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In this report, we have presented the theoretical investigation of anilinium hydrogen oxalate hemihydrate – an organic crystalline salt. The molecular geometry, as well as the vibrational parameter...

A novel nitrogen rich energetic salt 2,4-diamino-6-methyl-1,3,5-triazinium levulinate dihydrate (DMTLDH) has been grown by slow evaporation method at room temperature. The grown synthesized salt crystallizes in the centrosymmetric space group P21/n of monoclinic system. The intermolecular hydrogen bond N–H···N, N–H···O, C–H···O, O–H···O type interactions stabilizes the structure and leads to three dimensional network. In addition to that the crystal structure also possesses C–O···Cg interactions. Also, quantum chemical computational studies using DFT-B3LYP/6-311++G(d,p) and PBEPBE/6-31G(d,p) basis set is used to analyze the structural parameters and vibrational frequencies of grown crystal. Frontier molecular orbital analysis describes the charge transfer within the molecule and also other electronics parameters were calculated. The natural bonding orbital analysis has also been performed to study the stability of the molecule. Further, the crystal packing behaviour of DMTLDH was studied quantitatively with the aid of Hirshfeld surface analysis.

An organic crystalline salt 2,4-diamino-6-methyl-1,3,5-triazinium trifluroacetate (DMTFA) has been imposed for experimental and theoretical investigation. Gaussian 09 program has been used to compute the quantum chemical theoretical calculations. DFT/B3LYP-6-311++G(d,p) approach is adapted to optimize the structure. Structural and vibrational studies have been carried out by this approach followed by the correlation of experimental and theoretical results. Natural bonding orbital analysis, molecular electrostatic potential and frontier molecular orbital investigations substantiates the charge transfer besides the presence of strong inter and intra molecular interactions. Apart from the three dimensional Hirshfeld surface analysis and two dimensional fingerprint maps provides profund vision about the intermolecular interactions between the molecules.

The single crystals of p-nitroanilinium p-toluene sulphonate have been grown by slow solvent evaporation method at room temperature. X-Ray diffraction data have been collected from single crystal X-ray diffraction analysis and reveals that the crystal crystallizes in monoclinic system with centro symmetric space group P 21/n. The lattice parameters are calculated to be a = 6.2189 (14)A, b = 30.7201 (36)A, c = 7.4080 (12) A, α = γ = 90° and β = 97.25 (3)o. The volume of the unit cell is calculated to be = 1404.0 (4) (A)3. The hydrogen bond interactions between the singly protonated 4-nitroanilinium cation and single dissociated toluene sulphonate (1-) anions forms a three dimensional network. The crystallite size is calculated to be 14.264 μm from powder X-ray diffraction spectrum by using Debye-Scherrer's formula. The vibrational spectra provide the presence of NH3, CH3, SO3 and NO2 group of the title molecule. Further the 3D Hirshfeld surface analysis and 2D fingerprint maps were used for quantitative mapping out of the intermolecular interactions.

The comprehensive elucidation of the crystal structure, vibrational and Hirshfeld surface analysis of new crystalline product anilinium malonate C6H5NH3 +. C3H3O4 – are presented in this communication. Single crystals of anilinium malonate have been grown by the method of slow evaporation at room temperature. Single crystal XRD study has been carried out to study the structural properties of the grown crystal and it reveals that the crystal crystallizes in the monoclinic system with centrosymmetric space group P2(1)/n. Room temperature powder infrared and Raman spectra of the aniline malonic acid molecular complex (1:1) were carried out. All the characteristic frequencies present in the crystal gives the notable vibrational effect. Hirshfeld surface analysis has been carried out to know the intercontact between the atoms in the structure of the grown crystal.

The theoretical and experimental vibrational studies for poly thiourea silver nitrate (2:1) complex using DFT method are performed on the basis of experimental data. During the geometry optimization process one equilibrium structure was found. The Mulliken charges, harmonic vibrational frequencies, Infrared and Raman intensities were calculated on the basis of quantum chemical density functional calculations using firefly (PC GAMESS) Version 7.1G. The clear - cut assignments of observed bands are performed on the basis of potential energy distribution (PED) analysis. Highest Occupied Molecular Orbital (HOMO) and the Lowest Occupied Molecular Orbital (LUMO) are obtained and graphically illustrated with minimum energy. The energy difference between HOMO and LUMO is analyzed. The other molecular properties like molecular electrostatic potential, Mulliken charges and thermodynamic properties of the title compound have also been calculated.

The experimental and theoretical studies on the structure and vibrations of 1–acetyl–3–indolecarboxaldehyde (AIC) have been carried out by utilising FT–IR, FT–Raman, FT–NMR and quantum chemical density functional theory (DFT) method. The FT–IR and FT–Raman spectra are recorded in the region 4000–400 cm−1 and 4000–100 cm−1, respectively. The geometry of AIC is optimised by B3LYP method with 6–31G**, 6–311++G** and cc–pVTZ basis sets. The more stable minimum energy conformer has been found by analyzing the potential energy profile. The fundamental vibrational frequencies, infrared intensities, Raman intensities and bonding features of this compound are determined. The HOMO and LUMO energy difference show that, the charge transfer occurs within the molecule. The electrostatic potential and thermodynamic properties of the compound at the different temperatures have been calculated. 1H and 13C NMR chemical shifts of the compound are determined by Gauge Invariant Atomic Orbital (GIAO) by using B3LYP/6–311++G** method. The electrostatic potential of AIC lie in the range +1.22e × 10−2 to −1.22e × 10−2. The limits of total electron density of the complex is +4.906e × 10−2 to −4.906e × 10−2.

The new hydrogen bonded molecular complex 1,2,4–triazolium hydrogenselenate (THS) is prepared by the reaction of 1H–1,2,4–triazole and selenic acid. This complex is stabilised by N–H⋯O and C–H⋯O hydrogen bonding and electrostatic attractive forces between 1H and 1,2,4–triazolium cations and hydrogen selenate anions. The XRD studies revealed that intermolecular proton transfer occur from selenic acid to 1H–1,2,4–triazole molecule, results in the formation of 1,2,4–triazolium hydrogenselenate which contains 1,2,4–triazolium cations and hydrogenselenate anions. The molecular structure of THS crystal has also been optimised by using Density Functional Theory (DFT) using B3LYP/cc–pVTZ and B3LYP/6–311++G** methods in order to find the whole characteristics of the molecular complex. The theoretical structural parameters such as bond length, bond angle and dihedral angle determined by DFT methods are well agreed with the XRD parameters. The atomic charges and thermodynamic properties are also calculated and analysed. The energies of frontier molecular orbitals HOMO, LUMO, HOMO–1, LUMO+1 and LUMO–HUMO energy gap are calculated to understand the kinetic stability and chemical reactivity of the molecular complex. The natural bond orbital analysis (NBO) has been performed in order to study the intramolecular bonding interactions and delocalisation of electrons. These intra molecular charge transfer may induce biological activities such as antimicrobials, antiinflammatory, antifungal etc. The complete vibrational assignments of THS have been performed by using FT–IR and FT–Raman spectra.

Glycinium oxalurate (GO) single crystals has been synthesized and grown by the slow solvent evaporation method at room temperature. Single crystal X-ray diffraction study confirms that GO crystal crystallizes in the monoclinic system with centrosymmetric space group P121/c1. The grown crystals are built up from single protonated glycinium residues and single dissociated oxalurate anions. A combination of ionic and donor-acceptor hydrogen-bond interactions linking together the glycine and oxaluric acid residues forms a three-dimensional network. Hydrogen bonded network present in the crystal gives notable vibrational effect. The molecular geometry, vibrational frequencies and intensity of the vibrational bands have been interpreted with the aid of structure optimization based on HF and density functional theory B3LYP methods with 6-311++G(d,p) basis set. Frontier molecular orbital energies and other related electronic properties are calculated. The natural bonding orbital (NBO) charges have been calculated and interpreted. The molecular electrostatic potential map has been constructed and discussed in detail.

The conformational analysis of 1–(diaminomethylene)thiourea (MTU) has been done to find out the more stable conformer. The more stable geometry of MTU and 2–imino–4–thiobiuret (ITB) are optimised with B3LYP method using 6–311++G** and cc–pVTZ basis sets. The molecules are not planar. The complete molecular structural parameters and thermodynamic properties of the optimised geometry have been determined. The molecule of MTU is not a planar but twisted. The MEP of MTU lies in the region from +1.175e × 10 −2 to −1.175e × 10 −2 while the total electron density spread between +6.371e × 10 −2 and −6.371e × 10 −2 . The MEP of ITB distributed between +1.179e × 10 −2 and −1.179e × 10 −2 while the total electron density of ITB lies in the region +7.729e × 10 −2 and −7.729e × 10 −2 . The energies of important MOs of the compound were also evaluated from DFT method. The LUMO shows that the nitrogen and sulphur atoms are the most nucleophilic attacking sites whereas the HOMO reveals that nitrogen, sulphur and carbon atoms are for the electrophilic substitutions. The vibrational frequencies of the fundamental modes of the compounds have been precisely assigned, analysed and the theoretical results were compared with the experimental wavenumbers. 1 H and 13 C NMR isotropic chemical shifts were determined and the assignments are compared with the experimental values. In MTU molecule, the n → π* transitions such as n(N5) → π* C4–S6 and n(N1) → π* C2–N3 interactions are strongly stabilised by 66.60 and 41.24 kcal mol −1 , respectively. In the case of ITB compound, the stabilisation energy of lone pair donor orbital, n(N5) → σ* C4–S6 is 46.03 kcal mol −1 . The dual descriptors Δf k , Δs k and Δω k values clearly indicate that the order of nucleophilic attack in MTU is S6 > N11 > N1 > N5 > N3 while in ITB the order follows as N1 > N11 > N5>S6 > N3.

The hydrogen bonded molecular complex bis(1–hydroxy–2–methylpropan–2–aminium)selenate (C 8 H 24 N 2 O 6 Se) has been prepared by the reaction of 2–amino–2–methyl propanol and selenic acid. The X–ray diffraction analysis revealed that the intermolecular proton transfer from selenic acid (SeO 4 H 2 ) to 2–amino–2–methylpropanol results in the formation of bis(1–hydroxy–2–methylpropan–2–aminium)selenate (HMPAS) salt and the fragments are connected through H–bonding and ion pairing. The N–H⋯O and O–H⋯O interactions between 2–amino–2–methylpropanol and selenic acid determine the supramolecular arrangement in three–dimensional space. The salt crystallises in the space group P121/n1 of monoclinic system. The complete vibrational assignments of HMPAS have been performed by FTIR and FT–Raman spectroscopy. The experimental data are correlated with the structural properties namely the energy, thermodynamic parameters, atomic charges, hybridization concepts and vibrational frequencies determined by quantum chemical studies performed with B3LYP method using 6–311++G*, 6–31+G* and 6–31G** basis sets.

In the present communication, aniline with arsenic acid molecular complex has been taken as the subject for experimental and theoretical investigation. The anilinium arsenate (ANILAS) – a new crystalline product is grown by slow evaporation technique at room temperature. Density functional theoretical calculations have been computed with Gaussian 09 program. The structure is optimized with DFT/B3LYP-6–311G(d,p) basis set. The vibrational frequencies and electronic properties have been done with the help of Density Functional Theory (DFT) computations. The charge transfer, as well as occurrence of strong inter and intra molecular interactions were confirmed by frontier molecular orbital analysis, natural bonding orbital analysis (NBO) and molecular electrostatic potential. 1H and 13C NMR chemical shift of the studied compound has also been calculated using Gauge Independent Atomic Orbital (GIAO) method. Further, "the 3D Hirshfeld surface analysis and 2D fingerprint maps gives deep insight into the intermolecular interactions between the compound".

The science of advanced materials needs true computational prediction of material behaviour before experimentation. It is well known that Tert-butylamine and N-acetylglycine organic chemicals have versatile applications in the field of drug research and pharmaceutical industry. In the present study, the new crystalline organic complex - tert-butylammonium N-acetylglycinate monohydrate (TBANAG) has been grown and it’s structural, spectral and other properties are studied by both experimental and theoretical approach. The tert-butylammonium N-acetylglycinate monohydrate (TBANAG) crystallizes in centro symmetric space group P-1 with lattice parameters a = 6.2096(7)A, b = 9.8831(11)A, c = 10.1408(12)A and interfacial angles α = 76.514(10)o; β = 87.013(9)o; γ = 75.484(10)o. The detailed vibrational and electronic properties have been studied with the help of Gaussian 09 program by using B3LYP/6-311++G(d,p) basis set. The obtained vibrational wave numbers and optimized geometric parameters were seen to be in good agreement with the experimental data. From the frontier molecular orbital analysis, the chemical reaction of the grown compound is studied. Natural bonding orbital studies reveal the bonding pattern of electron pairs in the molecule. It also let out the charge transfer and various hyper conjugative intermolecular hydrogen bonding interactions in the molecular system. The intermolecular interactions such as O-H⋯O, N-H⋯N and N-H⋯O has significant impact on crystal packing of the molecule. Molecular electrostatic potential inculcate the knowledge of charge distribution in the molecule. Thus the present study aimed to analyse the molecular as well as electronic properties of the obtained compound in detail.

Melaminium N -acetylglycinate dihydrate, an organic material has been synthesized and characterized by X-ray diffraction, FT-IR, and FT-Raman spectroscopies for the protiated and deuteriated crystals. The title complex crystallizes in the triclinic system, and the space group is P-1 with a = 5.642(1) A, b = 7.773(2) A, c = 15.775(3) A, α = 77.28(1)°, β = 84.00(1)°, γ = 73.43(1)° and Z = 2. The molecular geometry, vibrational frequencies and intensity of the vibrational bands have been interpreted with the aid of structure optimization based on density functional method (B3LYP) with the 6–311++G(d,p) basis set. The obtained vibrational wavenumbers and optimized geometric parameters were seen to be in good agreement with the experimental data. The intermolecular hydrogen bonding interactions of the title compound have been investigated using the natural bonding orbital analysis. It reveals that the O-H···O, N-H···N and N-H···O intermolecular interactions significantly influence crystal packing of this molecule. The non-linear optical properties are also addressed theoretically. The predicted NLO properties of the title compound are much greater than ones of urea. In addition, DFT calculations of the title compound, molecular electrostatic potential, thermodynamic properties, frontier orbitals and chemical reactivity descriptors were also performed at 6–311++G(d,p) level of theory.

Thermal Decomposition Behaviour of Bis(4-Nitrophenol)-2,4,6-Triamino-1,3,5-Triazine Monohydrate N. Kanagathara, M.K. Marchewka and G. Anbalaganc,∗ School of Basic Sciences, Vel Tech University, Chennai-62, India Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 937, 50-950 Wroclaw 2, Poland Department of Nuclear Physics University of Madras Guindy Campus Chennai-600025

The stable conformers of trans –2–methoxycinnamic acid ( trans –2MCA) are determined by potential energy profile analysis. The energies of the s–cis and s–trans conformers of trans –2MCA determined by B3LYP/cc–pVTZ method are −612.9788331 Hartrees and −612.9780953 Hartrees, respectively. The vibrational and electronic investigations of the stable s–cis and s–trans conformers of trans –2–methoxycinnamic acid have been carried out extensively with FTIR and FT–Raman spectral techniques. The s–cis conformer (I) with a (C16–C17–C18–O19) dihedral angle equal to 0° is found to be more favoured relative to the one s–trans (II) with (C16–C17–C18–O19) = 180°, possibly due to delocalization, hydrogen bonding and steric repulsion effects between the methoxy and acrylic acid groups. The DFT studies are performed with B3LYP method by utilizing 6–311++G** and cc–pVTZ basis sets to determine the structure, thermodynamic properties, vibrational characteristics and chemical shifts of the compound. The total dipole moments of the conformers determined by B3LYP/cc–pVTZ method are 3.35 D and 4.87 D for s–cis and s–trans , respectively. It reveals the higher polarity of s–trans conformer of trans –2MCA molecule. The electronic and steric influence of the methoxy group on the skeletal frequencies has been analysed. The energies of the frontier molecular orbitals and the LUMO-HOMO energy gap have been determined. The MEP of s–cis conformer lie in the range +1.374e × 10 −2 to −1.374e × 10 −2 while for s–trans it is +1.591e × 10 −2 to −1.591e × 10 −2 . The total electron density of s–cis conformer lie in the range +5.273e × 10 −2 to −5.273e × 10 −2 while for s–trans it is +5.403e × 10 −2 to −5.403e × 10 −2 . The MEP and total electron density shows that the s–cis conformer is less polar, less reactive and more stable than the s–trans conformer. All the reactivity descriptors of the molecule have been discussed. Intramolecular electronic interactions and their stabilisation energies have analysed by NBO method.

The crystals of 1,3-diammonium propylselenate monohydrate (DAPS) were prepared and characterised X ray diffraction (XRD), FT-IR, FT-Raman spectroscopy, and DFT/B3LYP methods. It comprises protonated propyl ammonium moieties (diammonium propyl cations), selenate anions and water molecule which are held together by a number of hydrogen bonds and form infinite chains. The XRD data confirm the transfer of two protons from selenic acid to 1,3-diaminopropane molecule. The DAPS complex is stabilised by the presence of O-H center dot center dot center dot O and N-H center dot center dot center dot O hydrogen bonds and the electrostatic interactions as well. The N center dot center dot center dot O and O center dot center dot center dot O bond distances are 2.82-2.91 and 2.77 A, respectively. The FT-IR and FT Raman spectra of 1,3-diammonium propyl selenate monohydrate are recorded and the complete vibrational assignments have been discussed. The geometry is optimised by B3LYP method using 6-311G, 6-311+G and 6-311+G* basis sets and the energy, structural parameters, vibrational frequencies, IR and Raman intensities are determined. Differential scanning colorimetry (DSC) data were also presented to analyse the possibility of the phase transition. Complete natural bonding orbital (NBO) analysis is carried out to analyse the intramolecular electronic interactions and their stabilisation energies. The electrostatic potential of the complex lies in the range +1.902e x 10(-2) to -1.902e x 10(-2). The limits of total electron density of the complex is +8.43e x 10(-2) to 8.43e x 10(-2). (C) 2015 Elsevier B.V. All rights reserved.

Tapentadol is a novel opioid pain reliever drug with a dual mechanism of action, having potency between morphine and tramadol. Quantum chemical calculations have been carried out for tapentadol hydrochloride (TAP.Cl) to determine the properties. The geometry is optimised and the structural properties of the compound were determined from the optimised geometry by B3LYP method using 6–311++G(d,p), 6–31G(d,p) and cc–pVDZ basis sets. FT-IR and FT–Raman spectra are recorded in the solid phase in the region of 4000–400 and 4000–100 cm −1 , respectively. Frontier molecular orbital energies, LUMO–HOMO energy gap, ionisation potential, electron affinity, electronegativity, hardness and chemical potential are also calculated. The stability of the molecule arising from hyperconjugative interactions and charge delocalisation has been analysed using NBO analysis. The 1 H and 13 C nuclear magnetic resonance chemical shifts of the molecule are analysed.

Single crystals of melaminium benzoate dihydrate (MBDH) have been grown from aqueous solution by the slow solvent evaporation method at room temperature. Crystalline nature of the grown crystal has been confirmed by X-ray powder diffraction studies. The optimized geometry, frequency and intensity of the vibrational bands of MBDH were obtained by the Hartree-Fock and density functional theory using B3LYP/cam-B3LYP with 6-311++G(d,p) basis set. The harmonic vibrational frequencies were calculated and the scaled values have been compared with the experimental FT-IR and FT-Raman spectral values. The obtained vibrational wavenumbers and optimized geometric parameters are found to be in good agreement with the experimental data. UV-Visible spectrum was recorded in the region 200-400 nm and the electronic properties, HOMO-LUMO energies and other related electronic parameters are calculated. The isotropic chemical shifts computed by (1)H and (13)C NMR analysis also show good agreement with experimental observation. Natural bond orbital (NBO) analysis has been performed on MBDH compound to analyze the stability of the molecule arising from hyperconjugative interactions and charge delocalization. Molecular electrostatic potential surface (MEP) has also been performed by DFT/cam-B3LYP method with 6-311++G(d,p) basis set. Differential scanning calorimetric measurements performed on the powder sample indicate the phase transition point approximately at 368 and 358K for heating and cooling, respectively.

The crystals of the new melaminium arsenate (MAS) [C3H7N6+⋅H2AsO4−] were obtained by the slow evaporation of an aqueous solution at room temperature. Single crystal X-ray diffraction analysis reveals that the crystal belongs to triclinic system with centro symmetric space group P−1. The crystals are built up from single protonated melaminium residues and single dissociated arsenate H2AsO4− anions. The protonated melaminium ring is almost planar. A combination of ionic and donor–acceptor hydrogen-bond interactions linking together the melaminium and arsenate residues forms a three-dimensional network. Vibrational spectroscopic analysis is reported on the basis of FT-IR and FT-Raman spectra recorded at room temperature. Hydrogen bonded network present in the crystal gives notable vibrational effect. DSC has also been performed for the crystal shows no phase transition in the studied temperature range (113–293 K).

Melaminium glutarate monohydrate has been synthesised and FTIR and FT-Raman spectral investigations are carried out. The molecular geometry and vibrational frequencies of melaminium glutarate monohydrate in the ground state have been determined by using B3LYP method with 6-31++G**, 6-31++G and cc-pVDZ basis sets. The stability of the system, inter molecular hydrogen bonding and the electron donor–acceptor interactions of the complex have been investigated by using natural bonding orbital analysis. It reveals that the N H⋯O and O H⋯O intermolecular interactions significantly influence crystal packing of this molecular complex. The glutarate anion forms hydrogen bonds to the melaminium cation as the proton donor of the type N H⋯O with a distance (N⋯O) = 2.51 A. It is also linked by other hydrogen bonds to the water molecule of the type O H⋯O with (O⋯O) = 2.82 A and to the amino ( NH2) group of melaminium cation of the type N H⋯O with (N⋯O) = 2.82 A as the proton acceptor. The electrostatic potential of the complex is in the range +1.892e × 10−2 to −1.892e × 10−2. The limits of total electron density of the complex is +6.679e × 10−2 to −6.679e × 10−2.

The Fourier transform infrared (FTIR) and FT-Raman spectra of cis -2-methoxycinnamic acid have been measured in the range 4000–400 and 4000–100 cm −1 , respectively. Complete vibrational assignment and analysis of the fundamental modes of the compound were carried out using the observed FTIR and FT-Raman data. The geometry was optimised without any symmetry constrains using the DFT/B3LYP method utilising 6-311++G ∗∗ and cc-pVTZ basis sets. The thermodynamic stability and chemical reactivity descriptors of the molecule have been determined. The exact environment of C and H of the molecule has been analysed by NMR spectroscopies through 1 H and 13 C NMR chemical shifts of the molecule. The energies of the frontier molecular orbitals have also been determined. Complete NBO analysis was also carried out to find out the intramolecular electronic interactions and their stabilisation energy. The vibrational frequencies which were determined experimentally are compared with those obtained theoretically from density functional theory (DFT) gradient calculations employing the B3LYP/6-311++G ∗∗ and cc-pVTZ methods.

The various conformers and the exact geometry of the more stable conformer of trans 2-chloro- and trans-4-chlorocinnamic acids have been determined by analysing the potential energy profile of the compounds. The s–cis orientation of the carbonyl group (C=O) and the C=C bond appears as the only stable structure in 2CCA and is more stable by 0.6648 kcal mol–1 than the corresponding s–trans conformation. In 4CCA, the s–cis conformer is more stable than the s–trans conformer by 0.8939 kcal mol–1. The structure and vibrational characteristic of the compounds have been investigated by using both experimental and quantum chemical methods. The bond distances, bond angles, dihedral angles, the kinetic and thermodynamic stability of the molecule, global and local reactivity parameters, the energy gap between the frontier molecular orbitals, the probable electronic transitions and bonding concepts of the compounds are elaborated in the present investigation. The frontier orbital energy gap of 2CCA and 4CCA are 4.5533 eV and 4.4366 eV, respectively shows that 4CCA is highly reactive than 2CCA molecule. The bond pair donor orbital, πCC → π*CC interaction from C3–C4 bond pair to C1–C2 and C5–C6 antibonding orbitals have the stabilisation energies 252.31 and 203.28 kcal mol–1, respectively. In the case of 4CCA, πCC → π*CC interaction from C1–C2 bond pair to C3–C4 and C5–C6 antibonding orbitals gives the strongest stabilisation of 258.75 and 203.58 kcal mol–1. The global and local reactivity descriptors clearly reveals that C9 is more favorable for nucleophilic attack while the ring carbon atoms are favorable for both electrophilic and nucleophilic attack.

The thermal decomposition kinetics of melaminium bis(trichloroacetate) dihydrate (MTCA) has been studied by thermogravimetry and derivative thermogravimetry techniques using non-isothermal experiments at three different heating rates 10, 15, and 20 ◦C min−1. Non-isothermal studies of MTCA revealed that the decomposition occurs in three stages involving dehydration and decomposition. The apparent activation energy (Ea) and the pre-exponential factor (lnA) of each stage of thermal decomposition at various linear heating rates are calculated using Flynn Wall, Friedman, Kissinger, and Kim Park method. A signi cant variation of e ective activation energy (Ea) with conversion (α) indicates that the process is kinetically complex. The linear relationship between the A and Ea values is well established (compensation e ect). Isothermal kinetics of thermal decomposition of MTCA was found to obey Avrami Erofeev's (A4) and power law (P3) equations. In addition to the above, mechanical properties have been estimated by Vicker's microhardness test for the grown crystal.

Melaminium bis(trifluoroacetate) trihydrate (MTFA), an organic material has been synthesized and single crystals of MTFA have been grown by the slow solvent evaporation method at room temperature. X-ray powder diffraction analysis confirms that MTFA crystal belongs to the monoclinic system with space group P2/c. The molecular geometry, vibrational frequencies and intensity of the vibrational bands have been interpreted with the aid of structure optimization based on density functional theory (DFT) B3LYP method with 6-311G(d,p) and 6-311++G(d,p) basis sets. The X-ray diffraction data have been compared with the data of optimized molecular structure. The theoretical results show that the crystal structure can be reproduced by optimized geometry and the vibrational frequencies show good agreement with the experimental values. The nuclear magnetic resonance (NMR) chemical shift of the molecule has been calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results. HOMO–LUMO, and other related molecular and electronic properties are calculated. The Mulliken and NBO charges have also been calculated and interpreted.

O-desmethyltramadol is one of the main metabolites of tramadol widely used clinically and has analgesic activity. The FTIR and FT-Raman spectra of O-desmethyl tramadol hydrochloride are recorded in the solid phase in the regions 4000-400 cm(-1) and 4000-100 cm(-1), respectively. The observed fundamentals are assigned to different normal modes of vibration. Theoretical studies have been performed as its hydrochloride salt. The structure of the compound has been optimised with B3LYP method using 6-31G(**) and cc-pVDZ basis sets. The optimised bond length and bond angles are correlated with the X-ray data. The experimental wavenumbers were compared with the scaled vibrational frequencies determined by DFT methods. The IR and Raman intensities are determined with B3LYP method using cc-pVDZ and 6-31G(d,p) basic sets. The total electron density and molecular electrostatic potential surfaces of the molecule are constructed by using B3LYP/cc-pVDZ method to display electrostatic potential (electron+nuclei) distribution. The electronic properties HOMO and LUMO energies were measured. Natural bond orbital analysis of O-desmethyltramadol hydrochloride has been performed to indicate the presence of intramolecular charge transfer. The (1)H and (13)C NMR chemical shifts of the molecule have been anlysed.

A new organic-organic salt, 3-nitrophenol-1,3,5-triazine-2,4,6-triamine (2/1) (3-NPM) has been synthesized by slow evaporation technique at room temperature. Single crystal X-ray diffraction analysis reveals that 3-NPM crystallizes in orthorhombic system with centrosymmetric space group Pbca and the lattice parameters are a=15.5150(6) Å, b=12.9137(6) Å, c=17.8323(6) Å, α=β=γ=90° and V=3572.8(2)(Å)(3). The geometry, fundamental vibrational frequencies are interpreted with the aid of structure optimization and normal coordinate force field calculations based on density functional theory (DFT) B3LYP/6-311G(d,p) method. IR and Raman spectra of 3-NPM have been recorded and analyzed. The complete vibrational assignments are made on the basis of potential energy distribution (PED). The electric dipole moment, polarizability and the first order hyperpolarizability values of the 3-NPM have been calculated. (1)H and (13)C NMR chemical shifts are calculated by using the gauge independent atomic orbital (GIAO) method with B3LYP method with 6-311G (d,p) basis set. Moreover, molecular electrostatic potential (MEP) and thermodynamic properties are performed. Mulliken and Natural charges of the title molecule are also calculated and interpreted. Thermal decomposition behavior of 3-NPM has been studied by means of thermogravimetric analysis. The dielectric measurements on the powdered sample have been carried out and the variation of dielectric constant and dielectric loss at different frequencies of the applied field has been studied and the results are discussed in detail.

In this work, we report a combined experimental and theoretical study on molecular structure, vibrational spectra and NBO analysis of the potential nonlinear optical (NLO) material anilinium trichloroacetate. The FT-IR and FT-Raman spectra of the compound have been recorded together between 4000-80 cm(-1) and 3600-80 cm(-1) regions, respectively. The compound crystallizes in the noncentrosymmetric space group of monoclinic system. The optimized molecular structure, vibrational wavenumbers, IR intensities and Raman activities have been calculated by using density functional method (B3LYP) with 6-311++G(d,p) as higher basis set. The obtained vibrational wavenumbers and optimized geometric parameters were seen to be in good agreement with the experimental data. DSC measurements on powder samples do not indicate clearly on the occurrence of phase transitions in the temperature 113-293 K. The Kurtz and Perry powder reflection technique appeared to be very effective in studies of second-order nonlinear optical properties of the molecule. The non-linear optical properties are also addressed theoretically. The predicted NLO properties of the title compound are much greater than ones of urea. In addition, DFT calculations of the title compound, molecular electrostatic potential, frontier orbitals and thermodynamic properties were also performed at 6-311++G(d,p) level of theory. For title crystal the SHG efficiency was estimated by Kurtz-Perry method to be d(eff)=0.70 d(eff) (KDP).

New organic crystals of 2,4,6-triamino-1,3,5-triazin-1-ium 3-(prop-2-enoyloxy) propanoate acrylic acid monosolvate monohydrate (MAC) have been obtained from aqueous solution by the slow solvent evaporation method at room temperature. Single crystal X-ray diffraction analysis reveals that the compound crystallises in the triclinic system with centrosymmetric space group P-1. FT-IR and FT-Raman spectra of MAC have been recorded and analyzed. The molecular geometry and vibrational frequencies and intensity of the vibrational bands are interpreted with the aid of structure optimization based on density functional theory (DFT) B3LYP method with 6-31G(d,p) basis set. The results of the optimized molecular structure are presented and compared with the experimental X-ray diffraction data. The theoretical results show that the optimized geometry can well reproduce the crystal structure, and the calculated vibrational frequency values show good agreement with experimental values. A study of the electronic properties, such as HOMO and LUMO energies and Molecular electrostatic potential (MEP) were performed. Mulliken charges and NBO charges of the title molecule were also calculated and interpreted. Thermogravimetric analysis has been done to study the thermal behaviour of MAC. The 13 C and 1 H nuclear magnetic resonance (NMR) chemical shifts of the molecule are calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results.

An organic-organic salt, bis (4-nitrophenol) 2,4,6-triamino 1,3,5-triazine monohydrate (BNPM) has been prepared by slow evaporation technique at room temperature. Single crystal X-ray diffraction analysis reveals that the compound crystallizes in triclinic system with centrosymmetric space group P-1. IR and Raman spectra of BNPM have been recorded and analyzed. The study has been extended to confocal Raman spectral analysis. Band assignments have been made for the melamine and p-nitrophenol molecules. Vibrational spectra have also been discussed on the basis of quantum chemical density functional theory calculations using Firefly (PC GAMESS) Version 7.1 G. Vibrational frequencies are calculated and scaled values are compared with the experimental one. The Mulliken charges, HOMO–LUMO orbital energies are calculated and analyzed. The chemical structure of the compound was established by 1 H NMR and 13 C NMR spectra.

The crystal structure investigations of melamine with phosphorous acid, namely melaminium dihydrogenphosphite monohydrate (C 3 N 6 H 7 ·H 2 PO 3 ·H 2 O) have been investigated by means of single crystal X-ray diffraction method. The title compound crystallizes in monoclinic crystal system, and the space group is P 2 1 / c with a = 10.069 A, b = 21.592 A, c = 12.409 A and Z = 12. The vibrational assignments and analysis of melaminium dihydrogen phosphite monohydrate have also been performed by FTIR, FT-Raman and far-infrared spectral studies. The quantum chemical simulations were performed with DFT (B3LYP) method using 6-31G ** , cc-pVTZ, and 6-311++G ** basis sets to determine the energy, structural, thermodynamic parameters and vibrational frequencies of melaminium dihydrogen phosphite monohydrate. The hydrogen atom from phosphorous acid was transferred to the melamine molecule giving the singly protonated melaminium cation. The ability of ions to form spontaneous three-dimensional structure through weak O H···O and N H···O hydrogen bonds shows notable vibrational effects.

On the basis of prior X-ray crystallographic results published by J. Janczak and G. Perpetuo, detailed vibrational studies were performed. The FT-IR and Raman spectra at ambient temperature were measured. The NLO properties were determined with the Kurtz-Perry experiment. Theoretical vibrational spectra were calculated. A detailed potential energy distribution (PED) analysis was performed. Assignments of observed bands were made. On the basis of these results, the behaviour of hydrogen bonds in the investigated compound was analysed and discussed. The equilibrium geometry of L-leucinium perchlorate was obtained. The results were compared with experimental X-ray data. The DFT formalism was used in theoretical studies. Detailed TDDFT study of hyperpolarizbility of first and second order for the investigated molecule was performed. Results were compared with experiments. Theoretical population analysis was used to determine the local electron density and local charges in investigated molecule. Differential scanning calorimetric study (DSC) was performed.

The structural investigations of the molecular complex of melamine with maleic acid, namely melaminium maleate monohydrate have been carried out by quantum chemical methods in addition to FTIR, FT-Raman and far-infrared spectral studies. The quantum chemical studies were performed with DFT (B3LYP) method using 6-31G**, cc-pVDZ and 6-311++G** basis sets to determine the energy, structural and thermodynamic parameters of melaminium maleate monohydrate. The hydrogen atom from maleic acid was transferred to the melamine molecule giving the singly protonated melaminium cation. The ability of ions to form spontaneous three-dimensional structure through weak O H⋯O and N H⋯O hydrogen bonds shows notable vibrational effects.

Experimental and theoretical investigations on the molecular structural, electronic and the vibrational characteristics of 4-hydroxy-1-thiocoumarin are presented. Conformational analysis was carried out to obtain the more stable configuration of the compound. The vibrational frequencies were obtained by DFT/B3LYP calculations employing 6-311++G(d,p), 6-31G(d,p), cc-pVTZ basic sets and B3PW91 method with 6-311++G(d,p) basis set and are compared with FTIR and FT-Raman spectral data recorded in the region of 4000–400 and 4000–100 cm−1, respectively. The total electron density and molecular electrostatic potential surfaces of the molecule were constructed to display electrostatic potential (electron + nuclei) distribution. The electronic properties HOMO and LUMO energies were measured. 1H and 13C NMR spectra were recorded and 1H and 13C nuclear magnetic resonance chemical shifts of the molecule were calculated by using the Gauge-Independent Atomic Orbital (GIAO) method and analyzed. The picture of localized bonds and lone pairs, stabilization energy of the delocalization of electrons, the charge and hybridisation of the atoms of 4-hydroxy-1-thiocoumarin were clearly explained by NBO analysis.

The experimental and theoretical vibrational spectra of Bis(melaminium) terephthalate dihydrate were studied. The Fourier transform infrared (FT-IR) spectra of the Bis(melaminium) terephthalate dihydrate and its deuterated analogue were recorded in the solid phase. The molecular geometry and vibrational frequencies of Bis(melaminium) terephthalate dihydrate in the ground state have been calculated by using the density functional method (B3LYP) with 6-31++G(d,p) basis set. The results of the optimized molecular structure are presented and compared with the experimental X-ray diffraction. The molecule contains the weak hydrogen bonds of N-H···O, N-H···N and O-H···O types, and those bonds are calculated with DFT method. In addition, molecular electrostatic potential, frontier molecular orbitals and natural bond orbital analysis of the title compound were investigated by theoretical calculations. The lack of the second harmonic generation (SHG) confirms the presence of macroscopic center of inversion.

The molecular geometry and vibrational spectral investigations of melaminium formate, a potential material known for toxicity and NLO activity, has been performed. The FT IR and FT Raman spectral investigations of melaminium formate is performed aided by the computed spectra of melaminium formate, triazine, melamine, melaminium and formate ion, along with bond orders and PED, computed using the density functional method (B3LYP) with 6-31G(d) basis set and XRD data, to reveal intermolecular interactions of amino groups with neighbor formula units in the crystal, intramolecular H⋯H repulsion of amino group hydrogen with protonating hydrogen, consequent loss of resonance in the melaminium ring, restriction of resonance to N3C1N1 moiety leading to special type resonance of the ring and the resonance structure of CO2 group of formate ion. The 3D matrix of hyperpolarizability tensor components has been computed to quantify NLO activity of melamine, melaminium and melaminium formate and the hyperpolarizability enhancement is analyzed using computed plots of HOMO and LUMO orbitals. A new mechanism of proton transfer responsible for NLO activity has been suggested, based on anomalous IR spectral bands in the high wavenumber region. The computed MEP contour maps have been used to analyze the interaction of melaminium and formate ions in the crystal.

Density functional theory (DFT) (B3LYP and B3PW91) calculations have been carried out for 2,6-dimethyl-2,5-heptadien-4-one (DMHD4O) using 6–311++ G** basis set. Complete vibrational assignment and analysis of the fundamental modes of the compound were carried out from the FTIR and FT-Raman spectral data. The theoretical electronic absorption has been calculated by using time-dependent DFT (TD-DFT) methods and compared with the experimental spectra. The theoretically computed Frontier energy gaps and TD-DFT calculations are in good agreement with the experimental UV–vis spectral absorption. The chemical hardness measured from the Frontier molecular orbital energies of DMHD4O is 0.0693 eV. Electronic stability of the compound arising from hyperconjugative interactions and charge delocalisation were also investigated based on the natural bond orbital (NBO) analysis. Effective stabilisation energy E (2) associated with the interactions of the π and the lone pair of electrons was determined by the NBO analysis...

The experimental and theoretical vibrational spectra of melaminium nitrate were studied. The Raman and infrared (FT-IR) spectra of the melaminium nitrate and its deuterated analogue were recorded in the solid phase. Molecular geometry and vibrational frequency values of melaminium nitrate in the electronic ground state were calculated using the density functional method (B3LYP) with the 6-31++G(d,p) basis set. The calculated results show that the optimized geometry can well reproduce the crystal structure, and the theoretical vibrational frequency values show good agreement with experimental values. The NBO analysis reveals that the N–H···O and N–H···N intermolecular interactions significantly influence crystal packing in this molecule.

Single crystals of melaminium bis (trichloroacetate) dihydrate have been grown successfully by slow evaporation solution growth technique at room temperature. Single crystal X-ray diffraction analysis reveals that the compound crystallizes in monoclinic system with non -centrosymmetric space group C2 with lattice parameters a = 17.70 A, b = 8.44 A, c = 6.09 A, α = 90°, β = 100.24°, γ = 90° and V = 900 (A)3. The UV–Vis transmittance spectrum shows that the crystal has a good optical transmittance in the entire visible region with lower cutoff wavelength of 351 nm. The vibrational frequencies of various functional groups present in the crystal have been derived from FI-IR, FT-Raman and Confocal Raman analyses. The chemical structure of the compound was established by 1H and 13C NMR spectrum. TGA-DTA analysis reveals that the materials have good thermal stability and the melting point of the crystal is found to be 195 °C. The dielectric response of the crystals was studied in the frequency range 50 Hz to 5 MHz at different temperatures and the results are discussed. Etching studies show the growth pattern of the crystals. The second harmonic generation efficiency was measured in comparison with KDP by employing powder Kurtz method.

The structural investigations of the molecular complex of 2-methyl-4-nitroaniline with trichloroacetic acid, namely 2-methyl-4-nitroanilinium trichloroacetate trichloroacetic acid (C 11 H 10 Cl 6 N 2 O 6 ) have been performed by means of single crystal and powder X-ray diffraction method. The complex was formed with accompanying proton transfer from trichloroacetic acid molecule to 2-methyl-4-nitroaniline. The studied crystal is built up of singly protonated 2-methyl-4-nitroanilinium cations, trichloroacetate anions and neutral trichloroacetic acid molecules. The crystals are monoclinic, space group P 2 1 / c , with a = 14.947 A, b = 6.432 A, c = 19.609 A and Z = 4. The vibrational assignments and analysis of 2-methyl-4-nitroanilinium trichloroacetate trichloroacetic acid have also been performed by FTIR, FT-Raman and far-infrared spectral studies. More support on the experimental findings were added from the quantum chemical studies performed with DFT (B3LYP) method using 6-31G**, cc-pVDZ, 6-31G and 6-31++G basis sets. The structural parameters, energies, thermodynamic parameters and the NBO charges of 2M4NATCA were also determined by the DFT methods.

The molecular modeling of p-nitroanilinium perchlorate molecule was carried out by using B3LYP and HSEH1PBE levels of density functional theory (DFT). The IR and Raman spectra were simulated and the assignments of vibrational modes were performed on the basis of relative contribution of various internal co-ordinates. NBO analysis was performed to demonstrate charge transfer, conjugative interactions and the formation of intramolecular hydrogen bonding interactions within PNAPC. Obtained large dipole moment values showed that PNAPC is a highly polarizable complex, and the charge transfer occurs within PNAPC. Hydrogen bonding and charge transfer interactions were also displayed by small HOMO-LUMO gap and molecular electrostatic potential (MEP) surface. The strong evidences that the material can be used as an efficient nonlinear optical (NLO) material of PNAPC were demonstrated by considerable polarizability and hyperpolarizability values obtained at DFT levels.

Single crystals of melaminium perchlorate monohydrate (MPM) have been grown from aqueous solution by slow solvent evaporation method at room temperature. X-ray powder diffraction analysis confirms the title crystal crystallizes in the triclinic (P-1) structure and the calculated lattice parameters are a = 5.6275 ± 0.0780 A, b = 7.6926 ± 0.1025 A, c = 12.0878 ± 0.2756 A, α = 103.89 ± 1.01°, β = 94.61 ± 0.92°, γ = 110.22 ± 0.81°, and V = 468.95 A3. The thermal decomposition behavior of MPM has been studied by means of thermogravimetric analysis at three different heating rates 5, 10, and 20 °C min−1. The values of effective activation energy (E a), pre-exponential factor (ln A) of each stage of thermal decomposition for all heating rates were calculated by model free method: Kissinger, Kim–Park, and Flynn–Wall method. A significant variation of effective activation energy (E a) with conversion (α) indicates that the process is kinetically complex. The linear relationship between the A and E a values was established (compensation effect). Dielectric study has also been carried out and it is found that both dielectric constant (e′) and dielectric loss (e″) decreases with increase in frequency.

Crystal structures of 3-amino-1,2,4-triazolium chloride and bis(3-amino-1,2,4-triazolium) hexachloridostannate monohydrate were determined by means of X-ray single crystal diffraction. The route of protonation of organic molecule and tautomer equilibrium constants for the cationic forms were calculated using B3LYP/6-31G* method. The most stable protonated species is 2,4-H2-3-amino-1,2,4-triazolium ion, 24(3at)+. Very good agreement between theoretical and experimental frequencies was achieved due to very weak interactions existing in studied compounds. Significantly weaker intermolecular interactions are found in [24(3at)]2SnCl6·H2O than in [24(3at)]Cl. The differences in strength of interactions are manifested in red and blue shifts for stretching and bending motions, respectively. PED calculations show that for 24(3at)+ ion the stretching type of motion of two Nring H bonds is independent, whereas bending is coupled.

X-ray structure of new hybrid organic–inorganic compound, bis(4-amino-1,2,4-triazolium) hexachloridostannate(IV), [1t(4at)]2SnCl6 (P 1 ¯ space group) was determined. Crystal structure of 4-amino-1,2,4-triazole (Pbca space group) was reinvestigated. Non-planar orientation of NH2 group was found. The geometry of the amino group does not significantly change upon protonation. The route of protonation of 4-aminotriazole and tautomer equilibrium constants for the cationic forms were theoretically studied by means of B3LYP/6-31G* method. The most stable monoprotonated species is 1H-trans-4-amino-1,2,4-triazole, 1t(4at)+, whereas the final product of the protonation route is 12(4at)2+. Potential Energy Distribution (PED) analysis was carried out for two conformers, 1c(4at)+ and 1t(4at)+. Very good agreement between theoretical and experimental frequencies was achieved due to very weak interactions existing in [1t(4at)]2SnCl6. Infrared and Raman bands were assigned on the basis of PED analysis. Comparison of vibrational spectra of [1t(4at)]2SnCl6 and [1t(4at)]Cl indicates significantly weaker intermolecular interactions in the former compound.

Experimental FTIR and FT-Raman spectroscopic analysis of 2-chloro-4-methyl-3-nitropyridine (2C4M3NP) and 2-chloro-6-methylpyridine (2C6MP) have been performed. A detailed quantum chemical calculations have been carried out using B3LYP and B3PW91 methods with 6-311++G** and cc-pVTZ basis sets. Conformation analysis was carried for 2C4M3NP and 2C6MP. The temperature dependence of thermodynamic properties has been analysed. The atomic charges, electronic exchange interaction and charge delocalisation of the molecule have been performed by natural bond orbital (NBO) analysis. Molecular electrostatic surface potential (MESP), total electron density distribution and frontier molecular orbitals (FMOs) are constructed at B3LYP/6-311++G** level to understand the electronic properties. The charge density distribution and site of chemical reactivity of the molecules have been obtained by mapping electron density isosurface with electrostatic potential surfaces (ESP). The electronic properties, HOMO and LUMO energies were measured by time-dependent TD-DFT approach.

WOS: 000300600500022 Complexes of perchloric acid with interesting physical properties are investigated in details. Single crystals of 2-hydroxyanilinium perchlorate (abbreviated as 2HAP-ClO4), 3-hydroxyanilinium perchlorate (abbreviated as 3HAP-ClO4), and 4-hydroxyanilinium perchlorate (abbreviated as 4HAP-ClO4) were grown by the slow evaporation technique and vibrational spectral analysis was carried out using Far-IR and Fourier transform IR spectroscopy. The density functional theoretical (DFT) computations were also performed at the B3LYP/6-311++G(d,p) level to derive the equilibrium geometry, vibrational wavenumbers and intensities. The detailed interpretation of the vibrational spectra has been carried out with the aid of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology. (C) 2011 Elsevier B.V. All rights reserved. Ahi Evran UniversityAhi Evran University; National Science Centre [N N507 2218 40] The author (Y. Erdogdu) would like to thank Ahi Evran University Research Fund for its financial support. The work was financially supported by National Science Centre (Project No. N N507 2218 40).