Dinuclear Cd Research Articles

New Mn(II), Ni(II), Cd(II), Pb(II) complexes with 2-methylbenzimidazole and other ligands. Synthesis, spectroscopic characterization, crystal structure, magnetic susceptibility and biological activity studies

Synthesis and characterization of Mn(II), Ni(II), Cd(II) and Pb(II) mixed ligand complexes of 2-methylbenzimidazole with other ligands have been reported. The structure of the ligands and their complexes was investigated using elemental analysis, IR, UV–Vis, (1H, 13C) NMR spectroscopy, molar conductivity and magnetic susceptibility measurements. In all the studies of complexes, the 2-methylbenzimidazole behaves as a neutral monodentate ligand which is coordinated with the metal ions through the N atom. While benzotriazole behaves as a neutral bidentate ligand which is coordinated with the Ni(II) ion through the two N atoms. Moreover, the N-acetylglycine behaves as a bidentate ligand which is coordinated with the Mn(II), Ni(II) and Pb(II) ions through the N atom and the terminal carboxyl oxygen atom. The magnetic and spectral data indicate the tetrahedral geometry for Mn(II) complex, irregular tetrahedral geometry for Pb(II) complex and octahedral geometry for Ni(II) complex. The X-ray single crystal diffraction method was used to confirm a centrosymmetric dinuclear Cd(II) complex as each two metal ions are linked by a pair of thiocyanate N=S bridge. Two 2-methylbenzimidazole N-atom donors and one terminal thiocyanate N atom complete a highly distorted square pyramid geometry around the Cd atom. Besides, different cell types were used to determine the inhibitory effect of Mn(II), Ni(II), Cd(II) and Pb(II) complexes on cell growth using MTT assay. Cd(II) complex showed cytotoxic effect on various types of cancer cell lines with different EC50 values.

Synthesis, Crystal Structure and Luminescence Properties of a New Cd(II) Complex Based on 5-Methylisophthalic Acid and 1,3-Bis(1,2,4-triazole)propane

A new complex, [Cd2(mip)2(1,3-btp)(H2O)2]n [H2mip = 5-methylisophthalic acid; 1,3-btp = 1,3-bis(1,2,4-triazole)propane], has been obtained by hydrothermal reaction of Cd(II) acetate, H2mip and 1,3-btp ligands. Its crystal structure was characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. The X-ray crystal structure shows that the complex belongs to the triclinic system, P space group, a = 10.1350(11) Å, b = 12.1708(13) Å, c = 12.7495(14) Å, and α = 99.3140(10) °, β = 91.0330(10) °, γ = 113.2160(10) °. The dinuclear Cd(II) units are bridged by mip2− ligands to form a 1D chain and then these 1D chains are further bridged by 1,3-btp co-ligands to form a 2D layer. Adjacent 2D layers are linked by weak hydrogen bonding interactions to form a 2D double layer. In addition, the thermal behavior and luminescence properties of the title complex were investigated.

Bis(μ-5-carboxylatotetrazolido)bis[aqua(2,2′-bipyridyl)cadmium(II)

In the title dinuclear CdII complex, [Cd2(C2N4O2)2(C10H8N2)2(H2O)2], each Cd atom is in a slightly distorted octa­hedral coordination by two N atoms and one O atom of two 1H-tetra­zole-5-carboxyl­ate (TZC) ligands, two N atoms of a 2,2′-bipyridyl ligand and one water O atom. The TZC ligand acts in a tridentate N,O-chelating N-bridging mode to two symmetry-equivalent CdII atoms. The complex reveals mol­ecular C i symmetry. Extensive O—H⋯O hydrogen bonding plays an important role in the crystal packing.

Two di-nuclear Cd(II) and Mn(II) complexes with one new poly-dentate double Schiff base ligand derived from 1,10-phenanthroline: Syntheses, structures, and physical properties

A new poly-dentate double Schiff base ligand 1,10-phenanthroline-2,9-dicarboxaldehyde-di-2-hydroxybenzoylhydrazone (H 2 L) was synthesized and structurally characterized. Two Cd II and Mn II dimers of this ligand were also synthesized, and their crystal structures and photoelectronic spectra were characterized. In the two dimers, ligand L acts as a bridge in the interesting mono–poly-dentate bridging mode. The ligand and its Cd II complex strongly emit at 525 nm and 570 nm, respectively, and thus can be utilized as potential fluorescent materials. Furthermore, magnetization measurements for its Mn II dimer in the range 5–300 K indicate two magnetic orderings, at high temperature ( T > 230 K) a ferromagnetic ordering is observed, and below this temperature, an antiferromagnetic behavior takes place.

Temperature and Concentration Control over Interpenetration in a Metal−Organic Material

A pillared framework formed from 4,4'-bipyridine (bipy) and sheets of dinuclear Cd(2) nodes and 1,4-benzenedicarboxylic acid (bdc) linkers can be prepared in both interpenetrated and noninterpenetrated forms by simply varying the temperature or concentration of the reaction. These results demonstrate that higher temperatures and concentrations favor interpenetration over the corresponding noninterpenetrating structure, an observation that could have broad implications for controlling the synthesis of metal-organic materials.

Rhodium(III) and cadmium(II) complexes based on the polypyridyl ligand 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz)

Tppz (2,3,5,6-tetrakis(2-pyridyl)pyrazine) complexes [Rh(tppz)(bpy)Cl][PF 6] 2.acetylacetone (bpy = 2,2′-bipyridine) and [{CdCl 2} 2(μ-tppz)].ethylene glycol have been synthesized and characterized by elemental analyses, IR, 1H NMR, cyclic voltammetry, photoluminescence and electronic spectral studies. Solid state structures of both complexes have been determined by single-crystal X-ray crystallography. The structural determination shows that the dinuclear Cd(II) complex, [{CdCl 2} 2(μ-tppz)], is a 1D coordination polymer. An ORTEP drawing of [Rh(tppz)(bpy)Cl][PF 6] 2.acetylacetone shows that the coordination geometry around the Rh(III) center is a distorted octahedron. [{CdCl 2} 2(μ-tppz)] displays intraligand 1(π–π ∗) fluorescence and can potentially serve as a photoactive material. For the mononuclear Rh(III) complex, only a two-electron reduction process occurs at the metal with the elimination of Cl − ligand. The emission of this complex is assigned as πd ∗ phosphorescence.

A novel centrosymmetric dinuclear cadmium(II) Schiff base complex with unusual bridging carboxylate: Synthesis, crystal structure and luminescence properties

A novel centrosymmetric dinuclear Cd(II) complex [CdL (CH 3COO)] 2 ( 1) has been synthesized by the reaction of Cd(CH 3COO) 2·2H 2O with a Schiff base ligand HL [HL = ( E)-2-((pyridin-2-yl)methyleneamino)benzoic acid]. Title complex has been systematically characterized by elemental analysis, FT-IR, and thermal studies. Single crystal X-ray structural analysis reveals that Cd(II) centers in 1 adopt distorted monocapped octahedral geometry and held together by rare doubly μ-2, 2 carboxylato bridging which is believed to be first relating to anthranilic carboxylate. At room temperature, compound in the solid state exhibits moderate photoluminescence activities indicating its potential as promising photoactive material.

Cadmium(II), manganese(II) and zinc(II) compounds

Three new compounds, [Cd(μ 3 -Hpdh)(μ2-Cl)] n (1), Mn(Hpdh)2(H2O)2 (2) and Zn(Hpdh)2 (H2O)2 (3) (H2pdh = pyridine-2,3-dicarbo-2,3-hydrazide), have been synthesized and characterized by elemental analysis, IR spectra, TG and single-crystal X-ray diffraction. Under hydrothermal conditions, H2pdh is generated by an in situ acylation of H2pda (H2pda = pyridine-2,3-dicarboxylic acid) with hydrazine hydrate. Complex 1 features a 2D layer structure constructed by a dinuclear Cd(II) building block. In complexes 2 and 3, hydrogen bonding interactions connect mononuclear structures into 3D supramolecular frameworks.

Three-layer π-stacking in a dinuclear Cd(NO 3) 2 complex formed from a new four-armed thiopyridine ligand

The flexible four-armed ligand 1,2,4,5-tetrakis(2-pyridylmethylsulfanylmethyl)benzene ( 2tet) was synthesized and reacted with Cd(NO 3) 2 to produce a dinuclear complex. The ligand adopted a folded conformation about the seven and eight coordinate Cd(II) centres and displayed an intramolecular three-layered π-stacking arrangement.

Structure-activity studies on the cleavage of an RNA analogue by a potent dinuclear metal ion catalyst: effect of changing the metal ion.

Dinuclear Cd(II), Cu(II), and Zn(II) complexes of L2OH (L2OH = 1,3-bis(1,4,7-triazacyclonon-1-yl)-2-hydroxypropane) are compared as catalysts for cleavage of the RNA analogue HpPNP (HpPNP = 2-hydroxypropyl 4-nitrophenyl phosphate) at 25 degrees C, I = 0.10 M (NaNO(3)). Zn(II) and Cu(II) readily form dinuclear complexes at millimolar concentrations and a 2:1 ratio of metal ion to L2OH at neutral pH. The dinuclear Zn(2)(L2O) and Cu(2)(L2O) complexes have a bridging alkoxide group that brings together the two cations in close proximity to facilitate cooperative catalysis. Under similar conditions, the dinuclear complex of Cd(II) is a minor species in solution; only at high pH values (pH 10.4) does the Cd(2)(L2O) complex become the predominant species in solution. Analysis of the second-order rate constants for cleavage of HpPNP by Zn(2)(L2O) is straightforward because a linear dependence of pseudo-first-order rate constant on dinuclear complex is observed over a wide pH range. In contrast, plots of pseudo-first-order rate constants for cleavage of HpPNP by solutions containing a 2:1 ratio of Cd(II) to L2OH as a function of increasing L2OH are curved, and second-order rate constants are obtained by fitting the kinetic data to an equation for the formation of the dinuclear Cd(II) complex as a function of pH and [L2OH]. Second-order rate constants for cleavage of HpPNP by these dinuclear complexes at pH 9.3 and 25 degrees C vary by 3 orders of magnitude in the order Cd(2)(L2O) (2.8 M(-)(1) s(-)(1)) > Zn(2)(L2O) (0.68 M(-)(1) s(-)(1)) > Cu(2)(L2O) (0.0041 M(-1) s(-1)). The relative reactivity of these complexes is discussed in terms of the different geometric preferences and Lewis acidity of the dinuclear Zn(II), Cu(II), and Cd(II) complexes, giving insight into the importance of these catalyst properties in the cleavage of phosphate diesters resembling RNA.

Synthesis and Crystal Structure of an Azido-Bridged Cadmium(II) Dimer [L2Cd2(μ-N3)2(N3)2] (L=1,4,7-Triazacyclononane)

A new dinuclear Cd(II) complex, [L2Cd2(μ-N3)2(N3)2], containing two end-on bridging azide ligands, two monodentate N3 ligands and 1,4,7-triazacyclononane as the capping ligand, has been synthesized and its structure determined by X-ray crystallography. The complex crystallizes in the monoclinic space group P21/c with a=8.467(3), b=14.359(5), c=10.115(4)Å, β=95.026(6)° and z=4. The cadmium(II) centre is six-coordinate with distorted octahedral geometry, bonded to three N atoms of the 1,4,7-triazacyclononane, two nitrogen atoms of μ-azide bridges and one nitrogen atom of a monodentate azide ligand. Neighboring Cd(II) atoms are linked by the double end-on azide bridges.

Pendant‐armed Unsymmetrical Aza‐macrocycles: Syntheses, Coordination Behavior and Crystal Structure of a Dinuclear Cadmium Complex

AbstractTwo unsymmetrical tetradentate aza‐macrocycles with side arms attached to the Nsp3 atoms, L1 and L2, as well as their complexes with different metal cations were synthesized and characterized by EA, UV, IR, 1H NMR and MS spectra. Both the two ligands can efficiently transport alkali and transition metal cations across an organic membrane with high selectivity ratio. The structure of a dinuclear Cd (II) complex [L1] · (Cd‐Cl2)2 was elucidated by X‐ray crystallography and was solved by the heavy‐atom method to a final R value of 0.029 for 3084 reflections with |F| > 3σ (I). In the exo‐structure of the dinuclear complex each cadmium atom is five‐coordinated, bonding to three N atoms and two chlorine atoms.

Macrocyclic complexes derived from the cyclocondensation of sodium 2,6-diformyl-4-substituted phenolates with N,N-bis(2-aminoethyl)-2-hydroxybenzylamine and in situ transmetallation. An anticipated dinuclear Cd(II) pendant-arm macrocyclic complex and an unexpected mononuclear Fe(III) macrocyclic complex

The reaction between sodium 2,6-diformyl-4-X-phenolates (X=Me, Cl) and N,N-bis(2-aminoethyl)-2-hydroxybenzylamine (ahba) followed by in situ transmetallation of Cd(II)(ClO 4) 2 or Fe(III)(ClO 4) 3 resulted in the production of a dinuclear Cd(II) pendant-arm macrocyclic complex and a mononuclear Fe(III) macrocyclic complex, respectively. Two complexes as well as the pro-amine, N,N-bis[ N′-(salicylicdene)ethylimino]- N-methylphenolicamine (p-sema), have been crystallographically determined. In the cadmium complex, two metal atoms were bridged by two μ 2-phenoxy oxygen atoms of the tetra-imine macrocycle, and each Cd(II), located in a highly distorted octahedral hemisphere, is six-coordinated by two imine nitrogen atoms, one tertiary nitrogen atom and a pendant phenol moiety apart from two oxygen atoms. In the iron complex, an aryl group removed from the amine and a ring contraction occurring at one side arm during the reaction have led to the generation of a mononuclear Fe(III) complex, in which the six-coordinate metal atom has a distorted octahedral geometry of coordination. The pro-amine is a tripodal tertiary amine, which contains a 2-hydroxybenzyl group as one of the pods, apart from two salicylic Schiff base moieties as the other two. The investigation of the magnetic moment and the Mössbauer spectrum of the iron complex at room temperature has shown that Fe(III) is in a high-spin state.

Cinoxacin complexes with divalent metal ions. Spectroscopic characterization. Crystal structure of a new dinuclear Cd(II) complex having two chelate-bridging carboxylate groups. Antibacterial studies

Several cinoxacin (HCx) complexes with divalent metal ions have been prepared and characterized by spectroscopic techniques. The crystal structure of [Cd 2(Cx) 4(H 2O) 2] · 10H 2O has been determined by X-ray diffraction. The complex is triclinic, space group P 1 ̄ with unit-cell dimensions: a=10.412(2), b=11.119(2), c=13.143(6)Å, α=76.78(4)°, β=74.59(3)°, γ=77.12(3)°, V=1406.0(8) Å 3. In this complex each cadmium atom is heptacoordinated; the metal environment is formed by two O keto and two O carbox atoms from two different cinoxacinate monoanions, two carboxylate oxygen atoms from a third cinoxacinate ligand and by one water oxygen atom on the seventh position. Two of the cinoxacinate ions act as tridentate chelate and bridging ligands and the other one as a bidentate chelate ligand. In the bridging monoanions the carboxylate group is behaving as a chelate ligand. All the complexes were screened for their activity against several bacteria, showing activity similar to that of cinoxacin. Additionally, the number of bacteria killed after 3 h of incubation with cinoxacin, [Cu(Cx) 2] · 2H 2O and [Co(Cx) 3]Na · 10H 2O complexes was determined against E. coli ATCC 25922; the copper compound presents paradoxical effect which has been described and related to the mechanism of action of quinolones.