Synthesis, Structure, Thermal Decomposition and Computational Calculation of Heterodinuclear NiII - ZnII Complexes.

Mononuclear NiL complex was prepared by the use of bis-N,N'-salicylidene-1,3-propanediamine and Ni(II) salts. NiL was treated with ZnBr2 and pyrazole and 3,5-lutidine coligands in a dioxane medium to prepare the following diheteronuclear complexes: [NiL·ZnBr2·(pyrazole)2] and [NiL·ZnBr2·(3,5-lutidine)2]. The complexes were characterized by elemental analysis, TG, IR and mass spectrometry. The effects of heterocyclic one- and two- nitrogen atoms containing co-ligands were also examined. Theoretical formation enthalpies, dipole moments and the relative levels of HOMO and LUMO energies were determined by the use of Gaussian09 program. The occupancy levels of the atomic orbitals were determined by the NBO analysis of Gaussian09. The effect of pyrazole and lutidine upon the complex formation was evaluated by the use of X-ray diffraction, TG and theoretical calculations. NiL complex with lutidine forms a square pyramidal conformation since lutidine is a much stronger coligand than pyrazole.

Some Nitrogen Rich Energetic Material Synthesis by Nucleophilic Substitution Reaction from Polynitro Aromatic Compounds.

Three new nitrogen-rich energetic compounds, N-(5-chloro-2,4-dinitrophenyl)hydrazine (1), N-(5-chloro-2,4-dinitrophenyl)guanidine (2) and N-(5-chloro-2,4-dinitrophenyl)-4-aminopyrazole (3) prepared by the nucleophilic substitution reaction of 1,3-dichloro-4,6-dinitrobenzene with hydrazine, guanidinium carbonate and 4-aminopyrazole. The compounds were characterized by 1H NMR, 13C NMR, IR and mass spectroscopy. Only compound 2 could be prepared in a suitable crystal and molecular model was determined by X-ray analysis. Compounds were investigated by TG and DSC. Thermal degradation and thermokinetic behavior were investigated by Ozawa-Flynn-Wall and Kissinger-Akahira-Sunose techniques. Compounds were observed to be prone to exothermical thermal decomposition. HOMO and LUMO levels, theoretical formation enthalpy and electrostatic maps were calculated by Gaussian09. The detonation velocity and pressure were calculated by Kamlet-Jacobs equation. The compounds were assayed for antimicrobial properties.

NMR and XRD Study of Hydrogen Bonding in Picolinic Acid N-Oxide in Crystalline State and Solutions: Media and Temperature Effects on Potential Energy Surface.

Solvent and temperature effects on H-bonding in crystalline picolinic acid N-oxide (PANO) and in solutions were studied by NMR (1H MAS and 1H-13C CP/MAS) and X-ray diffraction (XRD) methods. The single-crystal XRD experiments on ß-polymorph were carried out at 105 and 299 K. 13C chemical shifts of PANO pyridine ring carbons were chosen as an effective diagnostic tool for the H-bond sensing. The crystal field in PANO forces the proton displacement from donor to acceptor atoms much stronger than the solvent reaction field, including that created by the most polar solvents. NMR and XRD data for crystalline PANO do not confirm any H-bond geometry changes in the studied temperature range. On the contrary, a considerable contraction of r(O-H) bond was observed for PANO in acetonitrile (ACN) solution upon heating. The relative contraction of r(O-H) bond with respect to R(O···O) perfectly fits the global dielectric scheme deduced for a vast set of common solvents and the dependence of the dielectric permittivity of ACN on temperature. The subtle H-bond changes can be explained by the temperature dependence of the shape of potential energy surface in the liquid state. Both factors, temperature and dielectric permittivity, are comparable in triggering this effect.

Large and negative magnetic anisotropy in pentacoordinate mononuclear Ni(ii) Schiff base complexes.

A series of pentacoordinate Ni(ii) complexes of the general formula [Ni(L5)] () with various pentadentate Schiff base ligands H2L5 (originating in a condensation of aromatic ortho-hydroxy-aldehydes and aliphatic triamines) was synthesized and characterized by X-ray structure analysis and magnetometry. The alternations of substituents on the H2L parent ligand resulted in the complexes with the geometry varying between the square-pyramid and trigonal-bipyramid. In the compounds whose chromophore geometry is closer to a trigonal-bipyramid, a large and negative uniaxial anisotropy (D = -64 cm(-1)) was identified. Moreover, the simple linear expression for the axial zero-field splitting (ZFS) parameter, D/cm(-1) = 32.7(4.8) - 151(10)τ, was proposed, where τ (in degrees) stands for the Addison parameter. The results of magnetic analysis were also supported by ab initio CASSCF/NEVPT2 calculations of the ZFS splitting parameters D and E, and g tensors. Despite large and negative D-values of the reported compounds, slow relaxation of magnetization was not observed either in zero or non-zero static magnetic field, thus no single-molecule magnetic behaviour was detected.

Hydrogen bonding in pyridine N-oxide/acid systems: proton transfer and fine details revealed by FTIR, NMR, and X-ray diffraction.

The H-bonded complexes of pyridine N-oxide (PyO) with H(2)O, acetic, cyanoacetic, propiolic, tribromoacetic, trichloroacetic, trifluoroacetic, hydrochloric, and methanesulfonic acids have been studied by FTIR and NMR spectroscopy, X-ray diffraction, and quantum chemical DFT calculations. Correlations between vibrational frequencies of the NO stretching and PyO ring modes and geometric parameters of the H-bond have been established. FTIR experiments show and DFT calculations confirm that definite discontinuity is present in the vicinity of the midpoint in the proton transfer pathway. The established correlations significantly aid in the understanding of fine effects such as the isotope (deuteration) effect, crystal-to-solution transition, or criticality of aqueous solutions induced by ionic pairs. Geometric isotope effect in the ionic H-bond aggregate of PyO·H(D)Cl was found to be extraordinary large. Measured FTIR, CP/MAS, and high-resolution (13)C NMR spectra indicate that H-bond in the PyO·HCl complex in polar solvent can potentially be more ionic than in the crystal. Vibrational modes of ionic pairs originating via proton transfer in H-bond complexes can provide new information concerning the interionic interaction and its role in the phase separation and mezo-structuring processes. The results are compared to the relevant data for PyO·HCl complex in argon matrix.

Tuning of spin crossover behaviour in iron(III) complexes involving pentadentate Schiff bases and pseudohalides.

Investigations on a series of eight novel mononuclear iron(III) Schiff base complexes with the general formula [Fe(L(5))(L(1))]·S (where H(2)L(5) = pentadentate Schiff-base ligand, L(1) = a pseudohalido ligand, and S is a solvent molecule) are reported. Several different aromatic 2-hydroxyaldehyde derivatives were used in combination with a non-symmetrical triamine 1,6-diamino-4-azahexane to synthesize the H(2)L(5) Schiff base ligands. The consecutive reaction with iron(III) chloride resulted in the preparation of the [Fe(L(5))Cl] precursor complexes which were left to react with a wide range of the L(1) pseudohalido ligands. The low-spin compounds were prepared using the cyanido ligand: [Fe(3m-salpet)(CN)]·CH(3)OH (1a), [Fe(3e-salpet)(CN)]·H(2)O (1b), while the high-spin compounds were obtained by the reaction of the pseudohalido (other than cyanido) ligands with the [Fe(L(5))Cl] complex arising from salicylaldehyde derivatives: [Fe(3Bu5Me-salpet)(NCS)] (2a), [Fe(3m-salpet)(NCO)]·CH(3)OH (2b) and [Fe(3m-salpet)(N(3))] (2c). The compounds exhibiting spin-crossover phenomena were prepared only when L(5) arose from 2-hydroxy-1-naphthaldehyde (H(2)L(5) = H(2)napet): [Fe(napet)(NCS)]·CH(3)CN (3a, T(1/2) = 151 K), [Fe(napet)(NCSe)]·CH(3)CN (3b, T(1/2) = 170 K), [Fe(napet)(NCO)] (3c, T(1/2) = 155 K) and [Fe(napet)(N(3))], which, moreover, exhibits thermal hysteresis (3d, T(1/2)↑ = 122 K, T(1/2)↓ = 117 K). These compounds are the first examples of octahedral iron(III) spin-crossover compounds with the coordinated pseudohalides. We report the structure and magnetic properties of these complexes. The magnetic data of all the compounds were analysed using the spin Hamiltonian formalism including the ZFS term and in the case of spin-crossover, the Ising-like model was also applied.

Synthesis, Spectroscopic, Spectrophotometric and Crystallographic Investigations of 4-{[(1E)-(3,4-dimethoxyphenyl)methylene]amino}-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one and 4-{[(1E)-(2-hydroxy-5-methoxyphenyl)methylene]amino}-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one.

Two new Schiff base ligands 4-[(1E)-(3,4-dimethoxyphenyl)methylene]amino-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (1) and 4-[(1E)-(2-hydroxy-5-methoxyphenyl)methylene]amino-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (2) have been prepared and characterized using elemental analysis, UV-vis, FT-IR, 1H and 13C NMR spectroscopy, and X-ray crystallographic technique. Tautomeric equilibria (phenol-imine, O-H...N and keto-amine, O...H-N forms) have been studied by using UV-vis absorption spectra for the compound 2 in some solutions. Crystal structure analyses showed that the title molecules 1 and 2 crystallize in the monoclinic space group P21/c and P21 with the unit cell parameters: a = 12.5665(3) Å and 5.6666(2) Å; b = 10.4791(2) Å and 12.2444(5) Å; c = 14.6240(3) Å and 12.1556(4) Å; V =1820.65(7) Å3 and 826.84(5) Å3; Dx = 1.282 g.cm-3 and 1.355 g.cm-3; and Z = 4 and 2, respectively.

2,2-Dichloro-N-(3,4-dimethyl-phen-yl)acetamide.

In the title compound, C(10)H(11)Cl(2)NO, the N-H bond is syn to the 3-methyl substituent in the aromatic ring, similar to that observed in N-(3,4-dimethyl-phen-yl)acetamide and to the 3-chloro substituent in 2,2-dichloro-N-(3,4-dichloro-phen-yl)acetamide, and contrasting with the anti conformation observed for the 3-methyl substituent in 2,2,2-trichloro-N-(3,4-dimethyl-phen-yl)acetamide. On the other hand, it is anti to the C=O bond. An inter-molecular N-H⋯O hydrogen bond links mol-ecules into infinite chains along the b axis.

2-Bromo-N-(4-bromo-phen-yl)acetamide.

In the title compound, C(8)H(7)Br(2)NO, the conformation of the N-H bond is anti to both the carbonyl and C-Br bonds in the side chain. In the crystal structure, mol-ecules are packed into supra-molecular chains along the c axis by N-H⋯O hydrogen bonds.

Poly[aqua-[µ-4-(4-chloro-phen-yl)-2-thioxo-2,3-dihydro-thia-zol-3-olato]-sodium(I)].

The packing of the title compound, [Na(C(9)H(5)ClNOS(2))(H(2)O)](n), in the crystal structure occurs by pairwise attachment of +sc- and -sc-arranged 4-(4-chloro-phen-yl)-2-thioxo-2,3-dihydro-thia-zol-3-olate subunits via S to sodium. Water mol-ecules that are bound in the axial position of the distorted octa-hedral coordination octahedron give rise to a stereogenic center at sodium.

Poly[ethano-lbis(µ(3)-2-thio-xo-1,2-dihydro-pyridin-1-olato)dilithium(I)].

The title compound, [Li(2)(C(5)H(4)NOS)(2)(C(2)H(6)O)](n), having two formula units in the asymmetric unit, forms infinite chains of Li(2)O(2) rhombi along b, consisting of four independent Li and O atoms. Metal binding to 2-thio-oxo-1,2-dihydro-pyridin-1-olate occurs in a bidentate fashion via O and S, and in a monodentate manner via the N-oxide O atom. π-π Inter-actions between polymeric chains are evident from centroid-to-centroid distances of pyridine-thione fragments of 3.461 (6)-3.607 (6) Å. The N-O and C-S bond lengths are distinctively different from those in hitherto investigated Ni(II), Zn(II) and (H(3)C)(2)Tl(III) complexes of 2-thio-oxo-1,2-dihydro-pyridin-1-olate, but correlate with those reported for 1-hydr-oxy- and 1-alkoxy-pyridine-2(1H)-thio-nes in the solid state.

Dichlorido-1κCl,3κCl-bis-{µ-2,2'-[pro-pane-1,3-diylbis(imino-methyl-ene)]di-phenol-ato}-1:2κO,N,N',O':O,O';2:3κO,O':O,N,N',O'-tricopper(II).

The title linear trinuclear copper(II) complex, [Cu(3)(C(17)H(20)N(2)O(2))(2)Cl(2)], was obtained from N,N'-bis-(2-hydroxy-benz-yl)-1,3-propane-diamine and CuCl(2). The overall charge of the three Cu(2+) ions is balanced by four deprotonated phenol groups and two Cl(-) ligands. The complex is centrosymmetric with the central Cu(2+) occupying a special position (). This Cu(2+) ion is coordinated by the four phenolate O atoms in a square-planar fashion. The second Cu(2+) occupies a general position in a square-pyramidal fashion. Two phenolate O atoms and two amine N form the basal plane, with Cl(-) ligands occupying the fifth coordination site.

Proton transfer in hydrogen-bonded pyridine/acid systems: the role of higher aggregation.

In this work the role of higher molecular aggregation in the proton transfer processes within hydrogen bond (H-bond) is investigated. The H-bonded complex consisting of 4-cyanopyridine (CyPy) with trichloroacetic acid (TCA) has been studied in the solutions of acetonitrile, carbon tetrachloride, chloroform and dichloroethane as solvent by FTIR spectroscopy and quantum chemical DFT calculations. In order to illustrate the effect of increasing H-bond strength FTIR investigations have also been performed on solutions of CyPy with H(2)O, acetic-, trifluoroacetic- and methanesulfonic acids. Proton states in the H-bond have been monitored using vibrational CyPy ring modes in FTIR spectra. The stabilization of the CyPy/TCA complex in its protonated form upon increasing polarity of the solvent has been evidenced. It was shown that formation of the CyPy/(TCA)(2) aggregates in the solutions favors the proton transfer process. An X-ray diffraction study has been performed on a single 1 : 2 co-crystal of pyridine/3,5-dinitrobenzoic acid. The H-bond motif found in this system exhibits the same connectivity by strong hydrogen bonds N-H(+)[dot dot dot]O(-) and O-H[dot dot dot]O as that in the CyPy/(TCA)(2) complex predicted by DFT calculation. Certain discrepancies are observed in C-H[dot dot dot]O connectivity only. The networks of H-bonds in both assemblies differ from those usually pictured for 1 : 2 base/carboxylic acid complexes in the literature.

Magnetic properties of a manganese(II) trinuclear complex involving a tridentate Schiff-Base ligand.

The Schiff condensation of 2-pyridinecarboxaldehyde N-oxide with 2-aminophenol gave a tridentate ligand, abbreviated as Hpoxap. This ligand bears the functionality of a terminating group in a trinuclear complex [Mn(poxap)Mn(ac)4Mn(poxap)], where ac- is the acetate bridge. The magnetic data were treated simultaneously during the fitting procedure with the spin Hamiltonian containing isotropic exchange, the zero-field splitting parameters, and the molecular-field correction and resulted in JMn-Mn/hc = -4.73 cm-1, gMn(t) = 1.96, DMn(t)/hc = -0.45 cm-1, and zj/hc = +0.45 cm-1 with ground state S = 5/2, where t = terminal atom. At low temperature, the features of a ferromagnetic correlation become evident.

Poly[diaqua(µ(2)-3-carboxypyrazine-2-carboxylato)(µ(2)-pyrazine-2,3-dicarboxylic acid)potassium(I)].

The structural unit of the title compound, [K(C(6)H(3)N(2)O(4))(C(6)H(4)N(2)O(4))(H(2)O)(2)](n), consists of one potassium cation, one hydrogen pyrazine-2,3-dicarboxyl-ate anion, one pyrazine-2,3-dicarboxylic acid mol-ecule and two water mol-ecules; this is twice the asymmetric unit, since the potassium cation lies on an inversion centre. Each anion or acid mol-ecule is linked to two potassium cations, while the potassium cation has contacts to four symmetry-equivalent organic ligands, with two different coordination modes towards this cation. In addition, each potassium cation is coordinated by two water O atoms, raising the coordination number to eight. One of the carboxyl groups of the acid retains its H atom, which forms a hydrogen bond to a coordinated water mol-ecule. The other carboxyl group is deprotonated in half of the ligands and protonated in the other half, taking part in a strong O-H⋯O hydrogen bond disordered over an inversion centre. The stabilization of the crystal structure is further assisted by O-H⋯O and O-H⋯N hydrogen bonds in which water acts as the donor.

2-Chloro-N-(3-methyl-phen-yl)acetamide.

The conformation of the N-H bond in the structure of the title compound, C(9)H(10)ClNO, is syn to the meta-methyl group, in contrast to the anti conformation observed with respect to the meta-nitro group in 2-chloro-N-(3-nitro-phen-yl)-acetamide. The asymmetric unit of the title compound contains two mol-ecules. The geometric parameters of the title compound are similar to those of 2-chloro-N-(4-methyl-phen-yl)-acetamide, 2-chloro-N-(3-nitro-phen-yl)acetamide and other acetanilides. Dual inter-molecular N-H⋯O hydrogen bonds link the mol-ecules in the direction of the a axis.

2,2-Dichloro-N-(3,5-dimethyl-phen-yl)-acetamide.

The structure of the title compound, C(10)H(11)Cl(2)NO, resembles those of 2,2-dichloro-N-phenyl-acetamide, 2,2-dichloro-N-(2-methyl-phen-yl)acetamide, 2,2-dichloro-N-(3-methyl-phen-yl)-acetamide, 2,2-dichloro-N-(4-methyl-phen-yl)acetamide, N-(3,5-dimethyl-phen-yl)acetamide and other acetanilides, with similar bond parameters. The mol-ecules in the title compound are linked into infinite chains through N-H⋯O and C-H⋯O hydrogen bonding.

2,2-Dichloro-N-(2,3-dimethyl-phen-yl)acetamide.

The conformation of the N-H bond in the title compound, C(10)H(11)Cl(2)NO, is syn to both the 2- and 3-methyl substituents in the aromatic ring, similar to that of the 2-chloro and 3-chloro substituents in 2,2-dichloro-N-(2,3-dichloro-phen-yl)acetamide and the 2-methyl substituent in 2,2-dichloro-N-(2-methyl-phen-yl)acetamide, but in contrast to the anti conformation observed with respect to the 3-methyl substituent in 2,2-dichloro-N-(3-methyl-phen-yl)acetamide. The bond parameters in the title compound are similar to those in 2,2-dichloro-N-phenyl-acetamide and other acetanilides. The mol-ecules of the title compound are linked into chains through N-H⋯O and C-H⋯O hydrogen bonding.

2-Chloro-N-(2,6-dimethyl-phen-yl)acetamide.

The crystal structure of the title compound (26DMPCA), C(10)H(12)ClNO, is closely related to those of side-chain-unsubstituted N-(2,6-dimethyl-phen-yl)acetamide and side-chain-substituted 2,2,2-trichloro-N-(2,6-dimethyl-phen-yl)-acet-amide and N-(2,6-dimethyl-phen-yl)-2,2,2-trimethylacet-amide, with slightly different bond parameters. The mol-ecules in 26DMPCA are linked into chains through N-H⋯O hydrogen bonding.

Dimethyl-ammonium bis-(3-oxidonaphthalene-2-carboxyl-ato)borate hemihydrate.

The title compound, C(2)H(8)N(+)·C(22)H(12)BO(6) (-)·0.5H(2)O, was synthesized under atmospheric conditions in the presence of dimethyl-formamide acting as a template. The structure is composed of [NH(2)(CH(3))(2)](+) cations, bis-(3-oxidonaphthalene-2-carboxyl-ato)borate anions and water mol-ecules. The water molecule lies on a twofold rotation axis. The stabilization of the crystal structure comes from electrostatic inter-actions and is assisted by inter-molecular O-H⋯O and N-H⋯O hydrogen bonds between the layers.