Cobalt(II) complexes with pentadentate Schiff bases 2,6-diacetylpyridine hydrazones: Syntheses and structures

Seven new cobalt(II) complexes based on the Schiff bases, 2,6-diacetylpyridine bis(isonicotinoylhydrazone) (H₂L¹) and 2,6-diacetylpyridine bis(nicotinoylhydrazone) (H₂L²), are synthesized and studied by X-ray diffraction analysis: [Co(H₂L¹)(NCS)₂] · 2.25H₂O (I), [Co(H₂L²)(NCS)₂] · CH₃OH (II), [Co(H₂L²)(NCS)(H₂O)]NCS (III), [Co(H₄L¹)(NCS)₂](NO₃)₂ · 2H₂O (IV), [Co(H₄L¹)(NCS)₂][Co(NCS)₄] · 0.75H₂O (V), [Co(H₄L²)(NCS)₂][Co(NCS)₄] · 1.75H₂O (VI), and [Co(H₂L²)(NCS)(CH₃OH)]₂[Co(NCS)₄] · 2CH₃OH (VII) (CIF files CCDC 941186 (I), 1457906 (Ia), 1457905 (II), 941187 (III), 1457907 (IV), 1457908 (V), 1457909 (VI), and 941188 (VII)). The organic ligands in the complexes act as pentadentate neutral H₂L or doubly protonated (H₄L)²⁺ coordinated through the same set of donor atoms N₃O₂. In all compounds I–VII, the coordination polyhedron of the Co²⁺ ion in a complex with the Schiff bases has a shape of a pentagonal bipyramid. The hydrazones are arranged in the equatorial plane of the bipyramid. Its axial vertices are occupied by the nitrogen atoms of the NCS￣ anions in compounds I, II, and IV–VI and by the nitrogen atoms of NCS￣ and oxygen of the water molecule in compound III or methanol in compound VII. The NO ₃ ^- anions or [Co(NCS)₄]^2￣ complex anions obtained by the reactions are involved along with the NCS￣ anions in the formation of compounds IV–VII.     

Synthesis, crystal structures, and DNA-binding properties of zinc(II) and nickel(II) complexes with tris[2-(N-ethyl)benzimidazylmethyl]amine and cinnamate ligands

Tris[2-(N-ethyl)benzimidazylmethyl]amine (Etntb) and two of its complexes, [Zn(Etntb)(cinnamate)]NO₃·2DMF (1) and [Ni(Etntb)(cinnamate)·(H₂O)]NO₃ (2) have been synthesized and characterized by physico-chemical and spectroscopic methods. Single-crystal X-ray diffraction revealed that the complexes have different structures. In complex 1, the coordination sphere around Zn(II) is distorted trigonal bipyramidal, whereas the coordination sphere around Ni(II) is distorted octahedral in complex 2. The DNA-binding properties of the free ligand and its complexes have been investigated by electronic absorption, fluorescence, and viscosity measurements. The results suggest that the ligand and both complexes bind to DNA via an intercalative mode, and their binding affinity for DNA follows the order 1 > 2> ligand.     

Influence of metal ions on the structures of Keggin polyoxometalate-based solids: Hydrothermal syntheses, crystal structures and magnetic properties

Three new Keggin polyoxometalate (POM)-based compounds linked to 3d metal complexes have been synthesized under hydrothermal conditions: [Cu(phen)₂]₂{[Cu(phen)]₂ [SiMo₁₂O₄₀(VO)₂]} (1), {[Zn(phen)₂]₂[GeMo₁₂O₄₀(VO)₂]}{[Zn(phen)₂(H₂O)]₂ [GeMo₁₂O₄₀(VO)₂]}·3H₂O (2) and {[Co(phen)₂]₂[PMo₁₂O₄₀(VO)₂]}{[Co(phen)₂(OH)]₂ [PMo₁₂O₄₀(VO)₂]}·2.5H₂O (3) (phen=1,10-phenanthroline). These three compounds present, as building blocks, the bicapped Keggin anions [XMo₁₂O₄₀(VO)₂] (X=Si, Ge and P). Compound 1 consists of a bicapped Keggin anion [SiMo₁₂O₄₀(VO)₂]²⁻ linked to two [Cu(phen)]⁺ complexes with two [Cu(phen)₂]⁺ countercations. Compound 2 contains two bicapped Keggin anions [GeMo₁₂O₄₀(VO)₂]⁴⁻, one linked to two [Zn(phen)₂(H₂O)]²⁺ cations and the other one linked to two [Zn(phen)₂]²⁺ cations. Compound 3 is a two-dimensional POM-based square network formed by bicapped Keggin anions [PMo₁₂O₄₀(VO)₂]⁴⁻ connected by [Co(phen)₂]²⁺ cations. Discrete bicapped Keggin anions [PMo₁₂O₄₀(VO)₂] linked to two [Co(phen)₂(OH)]⁺ cations are located between the layers. The magnetic properties show the presence of antiferromagnetic interactions among the reduced Mo(V) atoms (in the three compounds) plus a paramagnetic contribution from the V(IV) atoms (in 1 and 2). Compound 3 shows, in addition, an antiferromagnetic interaction between the Co(II) and the V(IV) ions directly linked through an oxygen bridge. The low-temperature ESR spectra of compound 3 confirm the presence of the reduced Mo(V) ions and the antiferromagnetic coupling between the Co(II) and the V(IV) ions.     

Synthesis, spectroscopic, thermal Studies, antimicrobial activities and crystal structures of Co(II), Ni(II), Cu(II) and Zn(II)-orotate complexes with 2-methylimidazole

The 2-methylimidazole complexes of Co(II), Ni(II), Cu(II) and Zn(II) orotates, mer-[Co(HOr)(H₂O)₂(2-meim)₂] (1), mer-[Ni(HOr)(H₂O)₂(2-meim)₂] (2), [Cu(HOr)(H₂O)₂(2-meim)] (3) and [Zn(HOr)(H₂O)₂(2-meim)] (4), were synthesized and characterized by elemental analysis, spectral (UV–Vis and FT-IR) methods, thermal analysis (TG, DTG and DTA), magnetic susceptibility, antimicrobial activity studies and single crystal X-ray diffraction technique. The complexes 1 and 2 have distorted octahedral geometries with two monodentate 2-methylimidazole and one bidentate orotate and two aqua ligands. The complexes 3 and 4 have distorted square pyramidal and trigonal bipyramidal geometry, respectively, with one 2-methylimidazole, bidentate orotate and aqua ligands. The orotate coordinated to the metal(II) ions through deprotonated nitrogen atom of pyrimidine ring and oxygen atom of carboxylate group as a bidentate ligand. The antimicrobial activities of 1 and 4 were found to be more active gram (+) than gram (−) and 4 could be use for treatment Staphylococcus aureus.     

Synthesis,crystal structures,and properties of three coordination polymers of 5-(1H-imidazol-1-yl) isophthalic acid

Three coordination polymers have been obtained by hydrothermal synthesis, namely [Zn(imip)(H₂O)₂]·0.5H₂O (1), [Co(imip)(H₂O)₂]·0.5H₂O (2), and [Cd₂(imip)₂(H₂O)₃] (3) [H₂imip = 5-(1H-imidazol-1-yl) isophthalic acid]. The coordination polymers were characterized by IR spectra, elemental analysis, powder X-ray diffraction, and thermogravimetric analysis. Furthermore, single-crystal X-ray analysis reveals that they have 2D structures, which are extended into 3D networks via O–H···O hydrogen-bonding interactions. The luminescent properties of these coordination polymers were investigated.     

Monomer,dimer, tetramer and salt: Structural variations in Zn(II) complexes of 4,4′-bipyridine-N,N′-dioxide

Complexes of Zn^II salts with 4,4′-bipyridine-N,N′-dioxide (bpdo) have been prepared by solvathermal and solvent layering methods. Three complexes were obtained from ZnBr₂: 1 is a 2D coordination polymer [Zn₂Br₄(bpdo)₂]_n, (2) a discrete trimetallic molecule [Zn₃Br₆(H₂O)₂(bpdo)₄] and 3 a salt [ZnBr₄][Zn(H₂O)₅(bpdo)]. Complexes 2 and 3 contain Zn^II ions in both octahedral and tetrahedral coordination geometry. While in 2, these are covalently linked by bridging bpdo ligands forming zwitterionic trimetallic molecules, in 3 there is complete charge separation into [ZnBr₄]²⁻ anions and [Zn(H₂O)₅(bpdo)]²⁺ cations. When Zn(NCS)₂ is used as starting material, a 1D coordination polymer [Zn(H₂O)₂ (bpdo)(NCS)₂]_n is obtained.     

Synthesis,Structures, and Thermal Properties of Cobalt(II) Thiocyanate Coordination Compounds with 2,5‐Dimethylpyrazine

Reactions of Co(NCS)₂ with 2,5‐dimethylpyrazine lead to the formation of five compounds of compositions Co(NCS)₂(H₂O)₄ · 4(2,5‐dimethylpyrazine) ( 1 ), Co(NCS)₂(H₂O)₄ · 3(2,5‐dimethylpyrazine) ( 2 ), Co(NCS)₂(2,5‐dimethylpyrazine)(H₂O)₂ · 3(2,5‐dimethylpyrazine) ( 3 ), [Co(NCS)₂]₂(H₂O)₆ · 4(2,5‐dimethylpyrazine) · 4H₂O ( 4 ), and Co(NCS)₂(2,5‐dimethylpyrazine)(MeOH)₂ ( 5 ). 1 and 2 are simple aqua complexes, in which the Co cations are octahedrally coordinated by two thiocyanate anions and four water molecules, whereas in 3 the Co cations are linked by the 2,5‐dimethylpyrazine ligands into chains. In compound 4 Co(NCS)₂](H₂O)₆ dimers are observed, which are linked by bridging water molecules. In compound 5 the Co cations are connected into chains by the 2,5‐dimethylpyrazine co‐ligand and are additionally coordinated by terminal anionic ligands and methanol molecules. Thermogravimetric measurements of compounds 1 – 4 show several mass steps, in which the water and the co‐ligands and the water molecules are stepwise removed. Elemental analysis, XRPD investigations, and IR spectroscopic investigations indicate that all of these compounds decompose into new phases of composition Co(NCS)₂(2,5‐dimethylpyrazine)₂ ( 6 ) that on further heating decompose into [Co(NCS)₂]₃(2,5‐dimethylpyrazine) ( 8 ) via Co(NCS)₂(2,5‐dimethylpyrazine) ( 7 ) as intermediate. Compound 7 can be directly obtained by thermal removal of methanol from compound 5 .     

Crystal and molecular structure of the mercury dichloride complex with the macrocyclic dibenzo-aza-14-crown-4 ether ligand containing the embedded Di(α-pyridyl)bispidone fragment, [Hg(L)Cl<Subscript>2</Subscript>]

The crystal and molecular structure of [Hg(L)Cl₂] (I), where L is dibenzo-aza-14-crown-4 ether with the embedded di(α-pyridyl)bispidone fragment, is studied by X-ray diffraction. The irregular five-vertex polyhedron of the Hg atom is formed by two Cl atoms and three N atoms of the dipyridylbispidone part of the L molecule. The O and N atoms of the macrocycle are not involved in metal coordination. The structure of complex I is compared with the structures of compounds [Zn(L)Cl₂] · C₂H₅OH, [Co(L)(H₂O)][CoCl₄], and [Cu(L)(H₂O)](ClO₄) · 2H₂O studied earlier.     

Yttrium thiocyanate-based supramolecular architectures: Synthesis, crystal structures, and thermal properties

The reaction of [Y(H₂O)₅(NCS)₃]·H₂O (1) with crown ether (18-crown-6) and KNCS in methanol afforded the complexes [Y(H₂O)₄(NCS)₃]·1.5(18-crown-6) (2) and [K(18-crown-6)(H₂O)_1.25]_2n{[K(18-crown-6)]₂[Y(NCS)₆]}_n·n(NCS) (3). In mononuclear complex 1, yttrium has a coordination number 8 and forms the coordination unit YO₅N₃. Complexes 1 are linked by hydrogen bonds to form a framework. The crystal structure of 2 contains the centrosymmetric ensembles [Y(H₂O)₄(NCS)₃]₂(18-crown-6)₃ formed via hydrogen bonds. In the crystal structure of 3, the [Y(NCS)₆]³⁻ anions and the [K(18-crown-6)]⁺ cations form one-dimensional polymeric chains (-Y-NCS-K-)_n. The thermal behavior of compounds 1 and 2 was investigated. It was shown that the supramolecular assembly has an effect on the temperature range for the removal of coordinated water molecules from the thiocyanate complex. The oxidative decomposition of the acido ligands in 1 and 2 occurs in a similar way to give Y₂O₂SO₄ as the final product (700 °С).     

Metal Chelates of N‐(2‐pyridylmethyl)iminodiacetate(2‐) Ion (pmda). Part II. Ternary pmda Chelates with M = Co,Cu or Zn and Creatinine as Auxiliary Ligand

The compounds [Cu(pmda)(crea)]·H₂O ( 1 ), [Zn(pmda)(crea)]·H₂O ( 2 ) and [Co(pmda)(crea)(H₂O)]·H₂O ( 3 ) were prepared and characterized by thermal, spectral and X‐ray diffraction methods. In compounds 1 and 2 the M^II coordination is of type 4+1 and approaches to a trigonal bipyramid (71.85 and 86.18 %, respectively) with rather linear N(pmda)‐M^II‐N(crea) trans‐apical angles, but with different longest coordination bond (Cu‐O(pmda) or Zn‐N(apliphatic, pmda), respectively). Both compounds are isotypic and one intra‐molecular interligand N‐H···O interaction reinforces the molecular recogniton crea‐M^II(pmda) chelate. In contrast, the compound 3 exhibits an octahedral coordination, imposed by the 3d⁷ electronic configuration of the cobalt(II) atom, and the crea‐chelate recognition involves the Co‐N(crea) coordination bond and one intramolecular ‘bifurcated’ H‐bonding interaction between one N‐H(crea) bond and one O(pmda) plus the O(aqua) atoms as ‘acceptors’.     

Syntheses,crystal structures and characterization of divalent transition metal sulfonate complexes with O-phenanthroline

Two new complexes, [Zn(phen)₂(H₂O)₂]2L·H₂O (1) and [Cu(phen)(L)(H₂O)₂]L·3H₂O (2), where HL?= 4-aminobenzenesulfonic acid and phen = o-phenanthroline, have been synthesized and their crystal structures determined by X-ray diffraction. In the complexes the Cu(II) and Zn(II) atoms revealed two different coordination environments. Complex 1 consists of a cation [Zn(phen)₂(H₂O)₂]²⁺, in which Zn(II) is six-coordinated by four nitrogen atoms from two o-phenanthroline molecules and by two water molecules. Complex 2 has two crystallographically unique Cu(II) ions, where Cu(II) ion is five-coordinate with two nitrogen atoms of o-phenanthroline, two water molecules and one sulfonate oxygen atom. The electrochemical behavior and FT-IR of the two compounds have also been studied in detail.     

Dinuclear nickel(II) complexes with Schiff base ligands: syntheses, structures and bio-relevant catalytic activities

Three Ni(II) complexes of cresol-based Schiff-base ligands, namely [Ni₂(L¹)(NCS)₃(H₂O)₂], (1) [Ni₂(L²)(CH₃COO)(NCS)₂(H₂O)] (2) and [Ni₂(L³)(NCS)₃] (3), (where L¹ = 2,6-bis(N-ethylpyrrolidineiminomethyl)-4-methylphenolato, L² = 2,6-bis(N-ethylpiperidineiminomethyl)-4-methylphenolato and L³ = 2,6-bis{N-ethyl-N-(3-hydroxypropyl iminomethyl)}-4-methylphenolato), have been synthesized and structurally characterized by X-ray single-crystal diffraction in addition to routine physicochemical techniques. Density functional theory calculations have been performed to understand the nature of the electronic spectra of the complexes. Complexes 1?C3 when reacted with 4-nitrophenyl phosphate in 50:50 acetonitrile?Cwater medium promote the cleavage of the O?CP bond to form p-nitrophenol and smoothly convert 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylquinone (3,5-DTBQ) either in MeOH or in MeCN medium. Phosphatase- and catecholase-like activities were monitored by UV?Cvis spectrophotometry and the Michaelis?CMenten equation was applied to rationalize all the kinetic parameters. Upon treatment with urea, complexes 1 and 2 give rise to [Ni₂(L¹)(NCS)₂(NCO)(H₂O)₂] (1??) and [Ni₂(L²)(CH₃COO)(NCO)(NCS)(H₂O)] (2??) derivatives, respectively, whereas 3 remains unaltered under same reaction conditions.     

Hybrid compounds of Keggin polyoxotungstate with transition metal ion as the central atom. Synthesis,structure and properties

The compounds (Hbipy)₂[Co(bipy)₂(H₂O)₄]₂(CoW₁₂O₄₀)·2bipy·7H₂O (1) and [Ni₂(Hbipy)₂(bipy)(H₂O)₄(H₂W₁₂O₄₀)]·5H₂O (2) (bipy = 4,4-bipyridine) were synthesized hydrothermally and characterized by elemental analysis, IR spectroscopy, TG analyses, solid ultraviolet diffuse spectroscopy and single crystal X-ray diffraction method. In 1 the complex ions, [Co(bipy)₂(H₂O)₄]²⁺, construct a supramolecular layer through π-π stacking interaction. The heteropolyanions with central Co atom and supramolecular layers are linked by hydrogen bonds. In 2 a 2D structure is formed from metatungstate anions and binuclear Ni-bipy complexes through the coordination of metatungstate anions and bipy to Ni ions. Between the layers and bipyridine molecules are the hydrogen bond interactions. The formation of 1 and 2 shows that the solution acidity and metal ions influence greatly the structure of the compounds. Solid ultraviolet diffusion results indicate that the compounds 1 and 2 are potential semiconductor materials. In 1 and 2 there exists a weak antiferromagnetic interaction.     

Synthesis, crystal structure, hydrogen bonding and spectroscopy of transition-metal complexes with the ligand (N,N′-bis(2-pyridylmethyl)-1,3-propanediamine)

Six mononuclear complexes are reported with the tetradentate ligand N,N′-bis(2-pyridylmethyl)-1,3-propanediamine, (abbreviated as pypn) i.e. [Cu(pypn)(ClO₄)₂](H₂O)_1/2 (1), [Fe(pypn)Cl₂](NO₃) (2), [Zn(pypn)Cl](ClO₄) (3), [Co(pypn)(NCS)₂](ClO₄) (4), [Co(pypn)(N₃)₂](ClO₄) (5), [Zn(pypn)(NCS)₂] (6). The synthesis and X-ray crystal structures of all six compounds and their spectroscopic properties are presented.The geometry of the Cu²⁺, Co³⁺, Zn²⁺, Fe³⁺ ions is essentially octahedrally based, with the mm conformation (for Cu) and m_sf conformations for the other 3 metal ions; in compound 3 the geometry around the Zn²⁺ is distorted trigonal bipyramidal. The stabilisation of the crystal lattices is maintained by interesting, relative strong hydrogen bonds.     

Metal naphthalenedicarboxylates with diverse network architectures: Synthesis,crystal structures and properties

Reactions of 1,4-naphthalenedicarboxylic acid (1,4-H₂nda) and a bent dipyridyl co-ligand 4-amino-3,5-bis(4-pyridyl)-1,2,4-triazole (4bpt) with Co^II, Zn^II, or Cd^II acetate afford four coordination polymers, [Co(1,4-nda)(4bpt)(H₂O)]_n (1), {[Co(1,4-nda)₂(4bpt)(H₂O)₂][Co(4bpt)(H₂O)₄](H₂O)_1.5}_n (2), {[Zn(1,4-nda)₂(4bpt)(H₂O)₂][Zn(4bpt)(H₂O)₄](H₂O)_1.5}_n (3), and {[Cd₂(1,4-nda)₂(4bpt)₂(H₂O)₂](DMF)_1.5(H₂O)₃}_n (4). In the structure of the Co^II complex 1, the polycatenation of inclined 2-D (4,4) coordination layers leads to the formation of a 3-D supramolecular framework, whereas two types of 1-D polymeric chains are observed in another Co^II coordination species 2, which are interconnected via H-bonding to result in an unusual 3-D host–guest lattice. Notably, complexes 1 and 2 have been prepared under similar hydrothermal conditions and their structural discrepancy can only be ascribed to a subtle change of basicity for the reaction solution. The Zn^II complex 3 is isostructural to 2, and the Cd^II complex 4 displays a 2-fold parallel interpenetrating array of undulating (4,4) coordination layers. By using the conventional solvent evaporation method, two Pb^II naphthalenedicarboxylates [Pb(1,4-nda)(DMF)]_n (5) and {[Pb₂(2,6-nda)₂(DMF)₂](DMF)}_n (6) have also been prepared (2,6-nda = 2,6-naphthalenedicarboxylate). Complex 5 has a unique 5-connected 3-D coordination architecture, whereas 6 represents a 3-fold interpenetrating framework of 4-connected diamond topology. Their structural difference suggests the significant isomeric effect of the naphthalenedicarboxylate tectons on structural assemblies. Thermal stability of these crystalline materials has been investigated by thermogravimetric and differential thermal analysis (TG–DTA) technique and solid-state luminescent properties of the Zn^II, Cd^II, and Pb^II complexes have also been explored.     

Versatility of copper(II) coordination compounds with 2,3-bis(2-pyridyl)pyrazine mediated by temperature,solvents and anions choice

Tuning reaction temperatures as well as the variation in starting copper salts and solvents led to the formation of a new series of Cu(II) coordination compounds with 2,3-bis(2-pyridyl)pyrazine (dpp): a mononuclear [Cu(acac)(dpp)(NO₃)] (1) complex, two dinuclear [Cu₂(acac)₂(dpp)(NO₃)(H₂O)]NO₃ (2) and [Cu₂(Hdpp)₂(ox)(Cl)₂(H₂O)₂]Cl₂·6(H₂O) (4) complexes, and four coordination polymers {[Cu₄(dpp)₂(ox)(Cl)₆]}_n (3), {[Cu₄(dpp)₂(ox)(NO₃)₆(H₂O)₂]∙1.2(H₂O)}_n (5), {[Cu(dpp)(NO₃)](NO₃)·(H₂O)}_n (6) and {[Cu(dpp)(SO₄)(H₂O)₂]}_n (7), where acac⁻ = acetylacetonate, ox²⁻ = oxalate. Remarkably, the treatment of Cu(II) chloride dihydrate with dpp in methanol solution led to an unusual in situ condensation of dpp with acac⁻ to produce [Cu₂(acdpp)₂(Cl)₄]·2(MeOH) (8). The structure of 1 consists of neutral, mononuclear [Cu(acac)(dpp)(NO₃)] units with acac⁻ and dpp acting as bidentate ligands. In 2, the dpp ligand coordinates in a bis-chelating mode to two Cu(II) ions and bridges them into a dimeric entity, whereas an oxalate linker joins [Cu(Hdpp)(Cl)₂(H₂O)]⁺ units into a dimer in 4. Compounds 3, 5, 6 and 7 are 1D chain coordination polymers, which incorporate two symmetry independent metal centers and different bridging ligands: Hdpp⁺ as a protonated cationic or dpp as a neutral chelating ligand and oxalate, Cl⁻ anions or sulfate di-anions as bridging ligands. Magnetic studies were performed on samples 1 and 2, and the analysis reveals a very weak magnetic exchange coupling mediated via the dpp ligand.     

Inhibitorial effect of the Cu(II) and Ni(II) complexes with polyamines and imidazole derivatives on the Ca,Mg-dependent ATP-ase substrate

The investigation of the inhibitory activity on the Ca,Mg-dependent ATP-ase substrate of some Cu(II) and Ni(II) complexes with polyamines and imidazole derivatives is reported. These results show that the Cu(II) complexes have high inhibitorial effect with the exception of the following very stable compounds: square planar [Cu(N-PropIm)₂(NCS)₂], distorted octahedral [Cu(bipy)₂(NCS)₂] and five coordinate [Cu(Me₆tren)(NCS)] (SCN). The Ni(II) derivatives present a medium inhibitorial activity except to the stable tetrahedral [Ni(N-PropIm)₂(NCS)₂], hexacoordinate [Ni(dpt)(tn)(NCS)] (SCN) and fivecoordinate [Ni(dpt)(tn)]Br₂ and [Ni(Me₆tren)(NCS)] (SCN). An explanation of these conclusions is reported.     

Synthesis,molecular structure and reactivity of sodium 5-sulfosalicylate dihydrate and sodium[triaqua(5-sulfosalicylato)copper(II)] 2 hemihydrate

The crystal and molecular structure of sodium 5-sulfosalicylate dihydrate, Na[(H₂Ssal)(H₂O)₂], (1) (H₃Ssal=5-sulfosalicylic acid) has been determined through X-ray diffraction analysis. The 5-sulfosalicylate anion has lost the proton at the SO₃H group but retains the usual intermolecular hydrogen bond between phenolic and carboxylic oxygen. The reaction in water of 1 with [Cu(II)(H₂O)₄]SO₄·H₂O, gives rise to the green sodium[triaqua(5-sulfosalicylato)copper(II)] 2 hemihydrate, Na[(H₂O)₃(Ssal)Cu(II)]·2×0.5H₂O, (2). The 5-sulfosalicylate anion, (Ssal³⁻), coordinates rather unusually in the syn–syn coordination mode since it binds bidentately the Cu(II) ion through the carboxylic and the phenolic oxygens, with Cu(II)O_carboxylic=1.909(4) Å and Cu(II)O_phenolic=1.885(4) Å distances. Copper(II) completes its square-planar coordination with two water molecules and in addition, perpendicularly to the square-planar coordination plane, another two water molecules with long bonds are present (Cu(II)O=2.518 and 2.912 Å). The green complex 2 reacts easily with adenine in water at pH 7 giving rise to the violet tetraadeninato(diaqua)-bis(copper(II)) dihydrate, [Cu₂(Ade)₄(H₂O)₂])]·2H₂O, (3) (Ade⁻=adeninato monoanion). This complex, that geometrically resembles copper(II) acetate monohydrate, was already described by Sletten. Finally, on the basis of the present results a possible mechanism for the anticancer activity of complex 2 and of other Cu(II)–salicylate complexes is proposed and discussed.     

Heterometallic complexes of macrocyclic oxamide with polycarboxylates: Syntheses,crystal structures,and magnetic properties

Three complexes with the formula [Co(Ip)(CuL)(H₂O)₂] · H₂O (I), [Co(Ip)(NiL)(H₂O)₂] · H₂O (II), [Co(CuL)₂(Hbtc)(H₂O)] (III), (H₂Ip = m-isophthalic acid; H₂L = 2,3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacyclo-pentadeca-7,13-dien; H₃Btc = 1,3,5-benzenetricarboxylic acid) were synthesized and structurally characterized by elemental analysis, IR and UV spectroscopy. Single-crystal X-ray analyses reveal that the complexes I and II contain neutral heterometallic binuclear CoM (for I and II, M = Cu, Ni, respectively) moieties, and complex III contains discrete neutral trinuclear CoCu₂ moieties. The structures of I–III consist of two-dimensional supramolecular architecture formed by strong O-H…O intermolecular hydrogen bonds. Furthermore, the magnetic properties of complex I were investigated and discussed in detail.     

Studies on Mn(II) and Mn(IV) Complexes of an Unsymmetrical Bidentate Donor,N(4-Chlorophenyl)-Pyridine-2-Aldimine (ClL): Crystal Structure of [Mn(ClL)2(NCS)2]

The synthesis, characterisation and X-ray structure of an Mn(II) compound, [Mn(ClL)₂(NCS)₂], is described. Oxidation of the compound by H₂O₂ leads to a mononuclear Mn(IV) compound [Mn(ClL)(ClL')(NCS)₂]ClO₄·2H₂O where one of the ClL ligands is oxidised to the corresponding amide ClL'. Oxidation of [Mn(ClL)₂(NCS)₂] by Ce(IV), however, leads to a binuclear Mn(IV) compound [Mn₂O(ClL')₃(ClL)(H₂O)₂](NCS)₂ClO₄·2MeCN. Electron transfer behaviour of the compounds was investigated by cyclic voltammetry and differential pulse voltammetry.