Its Cadmium Research Articles

Preparation, characterization and X-ray structure determinations of the 2-acetyl-2-thiazoline schiff base of hydrazine (ATH) and its cadmium(II) complex [Cd(NO 3) 2(ATH) 2

A novel ligand hydrazone derivative ATH (ATH = 2-acetyl-2-thiazoline hydrazone) and its Cd(II) complex, with the empirical formula [Cd(NO 3) 2(ATH) 2], have been prepared and characterized by elemental analysis, IR and NMR spectroscopy. Likewise, the structures of the free ligand and its Cd(II) complex have been determined by X-ray diffraction. The complex has a distorted octahedral geometry with two ATH ligands coordinated to the Cd atom as bidentate chelating agents via the thiazolinic nitrogen atoms and the iminic nitrogen atoms. The metallic atom completes six-coordination by two monodentate nitrate oxygen atoms. The structure of ATH in the complex suffers a significant change with regard to free ATH due to the different degree of rotation of the thiazoline rings around the C(1)–C(4) and C(6)–C(9) bonds, which permit the coordination through thiazolinic nitrogen atoms.

Effects on rat testes of the thiosemicarbazone derivative Schiff base (4-(1-phenylmethylcyclobutane-3-yl)-2-(2-hydroxybenzylidenehydrazino)thiazole) and its cadmium(II) complex

The aim of this study was to investigate structural and biochemical changes in testes of rats treated with the thiosemicarbazone derivative thiazole ring Schiff base, (4-(1-phenyl-methylcyclobutane-3-yl)-2-(2-hydroxybenzylidene-hydrazino) thiazole (L), and its Cd(II) complex (CdL(2)). The animals were divided into three groups. Group I was designated as control. The rats in groups II and III were injected subcutaneously with L or CdL(2) respectively at 150-mg kg(-1) doses at 3-day intervals for 15 days. At the end of the study, blood samples were collected for biochemical analysis, and testes were removed for histological examinations. Serum levels of vitamin A, E and MDA of the L-injected group were similar to the control group. While CdL(2) treatment decreased serum vitamin A and E levels, it increased the MDA level compared to other groups. Histologically, the testes structures of L-treated animals were similar to the control. Spermatogenic cells in seminiferous tubules of CdL(2)-treated animals displayed necrosis. Nuclei of spermatogonia and primary spermatocytes were pyknotic and heterochromatic. Homogenous pink particles were present in place of the spermatids. The interstitial areas were oedematous and intertubular vessels were plugged. In conclusion, the present results indicate that L does not cause biochemical and morphological alterations, but its Cd(II) complex has degenerative effects in normal rat testes.

A Novel Proton Transfer Self‐Associated Compound from Dipicolinic Acid and Guanidine and Its Cadmium(II) Complex: Synthesis, Characterization, Crystal Structure, and Solution Studies

AbstractA novel 1:2 proton transfer self‐associated compound LH2, (GH+)2(pydc2—), was synthesized from the reaction of dipicolinic acid, pydcH2, (2, 6‐pyridinedicarboxylic acid), and guanidine hydrochloride, (GH+)(Cl—). The characterization was performed using IR, 1H and 13C NMR spectroscopy and single‐crystal X‐ray diffraction. LH2 · H2O crystallizes in the space group C2/c of the monoclinic system and contains eight molecules per unit cell. The unit cell dimensions are: a = 26.480(5)Å, b = 8.055(2)Å, c = 14.068(3)Å. The first coordination complex (GH)2[Cd(pydc)2] · 2H2O, was prepared using LH2 and cadmium(II) iodide, and characterized by 1H and 13C NMR spectroscopy and X‐ray crystallography. The crystal system is triclinic with space group P1¯ with one molecule per unit cell. The unit cell dimensions are: a = 8.5125(7)Å, b = 11.0731(8)Å, c = 13.2404(10)Å. The cadmium(II) atom is six‐coordinated with a distorted octahedral geometry. The two pydc2— units are almost perpendicular to each other. The protonation constants of the building blocks of the pydc‐guanidine adduct, the equilibrium constants for the reaction of pydc2— with guanidine and the stoichiometry and stability of the Cd2+ complex with LH2 in aqueous solution were accomplished by potentiometric pH titration. The solution studies strongly support a self‐association between pydc2— and GH+ with a stoichiometry for the CdII complex similar to that observed for the isolated crystalline complex. In fact, the [Cd(pydc)2]2— complex was found as the most abundant species in solution (> 90 %) at a pH >5.

The preparation and characterization of mono- and bis -chelated cadmium(II) complexes of the di-2-pyridylketone Schiff base of S -methyldithiocarbazate (Hdpksme) and the X-ray crystal structure of the [Cd(dpksme) 2 ] · 0.5 MeOH complex

New cadmium(II) complexes of empirical formulae, [Cd(dpksme)X] (dpksme = anionic form of the Schiff base; X = NCS−, Cl−, I−) and [Cd(dpksme)2] · 0.5MeOH, respectively have been prepared and characterized. The mono-ligated cadmium(II) complexes, [Cd(dpksme)X] are four-coordinate and tetrahedral but the bis-ligand complex, [Cd(dpksme)2] · 0.5MeOH is six-coordinate and octahedral. The crystal and molecular structure of [Cd(dpksme)2] · 0.5MeOH has been determined by X-ray diffraction. The complex has a distorted mer-octahedral structure in which the ligands are coordinated as uninegatively charged tridentate chelating agents via the pyridine nitrogen atoms, the azomethine nitrogen atoms and the thiolate sulfur atoms. The distortion from regular octahedral geometry is ascribed to the restricted bite angles of the ligands. The Schiff base and its cadmium(II) complexes exhibit mild antibacterial activities against Shigella dysenteriae, Bacillus cereus, Staphylococcus aureus and Escherichia coli. They are also mildly fungitoxic against the phytopathogenic fungi, Alternaria alternata and Macrophomina phaseolina.

Mono- and poly-nuclear cryptate complexes of cage-like azamacrocyclic compounds: a thermodynamic and electrochemical approach

The compounds 4,7,10,17,23-pentamethyl-1,4,7,10,13,17,23-heptaazabicyclo[11.7.5]pentacosane (L1) and 4,7,10,23-tetramethyl-17-oxa-1,4,7,10,13,23-hexaazabicyclo[11.7.5]pentacosane (L2), respectively comprised of a tetraaza and a monooxatriaza macrocycle overstructured by a triazabridge, formed mononuclear complexes with CuII, ZnII and CdII in aqueous solutions. The co-ordination of these metal ions by L2 has been studied by means of potentiometric and NMR techniques. Thermodynamic and NMR data indicate that the metal ion is accommodated in the N4 and in the N3O fourteen-membered cyclic moiety in the cases of L1 and L2, respectively, while the triaza bridge does not participate in the co-ordination. The complexation of CuI by these macrocycles has been studied by means of electrochemical measurements (cyclic voltammetry); both compounds stabilize the lowvalent copper complexes. This behaviour can be ascribed to the presence of only tertiary nitrogen donors, which leads to a hydrophobic macrocyclic cavity in which the metal ion is encapsulated. Both compounds also form binuclear complexes with CuII in methanol solution. In the case of L1, binuclear assemblies are formed in aqueous solution, allowing for the determination of their stability constants. Mono- and di-hydroxo complexes of the type [M2L1(OH)]+ and [M2L1(OH)2] are formed in aqueous media. The macrobicycle 4,7,10,23-tetramethyl-14-oxo-17-oxa-1,4,7,10,13,23-hexaazabicyclo[11.7.5]pentacosane (L3) has been isolated as its cadmium(II) complex [Cd(HL3)Cl2]CIO4·H2O the crystal structure of which was determined.

Stability enhancement of heavy-metal–macrocycle complexes via pendant amide coordination

Formation of the pendant-arm macrocyclic ligand 1,4,7,10-tetrakis(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane L and subsequent generation of its cadmium(II) complex indicates very significant stabilisation of the complex, compared to that observed for related macrocyclic cadmium(II) complexes, which either lack pendant donors altogether, or have other types of neutral oxygen donors attached to the macrocycle, and compared to complexes of L with lighter metal ions.

Intramolecular exchange between square antiprismatic enantiomers of the pendant arm macrocyclic ligand complex N,N′,n″,n‴-tetrakis(2-hydroxyethyl)-1,4,7,10-tetraazacyclododecanelead(II)

Variable temperature 13C NMR studies of the pendant arm macrocyclic complex N,N′,N″,N‴-tetrakis(2-hydroxyethyl)-1,4,7,10-tetraazacyclododecanelead(II) and its cadmium(II) and mercury(II) analogues in [2H4]-methanol indicate that these complexes undergo rapid intramolecular exchange between two square antiprismatic enantiomers.

Prevention of adsorption of .ALPHA.,.BETA.,.GAMMA.,.DELTA.-tetrakis(1-methylpyridinium-4-yl) porphine and its cadmium(II) chelate on a glassware surface.

Complexation of cadmium(II) with α, β, γ, δ-tetrakis(1-methylpyridinium-4-yl)porphine (TMPyP) was examined in a micellar solution of sodium dodecylbenzenesulfonate (SDS). Although complexation in the absence of SDS quantitatively occurs within 5 min in the pH range 9 to 11.5, TMPyP and its cadmium(II) chelate in a basic solution give rise to adsorption on glassware surface, thus resulting in large errors in the determination of cadmium(II). The adsorption of TMPyP and its chelate was prevented by addition of SDS after complete complexation. When SDS was added before complexation, 40 h were required for full color development. The concentration of SDS should be higher than the critical micelle concentration (1 × 10-3 mol dm-3). SDS was also effective in preventing adsorption of other TMPyP chelates, such as lead(II), zinc(II) and copper(II), on the surface of glassware.