Theoretical and experimental study of molecular structure and vibrational spectra of <Emphasis Type="Italic">N</Emphasis>-(2-pyridylmethyl)-2-pyrazinecarboxamide

N-(2-Pyridylmethyl)-2-pyrazinecarboxamide was prepared and its crystal structure was investigated by X-ray analysis. The compound crystallizes in the triclinic space group \(P{\bar 1}\) with a = 4.262(3), b = 12.117(9), c = 20.840(18) Å, α = 91.802(6), β = 89.834(7), γ = 91.845(6)°, V = 1075.2(16) ų, Z = 4, and D = 1.323?Mg/m³. The structure was solved by direct method and refined to R = 0.0699 and wR ₂ = 0.1268 by full matrix anisotropic least-squares method. Using the Hartree-Fock and density functional method (B3LYP) with 6-31G(d) basis set, the molecular geometry and vibrational frequencies of the title compound has been investigated and compared with experimental ones from experimental studies. The optimized bond lengths obtained by RHF method and bond angles obtained by B3LYP method show better agreement with the experimental values. The vibrations computed of the title compound by the RHF and DFT methods are in good agreement with the observed IR spectra data.     

Structure and DFT calculations of 2-{[3-methyl-3-phenyl-cyclobutyl)-thiazol-2-yl]-hydrazonomethyl}-phenol

The title compound 2-{[3-Methyl-3-phenyl-cyclobutyl)-thiazol-2-yl]-hydrazonomethyl}-phenol (C₂₁H₂₁N₃S₁O₁) crystallizes in the P-1 triclinic space group with a = 5.8880(4) ?, b = 9.5618(5) ?, c = 17.0484(10) ?, α = 80.214(5)°, β = 80.532(5)°, γ = 80.116(5)°. In addition to molecular geometry and packing from X-ray experiment, we have also calculated the molecular geometry and vibrational frequencies of the title compound in the ground state using density functional theory DFT (B3LYP) with the 6–31G(d,p) basis set. Apart from this, the structure of the title compound is characterized by ¹H NMR, ¹³C NMR, IR and UV-vis. Spectra, and the experimental emission energies are compared with the HOMO-LUMO energy gaps calculated by the DFT method.     

Quantum Chemical Calculation Studies on 4-Phenyl-1-(Propan-2-Ylidene)Thiosemicarbazide

Ab initio calculations of the structure, atomic charges, natural bond orbital, and thermodynamic functions have been performed at HF/6-311G^∗∗ and B3LYP/6-311G^∗∗ levels of theory for the title compound of 4-phenyl-1-(propan-2-ylidene)thiosemicarbazide. The calculated results show that the sulfur atom and all of the nitrogen atoms have bigger negative charges and they are the potential sites to react with the metallic ions, which make the title compound become a multidentate ligand. The coordination ability of the sulfur atom and the nitrogen atom of C=N double bond will increase with the increase of the polarity of the solvent. Electronic absorption spectra have been calculated by time-dependent density functional theory (TD-DFT) method. The calculation of the second-order optical nonlinearity also has been carried out, and the molecular hyperpolarizability is 3.068×10⁻³⁰ esu.     

Synthesis,characterization, and quantum chemical calculational studies on 3-<Emphasis Type="Italic">p</Emphasis>-methylphenyl-4-amino- 1, 2, 4-triazole-5-thione

The title compound of 3-p-methylphenyl-4-amino-1, 2, 4-triazole-5-thione was synthesized and characterized by elemental analysis, IR, electronic spectra, and X-ray single crystal diffraction. Quantum chemical calculations of the structure, natural bond orbital, and thermodynamic functions of the title compound were performed by using B3LYP/6-311G** and HF-6-311G** methods. Both the methods can well simulate the molecular structure. Vibrational frequencies were predicted, assigned and compared with the experimental values, and B3LYP/6-311G** method is superior to HF/6-311G** method to predict the vibrational frequencies. Electronic absorption spectra calculated by B3LYP/6-311G** method have some red shifts compared with the experimental ones and natural bond orbitals analyses indicate that the two absorption bands are mainly derived from the contribution of n → π^* and π → π^* transitions. On the basis of vibrational analyses, the thermodynamic properties of the title compound at different temperatures have been calculated, revealing the correlations between C ⁰ _p,m , S ⁰ _m , H ⁰ _m , and temperatures.     

Experimental and computational studies on (<Emphasis Type="Italic">Z</Emphasis>)-1-((4-phenylamino)phenylamino)-methylene)naphthalen-2(1<Emphasis Type="Italic">H</Emphasis>)-one

The Schiff base compound (Z)-1-((4-phenylamino)phenylamino)methylene)naphthalen-2(1H)-one has been synthesized and characterized by IR, UV–Vis, and X-ray single-crystal determination. Molecular geometry from X-ray experiment of the title compound in the ground state have been compared using the Hartree–Fock (HF) and density functional method (B3LYP) with 6−31G(d,p) basis set. Calculated results show that density functional theory DFT and HF can well reproduce the structure of the title compound. Using the time-dependent density functional theory (TD-DFT) and Hartree–Fock (TD-HF) methods, electronic absorption spectra of the title compound have been predicted and a good agreement with the TD-DFT method and experimental ones is determined. The energetic behavior of the title compound in solvent media has been examined using B3LYP method with the 6−31G(d,p) basis set by applying the polarizable continuum model (PCM). The total energy of the title compound decreases with increasing polarity of the solvent. In addition, DFT calculations of the title compound, molecular electrostatic potential (MEP), natural bond orbital analysis (NBO), and non-linear optical (NLO) properties were performed at B3LYP/6−31G(d,p) level of theory.     

The Structure of 3-Phenyl-4-(N-Carbamyl-1,4,2-Oxathiazolimin-3-yl)Sydnone,C11H7N5O4S·0.8 CH2Cl2

The title compound (M_r = 373) crystalizes in the othorhombic space group P bna with a = 10.410(2), b = 11.658(4), c = 23.108(3) Å, V = 2804.4 Å Z = 8. The single crystal intensity data were collected using MoK∞ radiation (λ = 0.7093Å) at room temperature. The crystal and molecular structure was solved with the final agreement index R = 0.039 for 1046 observed reflections. The bond lengths N(1)- C(7) and C(7)-C(8) of the title compound are slightly longer than those of 3-substituted sydnone derivatives. This may be attributed to the steric effect arising from the interaction of the phenyl ring and the 4-substituent with the neighboring atoms of sydnone ring. Both the title compound and 4-acetyl-3-(p-tolyl)sydnone have smaller dihedral angles between the sydnone ring and the plane of the sp² orbital of the double bond of the 4-substituent and both have shorter C(7)-C(9) bond lengths than those of other similar sydnone derivatives.     

Crystal structure of 2-butylamino-3-(4-fluorophenyl) benzofuro[3,2-d]pyrimidin-4(3H)-one

The title compound (C₂₀H₁₈FN₃O₂, Mr = 351.37) is prepared and its crystal structure is determined by single crystal X-ray diffraction. The crystal is tetragonal, the P-42(1)c space group with a = 11.0922(6) ?, b = 11.0922(6) ?, c = 28.6271(15) ?, V = 3522.2(3) ?³, Z = 8, d _x = 1.325 g/cm³, F(000) = 1472, μ = 0.095 mm⁻¹, MoK _α radiation (λ = 0.71073), R = 0.0505, wR = 0.1090 for 2433 observed reflections with I > 2σ(I). The X-ray diffraction analysis reveals that all ring atoms in the benzo[4,5]furo[3,2-d]pyrimidinone moieties are almost coplanar.     

Quantum chemical calculation studies on 4-phenyl-1-(1-phenylethylidene)thiosemicarbazide

Ab initio calculations of the structure, atomic charges, natural bond orbital and thermodynamic functions have been performed at HF/6-311G^** and B3LYP/6-311G^** levels of theory for the title compound of 4-phenyl-1-(1-phenylethylidene) thiosemicarbazide. The calculated results show that the sulfur atom and all of the nitrogen atoms have bigger negative charges and that they are the potential sites to react with the metallic ions, which make the title compound a multidentate ligand. The coordination ability of the sulfur atom and the nitrogen atom of C=N double bond increases with the increase of polarity of the solvent. Electronic absorption spectra have been calculated by time-dependent density functional theory (TD-DFT) method. The calculation of the second-order optical nonlinearity has also been carried out with the PM3 semi-empirical method, resulting in the molecular hyperpolarisability is 5.477×10⁻³⁰ esu.     

Experimental and computational studies on zwitterionic (E)-2-(1-(2-(4-methylphenylsulfonamido)ethyliminio)ethyl) phenolate

The Schiff base compound (E)-2-(1-(2-(4-methylphenylsulfonamido)ethyliminio)ethyl) phenolate has been synthesised and characterized by IR, UV–Vis, and X-ray single-crystal determination. Ab initio calculations have been carried out for the title compound using the density functional theory (DFT) and Hartree–Fock (HF) methods at 6-31G(d) basis set. The calculated results show that the DFT/B3LYP and HF can well reproduce the structure of the title compound. Using the TD-DFT and TD-HF methods, electronic absorption spectra of the title compound have been predicted and a good agreement with the TD-DFT method and the experimental ones is determined. Molecular orbital coefficient analyses reveal that the electronic transitions are mainly assigned to n → π* and π → π* electronic transitions. To investigate the tautomeric stability, optimization calculations at B3LYP/6-31G(d) level were performed for the NH and OH forms of the title compound. Calculated results reveal that the OH form is more stable than NH form. In addition, molecular electrostatic potential and NBO analysis of the title compound were performed at B3LYP/6-31G(d) level of theory.     

Structural and aromatic aspects for tautomerism of (Z)-6-((4-bromophenylamino)methylene)-2,3-dihydroxycyclohexa-2,4-dienone

The molecular and crystal structure of (Z)-6-((4-bromophenylamino)methylene)-2,3-dihydroxycyclohexa-2,4-dienone were determined by single crystal X-ray diffraction and spectroscopic methods. Molecules of the compound can be regarded as a resonance hybrid of cis-keto tautomer and zwitterionic form. Pairs of molecules of the compound generate pseudocyclic centrosymmetric R₂² (10) R_{2}^{2} (10) supramolecular synthons with the aid of O–H···O type intermolecular H-bonds. Stacking of R₂² (10) R_{2}^{2} (10) synthons along b-axis is stabilized by π···π interactions. Changes in both covalent topology and molecular geometry of the compound accompanying proton transfer were monitored by a relaxed PES scan with respect to hydroxyl bond length used as redundant internal coordinate. Quantum chemical studies at 6-311 + G(d,p) level reveal that bond lengths which are indicative to tautomerization process cannot reach their expected values even if proton transfer occurs in gas phase and pseudo-aromatic chelate ring formation has primary effect on the stabilization of NH tautomer. Resonance-assisted intramolecular H-bond affects the electronic state of its neighboring aromatic fragments.     

Ferrocene Compounds. XXVII. Synthesis and Structure of 2-(Ferrocenylmethyl)propane-1,3-diol

The title compound was obtained by reduction of diethyl (ferrocenylmethyl)malonate with lithium aluminium hydride in diethyl ether. The structure of this novel ferrocene derivative was assigned by means of elemental analysis, IR, [¹H]NMR, and [¹³C]NMR spectroscopy. The structure was also confirmed by a single crystal X-ray study. The compound crystallizes in monoclinic P2₁/a space group with unit cell dimensions: a = 9.7360(6), b = 27.040(5), c = 14.767(3) Å, = 103.835(6)°, V = 3774.8(11) ų, Z = 12. The asymmetric unit contains three crystallographically independent molecules. In the ferrocenyl moieties, the Fe–C bond distance values are in the range 2.006(5)—2.051(3) Å and C–C distances in the range 1.366(7)–1.425(4) Å. The cyclopentadienyl rings in each of the molecules are mutually twisted by about 13° from the eclipsed conformation. The hydroxyl groups are involved in the intermolecular O–H...O hydrogen bond formation with O-O distances in the range 2.686(3)–2.801(4) Å forming infinite two-dimensional network in a [0 0 1] plane. The crystal structure is additionally stabilized by C–H-O weak intermolecular hydrogen bonds.     

Powder neutron diffraction of α-UB2C (α-UB2C-type)

The crystal structure of α-UB₂C (low temperature modification below T = 1675(25)°C) was determined from powder X-ray data (RT) and powder neutron diffraction data (at 29 K) employing the Rietveld-Young-Wiles profile analysis method. α-UB₂C crystallizes in the orthorhombic space group Pmma with a = 0.60338(3), B = 0.35177(2), C = 0.41067(2) nm, V = 0.0872 nm³, Z = 2. The residuals of the neutron refinement were R₁ = 0.032 and R_F = 0.043. The crystal structure of α-UB₂C is a new structure type where planar nonregular 6³-U-metal layers alternate with planar nonmetal layers of the type (B₆C₂)³. Boron atoms are in a typical triangular prismatic metal surrounding with a tetrakaidekahedral coordination B[U₆B₂C₁], whereas carbon atoms occupy the center points of rectangular bipyramids C[U₄B₂]. The crystal structure of α-UB₂C derives from the high temperature modification β-UB₂C (ThB₂C-type, ), which reveals a similar stacking of slightly puckered metal layers 6³, alternating with planar layers B₆ · (B₆C₃)². The phase transition from β-UB₂C to α-UB₂C is thus essentially generated by carbon diffusion within the B₆ · (B₆C₃)² layers to form (B₆C₂)³ layers.     

Selective bromination of dihydroquinopimaric acid

The reaction of dihydroquinopimaric acid methyl ester with bromine was found to be chemo- and stereoselective. Regardless of the solvent (acetic acid, methanol, dioxane), bromination of the title compound with an equimolar amount of bromine occurs as electrophilic addition at the double C¹⁹=C²⁰ bond with formation of 14α-hydroxy- or 14α-methoxy-19R-bromo derivatives. The reaction with excess bromine (3 equiv) leads to the formation of 16S-bromo derivatives. The bromination process is accompanied by formation of epoxy bridge between the C¹⁴ and C²⁰ atoms. X-Ray analysis revealed two polymorphic modifications of (16S,19R)-16,19-dibromo-14β,20-epoxydihydroquinopimaric acid methyl ester.     

Molecular Structure and Conformational Composition of 1-[(Methylthio)methyl]-2-nitrobenzene (MTMNB): A Theoretical and Experimental Study

The conformational composition of gaseous MTMNB and the molecular structures of the rotational forms have been studied by electron diffraction at 130^∘C aided by results from ab initio and density functional theory calculations. The conformational potential energy surface has been investigated by using the B3LYP/6-31G(d,p) method. As a result, six minimum-energy conformers have been identified. Geometries of all conformers were optimized using MP2/6-31G(d,p), B3LYP/6-31G(d,p), and B3LYP/cc-pVTZ methods. These calculations resulted in accurate geometries, relative energies, and harmonic vibrational frequencies for all conformers. The B3LYP/cc-pVTZ energies were then used to calculate the Boltzmann distribution of conformers. The best fit of the electron diffraction data to calculated values was obtained for the six conformer model, in agreement with the theoretical predictions. Average parameter values (r_a in angstroms, angle α in degrees, and estimated total errors given in parentheses) weighted for the mixture of six conformers are r(C–C) = 1.507(5), r(C–C)_{ring, av} = 1.397(3), r(C–S)_av = 1.814(4), r(C–N) = 1.495(4), r(N–O)_av = 1.223(3), ∠(C–C–C)_ring = 116.0–122.5, ∠ C6–C4–C7 = 118.2(4), ∠ C–C–S = 113.6(6), ∠ C–S–C = 98.5(12), ∠ N–C–C4 = 121.9(3), ∠(O–N–C)_av = 116.8(3), ∠ O–N–O = 127.0(4). Torsional angles could not be refined. Theoretical B3LYP/cc-pVTZ torsional angles for the rotation about C–N bond, φ_C−N, were found to be 30.5–36.5^∘ for different conformers. As to internal rotation about C–C and C–S bonds, values of φ_C−C = 68–118^∘ and φ_C−S = 66–71^∘ were obtained for the three most stable conformers with gauche orientation with respect to these bonds. Some conclusions of this work were presented in a short communication in Russ. J. Phys. Chem. 2005, 79, 1701.     

The crystal structure and conformation of N-[2,2-dimethyl-3-(2-methylpropenyl)- cyclopropylcarbonyl]-5-methylisoxazolin-3-one

The title compound has been synthesized and its crystal structure was determined by X-ray crystallographic method. The crystal is triclinic, space group P-1, with unit cell dimensions a = 6.146 (5), b = 8.473(6), c = 14.383(5) Å; α = 77.47 (4), β = 82.84 (4), γ = 69.00 (8)° and Z = 2. The results obtained reveal that the molecule of the title compound keeps a long conjugative system involving CC double bond, cyclopropane ring, carbonyl group and isoxazolinone ring and adopts a low energy conformation including s-trans of CC double bond, s-cis of carbonyl group with respect to the three-membered ring and like-s-trans of carbonyl group with the carbonyl group within the heterocyclic moiety.     

Synthesis, crystal structure and photoluminescence of a novel tetra-nuclear calcium complex [(Ca(C15H8O7S)-(H2O)(DMSO))3(Ca(C15H8O7S) (DMSO)2]·4DMSO

The sulfonate derivate of chrysin coordinates with Ca²⁺ to form a novel tetra-nuclear calcium complex [(Ca(C₁₅H₈O₇S)(H₂O)(DMSO)₃(Ca(C₁₅H₈O₇S)(DMSO)₂]·4DMSO. The structure of the complex is characterized by IR,¹H NMR and X-ray single-crystal diffraction analysis. The results show that the complex crystallizes in triclinic, space group PĪ, cell parametera = 1.4725(6) nm,b = 1.6480(7) nm,c = 2.1006(8) nm, α = 83.928(7)°, β= 85.938(7)°, γ= 85.212(7)°,V = 5.041(3) nm³,Dc = 1.476 g/cm³,Z = 2, μ=0.568 nm⁻¹,F(000) = 2324,R = 0.0778,wR = 0.1821. In the complex, four Ca²⁺ which are bridged by four 5-hydroxyanion-7-dihydro-xyfla-vone-6-sulfonate ligands with their carbonyl and 5-hydroxyanion group build an approximate square. The coordination number of Ca²⁺ is 7 and the coordinated atoms are all oxygen from the carbonyl, hydroxyl and suflo-group of 5-hydroxyanion-7-hydroxyflavone-6-sulfonate, H₂O and DMSO. Four ligands locate on two sides of the square. Two of them on the same side are almost paralleled and aromatic п-п stacking exists between them. Ligands on the opposite side are nearly perpendicular to each other. Meanwhile, the solid of title compound has the photoluminescent phenomenon. The title compound emits green fluorescence (λ_em = 520 nm) when it is excited at the wavelength of 410 nm and its photoluminescent mechanism is discussed.     

Synthesis, crystal structure and characterization of a 2-D network organic-inorganic hybrid polymer with [α-BW12O40]5? as building blocks

A two-dimensional network compound [Ce(DMF)₄(H₂O)][α-BW₁₂O₄₀]·H₂O·(HDMA)₂ (HDMA = protoned dimethylamine, DMF = N,N-dimethylformamide) was synthesized from α-H₅BW₁₂O₄₀·nH₂O, Ce(NO₃)₃·6H₂O and DMF and characterized by IR, UV spectra and TG-DTA. The result of the X-ray single crystal diffraction indicates that the crystal is monoclinic, space group P2₁/n, with unit cell dimensional: a = 1.1983(3), b = 2.4216(5), c = 1.9517(4) nm, β = 92.91(3)°, Z = 4, R ₁ = 0.07710, wR ₂ = 0.1416. Structural analysis indicates that every [Ce(DMF)₄(H₂O)]³⁺ building block is surrounded by three adjacent [α-BW₁₂O₄₀]⁵⁻ polyanions, meanwhile, every [α-BW₁₂O₄₀]⁵⁻ polyanion interconnects with three neighboring [Ce(DMF)₄(H₂O)]³⁺ subunits, by making use of which two-dimensional network structure can be constructed. The result of thermogravimetric analysis manifests that the title compound has two-stage weight loss and the decomposition temperature of the title polyanionic framework is 560°C. The electrochemical analysis shows the title polyanion has three-step redox processes in the pH = 4–7 media.     

4‐Iodo­anilinium 3‐nitro­phthalate(1–): tripartite sheets built from O—H...O and N—H...O hydrogen bonds

In the title compound, 4‐iodoanilinium 2‐carboxy‐6‐nitrobenzoate, C₆H₇IN⁺·C₈H₄NO₆⁻, the anions are linked by an O—H...O hydrogen bond [H...O = 1.78 Å, O...O = 2.614 (3) Å and O—H...O = 171°] into C(7) chains, and these chains are linked by two two‐centre N—H...O hydrogen bonds [H...O = 1.86 and 1.92 Å, N...O = 2.700 (3) and 2.786 (3) Å, and N—H...O = 153 and 158°] and one three‐centre N—H...(O)₂ hydrogen bond [H...O = 2.02 and 2.41 Å, N...O = 2.896 (3) and 2.789 (3) Å, N—H...O = 162 and 105°, and O...H...O = 92°], thus forming sheets con­taining R(6), R(8), R(13) and R(18) rings.     

Molecular and crystal structure of 4-trifluoro-2-[2-(4-fluorophenyl)hydrazine-1-ylidene]-1-(thiophen -2-yl)butane-1,3-dione

Single crystal X-ray diffraction is used to determine the crystal and molecular structure of 4-trifluoro-2-[2-(4-fluorophenyl)hydrazine-1-ylidene]-1-(thiophen-2-yl)butane-1,3-dione. Crystallographic data for C₁₄H₈F₄N₂O₂S are as follows: a = 8.2723(6) ?, b = 9.3009(7) ?, c = 9.9895(7) ?; α = 79.224(2)°, β = 75.851(2)°, γ = 72.337(2)°. Triclinic crystal system, P-1 space group, d _x = 1.622 g/cm³, V = 704.83(9) ?³, μ = 0.286 mm⁻¹, crystal size 0.30×0.20×0.20 mm, R1 = 0.0891, wR2 = 0.1989.     

Synthesis,characterization, crystal structure,and theoretical studies on Schiff-base compound 6-[(5-Bromopyridin-2-yl)iminomethyl]phenol

The title Schiff-base compound, 6-[(5-Bromopyridin-2-yl)iminomethyl]phenol (1), has been synthesized and characterized by elemental analyses, FT-IR, UV–Vis and ¹H-NMR spectroscopy, and X-ray single crystal diffraction. In the gas phase four isomers were found for title compound. Density functional (DFT) calculations have been carried out and it was found that the A isomer is the most stable one. The protonated imine N atom is involved in intra- and inter-molecular hydrogen bonds with the phenoxide group and H aromatic atoms, respectively. The title compound displays a trans configuration about the C=N double bond.