Pyridine Hydrogen Research Articles

Catalytic properties of selenium and phosphorus ionic liquids heterogenized on algae-based biochar

Catalytic performance of pyridinium hydrogen selenate (PHSe) and pyridinium dihydrogen phosphate (PH2P) ionic liquids immobilized on algae-based biochar (AC) was studied for the first time. For that purpose, acetic acid esterification with butanol was used as a test reaction. To investigate the surface effects, textural properties and thermal behavior for PHSe/AC and PH2P/AC, physicochemical methods such as X-ray powder diffraction (XRD), nitrogen adsorption–desorption isotherms (SBET) scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) were applied. In addition, influence of the catalyst content (5–12 wt%) and reaction temperature (60–80 °C) on the butyl acetate yield and rate constant of esterification were evaluated. SBET and SEM measurements revealed that all of the samples (AC, PHSe/AC and PH2P/AC) obtained are mixed microporous-mesoporous materials. XRD and XPS data showed more highly dispersed PH2P particles than PHSe on the carrier surface due to stronger surface ionic liquid-support interaction for PH2P/AC in comparison with PHSe/AC. The latter was responsible for higher thermal stability of PH2P/AC with respect to PHSe/AC. In addition, more obvious PH2P sites (than PHSe) on the biochar surface favored the ester production in the presence of PH2P/AC (77.4 % and 53.26 × 10−4 l/mol × min) more evidently than PHSe/AC (58.1 % and 28.82 × 10−4 l/mol × min).

Theoretical Investigation of the Pyridinium-Inspired Catalytic Dehydration of Heptafluoro-Iso-Butyramide for the Synthesis of Environmentally Friendly Insulating Gas Heptafluoro-Iso-Butyronitrile.

Heptafluoro-iso-butyronitrile (i-C3F7CN) represents a feasible eco-friendly replacement gas for the most potent greenhouse gas sulfur hexafluoride in various high-voltage power transmission equipment. The reaction mechanisms for the in situ synthesis of i-C3F7CN from heptafluoro-iso-butyramide [i-C3F7C(O)NH2] in the presence of trifluoroacetic anhydride (TFAA) and pyridine (Py) in dimethylformamide solution have been studied within density functional theory with M06-2X exchange-correlation functional with the 6-311++G(d,p) basis set and the high-level ab initio complete basis set quadratic CBS-QB3 method. It is revealed that the unimolecular dehydration of i-C3F7C(O)NH2 can be catalyzed efficiently by TFAA in terms of both kinetic and thermodynamic aspects, producing i-C3F7CN and trifluoroacetic acid (TFA). Furthermore, Py is capable of reducing the energy barrier of the rate-determining step through hydrogen abstraction to form pyridinium hydrogen. The synergic effect of the TFAA/Py co-catalyst plays a pivotal role in the production of i-C3F7CN as the Gibbs free energy barrier can be lowered by more than 40 kcal/mol with the ratio of TFAA:2Py, in accordance with the experimental observation. The present theoretical work provides new insights into the rational design on the novel catalysts for large-scale synthesis of the perfluorinated nitriles.

Chain-Length-Dependent Hydrogen-Bonded Self-Assembly of Terminally Functionalized Discrete Polyketones

Here, we report the synthesis and the chain-length-dependent self-assembling behaviors of discrete di-, tetra-, and hexaketones terminally functionalized with hydrogen-bonding carboxyl (C1, C2, and C3) and 3-acylaminopyridine groups (P1, P2, and P3). These polyketones were prepared by the coupling reactions of silylated analogues of 3,3-dimethylpentane-2,4-dione and t-butyl 2,2-dimethyl-3-oxobutanoate and the subsequent hydrolysis or amidation with 3-aminopyridine. Single-crystal X-ray diffraction analysis revealed that C1 and C2 form helical assemblies in which the components are connected by the dimerization of terminal carboxyl groups, whereas the longer C3 showed infinite hydrogen-bonded chains mediated by 1,4-dioxane used as a crystallization solvent. Pyridine-terminated P1 exhibited a three-dimensional hydrogen-bonded network owing to multiple NH···N(pyridine) hydrogen bonds in the solid state. P2 generated a double-helix-like fiber structure in the crystalline state. Among the pyridine-terminated polyketones P1–P3, only P2 showed gelation behavior in chloroform (100 mM concentration) at 25 °C. The scanning electron microscopy measurement of xerogel P2 revealed the formation of rod-like structures with a thickness of approximately 0.5–3.5 μm. These results demonstrate that the precise control of the polyketone chain length can significantly alter hydrogen-bonded self-assembly in the solid state and in solution even with the same terminal structures.

Producing Lignin and Ethyl Levulinate from Wheat Stalk Using 1-(3-Sulfobutyl) Triethylammonium Hydrogen Sulfate and USY Zeolite

The facile, green, and efficient strategy for the separation of lignin from straw and subsequent production of value-added chemicals is crucial to the current utilization of straw. Herein, up to 23.72% of lignin was isolated from wheat stalk over cheap and green 1-(3-sulfobutyl) triethylammonium hydrogen sulfate ([BSTEA]HSO4) in aqueous ethanol (Vethanol: Vwater = 4:1). The acquired lignin was verified as a p-hydroxyphenyl-guaiacyl-syringyl type, which had a narrower molecular weight distribution, better thermal stability, and higher purity compared with those of the lignin obtained using 1-methyl-3-(4-sulfobutyl)-imidazolium hydrogen sulfate and 1-(3-sulfobutyl) pyridinium hydrogen sulfate. Moreover, a carbohydrate-rich liquid containing [BSTEA]HSO4 was obtained by water removal from the waste liquid after lignin separation and further converted to ethyl levulinate (EL) by a one-pot process in the presence of inexpensive and stable USY zeolite. The yield of EL reached 30.23% at 200 °C for 60 min over the presence of 40% [BSTEA]HSO4 and 60% USY zeolite. Under optimal conditions, the yields of lignin and EL can respectively reach 83.89 and 72.28% of those catalyzed by a fresh catalyst after five cycles. In short, the above-mentioned methods present a green, economic, and efficient route for the extraction of lignin and further treatment of the liquid waste generated during the extraction process.

Different conformations and packing motifs in the crystal structures of four thio-phene-carbohydrazide-pyridine derivatives.

The crystal structures of four thio-phene-carbohydrazide-pyridine derivatives, viz. N'-[(E)-pyridin-3-yl-methyl-idene]thio-phene-2-carbohydrazide, C11H9N3OS, (I), N'-[(E)-pyridin-2-yl-methyl-idene]thio-phene-2-carbohydrazide, C11H9N3OS, (II), N-methyl-N'-[(E)-pyridin-2-yl-methyl-idene]thio-phene-2-carbohydrazide, C12H11N3OS, (III) and N'-[(E)-pyridin-2-yl-methyl-idene]-2-(thio-phen-2-yl)ethano-hydrazide, C12H11N3OS, (IV) are described. The dihedral angles between the thio-phene ring and the pyridine ring are 21.4 (2), 15.42 (14), 4.97 (8) and 83.52 (13)° for (I)-(IV), respectively. The thio-phene ring in (IV) is disordered over two orientations in a 0.851 (2):0.149 (2) ratio. Key features of the packing include N-H⋯Np (p = pyridine) hydrogen bonds in (I), which generate C(7) chains propagating in the [001] direction; N-H⋯Np links also feature in (II), but in this case they lead to C(6) [001] chains; in (IV), classical amide (C4) N-H⋯O links result in [010] chains; in every case adjacent mol-ecules in the chains are related by 21 screw axes. There are no classical hydrogen bonds in the extended structure of (III). Various weak C-H⋯X (X = O, N, S) inter-actions occur in each structure, but no aromatic π-π stacking is evident. The Hirshfeld surfaces and fingerprint plots for (I)-(IV) are compared.

Cation-anion interaction effect on the nonlinear optical behavior of pyridinium-based ionic liquids

Influence of the cation–anion interaction (expressed as internal hydrogen bonds) on the nonlinear optical properties (dipole moment, polarizability, anisotropy of polarizability and first-order hyperpolarizability) for the ionic liquids pyridinium hydrogen sulfate (PHS) and pyridinium bis(dihydrogen phosphate) (P2HP) was investigated in this paper. It was achieved analyzing vibrational modes (FT-IR) and electronic transitions (UV–vis) in PHS and P2HP. Molecular geometry of the title compounds was optimized by means of density functional theory calculations at B3LYP/6–311++G(2d,2p) level.Structural analysis exposed stronger internal hydrogen bonds (H7···O3 and H18···O4) between cationic and anionic fragments in the pyridinium hydrogen sulfate than these (H26···O4 and H25···O12) in pyridinium bis(dihydrogen phosphate). These observations are confirmed by FT-IR and UV–vis methods, where: (i) the infrared bands due to H···O and N–C interactions in P2HP appear at lower frequencies than the same ones in the spectrum of PHS and (ii) the n → π* electron transitions in PHS are more pronounced in comparison with these in P2HP. Based on the weaker cation–anion interaction in P2HP with respect to PHS, the former one is characterized with a remarkably higher first-order hyperpolarizability value. Hence, the ionic liquid P2HP was referred as a better nonlinear optical material than PHS.

Crystal Engineering of a Tetraphenol with Bispyridines toward Hydrogen-Bonded Emissive Cocrystals

Herein, we report the cocrystals of an AIEgenic tetraphenol, namely tetrakis(4-hydroxybiphenyl)ethylene (THBPE), with a few bispyridyl aza donors, built with phenol···pyridine hydrogen bonding. We ...

Biodiesel (methyl oleate) synthesis in the presence of pyridinium and aminotriazolium acidic ionic liquids: Kinetic, thermodynamic studies

Kinetics and thermodynamics of biodiesel (methyl oleate) synthesis using the protic ionic liquids pyridinium hydrogen sulfate (PHS), pyridinium nitrate (PN) and 4-amino-1H-1,2,4-triazolium nitrate (ATN) as catalysts are studied in the current work for the first time. Rate of the biodiesel production is directly related to acidity of the ionic liquids used and their internal hydrogen bonding extent. A detailed thermodynamic analysis on the title reaction is conducted as well. To optimize the reaction conditions, influence of the reaction temperature (25–55 °C), initial alcohol-to-acid molar ratio (1.0–15.0) and catalyst loading (5–15 wt% with respect to the substrate mass) is investigated in details. Catalyst reusability is evaluated for five cycles. Based on the experimental data, a plausible mechanism of biodiesel synthesis is offered. Catalytic performance of the PHS sample in the biodiesel synthesis is remarkably higher than that of the nitrate anion-based ionic liquids. Reaction temperature of 55 °C, an initial reactants molar ratio of 7.0 and a catalyst loading of 10 wt% are established as optimal conditions for the process of biodiesel production. Values of 43.09 kJ/mol and 91.29 × 105 l/mol × min are calculated as activation energy and pre-exponential factor, respectively. ΔSr° and ΔHr° for the process of biodiesel synthesis are found to be 42.32 J/mol × K and 9.64 kJ/mol, respectively. Moreover, ΔH≠ (40.49 kJ/mol) and ΔS≠ (−162.31 J/mol × K) are established as well. The respective ΔGr° (−4.241 kJ/mol) and ΔG≠ (93.727 kJ/mol) at reaction temperature of 55 °C are obtained.

Surface, textural and catalytic properties of pyridinium hydrogen sulfate ionic liquid heterogenized on activated carbon carrier

Pyridinium hydrogen sulfate ionic liquid (PHS) heterogenized on activated carbon (AC) is investigated for the first time in the current paper. For that purpose, the xPHS/AC (x = 8, 17, 33 and 66 wt%) samples are analyzed by a number of physicochemical methods such as N2 adsorption–desorption measurements, X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Catalytic activity and reusability of xPHS/AC are evaluated in the reaction of butyl acetate synthesis. Effect of the reaction temperature and catalyst loading on the butyl acetate yield are examined in this work as well. Important thermodynamic parameters such as equilibrium constant, activation energy, Gibbs free energy and activation energy barrier for the reaction of butyl acetate synthesis in the presence of xPHS/AC are determined.Textural characterization revealed the that xPHS/AC are mixed micro-mesoporous materials. The PHS heterogenization on AC affects both ionic liquid and support phases due to a surface PHS–AC interaction. FT-IR and XPS showed that this interaction is: (i) manly expressed as a close contact between the pyridinium cation and the functional groups on the AC surface and (ii) electrostatic in nature. The existence of a PHS–AC interaction is found to be responsible for the formation of surface PHS particles of various size. However, the catalytic activity of xPHS/AC is established to be affected by the surface active phase amount, but not the PHS particle size.

Theoretical investigation of the stability, reactivity, and the interaction of methyl-substituted peridinium-based ionic liquids

Abstract This research work focuses on the reactivity, stability, and electronic interaction of pyridinium hydrogen nitrate (PHN)-based ionic liquids and the influence of methyl substituent on this class of ionic liquids: Ortho- (O-MPHN), meta- (M-MPHN), and para- (P-MPHN) substitution. Natural bond orbital (NBO) calculations were performed at the density functional theory (DFT) with Becke’s Lee Yang and Parr functional (B3LYP) methods and DFT/B3LYP/6-311++G(d,p) as basis set using GAUSSIAN 09W and GAUSSVIEW 6.0 software and the most important interaction between donor (Filled Lewis-type NBO’s) and the acceptor (vacant non-Lewis NBOs) were observed. From our natural bond orbital (NBO) result, it could be deduced that the higher the stabilization energy value, the greater the interaction between the donor and acceptor NBOs. The stability of the studied compounds is said to follow the order from O-MPHN > PHN > P-MPHN > M-MPHN based on the hyperconjugative interaction (stabilization energy) of the most significant interaction. The result of the highest occupied molecular orbital (HOMO), shows that PHN has the highest HOMO while the substituted derivatives have similar HOMO values between −7.70 and −7.98 eV thus PHN complex is the best electron donor while the substituted derivatives act as electron acceptors due to the presence of methyl group substituent which is observed to be electron deficient as a result of its withdrawal effect from the aromatic ring. Furthermore, the electron density, real space functions such as energy density and Laplacian of electron density at bond critical point (BCP) of the hydrogen bond interaction of the studied compounds were analyzed using Multifunctional Wavefunction analyzer software version 3.7 and it was observed that the hydrogen at position 6 and oxygen at position 11 (H6–O11) of M-methyl pyridinium nitrate with bond distance of 4.59 (Å) gave binding energy with the strongest electrostatic interaction between the cation and anion of the compounds under investigation. We also observed from our results that, substitution at the ortho position enhances the stability and strengthen the extent of charge transfer. This therefore implies that substitution at ortho position is more favorable for inter- and intramolecular interactions resulting to stabilization of the studied molecules.

Quaternary Cocrystals of 3,5-Dihydroxybenzoic Acid

One-pot synthesis of a series of four quaternary cocrystals of 3,5-dihydroxybenzoic (DHB) acid is outlined strategically based on the long-range synthon Aufbau modules (LSAM) approach exploiting hierarchical hydrogen bonding interactions. In these quaternary cocrystals, heteromeric O-H(phenolic)···N(pyridine) hydrogen bonds form a discrete closed synthon and additional heteromeric O-H(carboxylic)···N(pyridine) hydrogen bonds which lead to the formation of a one-dimensional structure. Of four quaternary cocrystals isolated, two pseudopolymorphs of DHB with tetramethylpyrazine (TMP), phenazine (PHE), and pyrene (PYR) (2:1:2:1 and 2:2:1:2 stoichiometric ratio) are observed. Both these pseudopolymorphs are composed of closed 0D tetrameric synthons consisting of two identical and distinct linker bases. Among these two, the quaternary cocrystals with stoichiometry of 2:1:2:1 are linked through DHB and PHE forming a symmetrical closed tetramer synthon, whereas quaternary cocrystals with 2:2:1:2 stoichiometric ratio are connected through DHB, TMP, and PHE forming an unsymmetrical closed tetramer synthon (anomalous synthon). ©

Synthesis and crystal structure of the pyridinium acid nitrate [(PyH)2(NO3)][H2(NO3)3] containing a dihydrogen trinitrate anion

A new protic room-temperature ionic liquid (Tc = 14 ± 1 °C) – pyridinium hydrogen dinitrate – was obtained from a solution of pyridinium nitrate in anhydrous nitric acid in a desiccator with P2O5. According to single crystal X-ray diffraction data, the solid state structure of [(PyH)2(NO3)][H2(NO3)3] consists of hydrogen bonded cations [(PyH)2(NO3)]+ and anions [(NO3)(HNO3)2]− with a previously unknown configuration containing two HNO3 molecules linked via hydrogen bonds to the central N O 3 − anion by the sin–anti type.

Synthesis and crystal structure of the pyridinium acid nitrate [(PyH)2(NO3)][H2(NO3)3] containing a dihydrogen trinitrate anion

A new protic room-temperature ionic liquid ( T c = 14 ± 1 °C) – pyridinium hydrogen dinitrate – was obtained from a solution of pyridinium nitrate in anhydrous nitric acid in a desiccator with P 2 O 5 . According to single crystal X-ray diffraction data, the solid state structure of [(PyH) 2 (NO 3 )][H 2 (NO 3 ) 3 ] consists of hydrogen bonded cations [(PyH) 2 (NO 3 )] + and anions [(NO 3 )(HNO 3 ) 2 ] − with a previously unknown configuration containing two HNO 3 molecules linked via hydrogen bonds to the central N O 3 − anion by the sin–anti type.

Hydrogen bonding effect on the thermal behavior of acidic ionic liquids

A relationship between the thermal performance (melting and thermal decomposition) and the internal hydrogen bonds for the protic ionic liquids pyridinium nitrate ([H–Pyr]+[NO3]–), pyridinium hydrogen sulfate ([H–Pyr]+[HSO4]–), pyridinium dihydrogen phosphate ([H–Pyr]+[H2PO4]–) and 4-amino-1H-1,2,4-triazolium nitrate ([4-AT]+[NO3]–) is investigated in the current work. For that purpose, melting/decomposition points, non-covalent bonding and intermolecular interaction are studied by means of TGA/DSC, reduced density gradient method and a Hirshfeld surface analysis.Results established that strong hydrogen bonds, rather than van der Waals interactions, influence the thermal behavior of the aforementioned ionic liquids in a great extent. Melting points of the compounds under investigation are found to decrease in order [H–Pyr]+[NO3]– > [4-AT]+[NO3]– > [H–Pyr]+[H2PO4]– > [H–Pyr]+[HSO4]– due a various hydrogen bonding degree. Overall decomposition of the pyridinium-based ionic liquids includes simple pyridine evaporation and protic acid (HNO3, H2SO4 and H3PO4) decay. However, decomposition of 2-aminotriazolium fragment (except HNO3) is also detected during [4-AT]+[NO3]– decay upon heating.

Porous Carbon Nitride Thin Strip: Precise Carbon Doping Regulating Delocalized π-Electron Induces Elevated Photocatalytic Hydrogen Evolution.

The photocatalytic efficiency of polymeric carbon nitride is hampered by high carrier recombination rate and low charge transfer. Herein, these issues are addressed by constructing 1D strip-like carbon nitride with a large π-electron conjugated system from carbon-doping, realizing the synchronization control of its electronic structure and morphology. Nicotinic acid, a monomer with the carboxyl group and pyridine ring, and melamine are selected for assembling the strip-like supramolecular via hydrogen bond under hydrothermal process. Both peripheral pyridine unit and hydrogen bond have significant effect on self-assembly process of nicotinic acid and melamine along one dimension to form a strip-like precursor. Subsequently, 1D thin porous strip-like carbon nitride is obtained by calcination treatment of precursor. The as-prepared 1D strip-like carbon nitride with effective π delocalization from carbon-doping and porous structure can accelerate charges and mass transfer and provide extra active sites. Both theoretical and experimental results demonstrate that carbon doping (pyridine heterocycle) narrows the bandgap via manipulating the band position and increases the π electron density. Thus, the 1D porous thin strip-like carbon nitride realizes compelling hydrogen evolution rate (126.2µmol h-1 ), far beyond (≈18 fold) the value of polymeric carbon nitride (PCN) (7.2µmol h-1 ) under visible light irradiation.

Effect of the active phase-support interaction on the electronic, thermal and catalytic properties of [H–Pyr]+[HSO4]−/support (support = rice husk ash; corundum)

Influence of the surface active phase-support interaction on the electronic, thermal and catalytic performance of pyridinium hydrogen sulfate ([H–Pyr]+[HSO4, PHS]−) ionic liquid immobilized by a wetness impregnation method on rice husk ash (RHA) and corundum (Al-NA) carriers has been investigated in the current work. For that purpose, both the developed supports and the corresponding catalysts (PHS/Al-NA and PHS/RHA) were characterized in details by means of analytical methods such as N2 adsorption-desorption measurements, X-ray diffraction, X-ray photoelectron spectroscopy, spectroscopy in the ultraviolet and visible regions, infrared spectroscopy and thermogravimetric analysis. To compare the catalytic activity of PHS/Al-NA and PHS/RHA, a process of butyl acetate synthesis was applied as a test reaction. The physicochemical characterization revealed that the active phase-support interaction in the case of PHS/RHA catalyst is stronger than that between PHS phase and Al-NA. Based on this, the catalytic performance of PHS/RHA sample (expressed by substrate conversion degree) in the reaction of acetic acid esterification with butanol was found to be more pronounced with respect to that of Al-NA supported pyridinium hydrogen sulfate.

Synthesis, structural and mass spectrometric investigations of pyridinium bis(thiosalicylato)mercurate(II)

This work investigates the synthesis and structural properties of a hydrogen-bonded salt of the [Hg(SC6H4-2-CO2)2]2− ion. The known bis(thiosalicylato)mercury(II) complex [Hg(SC6H4-2-CO2H)2], dissolves in pyridine (py), from which the crystalline pyridinium salt (pyH)2[Hg(SC6H4-2-CO2)2] can be isolated. Single crystal X-ray crystallography reveals two distinct three-molecule aggregates, namely {Hg[SC6H4-2-C(=O)OH]2(NC5H5)2} and {Hg[SC6H4-2-C(=O)O]2(HNC5H5)2}, which differ in the location of the acidic hydrogen atoms, i.e. either compound-bound for the former species or located on the pyridinium cations in the latter. The thiolate ligands are S,O-chelating and the resultant O2S2 four-coordinate geometries are each based on a distorted disphenoidal geometry. The three-molecule aggregates are sustained by hydroxylOH⋯N(pyridine) hydrogen bonds in the case of {Hg[SC6H4-2-C(=O)OH]2(NC5H5)2} whereas the second aggregate features charge-assisted pyridiniumNH⋯O(carboxylate) hydrogen bonds. (pyH)2[Hg(SC6H4-2-CO2)2] was also characterised by negative-ion ESI mass spectrometry, where it showed appreciable stability towards capillary exit voltage-induced fragmentation. In contrast, the S-bonded monodentate thiosalicylate complexes RHg(SC6H4-2-CO2)− (R = Et, Ph or ferrocenyl) undergo facile decarboxylation at relatively low voltages, with the phenyl and ferrocenyl complexes subsequently forming RHgS− as an additional fragment ion at high voltages. Aggregate ions formed with the sodium counter-cations of the type [(RHgSC6H4-2-CO2)nNan−1]− show appreciable stability towards fragmentation.

Quantum mechanical and reaction dynamics investigation of butyl acetate synthesis in the presence of pyridinium hydrogen sulfate

The thermodynamic and kinetic aspects of the mechanism of butyl acetate synthesis catalyzed by the diprotic ionic liquid pyridinium hydrogen sulfate ([H–Pyr]+[HSO4]−) were investigated using density functional theory (DFT) at B3LYP/6-311 + G(d,p) level of calculation. Electronic structure and geometry for individual molecules (substrate, catalyst) were clarified using molecular electrostatic potential surface, natural bond orbital analysis and atoms in molecules theory. The DFT results elucidated the catalytic cycle, which involved the formation of a transition state via substrate-BAIL interaction. Hydrogen bond interactions were found to exist throughout the process of the catalytic cycle, which are of special importance for stabilizing the transition state. Thus, a mechanism involving cooperative hydrogen bonding for BAIL catalyzed butyl acetate synthesis was established. Based on the above mechanism, the calculated thermodynamic parameters were validated by the subsequent kinetic study. Such results may provide fundamental insights into the design of ionic liquid-based homogeneous catalysts for esters production.

Hydrogen-bonding chain and dimer motifs in pyridinium and morpholinium hydrogen oxalate salts.

We present here three compounds consisting of pyridinium or morpholinium hydrogen oxalates, each displaying different hydrogen-bonding motifs, resulting in chains for 4-(di-methyl-amino)-pyridinium hydrogen oxalate 0.22-hydrate, C7H11N2 +·C2HO4 -·0.22H2O (1), dimers for 4-tert-butyl-pyridinium hydrogen oxalate, C9H14N+·C2HO4 - (2), and chains for morpholin-ium hydrogen oxalate, C4H10NO+·C2HO4 - (3).

The effect of malonic acid on the physico-chemical characterisation of 4-hydroxy pyridine: A new third order NLO single crystal

The proton transfer complex of 4-hydroxy pyridinium hydrogen malonate (4HPMA) single crystal was grown successfully by slow evaporation solution growth technique (SEST) at ambient temperature. Cell parameters and crystal structure of 4HPMA have been determined by single crystal X-ray diffraction (SCXRD) method. The UV–Vis absorption spectrum reveals that 4HPMA grown crystal exhibits 70% optical transparency in the range of 300–850 nm. Photoluminescence study suggests as-grown crystal has violet emission nature. FTIR and Raman spectral analysis have been used to identify the presence of various functional groups. 1 H and 13 C NMR spectral analyses were used to identify the presence of proton and carbon. Thermal behaviour of grown crystal has been identified by Thermogravimetric (TGA) and Differential thermogravimetric analyses (DTA). Third-order nonlinear optical studies have been evaluated with nonlinear refractive index (n2), nonlinear absorption coefficient (β) and third-order nonlinear optical susceptibility χ(3) of the grown crystal. Hirshfeld surface analyses were used to predict the existence of all intermolecular interactions.