Dibromido{N′-[1-(pyridin-2-yl)ethyl­idene]picolinohydrazide-κ2 N′,O}cadmium

The title compound, [CdBr2(C13H12N4O)], was obtained from the reaction of Cd(NO3)2·4H2O with meth­yl(pyridin-2-yl)methanone picolinoylhydrazone and sodium bromide. The Cd2+ cation is ligated by one O atom and two N atoms of the tridentate ligand and two bromide anions, forming a Br2CdN2O polyhedron with a distorted trigonal–bipyramidal coordination geometry. In the crystal, non-classical C—H⋯Br hydrogen bonds are observed. In addition, π–π stacking inter­actions [centroid–centroid distance = 3.7455 (19) Å] contribute to the stabilization of the crystal structure

Structural versatility of the quasi-aromatic Möbius type zinc(II)-pseudohalide complexes : experimental and theoretical investigations

In this contribution we report for the first time fabrication, isolation, structural and theoretical characterization of the quasi-aromatic Mobius complexes [Zn(NCS)(2)L-I] (1), [Zn-2(mu(1,1)-N-3)(2)(L-I)(2)][ZnCl3(MeOH)](2)center dot 6MeOH (2) and [Zn(NCS)L-II](2)[Zn(NCS)(4)]center dot MeOH (3), constructed from 1,2-diphenyl-1,2-bis((phenyl(pyridin-2-yl)methylene)hydrazono)ethane (L-I) or benzilbis(acetylpyridin-2-yl)methylidenehydrazone (L-II), respectively, and ZnCl2 mixed with NH4NCS or NaN3. Structures 1-3 are dictated by both the bulkiness of the organic ligand and the nature of the inorganic counter ion. As evidenced from single crystal X-ray diffraction data species 1 has a neutral discrete heteroleptic mononuclear structure, whereas, complexes 2 and 3 exhibit a salt-like structure. Each structure contains a Zn-II atom chelated by one tetradentate twisted ligand L-I creating the unusual Mobius type topology. Theoretical investigations based on the EDDB method allowed us to determine that it constitutes the quasi-aromatic Mobius motif where a metal only induces the pi-delocalization solely within the ligand part: 2.44|e| in 3, 3.14|e| in 2 and 3.44|e| in 1. It is found, that the degree of quasi-aromatic pi-delocalization in the case of zinc species is significantly weaker (by similar to 50%) than the corresponding estimations for cadmium systems - it is associated with the Zn-N bonds being more polar than the related Cd-N connections. The ETS-NOCV showed, that the monomers in 1 are bonded primarily through London dispersion forces, whereas long-range electrostatic stabilization is crucial in 2 and 3. A number of non-covalent interactions are additionally identified in the lattices of 1-3

Modulation of coordination in pincer-type isonicotinohydrazone Schiff base ligands by proton transfer

We present here two different coordination polyhedra of pincer type N2O hydrazone based ligands supplemented with thiocyanate ions. The compounds namely [Hg(SCN)2(HL1)] (1) and [Hg(SCN)2(HL2)] (2) have a common isonicotinohydrazone fragment and have been prepared by using a coordination driven self-assembly of the Hg(SCN)2 with two different ligands including 2-benzoylpyridine-isonicotinoylhydrazone (HL1), and 2-acetylpyridineisonicotinoylhydrazone (HL2). In compound 1 the ligand coordinated to the mercury center in the keto form (=N–NH=C=O) whereas, in compound 2, the proton at the hydrazine group have been shifted to the uncoordinated pyridine ring and the ligand acted as a zwitterion. The structures provide a complementary system for proton transfer within the ligand molecule involving the keto-enol tautomerization of amide group and 4-pyridyl N protonation. As a result, the relative location of orbitals and ligands in the complexes are different as well as the bonding strength and the coordination polyhedra. We have also studied electrostatically enhanced π···π (either conventional or involving the chelate ring) interactions observed in the solid state of both compounds and analyzed them using DFT calculations, Molecular Electrostatic Potential surface and the Bader’s theory of atoms in molecules

Syntheses, Characterization and Study of the Use of Cobalt (II) Schiff–Base Complexes as Catalysts for the Oxidation of Styrene by Molecular Oxygen

Schiff-Base complexes of bis-5-phenylazosalicylaldehyde ethylenediimine and bis-5-phenylazosalicylaldehyde-O-phenylenediimine ligands with Co(II) (I and II) have been synthesized and characterized by their IR spectra and elemental analyses. These complexes catalyze the oxidation of styrene in the presence of dioxygen and excess pyridine. The effect of the reaction conditions on the oxidation of styrene was studied by varying solvent, nature and amount of the catalyst and substrate. The catalytic behavior of the studied complexes was shown to be dependent on the conditions applied. In all reactions, acetophenone and 1- phenylethanol were the only observed products

A new binuclear Ni(II) complex, an effective A3-coupling catalyst in solvent-free condition

A newly binuclear nickel(II) complex, [Ni2(en)4(ox)](ClO4)2 (1) (where en = ethylenediamine, and ox = oxalate), has been isolated from a reaction of NiCl2·6H2O, ethylenediamine, ammonium oxalate and sodium perchlorate in water and its crystal structure has been determined by X-ray crystallography and infra-red techniques. Compound 1 was successfully employed to promote the one-pot reaction of aldehydes, amines and acetylenes for the construction of corresponding propargylamines under solvent-free media with fine yields. Further studies reveal this catalytic system can be refreshed and used again in five runs

Synthesis, characterization, spectrophotometric and electrochemistry studies, and DNA cleavage of copper(II) complexes of a new azacrown bis-macrocycle and its mono-cyclic analogue

A new azacrown bis-macrocycle (5) and its mono–cyclic analogue (7) were synthesized and characterized by FT-IR, 1H NMR, 13C NMR, DEPT 13C NMR, MS, and elemental analysis. The reaction with copper(II) nitrate yielded the corresponding complexes, formulated as Cu(5)(NO3)2·3H2O (8), and Cu(7)(NO3)2·2.5H2O (9). Also the stoichiometries of the complexes were determined in alcoholic solution and the results show that for both complexes the ratio of ligand to metal was 1:1 in methanol. The redox behavior of both complexes has been studied by cyclic voltammetry in DMF. Cyclic voltamogram of 8 shows quasi-reversible CuII/CuI redox couple whereas 9 shows a reversible CuII/CuI redox couple. Mono- and bis-macrocycle copper(II) complexes (8 and 9 respectively) cleaved plasmid pGS2 DNA by using an oxidative mechanism with 3- mercaptopropionic acid (MPA) as the reductant under aerobic conditions. The bis-macrocycle copper(II) complex 8 showed higher cleavage efficiency than their mono-macrocycle analogue 9 at the same Cu2+ concentration

Copper(II) and zinc(II) complexes of mono- and tri-linked azacrown macrocycles: Synthesis, characterization, X-ray structure, phosphodiester hydrolysis and DNA cleavage

A new tri-linked azacrown macrocycle (L2) was synthesized from mono macrocycle analogue (L1) by Williamson etherification and characterized by FT-IR, H-1 NMR, C-13 NMR, DEPT C-13 NMR, MS, and elemental analysis. The reaction of copper(II) and zinc(II) salts yielded corresponding complexes and formulated as CuL1Cl(2) (1), CuL1(NO3)(2).3H(2)O (2), Cu(2)L2(NO3)(4.)4H(2)O (3), ZnL1(OAc)(2) (4) and Zn(3)L2(OAc)(6).3H(2)O (5). Mono and trinuclear zinc(II) complexes 4 and 5, respectively, have been tested as catalysts for hydrolysis of 2-hydroxylpropyl-4-nitrophenyl phosphate (HNPP). At pH 8.5 the mononuclear complex 4 was found to be inactive. In contrast, trinuclear complex 5 was hydrolyzing phosphodiester and the reaction was up to 35-fold faster than the unpromoted reaction. Mono and dinuclear copper(II) complexes 2 and 3 cleave plasmid pG2 DNA by using an oxidative mechanism under aerobic conditions. Dinuclear copper(II) complex 3 showed a much higher cleavage efficiency than its mononuclear analogue 2 at the same Cu2+ concentration. The X-ray structure of 1 is reported. In this complex, the Cu(II) is bound by three amine nitrogens from the macrocyclic ligand L1 and two chloride anions as distorted trigonal bipyramidal geometry

Syntheses, studies and crystal structures of coordination polymers and dinuclear complexes of mercury(II) halides and thiocyanate with a symmetrical Schiff base ligand

A series of mercury(II) compounds, [Hg-2(mu-L)(SCN)(4)](n) (1), [Hg-2(mu-L)(mu-Cl)(2)Cl-2](n) (2), [Hg-2(mu-L)Br-4]center dot[Hg-2(mu-L)(mu-Br)(2)Br-2](n) (3) and [Hg-2(mu-L)I-4] (4) {L = N,N'-(bis-(pyridin-2-yl)benzylidene)-1,2-ethanediamine} have been prepared and characterized by using microanalytical, spectroscopic, thermal and X-ray crystallographic results. In solid states 1 and 2 have 2D and 1D coordination polymer structure, respectively. Solid state 3 consists of both 1D coordination polymers and dinuclear units. Solid state 4 is only composed of dinuclear units. In the polymeric structures, each mercury(II) center is five coordinated with trigonal bipyramidal geometry in 1D and square pyramidal environment in 2D coordination polymers. Coordination geometry around Hg centers in dinuclear units is tetrahedral. HOMO and LUMO of the title compounds and also the energy gap among them have been studied by using the density functional theory (DFT/B3LYP) method with the LANL2DZ pseudo-potential.University of Tabriz Research Counci

catena-Poly[[(benzil bis{[(pyridin-2-yl)methylidene]hydrazone}-κ4N,N′,N′′,N′′′)mercury(II)]-μ-chlorido-[dichloridomercury(II)]-μ-chlorido]

In the title coordination polymer, [Hg2Cl4(C26H20N6)]n, one HgII ion is coordinated by four N atoms from the benzylbis((pyridin-2-yl)methylidenehydrazone) ligand and two Cl− ions in a very distorted cis-HgCl2N4 octahedral geometry. The other HgII ion is coordinated in a distorted tetrahedral geometry by four Cl− ions. Bridging chloride ions link the HgII ions into a chain propagating in [010]: the Hg—Cl bridging bonds are significantly longer than the terminal bonds. The dihedral angle between the central benzene rings of the ligand is 83.3 (2)°. The packing is consolidated by weak C—H...Cl hydrogen bonds and C—H...π interactions