl-Pyridinium Organic Cation: Synthesis, Structure, Hirshfeld Surface, Characterizations and Antibacterial Activity

In this paper, we report on the chemical preparation, crystal details, vibrational, optical, and thermal behavior, and antibacterial activity of a new non-centrosymmetric compound: 4-ter-butyl-pyridinium tetrachloridocuprate. X-ray diffraction analysis shows that the structure has a 3Dnetwork made up of C–H…Cl and N–H…Cl H-bonds, and [CuCl4]2− anions have a shape halfway between a tetrahedron and a square planar structure in this compound’s monoclinic system. Hirshfeld surface analysis was used to explain the nature and extent of intermolecular interactions, highlighting the importance of the H-bonds and the C–H⋯π interactions in the structure’s stabilization. Additionally, SEM/EDX experiments were conducted. The powder X-ray diffraction investigation at room temperature validated the material purity. Moreover, the different functional groups were identified using FT-IR spectroscopy. In addition, the optical properties were investigated using UV-Vis absorption. The thermal stability of (C9H14N)2[CuCl4] was performed by TGA-DTA. The bactericidal potency of the title compound was surveyed.

Synthesis and structural characteristic of pyridine carboxylic acid adducts with squaric acid

Squaric acid was used as a coformer to pyridine carboxylic acid cocrystallization. Adducts were obtained by evaporation from solution. Spectroscopic and theoretical studies were also performed. Thermal analysis reveals the high thermal stability of the obtained complexes.

Crystal structure, Hirshfeld surface analysis and physicochemical characterization of bis-[4-(di-methyl-amino)-pyridinium] di-μ-chlorido-bis[di-chlorido-mercurate(II)]

The title mol-ecular salt, (C7H11N2)2[Hg2Cl6], crystallizes with two 4-(di-methyl-amino)-pyridinium cations (A and B) and two half hexa-chlorido-dimercurate(II) anions in the asymmetric unit. The organic cations exhibit essentially the same features with an almost planar pyridyl ring (r.m.s. deviations of 0.0028 and 0.0109 Å), which forms an inclined dihedral angle with the dimethyamino group [3.06 (1) and 1.61 (1)°, respectively]. The di-methyl-amino groups in the two cations are planar, and the C-N bond lengths are shorter than that in 4-(di-methyl-amino)-pyridine. In the crystal, mixed cation-anion layers lying parallel to the (010) plane are formed through N-H⋯Cl hydrogen bonds and adjacent layers are linked by C-H⋯Cl hydrogen bonds, forming a three-dimensional network. The analyses of the calculated Hirshfeld surfaces confirm the relevance of the above inter-molecular inter-actions, but also serve to further differentiate the weaker inter-molecular inter-actions formed by the organic cations and inorganic anions, such as π-π and Cl⋯Cl inter-actions. The powder XRD data confirms the phase purity of the crystalline sample. Furthermore, the vibrational absorption bands were identified by IR spectroscopy and the optical properties were studied by using optical UV-visible absorption spectroscopy.

Crystal structure of bis(4-dimethylamino-pyridin-1-ium)tetrafluorosuccinate, C18H22F4N4O4

C18H22F4N4O4, triclinic, P1̄ (no. 2), a = 7.3295(9) Å, b = 8.6026(9) Å, c = 8.8041(11) Å, α = 77.240(4)°, β = 72.215(4)°, γ = 71.531(4)°, V = 496.61(10) Å3, Z = 1, R gt(F) = 0.1022, wR ref(F 2) = 0.1587, T = 294(2) K.

Hydrogen bonding, π-π stacking and van der Waals forces-dominated layered regions in the crystal structure of 4-amino-pyridinium hydrogen (9-phosphono-non-yl)phospho-nate

The asymmetric unit of the title mol-ecular salt, [C5H7N2+][(HO)2OP(CH2)9PO2(OH)-], consists of one 4-amino-pyridinium cation and one hydrogen (9-phos-phono-non-yl)phospho-nate anion, both in general positions. As expected, the 4-amino-pyridinium moieties are protonated exclusively at their endocyclic nitro-gen atom due to a mesomeric stabilization by the imine form which would not be given in the corresponding double-protonated dicationic species. In the crystal, the phosphonyl (-PO3H2) and hydrogen phospho-nate (-PO3H) groups of the anions form two-dimensional O-H⋯O hydrogen-bonded networks in the ab plane built from 24-membered hydrogen-bonded ring motifs with the graph-set descriptor R66(24). These networks are pairwise linked by the anions' alkyl-ene chains. The 4-amino-pyridinium cations are stacked in parallel displaced face-to-face arrangements and connect neighboring anionic substructures via medium-strong charge-supported N-H⋯O hydrogen bonds along the c axis. The resulting three-dimensional hydrogen-bonded network shows clearly separated hydro-philic and hydro-phobic structural domains.

Self-assembled supramolecular structure of 4-dimethylaminopyridinium p-hydroxy benzoate pentahydrate: synthesis, growth, optical and biological properties

A single crystal of 4-dimethylaminopyridinium p-hydroxybenzoate pentahydrate (DMAPHB) was obtained via a slow evaporation solution growth technique.

1-(7-Chloro-1,4-dihydroquinolin-4-ylidene)thiosemicarbazide and its hydrochloride: evidence for the existence of a stable imine tautomer in the solid state of 4-aminoquinoline free bases, an anomalous case in nitrogen heterocycles

In the solid state, crystals of both 1-(7-chloro-1,4-dihydroquinolin-4-ylidene)thiosemicarbazide–methanol–water (2/1/1), 2C10H9ClN4S·CH3OH·H2O, (I), and its hydrochloride salt {systematic name: [(7-chloro-1,4-dihydroquinolin-4-ylidene)azaniumyl]thiourea chloride}, C10H10ClN4S+·Cl−, (II), assume the imine tautomeric form, contrary to other 4-amino-7-chloroquinolines. Of particular interest are the N—C bond lengths, which have appreciable double-bond character, and the C—N—C aromatic ring bond angle. Both of these parameters have been studied extensively in 4-amino-substituted quinolines. The crystal structures of (I) and (II) in this study provide interesting examples of the amino–imino tautomerism which exists in this class of compound and is, to the best of our knowledge, hitherto unreported.

3-Phenylpyridinium hydrogen squarate: experimental and computational study of a nonlinear optical material

The detailed investigation of an organic nonlinear optical (NLO) squarate salt of 3-phenylpyridinium hydrogen squarate (1), C11H10N+·C4HO4(-), was reported in this study. The XRD data indicates that the crystal structure of the title compound is in the triclinic P-1 space group. In the asymmetric unit, the 3-phenylpyridine molecule is protonated by one hydrogen atom donation of squaric acid molecule, forming the salt (1). The X-ray analysis shows that the crystal packing has hydrogen bonding ring pattern of D2(2)(10) (α-dimer) through NH···O interactions. The structural and vibrational properties of the compound were also studied by computational methods of ab initio at DFT/B3LYP/6-31++G(d,p) (2) and HF/6-31++G(d,p) (3) levels of theory. The calculation results on the basis of two models for both the optimized molecular structure and vibrational properties for the 1 are presented and compared with the experimental results. Non-linear optical properties (NLO) of the title compound together with the molecular electrostatic potential (MEP), electronic absorption spectrum, frontier molecular orbitals (FMOs) and conformational flexibility were also studied at the 2 level and the results were reported. In order to evaluate the suitability for NLO applications thermal analysis (TG, DTA and DTG) data of 1 were also obtained.

2-Pyridinium propanol hydrogen squarate: experimental and computational study of a nonlinear optical material

The experimental and theoretical investigation of a novel organic nonlinear optical (NLO) squarate salt of 2-pyridinium propanol hydrogen squarate (1), C8H12ON(+)·C4HO4(-), were reported in this study. The crystal structure of the title compound was found to crystallize in the triclinic P-1 space group. In the asymmetric unit each squaric acid molecules have donated one H atom to the pyridines N1 and N2 atoms of a 2-pyridine propanol molecule, forming the salt (1). The X-ray analysis clearly indicated that the crystal packing has shown the hydrogen bonding ring pattern of D2(2)(10) (α-dimer) through N-H⋯O interactions. The structural and vibrational properties of the compound were also studied by computational methods of ab initio performed on the compound at DFT/B3LYP/6-31++G(d,p) (2) and HF/6-31++G(d,p) (3) level of theory. The calculation results on the basis of two models for both the optimized molecular structure and vibrational properties for the 1 are presented and compared with the X-ray analysis result. The molecular electrostatic potential (MEP), electronic absorption spectra, frontier molecular orbitals (FMOs), conformational flexibility and non-linear optical properties (NLO) of the title compound were also studied at the 2 level and the results are reported. In order to evaluate the suitability for NLO applications thermal analysis (TG, DTA and DTG) data of 1 were also obtained.

Synthesis, an experimental and quantum chemical computational study: proton sharing in 4-Morpholinium bis(hydrogen squarate)

The experimental and theoretical investigation results of a novel organic squarate salt of 4-Morpholinium bis(hydrogen squarate) (1), C₆H₁₄ON(+)·C₈H₃O₈(-), were reported in this study. The crystal structure of the title compound was found to crystallize in the triclinic P-1 space group. In the crystals of 1 the morpholine ring adopts the chair conformation with the ethyl group in the equatorial and hydrogen atoms in axial positions. The hydrogen squarate anions are linked into a homoconjugated anion, [(HSQ)₂H], by a short symmetric, nonlinear O₈⋯H₂⋯O₂ hydrogen bond of 2.444 (2)Å. The structural and vibrational properties of the compound were also studied by computational methods of ab-initio performed on the compound at DFT/B3LYP/6-31++G(d,p) (2) and HF/6-31++G(d,p) (3) level of theory. The obtained calculation results on the basis of two models for both the optimized molecular structure and vibrational properties for the 1 obtained are presented and compared with the X-ray analysis result. On the other hand the molecular electrostatic potential (MEP), electronic absorption spectra, frontier molecular orbitals (FMOs), conformational flexibility and non-linear optical properties (NLO) of the title compound were also studied at the 2 level and the results are reported. In order to evaluate the suitability for NLO applications thermal analysis (TG, DTA and DTG) data of 1 were also obtained.

Synthesis, an experimental and quantum chemical computational study of a new nonlinear optical material: 2-picolinium hydrogensquarate

The experimental and theoretical investigation results of a novel organic non-linear optical (NLO) organic squarate salt of 2-Picolinium hydrogensquarate (1), C6H8N+·C4HO4-, were reported in this study. The space group of the title compound was found in the monoclinic C2/c space group. It was found that the asymmetric unit consists of one monohydrogen squarate anion together with mono protonated 2-Picolinium, forming the (1) salt. The X-ray analysis clearly indicated that the crystal packing has shown the hydrogen bonding ring pattern of D2(2)(10) (α-dimer) through NH⋯O interactions. The hydrogensquarate anions form α-dimer, while 2-Picolinium molecule interacts through NH⋯O and CH⋯O with the hydrogensquarate anion. The structural and vibrational properties of the compound were also studied by computational methods of ab initio performed on the compound at DFT/B3LYP/6-31++G(d,p) (2) and HF/6-31++G(d,p) (3) level of theory. The calculation results on the basis of two models for both the optimized molecular structure and vibrational properties for the 1 obtained are presented and compared with the X-ray analysis result. On the other the molecular electrostatic potential (MEP), electronic absorption spectra, frontier molecular orbitals (FMOs), conformational flexibility and non-linear optical properties (NLO) of the title compound were also studied at the 2 level and the results are reported. In order to evaluate the suitability for NLO applications thermal analysis (TG, DTA and DTG) data of 1 were also obtained.

NH⋯O and OH⋯O interactions of glycine derivatives with squaric acid

Hydrogen-bonded complexes of glycine, sarcosine, dimethylgycine and betaine with squaric acid have been synthesized and characterized by X-ray diffraction, FTIR, NMR and DFT methods.

Stable Molecular Complex of Squaric Acid with 2-(Quinuclidinium)propionate

Squaric acid (3,4-dihydroxy-3-cyclobuten-1,2-dione, H2SQ) forms a complex with 2-(quinuclidinium)propionate (QNPr). In crystals, the molecules of H2SQ and zwitterions of QNPr are bridged by two strong non-equivalent O–H⋯O hydrogen bonds of 2.476(2) and 2.482(1) Å. The complex is investigated by X-ray diffraction, FTIR, and NMR techniques, and the results are supported by density functional theory calculations. The solid-state aggregation is consistent with the NMR results, recorded for an aqueous solution, and is also reproduced for the structure optimized at the B3LYP/6-311++G(d,p) level of theory. The calculated IR frequencies for the optimized structure have been used for the assignment of the experimental FTIR spectrum, where the broad absorption at ~2400 cm–1 corresponds to the short asymmetric OH⋯O bonds.

Chiral solvating agents for cyanohydrins and carboxylic acids

We have shown that a structure as simple as an ion pair of (R)- or (S)-mandelate and dimethylamminopyridinium ions possesses structural features that are sufficient for NMR enantiodiscrimination of cyanohydrins. Moreover, (1)H NMR data of cyanohydrins of known configuration obtained in the presence of the mandelate-dimethylaminopyridinium ion pair point to the existence of a correlation between chemical shifts and absolute configuration of cyanohydrins. Mandelate-DMAPH(+) ion pair and mandelonitrile form a 1:1 complex with an association constant of 338 M(-1) (DeltaG(0), -3.4 kcal/mol) for the (R)-mandelonitrile/(R)-mandelate-DMAPH(+) and 139 M(-1) (DeltaG(0), -2.9 kcal/mol) for the (R)-mandelonitrile/(S)-mandelate-DMAPH(+) complex. To understand the origin of enantiodiscrimination, the geometry optimization and energy minimization of the models of ternary complexes of (S)-mandelonitrile/(R)-mandelate/DMAPH(+) and (S)-mandelonitrile/(S)-mandelate/DMAPH(+) complexes was performed using DFT methodology (B3LYP) with the 6-31+G(d) basis set in Gaussian 3.0. Further, analysis of optimized molecular model obtained from theoretical studies suggested that (i) DMAP may be replaced with other amines, (ii) the hydroxyl group of mandelic acid is not necessary for stabilization of ternary complex and may be replaced with other groups such as methyl, (iii) the ion pair should form a stable ternary complex with any hydrogen-bond donor, provided its OH bond is sufficiently polarized, and (iv) alpha-H of racemic mandelic acid should also get resolved with optically pure mandelonitrile. These inferences were experimentally verified, which not only validated the proposed model but also led to development of a new chiral solvating agent for determination of ee of carboxylic acids and absolute configuration of aryl but not alkyl carboxylic acids.