Search

Cu(II) complexes of the tridentate thiosemicarbazone ligands diacetyl monooxime thiosemicarbazone (dmoTSCH2) and diacetyl monooxime (4-phenyl)thiosemicarbazone (dmoPhTSCH2) have been synthesized. X-ray crystal structures of dmoPhTSCH2 and [Cu(dmoTSCH)Cl]2·H2O (1·H2O) are also reported. The Cu(II) compound 1·H2O is a dinuclear complex, where the Cu(II) centers have a square pyramidal geometry and are bridged by two thiolato ligands. A C2 axis passes through the middle of Cu2S2 rectangle. Variable temperature susceptibility measurement for 1·H2O shows that this compound exhibits a very weak antiferromagnetic behavior (in the solid state) with J1 = −2.97 cm−1, using the Heisenberg isotropic spin Hamiltonian (H = −J1S1·S2). DFT calculations show that the intramolecular magnetic interaction should be ferromagnetic, and the net antiferromagnetic behavior is due to competition with antiferromagnetic intermolecular interactions through hydrogen bonds.

Two mononuclear Cu(II) complexes, [Cu(L1H2)](ClO4)1.25Cl0.75·1.25H2O (1) and [Cu(L2H2)](ClO4)2 (2), of the pyridoxal Schiff base ligands N,N′-dipyridoxylethylenediimine (L1H2) and N,N′-dipyridoxyl-1,3-propanediimine (L2H2) are reported. X-ray crystal structures of both complexes are also reported. In both complexes the pyridoxal nitrogen atoms remain protonated. In the solid state, the tetradentate Schiff base ligand is virtually planar in 1, while in 2 the ligand conformation is like an inverted umbrella. In cyclic voltammetry experiments it is found that in these complexes the Cu(III) and Cu(I) states are more easily accessible than in their salen type analogs. The pyridoxal Schiff base complexes are also found to be resistant to oxidative electro-polymerization, unlike their corresponding salicyl aldehyde Schiff base complexes.

The single crystal X-ray structures and the spectroscopic properties of complexes of monensic acid (C36H62O11·H2O) with toxic metal ions of Cd(II) and Hg(II) are discussed. The cadmium(II) complex (1) is of composition [Cd(C36H61O11)2(H2O)2] and crystallizes in the monoclinic system (space group P2(1), Z = 2) with a = 12.4090(8), b = 24.7688(16), c = 14.4358(11) Å, β = 91.979(7)°. Two ligand monoanions are bound in a bidentate coordination mode to Cd(II) via the carboxylate and the primary hydroxyl oxygens occupying the equatorial plane of the complex. The axial positions of the inner coordination sphere of Cd(II) are filled by two water molecules additionally engaged in intramolecular hydrogen bonds. The Hg(II) complex (2), [Hg(C36H60O11)(H2O)], crystallizes in the orthorhombic system (space group P2(1)2(1)2(1), Z = 4) with a = 12.7316(2), b = 16.4379(3), c = 18.7184(4) Å. The monensic acid reacts with Hg(II) in a tetradentate coordination manner via both oxygen atoms of the carboxylate function and oxygens of two hydroxyl groups. The twofold negative charge of the ligand is achieved by deprotonation of carboxylic and secondary hydroxyl groups located at the opposite ends of the molecule. Hg(II) is surrounded by five oxygen atoms in a distorted square pyramidal molecular geometry.

Ephedrinum violurate dihydrate was synthesized, spectroscopically and structural elucidated. The data are compared with those of the free-base ephedrine hemihydrate. Discussion on the stable conformer of the ephedrinum cation is carried out. Quantum chemical calculations were performed for the theoretical elucidation of the conformational preference of the ephedrinum cation and its vibrational properties. The model systems neutral ephedrine hemihydrate ( 1 ) and violurate salt dihydrate ( 2 ) are elucidated.

Mononuclear transition metal complexes of the polyether ionophorous antibiotic monensin (monensic acid, MonH) with nickel(II) and zinc(II) were prepared and characterized using single crystal X-ray diffraction and spectral methods. Monensin complexes crystallize as [Ni(Mon) 2 (H 2 O) 2 ]·H 2 O·5MeCN ( 1 ) and [Zn(Mon) 2 (H 2 O) 2 ]·H 2 O·4.5MeCN ( 2 ), respectively, in the monoclinic space group P 2 1 . Compounds 1 and 2 consist of two monoanionic monensic acid ligands (monensinates) bound in a bidentate coordination mode to the transition metal ion. The metal center is placed in an octahedral environment with monensin anions occupying the equatorial plane of complexes via oxygens of carboxylate and hydroxyl groups located at the both ends of ionophore molecule. The strongly folded antibiotic anions are supported by intramolecular H-bonds, most of them originating from the two aqua ligands attached to the metal(II) ions in axial positions and completing their 6-fold coordination. The bioactivity assay reveals that the presence of divalent metal ion in the monensin complexes influences the biological properties of the ligand and should be taken into account when discussing its mode of action.

The correlation between the structural and the physical properties in solid state of two novel salts of cinchonine, cinchoninium violurate monohydrate (1) and cinchoninium squarate tetrahydrate (2), has been studied in dependence on protonation mode, using the methods of single crystal X-ray diffraction, IR-LD spectroscopy of oriented samples as a suspension in nematic liquid crystals, UV–vis spectroscopy and 1

Two novel anyles of 4-benzolylpyridine, namely N , N -diethyl- N ′-[( Z )-phenyl(pyridin-4-yl)methylidene]benzene-1,4-diamine and its N -ethylpyridinium salt were synthesized and elucidated in detail spectroscopically, thermally and structurally, using linear polarized solid-state IR-spectroscopy, UV-spectroscopy, TGA, DSC, DTA and positive and negative ESI MS. Quantum chemical calculations were used to obtain the electronic structure, vibrational data and electronic spectra of the compounds. The crystal structure of an anyle-pyridine derivative, N , N -diethyl- N ′-[( Z )-phenyl(pyridin-4-yl)methylidene]benzene-1,4-diamine, is reported for the first time; the material crystallized in the triclinic P -1 space group and only one short contact of length 3.16 A was observed between two neighbouring pyridine fragments. A bathochromic shift in λ max of 170 nm resulted from N -anylation and a 95 nm solvatochromic shift of N , N -diethyl- N ′-[( Z )-phenyl(pyridin-4-yl)methylidene]benzene-1,4-diamine were obtained depending on solvent type.

The novel pyridyl-substituted coumarin (1) and its perchlorate salt (2) have been synthesized and their structure and properties elucidated in detail spectroscopically, thermally and structurally, using single crystal X-ray diffraction for 2, linear-polarized solid state IR-spectroscopy, UV-spectroscopy, TGA, DSC, DTA, and positive and negative ESI MS. Quantum chemical calculations were used to obtain the electronic structure, vibrational data and electronic spectra. The studied compound crystallizes in the centrosymmetric space group P-1 and exhibits an infinite layered structure with the ions linked by means of the intermolecular N+H…OClO3 (2.795 A) interactions. The cations are disposed in a manner leading to a significant π-stacking effect with a distance of 2.980 A. The effects of Npy protonation on the optical and magnetic properties are elucidated by comparing the data of the protonated and neutral compounds. Copyright © 2009 John Wiley & Sons, Ltd.

The novel salt of a geminal diol 4-(dihydroxymethyl)pyridinium hydrogensquarate was derived from isonicotinaldehyde and squaric acid in water. Two polymorphs were characterized by means of single crystal X-ray diffraction and linear-polarized infrared (IR-LD) spectroscopy of oriented colloids in nematic host. UV spectroscopy was employed to confirm the stabilization of the geminal diol form in aqueous solution. Depending of the reaction conditions two polymorphs of 4-(dihydroxymethyl)pyridinium hydrogensquarate are determined – monoclinic (1) and a triclinic (2) polymorph. The monoclinic (1) crystallizes in the centrosymmetric space group P21/c, while (2) crystallizes in the centrosymmetric space group P 1 ¯ , respectively. The hydrogensquarate anions in both forms form the α chain motif via interanionic hydrogen bonding interactions 2.664(7) A (1) and 2.517(5) A (2), respectively. The geminal diol group of the cations in (1) are directed to an adjacent hydrogensquarate ion via two O–H···O hydrogen bonds with an averaged donor–acceptor distances forming an eight membered ring. In contrast to (1), in (2) the infinite hydrogen bonded two-dimensional layers formed by cations and anions are connected via a hydrogen bond between hydroxyl groups of adjacent symmetry related cations.

Two novel hydrogensquarates of 3-nicotinoyl (1) and 3-isonicotinoyl (2) coumarin have been synthesized and their structures and properties elucidated spectroscopically and structurally, using single crystal X-ray diffraction, linear-polarized solid-state IR-spectroscopy, UV-spectroscopy and negative ESI MS. Quantum chemical calculations were used to obtain the electronic structure, vibrational data and electronic spectra. The IR-spectroscopic elucidation is carried out by a comparison with the characteristics of corresponding neutral 3-nicotinoyl and 3-isonicotinoyl coumarins.

A centrosymmetric binuclear [{Cu(PPh3)2}2(piperzdtc)] (1) [piperzdtc2– = piperazinebis(dithiocarbamate)] and another mononuclear [{Cu(PPh3)2}(BzMedtc)] (2) (BzMedtc– = N-benzyl-N-methyldithiocarbamate) complex have been synthesized and characterized by elemental analyses, IR, 1H, 13C, and 31P NMR spectroscopy and by X-ray crystallography. The nonlinear optical properties of 2 have been investigated by density functional theory and its electronic absorption bands have been assigned by time-dependent density functional theory (TD-DFT). Both complexes are weakly conducting (σrt ≈ 10–8 S cm–1) because of the absence of M···S/S···S intermolecular stacking and exhibit semiconductivity with band gaps of 0.94 and 1.24 eV, respectively.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

We report the synthesis, spectroscopic and structural elucidation of two prolinamide derivatives of squaric acid, i.e. prolinamide ester amide of squaric acid ethyl ester (1) and prolinamide diamide of squaric acid dihydrate (2). Both compounds crystallize in non-centrosymmetric space groups, monoclinic P2(1) (1) and orthorhombic P2(1)2(1)2(1) (2), respectively. For first time in the literature the crystal structure of homodiamide of amino acid amide of squaric acid is reported. The data for heterodiamides is also absent. Supramolecular zig-zag chains by hydrogen bonds of H(2)N-C=O ..., HNH (3.020 A) and HNH ..., OC((S(q))) (2.972 A) types with the participation of amide and squaric acid (S(q)) fragments, -CO=NH(2) and O=C((S(q))) are refined in (1). A helix supramolecular structure is formed in (2) by moderate intermolecular HNH ... O=C(NH(2)) hydrogen bond with length of 2.947A. The two crystallographical non-equivalent water molecules stabilized the helix by interactions of types HOH...OC((Sq)) (2.917A), HOH...O=C(NH(2)) (2.899A), H(2)O...NH(2)(C=O) (2.972A), respectively. Optical and magnetic properties are investigated with a view to explain the correlation structure-properties of the newly synthesized molecules.

(E)-4-(Hydroxyiminomethyl)-pyridinium hydrogenoxalate (1) and bis((E)-4-(hydroxyiminomethyl)-pyridinium) squarate (2) were synthesized and their crystal structures determined by means of single crystal X-ray diffraction. The structures of (1) and (2) consist of infinite layers and chains, respectively, formed by (1): N–H···O (2.852(2), 2.827(2) A) and O–H···O (2.665(2) A) and (2): N–H···O (2.620(2) A) and O–H···O (2.600(1) A) intermolecular hydrogen bonds between the cations and anions. Hydrogenoxalate ions form chains within the infinite layers by strong interanionic O–H···O interactions (2.583(2) A). Antiperiplanar conformations of the cations for (1) and (2) (CC N–OH) dihedral angle of 178.9(1)° (1) and 179.4(1)° (2) are observed. Spectroscopic properties both in solution and in the solid state were elucidated by means of 1H- and 13C-NMR, UV-spectroscopy and conventional and linear polarized IR- (IR-LD) spectroscopy. Quantum chemical calculations at the DFT, MP2 and CIS level of theory and the 6-31++G∗∗ basis set were employed for predicting and supporting experimentally observed optical propertied and electronic structures of the protonated (E)-4-(hydroxyiminomethyl)-pyridine.

1-methyl-4-[2-(3-methoxy-4-hydroxyphenyl)ethenyl)]pyridinium] hydrogensquarate monohydrate (1) has been synthesized and its structure obtained by single crystal X-ray diffraction. Optical properties have been elucidated by means of linear-polarized solid state IR-spectroscopy, UV-spectroscopy as well as nuclear magnetic resonance and thermal analysis. The polarization tool of oriented colloid suspensions in nematic host is used. Quantum chemical calculations have performed with a view to obtaining the electronic structure and optical properties of the novel compound. The compound crystallizes in the space group P-1 and the structure consists of infinite layers, resulting from intermolecular OH…O=C(Sq) (2.684 A) and (Sq)OH…OH2 (2.575 and 2.850 A) hydrogen bonds between the cation and anions as well as solvent molecules.

Two novel l -lysinium hydrogensquarate monohydrate (1) and the corresponding salt of the l -lysinium dication (2) are synthesized and their structure and properties elucidated in detail spectroscopically, thermally and structurally, using single crystal X-ray diffraction, linear-polarized solid-state IR-spectroscopy oriented colloid suspensions in nematic host, TGA, DSC, DTA methods, positive and negative HPLC tandem mass spectrometry (ESI-MS·MS). Quantum chemical methods are used to calculate the electronic structure, vibrational data and electronic spectra. Two novel structural motifs have been obtained, isolated [(HSq−)] and tetramolecular [(H2Sq)(HSq)2(Sq)]4− anion, respectively. Preliminary second harmonic generation measurements are also performed.

Two novel adducts of codeinone with barbituric and 2-thiobarbituric acids have been synthesized via Michael addition. The compounds were spectroscopically elucidated by means of IR-LD spectroscopy of oriented samples as a suspension in nematic liquid crystals, UV spectroscopy and 1H and 13C NMR spectroscopy. The 2-thiobarbituric adduct was characterized by X-ray crystallography. HPLC tandem mass spectrometry (HPLC ESI MS/MS) and thermal methods were also employed. Quantum chemical calculations have been performed with a view to obtaining the electronic structure and vibrational properties of the novel compounds.

IR-spectroscopic characterization of the coumarin-3-phosphonic acid and 1,2-benzoxaphosphorine-3-carboxylic acid ethyl esters has been carried out by means of linear-polarized IR (IR-LD) spectroscopy of oriented colloid suspensions in a nematic host. Quantum chemical DFT calculations at the B3LYP level of theory and 6-311++G** basis set were performed. The electronic structure and vibrational properties of both compounds are discussed. The spectroscopic data for 2-benzoxaphosphorine-3-carboxylic acid ethyl ester are in accordance with the crystal structure determined by single crystal X-ray diffraction. The compound C13H15O5P crystallizes in the noncentrosymmetric space group P212121, and its structure consists of a 3D network formed by short contacts of the type P=O···HC(Ar) with distances of 3.420 and 2.467 A. The geometry of the PO3C fragment exhibits a pseudo T d symmetry.

The novel, 1-methyl-4-[2-(4-hydroxyphenyl)ethenyl]pyridinium dihydrogenphosphate salt was synthesized and its structure and properties elucidated spectroscopically, thermally and structurally, using single crystal X-ray diffraction, linear-polarized solid-state IR spectroscopy (IR-LD), UV–vis spectroscopy, TGA, DSC, DTA and MS. The compound crystallizes in the monoclinic P21/c space group and exhibits a pseudo layer structure with molecules linked by strong OH⋯O–P intermolecular hydrogen bonds of length 2.593 A. The dihydrogenphosphate anions themselves form infinite chains through strong OH⋯O–P intermolecular hydrogen bonds of lengths 2.636 and 2.658 A. The crystallographic disorder of these systems and its effect on IR-LD spectra in the solid state are discussed. Solutions of different polarity show a significant CT band shift of up to 70 nm, corresponding to a molecular first hyperpolarizability value.

The title compound was synthesized and characterized by single crystal X-ray diffraction and solid-state polarized IR-spectroscopy of oriented colloids in a nematic host. The compound crystallizes in the monoclinic space group P21/c and its structure consists of a 3D supramolecular network of tyrammonium cations, water and sulfate anions directed by intermolecular hydrogen bonding interactions. Two non-equivalent tyrammonium cations are observed with pseudo T and T trans configurations, respectively. The vibrational characteristics of the non-equivalent molecules are assigned using solid-state polarized IR-spectroscopy. The structural and spectroscopic data are compared with theoretical calculations at the MP2/6-31++G∗ level of theory and basis set using the tyrammonium cation heptahydrate as a model system.

The novel 3,4-diaminopyridinium hydrogentartarate dihydrate has been synthesized and its structure and properties elucidated in detail spectroscopically, thermally and structurally, using single crystal X-ray diffraction, linear-polarized solid state IR-spectroscopy, UV-spectroscopy, TGA, DSC, DTA and positive and negative ESI-MS. Quantum chemical calculations were used to obtain the electronic structure, vibrational data and electronic spectra. The studied compound crystallizes in the noncentrosymmetric space group P212121 and exhibits a 3D network with molecules linked with participation of cations, anions and solvent molecules. Hydrogentartarates form infinite chains through strong O COH…OCO interaction. The effects of N1 protonation on the optical and magnetic properties of 3,4-diaminopyridine are elucidated by comparison with the data of the neutral form.

Benzamidinium d -glucuronate (1) crystallizes in the orthorhombic space group P212121 and exhibits a 3 D network with molecules linked by moderate intermolecular hydrogen bonds (HNH…O(solvent) 2.993 A, HNH…OCO 2.894 A, HNH…O(cycle) 2.844 A, OH…NH2 2.931 A, OH…O(solvent) 2.894, 2.924 and 2.715 A (stronger)) with participation of cations, anions and solvent molecules. The IR-band assignment of carbohydrate moieties is elucidated by a comparison between the types and bond lengths of intermolecular interactions with participation of OH groups in d -glucuronate and linear polarized IR-(IR-LD) spectroscopic data. Experimental results are supported by theoretical ab initio calculations of benzamidinium cation and d -glucuronate anion.

Synthesis, isolation, spectroscopic and structural elucidation of tyrosinamide hydrogensquarate monohydrate (I) is reported on the basis of quantum chemical DFT calculations, vibrational analysis and experimental linear-polarized IR-spectroscopy in solid state. These data are compared with those obtained using single crystal X-ray diffraction, which show that the molecules of (I) in the unit cell formed 3D network through moderate intermolecular (Tyr)OH...O = C(Sq) (2.727 A), O=C-NH2...OH(Tyr) (2.991 A), O=C-NH2...OH(Sq) (2.988 A), O=C-NH2...O=C-NH2 (3.068 A), N+H3...O=C(Sq) (2.737, 2.953, 2.954 A), OH2...O=C(Sq) (2.839 A) and (Sq)OH...OH2 (2.607 A) hydrogen bonds. The relationship between the structure and spectroscopic properties is studied.

The synthesis, isolation, spectroscopic and structural elucidation of sympathomimetic amine, tyramine dihydrogenphosphate are of interest due to its biological activity and the establishing correlation between spectroscopic properties and structure. The complex approach for investigation included single crystal X-ray diffraction, new technique in linear-polarized IR-spectroscopy in solid state and quantum chemical calculations with a view to predict the electronic structure and vibrational data of interacting species in entitled compound, the correlation structure-spectroscopic properties as well as the influence of intermolecular interaction on IR-characteristic bands are carried out.

The novel hydrogensquarate salt of 4-cyanopyridine was synthesized, and its structure and properties were elucidated in detail spectroscopically, thermally, and structurally, using single-crystal X-ray diffraction, linear-polarized solid-state IR spectroscopy, UV spectroscopy, TGA, DSC, DTA, and positive and negative ESI MS as well as 1H and 13C NMR methods. Quantum chemical methods were used to calculate the electronic structure, vibrational data, and electronic spectra. 4-Cyanopyridinium hydrogensquarate monohydrate crystallizes in the space group P and exhibits a layered structure with molecules linked by intermolecular NH...O(HSq-) (2.651 A) and HOH...O(HSq-) (2.792 and 2.563 A) hydrogen bonds with participation of cations, anions, and the solvent molecule. The formation of stable layers of the type (2HSq-.2H2O)n and the observation of a red color in the solid state is discussed. The optical and magnetic properties were elucidated in comparison to the data for neutral 4-cyanopyridine as well as its four known salts.

Mononuclear neutral manganese(II) and cobalt(II) complexes with the antibiotic Sodium Monensin A (Mon-Na, 1b ) were synthesized and characterized. The crystal structures of M(Mon-Na) 2 Cl 2 · H 2 O (M = Mn, 2 ; M = Co, 3 ) were determined by X-ray crystallography. The complexes crystallize in monoclinic space group C2 with a tetrahedrally coordinated transition metal attached to oxygen atoms of deprotonated carboxyl groups of two Sodium Monensin molecules and two chloride ions. The sodium ion remains in the cavity of the ligand and cannot be replaced by Mn(II) or Co(II). The complexes were additionally characterized by different spectroscopic techniques (UV–Visible, EPR, FAB-MS). A preferable octahedral environment around the transition metal centers is observed in polar solvents while the complexes retain their tetrahedral structure in non-polar media. The antimicrobial activity of 1b , 2 and 3 was tested against Gram(+) and Gram(−) bacteria.

Tryptammonium hydrogentartarate (1) crystallizes in the orthorhombic space group P212121 and exhibits a crystal structure consisting of the tryptammonium cation, hydrogentartarate anion and a solvent methanol. The cations and anions are joined into a 3D network by intermolecular NH···OH(CH3) and NH3···O(tart) bonds with lengths of 2.998, 2.772, 2.902, and 2.847 A, respectively. Hydrogentartarate anions are themselves connected by strong intermolecular O···H-O hydrogen bonds with lengths of 2.481 A into infinite chains. The anions also participate in moderate hydrogen bonding with solvent methanol molecules of the (tart)O···O(CH3) type with bond lengths of 2.736 and 2.762 A). The conformational preference of the tryptammonium cation is discussed by comparing the results with the data for other crystallographically determined structures of salts. Quantum chemical calculations at (density functional theory) DFT (B3LYP) level of theory and 6-311++G** basis set are performed for the interacting system tryptammonium cation/H2O with a view to predicting the geometry of the most stable conformer. The optical properties of tryptammonium hydrogentartarate have been elucidated in the solid-state by means of linear-polarized solid state IR-spectroscopy (IR-LD) of oriented solids as a colloid suspension in nematic hosts. Some limitations of the method are discussed as well.

The structure of ammonium hydrogensquarate squaric acid monohydrate has been determined by single crystal X-ray diffraction. The compound crystallizes in the monoclinic space group C2/c and exhibits a 3D network with molecules linked by intermolecular interactions with participation of the H2Sq, HSq−, NH4 +, and H2O species. The HSq− anion and the neutral H2Sq form a strong head-to-tail dimer through O–H···O hydrogen bonding with lengths of 2.587 and 2.494 A (protected space between numeral and unit). The layers are connected by ammonium cations and water molecules in a plane through the O···N (2.950, 2.978, 3.036 A) and O···O (2.953, 2.781 A) bonds. Another such layer is connected to the NH4 + cation in the adjacent plane through bifurcated N–H···O hydrogen-bonding to form a double layer (NH···O bond lengths are 3.036, 2.978, 2.857, 2.909, 2.958, and 2.742 A, respectively). The IR-band assignment of the compound was achieved using the polarized IR-spectroscopy of oriented colloids in a nematic host. Theoretical ab initio calculations were performed and achieved with a view to explain the IR-bands of the H2Sq.HSq− motif.

3,4-diaminopyridinium bis(perchlorate) has been synthesized and its crystal structure has been solved by single crystal X-ray diffraction. The optical and magnetic properties of the N1, N4 protonated 3,4-diaminopyridinium dication have been elucidated in solution and in the solid-state by means of linear-polarized solid state IR-spectroscopy (IR-LD), UV-spectroscopy, TGA, DSC, and positive and negative ESI MS. Quantum chemical calculations were used to obtain the electronic structure, vibrational data, and electronic spectra of the dication. The studied compound crystallizes in the noncentrosymmetric space group Cc and exhibits infinite molecular chains formed by 3,4-diaminopyridinium dications and ClO 4 − anions along the c-axis by moderate intermolecular NH 3 + ···OClO 3 − interactions with bond lengths of 3.031, 3.024, 2.825, and 2.875 A. The NH group participates in intermolecular NH···OClO 3 − contacts with bond lengths of 3.220 and 3.172 A, respectively. The effect of N1, N4 diprotonation on the optical and magnetic properties of the 3,4-diaminopyridinium dication is discussed.

This work describes the synthesis and X-ray crystallographic characterization of three nickel(II) complexes [Ni(3,2,3-tet){Ag(CN)2}2] (1), [Ni(3,2,3-tet)(μ-tp)]n · 1.5nH2O (2) and {[Ni(3,2,3-tet)(μ1,5-dca)](ClO4)}n (3) where 3,2,3-tet = N,N′-bis(3-aminopropyl)-1,2-ethylenediamine, tp = terephthalate and dca = dicyanamide. Compound 1 is a heterotrinuclear discrete distorted octahedral molecule whereas compound 2 forms a 1D polymeric network and an extended 2D network is formed by intermolecular hydrogen bonding. Interestingly, two adjacent 1D chains execute a novel double-helical network constructed by Ni(II) and the bridging dca ligand in compound 3. The variable temperature magnetic susceptibility measurements for compounds 2 and 3 were also carried out.

The coordination chemistry of two aminebis(phenolate) ligands (H2L1 and H2L2) around vanadium(V) is described. Vanadium(V) oxo complexes (1, 2 and 3) of all the ligands were obtained readily by the reaction between the ligand precursors and [VO(acac)2]. Single crystal X-ray structure analysis showed that all of the complexes are penta-coordinated with trigonal bipyramidal geometry in NO4 coordination environment. The tripodal nitrogen atom of the respective ligands and monodentate alkoxo group occupy apical positions. These complexes structurally resemble very closely to the active sites of vanadium haloperoxidases (VHPO) and were found to catalyze the oxidation of toluene to benzoic acid and isomers of xylene to the corresponding hydroxy acids with turn over numbers ranging between 134 and 188. Based on mass spectra the mechanism of the catalytic process was proposed to proceed through the formation of hydroxo–hydroperoxo intermediate, which is different from halo peroxidase reactions.

A cyano-bridged hetero-trinuclear complex, [Cu(HL)] 2 [Ni(CN) 4 ] ( 2 ) (H 2 L = 3,9-dimethyl-4,8-diazaundec-3,8-diene-2,10-dione-dioxime) has been synthesized and characterized by single crystal X-ray structure determination. The square planar [Cu(HL)] + cation ( 1 ), otherwise reluctant to bind axially, is converted to a square pyramidal geometry through axial ligation by the cyano group of [Ni(CN) 4 ] 2− ion in di- trans fashion. Electrochemical studies in MeCN give (i) E 1/2 (Cu II/I ) = −0.52 V and −0.55 V and (ii) E 1/2 (Cu III/II ) = 1.15 and 1.23 V versus Ag/AgCl for complexes 1 and 2 respectively, whereas in aqueous solution, the corresponding E 1/2 (Cu II/I ) appear at −0.61 V and −0.58 V. The E 1/2 (Cu III /Cu II ) appears at 1.04 V for 2 only; no such process is encountered for the complex 1 at potential ⩽1.20 V. In addition to these there is a redox process, occurring in aqueous solution only, for the copper(II) bound ligand oxidation at 0.63 and 0.60 V versus Ag/AgCl for the complex 1 and 2 respectively. Both the complexes undergo acid catalyzed decomposition with a second-order dependence in H + . It is found that complex 2 decomposes at a rate ∼2 times faster than the complex 1 . The kinetic studies on the periodate oxidation reveal that both HIO 4 and IO 4 - are reacting species for the oxidation of 1 , while HIO 4 is the sole reacting species for the complex 2 . Again, complex 2 reacts faster than 1 . An inner-sphere mechanism has been invoked for both the complexes based on large Q , the association constant values.

Reaction of thiosemicarbazones of salicylaldehyde and 2-hydroxyacetophenone (H2L1 and H2L2) with [Ir(PPh3)3Cl] affords complexes of type [Ir(PPh3)2(L)(H)] (L = L1 or L2) in ethanol. A similar reaction carried out in toluene affords the [Ir(PPh3)2(L)(H)] complexes along with complexes of type [Ir(PPh3)2(L)Cl], where a chloride is coordinated to iridium instead of the hydride. The structure of the [Ir(PPh3)2(L2)(H)] and [Ir(PPh3)2(L2)Cl] complexes has been determined by X-ray crystallography. Crystal data for [Ir(PPh3)2(L2)(H)]: space group, P21/c; crystal system, monoclinic; a=12.110(2) A, b=17.983(4) A, c=18.437(4) A, β=103.42(3)°, Z=4; R1=0.0591, wR2=0.1107. Crystal data for [Ir(PPh3)2(L2)Cl]: space group, P21/c; crystal system, monoclinic; a=17.9374(11) A, b=19.2570(10) A, c=24.9135(16) A, β=108.145(5)°, Z=4; R1=0.0463, wR2=0.0901. In all the complexes the thiosemicarbazones are coordinated to the metal center as dianionic tridentate O, N, S-donors and the two triphenylphosphines are trans. The complexes are diamagnetic (low-spin d 6, S=0) and show intense MLCT transitions in the visible region. Cyclic voltammetry on all the [Ir(PPh3)2(L)(H)] and [Ir(PPh3)2(L)Cl] complexes shows a quasi-reversible Ir(III)–Ir(IV) oxidation within 0.55–0.78 V vs. SCE followed by an irreversible oxidation of the thiosemicarbazone within 0.91–1.27 V vs. SCE. An irreversible reduction of the thiosemicarbazone is also observed within −1.10 to −1.23 V vs. SCE.

Two coordination compounds of compositions [Ni(L1)(idba)(H2O)]·1.5 H2O (1) and [Ni(L2)Fe(CN)5NO]·C2H5OH (2) where L1 is N, N′-bis(3-aminopropyl)ethylenediamine, L2 is 2,12-dimethyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),2,11,13,15-pentaene, and idba2− is 2,2′-iminodibenzoate have been synthesized and characterized by elemental analysis, IR spectroscopy, thermal analysis, and single-crystal X-ray diffraction. Complex 1 crystallizes in the monoclinic space group P21/n (No. 14) with a=9.810(2) A, b=10.230(2) A, c=25.350(5) A, V=2543.6(9) A3, Z=4, and R=0.0727. The nickel atom is six-coordinated by four N atoms of amine and two O atoms of water and idba2−. The molecular packing of the complex comprises of an infinite one-dimensional layered network in which the molecules in the crystal are held together by a system of hydrogen bonding. Complex 2, however, crystallizes in the space group C2/c (No. 15) of the monoclinic system with a=19.7990(4) A, b=14.9440(3) A, c=19.8800(3) A, V=5115.90(17) A3, Z=4, and R=0.0540. The Ni ion in compound 2 has a slightly distorted octahedral arrangement of the N4 donor atoms of primary ligand L2 and two N-donor atoms of the secondary nitroprusside ligand. The structure of 2 displays an extended one-dimensional network formed by linear [—Ni—NC—Fe—CN—] units. A cyclic voltammetric study shows that compound 1 undergoes a quasireversible oxidation attributable to Ni2+ → Ni3+ in the range 300–420 mV vs SCE.

The synthesis and crystal structure of N,N′-diethyl-4-vinylbenzamidinium squarate (I) (C15H19N2O2) are reported. The squarate dianion (Sq2−) and (E,Z)-configured amidinium groups are linked through two intermolecular N···O hydrogen bonds with distances of 2.725 A for E and 2.731 A for the Z configurated amidinium parts, thus forming an infinite three-dimensional network. The torsion angle between phenylene ring and amidinium group is 66.1(2)° and the analogous one between the first fragment and the vinyl group 9.6(8)°. The IR-characteristic band assignment both in solution and in solid state has been carried out by means of non- and linear polarized IR- spectral analysis.

This work describes the synthesis and characterization of two Pd(II) complexes [(3,5-Hdmpz)2Pd2(μ-3,5-dmpz)2(2,6-dipic)] (1) and [Na2(H2O)4Pd(2,6-dipic)2] (2) (3,5-Hdmpz = 3,5-dimethylpyrazole and 2,6-dipic = 2,6-pyridinedicarboxylate). The X-ray molecular structure determination shows that 1 is a binuclear complex bridged by two 3,5-dmpz units and is completely unsymmetric since one palladium atom contains two protonated 3,5-Hdmpz ligands and the other one contains the 2,6-dipic2− unit that coordinates in a bidentate fashion. The central six-member Pd2N4 core shows a boat-like conformation where the palladium atoms are positioned at the vertices of the boat. The molecules are assembled in an extended zigzag one-dimensional network formed through 3,5-Hdmpz-carboxylate (2,6-dipic2−) hydrogen bonds. The packing of complex 2 is constructed of cationic Na+–H2O and anionic Pd-2,6-dipic2− units joined together to form an extended two dimensional network. Alternate short and long Na–Na distances are observed in the cationic layer. A detailed quantum-chemical calculation on the Na-chains in 2 has been made. Complex 1 shows a luminescence property and antimicrobial activity against Bacillus subtilis, Escherichia coli and Aspergillus niger where the MIC has been found to be 100 μg/mL for all three species.

A new Cu(II)-complex of 3-aminopyridine, [CuCl(3-AP)4][Cu(3-AP)4(H2O)]Cl3 · 2H2O (1), containing two contrasting complex cations has been synthesized and structurally characterized by single crystal X-ray diffraction and solid-state linear-dichroic infrared (IR-LD) spectral analysis. In both cations four 3-AP molecules coordinate the Cu(II) atom in a monodentate fashion through their endocyclic (Npy) nitrogens, thereby generating a square-planar coordination geometry for the CuN4 chromophor. Perpendicular to the N4 plane, the metal ion is coordinated by a chloride anion in the first cation and a water ligand in the second cation. One of three additional water molecules of crystallization occupies the vacant octahedral site of the second cation and participates in a weak Cu···OH2 interaction. An IR-LD spectral analysis of the samples, oriented as a suspension in a nematic liquid crystal confirmed the crystallographic data and the retention of the pyridine ring aromatic character after coordination. The presented results are additionally supported by UV, 1H-NMR, EPR and MS analysis and by thermogravimetric and calorimetric data.

Valinamide ester amide of squaric acid has been synthesized and structurally characterized by single crystal X-ray diffraction. Individual molecules are linked into zig-zag helix chains running parallel to [0 1 0] by N–H ⋯ O hydrogen bonds of length 2.7908(19) A and 2.980(2) A involving the valinamide nitrogen atoms and the amide carbonyl oxygen atom. An experimental IR spectroscopic characterization and theoretical vibrational analysis have also been performed, using the possibilities of polarized linear-dichroic IR-spectroscopy (IR-LD), based on an orientation technique of the molecules as a suspension in a nematic liquid crystal.

As part of an investigation on the coordination ability of peptides, structural analyses of the solid tripeptide glycyl-methionyl-glycine (H-Gly-Met-Gly-OH) and its hydrochloride have been carried out. The quantum chemical calculations (B3LYP/6-31+G(d) and UHF/6-31G**) and linear-dichroic infrared (IR-LD) spectroscopy predict a near to linear structure of the pure ligand, but the experimental IR-LD data are in accordance with a cross-linked disposition of both amide fragments in the protonated form. This result is confirmed by an X-ray diffraction study of latter compound. The presented work also demonstrates the possibilities of IR-LD spectral analysis for the structural characterization of an amorphous system such as the investigated tripeptide.

The aromatic character, distortion and stabilization of the imino-form as a result of protonation of 4-aminopyridine was proved by IR-, UV- and 1H NMR-spectral analysis of the 4-aminopyridinium tetrachloropalladate(II) complex salt. In particular, linear-dichroic IR-spectroscopy coupled with the orientation technique of solid samples as a liquid crystal suspension was applied for identification of the IR-bands, characteristic for the structural fragments of the discussed imino-isomer. The spectral results obtained were compared and confirmed by a single crystal X-ray study of the used model system. It is formed by a discrete PdCl 4 2 - anion and two Npy protonated C 5 H 7 N 2 + cations. The Pd(II) ion is square planar coordinated with four Cl− ligands.

Two novel isostructural ( Π = 0.0045, I v = 93.292) one-dimensional mono-halo-bridged octahedral copper (II) polymeric complexes [Cu(L)Cl] n (ClO 4 ) n ( 1 ) and [Cu(L)Br] n (ClO 4 ) n ( 2 ) (L = 1,9-diamino-5-methyl-5-nitro-3,7-diazanonane) were prepared and characterized by CHN, IR, EPR and magnetic moment studies under a tetra coordinating (diaza-diamine type) ligand environment. The X-ray structure analysis indicates that in both 1 and 2, independent consecutive [Cu( L )X] + (X = Cl or Br) cations with crystallographic C s symmetry propagate through the a glide plane of the orthorhombic space group Pnma to give the polymeric chain structure along the a axis. In 1 , the Cu–Cl bond length is 2.740 which under bridging condition elongates to 3.024 and the bridging angle, Cu–Cl–Cu, is 164.9 while parameters for 2 are 2.961(2), 3.074(2) and 157.4(5), respectively. Each monomeric unit in both the complexes is under extensive intra and inter-molecular hydrogen bonding, leading to three dimensional structures.

A new mononuclear Cu(II) complex of 4-aminopyridine (4AP), [Cu(4AP)4]Cl2·2CH3OH (1), was obtained and structurally characterized by single-crystal X-ray diffraction methods. The complex is square-planar involving four monodentate 4AP molecules coordinated through the Npy atoms. A solid-state linear-dichroic spectroscopic analysis (IR-LD) as a suspension in a nematic liquid crystal was carried out over the 4000–400 cm−1 range and determined stereochemical parameters compared crystallographic data. Detailed IR characteristics are reported.

Two hydrogen-bonded palladium(II) and platinum(II) complexes, [Pd(Hida)2] (1) and [Pt(Hida)2] (2) (Hida− = iminodiacetate), have been synthesized and characterized by single crystal X-ray diffraction analyses. Hida− serves as a bidentate ligand coordinating to both Pd(II) and Pt(II) through its nitrogen and oxygen atom, exhibiting a square planar geometry with a trans configuration. The uncoordinated carboxylic group and the imino group of the ligand are involved in strong intermolecular hydrogen bonding to form a two dimensional layered network in both the complexes. The network is propagated along the ac-plane and stacks orthogonally to the b-axis. The thermogravimetric analyses for complexes 1 and 2 reveal stepwise decomposition processes indicating the probable decarboxylation of the free and bonded carboxylates. As there are two types of hydrogen bonding (N–H⋯O, O–H⋯O) present in both the complexes, two endothermic peaks regarding heat change are evident from their DSC diagrams.

Reaction of chloranilic acid (H2ca) with [Os(bpy)2 Br2] (bpy = 2,2'-bipyridine) affords a dinuclear complex of type [{Os(bpy)2}2 (ca)]2+, isolated as the perchlorate salt. A similar reaction of H2ca with [Os(PPh3)2 (pap)Br2] (pap = 2-(phenylazo)pyridine) affords a dinuclear complex of type [{Os(PPh3)2 (pap)}2 (ca)]2+ (isolated as the perchlorate salt) and a mononuclear complex of type [Os(PPh3)2 (pap)(ca)]. Reaction of H2ca with [Os(PPh3)2(CO)2(HCOO)2] gives a dinuclear complex of type [{Os(PPh3)2(CO)2}2 (r-ca)], where r-ca is the two electron reduced form of the chloranilate ligand. The structures of the [{Os(PPh3)2 (pap)}2 (ca)](ClO4)2, [Os(PPh3)2 (pap)(ca)], and [{Os(PPh3)2(CO)2}2 (r-ca)] complexes have been determined by X-ray crystallography. In the [{Os(bpy)2}2 (ca)]2+ and [{Os(PPh3)2 (pap)}2 (ca)]2+ complexes, the chloranilate dianion is serving as a tetradentate bridging ligand. In the [Os(PPh3)2 (pap)(ca)] complex, the chloranilate dianion is serving as a bidentate chelating ligand. In the [{Os(PPh3)2(CO)2}2 (r-ca)] complex, the reduced form of the chloranilate ligand (r-ca(4-)) is serving as a tetradentate bridging ligand. All the four complexes are diamagnetic and show intense metal-to-ligand charge-transfer transitions in the visible region. The [Os(PPh3)2 (pap)(ca)] complex shows an Os(II)-Os(III) oxidation, followed by an Os(III)-Os(IV) oxidation on the positive side of a standard calomel electrode. The three dinuclear complexes show two successive oxidations on the positive side of SCE. The mixed-valent Os(II)-Os(III) species have been generated in the case of the two chloranilate-bridged complexes by coulometric oxidation of the homovalent Os(II)-Os(II) species. The mixed-valent Os(II)-Os(III) species show intense intervalence charge-transfer transitions in the near-IR region.

The work describes characterization of salicylaldazine by IR, NMR and single crystal X-ray diffraction studies. The compound crystallizes in the monoclinic crystal system with the space group P21/n, a=8.554(3), b=6.338(2), c=11.864(5) A, and β=107.89(2)°. There are two strong intramolecular hydrogen bonds of the type O–H⋯N and two weak hydrogen bridges of the type C–H⋯O which help the molecules to pack in a layered structure. Semi-empirical calculations have been performed to predict theoretically the feasibility of intramolecular ground and/or excited state proton transfer reaction/s. Potential energy curves have been generated in the ground (S0) and the lowest excited (S1) singlet states to judge the feasibility of intramolecular single and double proton transfer reactions. Semi-empirical (AM1) calculations suggest that only the excited state intramolecular single proton transfer process is favored both thermodynamically and kinetically. No other prototropic processes are theoretically feasible.

A cyano-bridged CuII–NiII dimeric complex [Cu(Me6Cy)][Ni(CN)4] has been synthesized and characterized by its single crystal X-ray structure determination. The square planar [Cu(Me6Cy)]2+ cation is converted to a distorted trigonal bipyramidal (TBP) geometry through ligation to one of the cyano groups of [Ni(CN)4]2− in the equatorial plane, keeping the other three as terminal. Inspection of the X-ray data reveals that the Cu–N(6)–C(6) angle of the bridging cyano group is perfectly linear (180°). The room temperature (RT) EPR spectrum of polycrystalline [Cu(Me6Cy)][Ni(CN)4] is typical for mononuclear copper(II) complexes of axial symmetry, where the flattened out symmetry axis is characterized by g⊥ = 2.143 ± 0.005 and g‖ = 2.002 ± 0.005. No half field (ΔM = 2) signals were observed. RT EPR spectrum of polycrystalline [CuII(Me6Cy)](ClO4)2 yields an EPR signal with g‖ = 2.394 ± 0.005 and g⊥ = 2.045 ± 0.005, indicating that this parent compound has a different geometry than [Cu(Me6Cy)][Ni(CN)4]. Variable temperature magnetic moment studies on [Cu(Me6Cy)][Ni(CN)4] indicate a very weak long-range ferromagnetic exchange through hydrogen bonding between copper(II) ions (S = ½). The present investigation provides a unique example where the original square planar [Cu(Me6Cy)]2+ moiety rearranges itself to a trigonal bipyramidal geometry under the influence of [Ni(CN)4]2−. This is probably only the second, rare example, and perhaps the first, for a macrocyclic precursor using only one cyano group of [Ni(CN)4]2− for bridging, leading to a discrete dinuclear complex.

The salicylhydrazone of anthranilhydrazide (H2L) reacted with MoO2(acac)2 in refluxing alcohols to yield compounds of the general formula MoO2L(ROH) (where R = CH3, C2H5, n-C3H7, n-C4H9). The complex MoO2L(C2H5OH) is found to undergo facile reaction with heterocyclic bases to form MoO2L(Q)-type complexes where Q = pyridine, 4-picoline, imidazole and substituted imidazoles. Single crystal X-ray structural studies on the ligand H2L (1) and the complexes MoO2L(C2H5OH) (2) and MoO2L(Imz) (3) indicate that the free ligand exists in its keto form, but in the two complexes 2 and 3 the ligand coordinates to the MoO22+ core through the enolate oxygen, the phenolate oxygen and the azomethine nitrogen. Reaction of MoO2L(C2H5OH) with PPh3 in CH3CN under dry dinitrogen, in the absence and presence of bipy, produced MoIVOL (2a) (brown) and MoIVOL(bipy) (2b) (green) respectively along with Ph3PO. This reaction is reminiscent of the oxotransfer reaction from the MoO2+2 core of a molybdoenzyme to the substrate PPh3. Complexes 2 and 3 crystallized in the P21/n and P21/c space groups respectively and for both of them Z = 4. The structures clearly show that 2 and 3 have distorted octahedral coordination environments in which the Mo–O(ethanol) bond of 2 and the Mo–N (imidazole) bond of 3 are significantly longer than is usually observed. This is indicative of the weak bonding of ethanol and imidazole to the MoO22+ core and points to the inherent weakness of the sixth coordination position of the coordination polyhedron of the MoO22+ core in MoO2L(C2H5OH) and MoO2L(Imz).

The crystal structure of the title compound was incorrectly reported as a methanol solvate [Koleva et al. in Struct Chem 19:147–154, 2008] on the basis of room temperature X-ray diffraction data. We have now established the presence of a disordered water molecule rather than the methanol molecule using a low temperature data set collected at 110 K.

Reaction of 5,5,5-trifluoro-4-(trifluoromethyl)penta-3-en-2-one ( 1 ) with p -toluene-sulfonylhydrazines under basic conditions provided anti-Michael addition products. Acid-catalyzed reactions yielded the expected hydrazones. In the absence of solvent the reaction of (CH 3 ) 3 SiCl with 1 gave the corresponding silylenolether ( 3 ), which did not yield cross condensation products with ketones. In the presence of TiCl 4 silylenolether ( 3 ) reacted at −78°C to give the corresponding nonadienone ( 11 ). Analogously at 20°C condensation with water elimination gave the pyran system ( 12 ). The yields of 11 and 12 were increased by adding ZnCl 2 . It is interesting to note that trimethylsiloxycyclohexene reacted with 1 in a Mukaiyama-aldol-condensation to the corresponding cross condensation product 13 . Starting from (CF 3 ) 2 CC(CN) 2 and a mixture of ( E / Z )-1,3-pentadiene the expected cyclohexene was formed. One of the two CN-groups was removed with NaOH in C 2 H 5 OH/H 2 O. A second double bond was introduced in an allylic position of the hexene ring by bromination and elimination with (C 2 H 5 ) 3 N to yield the diene. Reduction with DIBAlH provided the aldehyde 7,7,7,8,8,8-hexafluorosafranal. Hydrogenation of the C3–C4 double bond in the presence of palladium on a charcoal catalyst led to 7,7,7,8,8,8-hexafluoro-β-cyclocitral. X-ray structures of selected compounds are provided.

By a Michael addition / nucleophilic substitution / elimination sequence the stereocontrol at C-2′ in strigol-typed compounds is in principle possible. However, the method is unsuitable for practical application since it has been shown that a stereolabile intermediate is involved.