Synthesis and spectroscopic characterization of cadmium(II) complexes of thiones and thiocyanate

Cadmium(II) complexes of thiones and thiocyanate, [(>C=S)₂Cd(SCN)₂], have been prepared and characterized by IR and NMR spectroscopy. An upfield shift in the >C=S resonance of thiones in the ¹³C NMR and downfield shift in N–H resonance in ¹H NMR are consistent with sulfur coordination to cadmium(II). The presence of ν(N–H) of thiones in IR spectra of the complexes indicates the thione forms of the ligands in the solid state; some contribution of the thiolate form was observed in one complex. The appearance of a band around 2100 cm^?1 in IR and a resonance around 132 ppm in ¹³C NMR indicates the binding of thiocyanate to cadmium(II).     

Synthesis and spectral characterization of zinc(II) and cadmium(II) complexes of acetone-N(4)-phenylsemicarbazone: Crystal structures of acetone-N(4)-phenylsemicarbazone and a cadmium(II) complex

Seven Zn(II) and Cd(II) complexes of ON donor acetone-N(4)-phenylsemicarbazone (HL) have been synthesized and physico-chemically characterized by partial elemental analyses, molar conductance measurements, infrared, electronic and ¹H NMR spectral studies. The semicarbazone binds the metal as a neutral bidentate ligand in all the complexes. The crystal structures of acetone-N(4)-phenylsemicarbazone and [Cd(HL)₂Cl₂] have been determined by X-ray diffraction studies. The coordination geometry around cadmium(II) in the complex [Cd(HL)₂Cl₂] is distorted octahedral.     

Tris(dimethylamino)phosphine Selenide Complexes of Cadmium(II): Synthesis and Multinuclear (31P, 77Se,and 113Cd) NMR Characterization in Solution

The complexes CdL₄(ClO₄)₂ (1), CdL₂(NO₃)₂ (2), and CdL₂Cl₂ (3) (L = (Me₂N)₃P(Se)) have been prepared and characterized by elemental analysis, conductivity measurements, IR, and multinuclear (³¹P, ⁷⁷Se, and ¹¹³Cd) NMR spectroscopy. ³¹P and ⁷⁷Se NMR data were informative of changes associated with complex formation. The structure of the prepared complexes was further confirmed in solution by their ¹¹³Cd NMR spectra, which show a quintuplet for the perchlorate complex and a triplet for each of the nitrate and chloride complexes due, respectively, to coupling with four and two equivalent phosphorus atoms, consistent with a four coordinate tetrahedral geometry for the cadmium center. The NMR data are discussed and compared with those reported for related complexes.     

Alkyldiamine bis(selenocyanato)cadmium(II) complexes: Synthesis, Cd, Se, N and C NMR spectroscopy and X-ray structure of a 2D metal-organic framework

Complexes of cadmium(II)-selenocyanate with several alkyldiamine ligands have been synthesized and characterized by IR, ¹¹³Cd, ⁷⁷Se, ¹⁵N and ¹³C NMR spectroscopy. The X-ray structure of the complex [Cd(SeCN)₂-en] reveals two non-equivalent metal ion centers, both with a distorted octahedral geometry. The combined bridging modes of selenocyanate and ethylenediamine with the blocking mode of a chelating ethylenediamine generate a 2D metal-organic framework.     

Synthesis,structural and spectroscopic characterization of a new cadmium(II) complex containing imidazole (Im) as ligand, [Cd(Im)6](ClO4)2

Reaction between the 1,1′-carbonyldiimidazole ligand and mixtures of cadmium(II) acetate with sodium perchlorate provided the unusual crystalline material [Cd(Im)₆](ClO₄)_2, (Im?=?imidazole). This new Cd^II complex, has been characterized by elemental analysis, IR-, ¹H NMR-, ¹³C NMR and ¹¹³Cd NMR spectroscopy. The coordination number in this complex is six, CdN₆ and coordination environment around the Cd(II) may be described as distorted octahedral with a D_2h point group. There are both edge-to-face π–π stacking and C–H(Im)?···?π interactions between aromatic “Im” rings belonging to adjacent chains in this network.     

Synthesis and characterization of novel Cd(II), Zn(II) and Ni(II) complexes with 2-quinolinecarboxaldehyde selenosemicarbazone. Crystal structure of bis(2-quinolinecarboxaldehyde selenosemicarbazonato)nickel(II)

New complexes of Cd(II), Zn(II) and Ni(II) with 2-quinolinecarboxaldehyde selenosemicarbazone (Hqasesc) were synthesized and structurally characterized. The structure of the ligand, Cd(II) and Zn(II) complexes was determined by NMR and IR spectroscopy, elemental microanalysis and molar conductivity measurements. Both complexes occur in solution in two forms, the major tetrahedral and minor octahedral. In the major Cd(II) complex one qasesc⁻ ligand is coordinated as a tridentate, the fourth coordination site being occupied by acetate, while in the major Zn(II) complex two qasesc⁻ ligands are coordinated as bidentates. In both minor complexes two qasesc⁻ ligands are coordinated as tridentates forming the octahedral geometry around the central metal ion. The only paramagnetic complex in the series is Ni(II) complex for which X-ray structure analysis was performed. The complex has the angularly distorted octahedral geometry with two qasesc⁻ ligands coordinated as tridentates, in a similar way as in the minor complexes of Cd(II) and Zn(II).     

Hg(II) and Cd(II) complexes with mixed donor macrocyclic thioethers: The oxophobicity of mercury(II)

A series of Hg(II) and Cd(II) homoleptic complexes with mixed donor (O,S and N,S) macrocycles is reported. The macrocyclic oxa thiacrowns 9S2O (1-oxa-4,7-dithiacyclononane) and 18S4O2 (1,10-dioxa-4,7,13,16-tetrathiacyclooctadecane) bind to Hg(II) to form distorted tetrahedral S4 geometries without coordination of the oxygen atoms. In contrast, the two macrocycles coordinate to Cd(II) through all ligand donors to form S4O2 environments. We also report the structure of bis(9N2S (1,4-diaza-7-thiacyclononane))cadmium(II), [Cd(9N2S)₂]²⁺ which shows octahedral coordination in a trans N4S2 environment. Furthermore, two new homoleptic Cd(II) complexes with the related hexadentate macrocycles 18N6 (1,4,7,10,13,16-hexaazacyclooctadecane) and 18S6 (1,4,7,10,13,16-hexathiayclooctadecane) are described. Among the Cd(II) complexes, we highlight a trend in ¹¹³Cd NMR that shows progressive upfield chemical shifts as secondary amine donors replace thioether S donors.     

Multinuclear Magnetic Resonance Study of Zinc(II) and Cadmium(II) Complexing with Isothiocyanate

A study of zinc(II) and cadmium(II) complexes with isothiocyanate ion has been completed, using a low-temperature, multinuclear magnetic resonance technique that permits the observation of separate resonance signals for bound and free ligand, and Cd(II) metal ion. The Zn²⁺–NCS^– complexes were studied by ¹H, ¹³C, and ¹⁵N NMR spectroscopy. In the ¹H spectra, the intensity of the coordinated water signal, corresponding to a Zn(II) hydration number of six in the absence of NCS^–, decreases dramatically as this anion is added, indicating the complexing process involves more than a simple 1:1 ligand replacement. The ¹³C and ¹⁵N NMR spectra reveal signals for four species, most reasonably assigned to a series of tetrahedrally coordinated Zn²⁺–NCS^– complexes. In the Cd²⁺–NCS^– solution spectra, the ¹³C and ¹⁵N signals for four complexes also are observed and they are three line patterns, corresponding to a doublet from ¹¹³Cd J-coupling, and a dominant central peak, resulting from bonding to magnetically inactive Cd isotopes. The ¹¹³Cd spectra, showing signals for four complexes, correlate well in all respects with the ¹³C and ¹⁵N results, including coupling in specific cases. The spectral results for both metal ions reflect binding at the nitrogen atom of NCS^–, with the complexes changing from an octahedral to a tetrahedral configuration when doing so. Confirming evidence for these conclusions also was provided by several infrared measurements of these metal–ion systems.     

Cobalt(II), nickel(II), and copper(II) complexes of 14-membered hexaazamacrocycles: synthesis and characterization

Cobalt(II), nickel(II), and copper(II) complexes containing 5,12-di(4-bromophenyl)-7,14-dimethyl-1,2,4,8,9,11-hexaazacyclotetradeca-7,14-diene-3,10-dione (H₂L¹) and 5,12-diphenyl-7,14-dimethyl-1,2,4,8,9,11-hexaazacyclotetradeca-7,14-diene-3,10-dione (H₂L²) have been synthesized. All complexes were characterized by elemental analysis, MALDI TOF-MS spectrometry, and electronic absorption spectroscopy. The crystal structures of two compounds, [Cu₂(H₂L¹)Cl₄]_n and [NiL²], were determined by X-ray powder diffraction. In the polymeric [Cu₂(H₂L¹)Cl₄]_n, the Cu₂Cl₄ units and H₂L¹ molecules are situated on inversion centers. Each Cu(II) has a distorted trigonal-bipyramidal coordination environment formed by N and O from H₂L¹ [Cu–N 2.340(14)?Å, Cu–O 1.952(11)?Å], two bridging chlorides [Cu–Cl 2.332(5), 2.279(5)?Å] and one terminal chloride [Cu–Cl 2.320(6)?Å]. In the [NiL²] complex, the Ni(II) situated on inversion center has a distorted square-planar coordination environment formed by four nitrogens from L² [Ni–N 1.860(11), 1.900(11)?Å].     

Zn(II), Cd(II) and Hg(II) complexes with 1-(p-methoxybenzyl)-2-(p-methoxyphenyl)benzimidazole: Syntheses, structures and luminescence

Five coordination compounds Zn(mbmpbi)₂Cl₂ (1), Zn(mbmpbi)₂Br₂ (2), Cd(mbmpbi)₂Cl₂ (3), Hg(mbmpbi)₂Cl₂ (4) and Hg(mbmpbi)₂Br₂ (5) were synthesized by the reaction of 1-(p-methoxybenzyl)-2-(p-methoxyphenyl)benzimidazole (mbmpbi) with the corresponding metal halides. The complexes have been characterized by elemental analysis, conductance measurements, FT-IR, ¹H NMR and photoluminescence spectral studies. The ligand mbmpbi exhibits the N-benzimidazole coordination. The structures of 3-5 have been determined by single crystal X-ray diffraction. These three complexes are isostructural, crystallizing in the monoclinic system, P2/n space group with a distorted tetrahedral geometry around the metal ion. Zn(II) and Cd(II) complexes show strong blue emission in solid state at room temperature.     

Bis(Tetramethylselenophosphoramidoyl) Methylamine Complexes of Cd(Ii) and Zn(Ii): Synthesis and Multinuclear (31P, 77Se,and 113Cd) Nmr Characterization in Solution

Abstract

Five new complexes ZnL₂(ClO₄)₂ (1), CdL₂(ClO₄)₂ (2), CdL₂(BF₄)₂ (3), CdLCl₂ (4), and CdL(NO₃)₂ (5) [L = ((Me₂N)₂PSe)₂NMe] have been synthesized and characterized by elemental analysis, infrared (IR) and multinuclear (³¹P, ⁷⁷Se, and ¹¹³Cd), and nuclear magnetic resonance (NMR) spectroscopy. The ³¹P and ⁷⁷Se NMR data showed that the title ligand is coordinated in a bidentate fashion to the metal center via its both P=Se groups. The solution structure of the cadmium complexes was further confirmed by its ¹¹³Cd NMR spectra, which displayed a quintuplet for the perchlorate complex and a triplet for each of the nitrate and chloride complexes, respectively due to coupling with four (two ligands) and two (one ligand) equivalent phosphorus nuclei, consistent with a four-coordinate tetrahedral geometry for the cadmium center. The results are discussed and compared with the corresponding oxo and thio analogues.     

Zinc(II) and Cadmium(II) Metal Complexes with Bis(tetrazole) Ligands: Synthesis and Crystal Structures

Two new metal complexes [Zn( L¹ )]_n ( 1 ) and [Cd₃( L² )₂Cl₂(H2O)6]_n ( 2 ) (H₂ L¹ = 1,5‐bis(tetrazol‐5‐yl)‐3‐oxapentane, H₂ L² = bis(tetrazol‐5‐yl)methane) have been synthesized and characterized by elemental analysis, IR spectroscopy and single‐crystal X‐ray diffraction analysis. Complex 1 was a 2‐D sheet constructed by L¹ and Zn(II) center, further assembled to form a three‐dimensional (3‐D) supramolecular networks through weak hydrogen‐bonding interactions. In the complex 2 , there were two unequivalent Cd(II) centers, and some of ligands L² adopted chelate coordination mode, and others adopted bridge coordination mode linking the Cd1 center and simultaneously bridging the Cd2 center, the Cl^‐ anions adopted μ₂ bridging mode, ligands L² and the Cl^‐ anions linked the Cd(II) centers to form a 3‐D supramolecular networks.     

Synthesis,characterization, structural investigation,and antimicrobial studies of mononuclear Zn(II), Cd(II), and Ag(I) complexes of an N3O Schiff base

An N₃O Schiff base (L), 1?:?1 condensate of benzil monohydrazone and 4-pyridine carboxaldehyde, and its Zn(II), Cd(II), and Ag(I) complexes were synthesized and characterized by elemental analyses and various spectroscopic techniques. The crystal structures of [ZnL₂Br₂] (1), [CdL₂I₂]·CH₂Cl₂, (2)·CH₂Cl₂, and [Ag(L)₂]ClO₄ (3) have been determined using X-ray crystallography. The Zn(II) and Cd(II) complexes show a tetrahedral configuration whereas in the asymmetric unit of 3, two independent coordination units of Ag(I) are present. Carbonyl–silver interaction, weak C–H?O interaction, and also π–π interaction are present in 3 in the solid state. The synthesized complexes have antibacterial activity against Klebsiella pneumoniae 114, Escherichia coli K88, Salmonella typhi ATCC 34, Bacillus subtilis UC564, and Staphylococcus aureus ATCC25923. The results showed that in some cases the antibacterial activities of the complexes were comparable to standard antibiotics Tetracycline and Streptomycin. The antifungal activities of the complexes were also studied for Aspergillus niger, Aspergillus oryzae, Penicillium notatum, and Saccharomyces cerevisiae. MIC values of 1, 2·CH₂Cl₂, and 3 are less than the Nystatin standard.     

Synthesis,characterization and in vitro cytotoxicity of platinum(II) complexes of selenones [Pt(selenone)2Cl2]

Platinum(II) complexes with various selenones (L) having the general formula [PtL₂Cl₂] were prepared and characterized by elemental analysis and, IR and NMR (¹H, ¹³C, and ⁷⁷Se) spectroscopies. A decrease in the IR frequency of the >C=Se mode and an upfield shift in ¹³C NMR for the >C=Se resonance of selenones are consistent with their selenium coordination to platinum(II). The NMR data show that the complexes are stable in solution and do not undergo equilibration at 297 K. The geometrical structures of the complexes were predicted theoretically (with DFT method) using Gaussian09 program. DFT calculations predicted that the trans configurations were up to 1.7 kcal/mol more stable than the cis forms in gas phase, while in solution form the cis isomers were predicted to be more stable. The UV–vis spectra of the two complexes, 6 and 7 were also recorded at room temperature for 24 h and it was observed that the complexes were stable and did not undergo decomposition. The in vitro antitumor properties of the complexes as well as of cisplatin were evaluated on two human cancer cell lines, HeLa (cervical cancer cells) and MCF7 (breast cancer cells) using MTT assay. The results indicated that the prepared complexes exerted significant inhibition on the selected cancer cells.     

Syntheses and characterization of mixed-anion cadmium(II) complexes,structural characterization of [Cd(phen)2(NO2)1.65(NO3)0.35], as a new eight-coordinate Cd(II) complex

New mixed-anion cadmium(II) complexes of 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen) ligands, [Cd(phen)₂(NO₂)_1.65(NO₃)_0.35] and Cd(bpy)(ClO₄)(CH₃COO) have been synthesized and characterized by elemental analysis, IR-, ¹H NMR-, ¹³C- NMR and ¹¹³Cd NMR spectroscopy. The single crystal X-ray data of [Cd(phen)₂(NO₂)_1.65(NO₃)_0.35] show the complex to be a monomer and that the Cd atom has an unsymmetrical eight-coordinate geometry, being coordinated by four nitrogen atoms of ‘phen’ ligands and four oxygen atoms of the nitrite and nitrate anions. There is a short π–π stacking interaction between parallel aromatic rings.     

Synthesis and structure of enaminoketones of pyrazole containing 2-thione(selenone)benzimidazolyl fragments and their zinc and cadmium complexes

New ligand systems based on 4-formyl-5-hydroxypyrazole and 1-aminobenzimidazole derivatives are synthesized. The obtained enamines and their Zn²⁺ and Cd²⁺ metal complexes of composition ML₂ were investigated using the IR, heteronuclear (¹H, ¹³C, ¹⁵N, ⁷⁷Se, ¹¹³Cd) and two-dimensional NMR spectroscopy (COSY, HSQC, HMBC). The data of physicochemical investigations and quantum-chemical calculations showed that the ligands exist in the ketoamine tautomeric form. Quantum-chemical simulation of Zn(II) and Cd(II) complexes showed that the zinc complexes adopt the pseudo-tetrahedral and the cadmium complexes pseudo-octahedral configuration.     

Solution and solid-state NMR studies of some cadmium-selenone complexes

Cadmium(II) complexes of Imidazolidine-2-selenone (ImSe) and its derivatives have been prepared with the general formula Cd(RImSe)2Cl2 (where R=Me, Et, Pr, etc.). These complexes are characterized by elemental analysis, IR and NMR (1H, 13C, 77Se and 113Cd) spectroscopy. An upfield shift in C=Se resonance of selenones in 13C NMR and in 77Se and high-frequency shifts in N-H resonances in 1H are consistent with the selenium coordination to Cd(II). The 77Se nucleus in Cd(ImSe)2Cl2 is shielded by 38 ppm on coordination, relative to the free ligand. The principal components of the 77Se, 113Cd and 13C shielding tensors for the complexes were determined from solid-state NMR data. Large selenium chemical shift anisotropies were observed for these complexes.     

Chemistry of N,N-Dimethylaminoalkylchalcogenolate Complexes of Palladium(II) and Platinum(II)

Abstract

Four different series of N,N-dimethylaminoalkylchalcogenolates, viz. Me₂NCH₂ CH₂E^?, Me₂NCH(Me)CH₂E^?, Me₂NCH₂CH(Me)E^?, and Me₂NCH₂CH₂CH₂E^? (E = S, Se, Te), (referred as E^∩N) have been synthesized and characterized. Their reactions with palladium(II) and platinum(II) precursors have been explored. Complexes of the general formula, [MCl(E^∩N)]_n, [MCl(E^∩N)₂]_n, [MCl(E^∩N)(PR₃)], [M₂Cl₂(μ-E^∩N)₂(PR₃)₂], [M₂(μ-E^∩N)₂(P^∩P)₂]²⁺, etc. have been isolated. All the complexes have been characterized by elemental analysis, IR, NMR (¹H, ¹³C, ³¹P, ⁷⁷Se, ¹²⁵Te, ¹⁹⁵Pt), UV-vis, and FAB mass spectral data. A weak absorption in the electronic spectra of [MCl(E^∩N)(PR₃)] has been attributed to metal mediated ligand-to-ligand charge transfer and showed pronounced chalcogen dependence being red shifted on moving from S → Se → Te. Structures of several complexes have been established by X-ray diffraction analyses. Thermal behavior of some of these complexes has been investigated by TGA.     

Synthesis,characterization and fluorescence spectra of mononuclear Zn(II), Cd(II) and Hg(II) complexes with 1,10-phenanthroline-5,6-dione ligand

The mononuclear complexes of Zn(II), Cd(II) and Hg(II), [Zn(phen-dione)Cl₂], [Cd(phen-dione)Cl₂] and [Hg(phen-dione)Cl₂], where phen-dione?=?1,10-phenanthroline-5,6-dione, have been synthesized and characterized by elemental analysis and IR, ¹H?NMR and electronic absorption spectroscopies. The ν(C=O) of coordinated phen-dione ligands in these complexes shows that the phen-dione is not coordinated to metal ion from its C=O sites. Electronic spectra of the complexes show two absorption bands for intraligand transitions. These absorption bands show dependence on the dielectric constant of solvents. These complexes exhibit an intense fluorescence band around 545?nm in DMSO when the excitation wavelengths are 200?nm at room temperature.     

Synthesis,characterization, DFT calculations and antimicrobial activity of pentagonal-bipyramidal Zn(II) and Cd(II) complexes with 2,6-diacetylpyridine-bis(trimethylammoniumacetohydrazone)

Isothiocyanate complexes of Zn(II) and Cd(II) with the condensation product of 2,6-diacetylpyridine and trimethylammoniumacetohydrazide (Girard’s T reagent) were synthesized, characterized, and their antimicrobial activities were evaluated. The structures of the complexes were determined by elemental analysis, IR, and NMR spectroscopy. The crystal structure of the Zn(II) complex was also determined. Quantum-chemical calculations of the geometry and total energy of isomers of 2,6-diacetylpyridine-bis(trimethylammoniumacetohydrazone) were performed in vacuum and methanol solution, with the aim to explain conformational behavior and E/Z isomerism of this compound. DFT calculations of the molecular structures and the relative stabilities of linkage isomers of the Cd(II) complex showed that the isomer with N–Cd–N coordination of SCN^? is the most stable. Complexes of Zn(II) and Cd(II) exhibited low to moderate activity against the tested microbial strains.