Binuclear Cadmium Research Articles

Reversible mechanochromic luminescence in a binuclear zero-dimensional Cd(II) complex through transformation between exciplex and excimer

In this work, the mechanochromic luminescence (MCL) property of a binuclear zero-dimensional cadmium complex with a variety of weak interactions is investigated. It exhibits a reversible transition between blue (445 nm) and yellow-green (470 nm) emission under the alternating treatments of grinding and CH3CN fumigation. The mechanism of MCL is proposed by combining the structural features, characterization results and theoretical calculations. During the grinding process, the ordered stacking of the structural units is disrupted and the crystalline state is transformed into an amorphous state, which is accompanied by a transition of the luminescent center from exciplex to excimer. In addition to exploring the MCL properties of a binuclear cadmium complex, this work provides feasible ideas for studying the response mechanism.

Mono and binuclear cadmium complexes: X-ray crystal structures, Hirshfeld surface analysis and antimicrobial/antioxidant studies

A bidentate Schiff base ligand(L) and two new mono and binuclear cadmium(II) complexes formulated as [CdL2(NO3)](NO3) and [Cd2L2Cl4] were synthesized and their structures were characterized by physical and spectral techniques Moreover, the structures of the cadmium(II) complexes were identified using single crystal X-ray analysis. Hirshfeld surface analysis was used to characterize various interactions in the solid state framework. Thermal behaviors of the compounds were investigated from room temperature to 800 °C. Furthermore, the antimicrobial bioassays on the cadmium(II) complexes were performed in vitro against two gram-positive and two gram-negative bacterial strains and also against two fungal strains. Finally, the antioxidant capabilities of the Schiff base ligand and its complexes were investigated by means of two in vitro methods of ABTS and DPPH as compared with Trolox as a standard compound.

Rapid and Specific Enhanced Luminescent Switch of Aniline Gas by MOFs Assembled from a Planar Binuclear Cadmium(II) Metalloligand.

Due to the low vapor pressure of aniline, it is challenging to develop a specific rapid fluorescence detection material for low concentrations of aniline gas, which is suspected to result in carcinogenicity when people are exposed by ingestion, inhalation, and skin contact. Herein, the easy-preparing Schiff base ligands were employed to construct the binuclear cadmium(II) compounds featuring a good plane and fine luminescent property, and then, the end groups were changed, making the compounds metalloligands to further build the 3D metal-organic frameworks (MOFs), named MECS-2. It is found that MECS-2 can achieve specific luminescent enhancement response for aniline gas. Furthermore, a large-scale MECS-2a film could be easily prepared by electrospinning nanoMECS-2, which presents the highly efficient and visual detection for aniline gas with the luminescent enhancement effect up to 20 times and good repeatability. Our work provides a good example for the efficient construction of MOF-based films with the fluorescence detection function for organic aromatic gases.

Reactivity of the dodecahydro-closo-dodecaborate anion in zinc(II) and cadmium(II) complexation at the presence of azaheterocyclic ligands

The process of zinc(II) and cadmium(II) complexation with the dodecahydro-closo-dodecaborate anion in the presence of azaheterocyclic ligands L (L = bipy, bpa, phen) has been studied. A significant influence of the process parameters (the nature of the metal and azaheterocyclic ligands, the source of the metal and dodecahydro-closo-dodecaborate anion) on the composition and structure of the resulting compounds has been established. Complex [Cd(DMF)6][B12H12] has been found to be used as precursor for the synthesis of mixed-ligand complexes with the coordinated [B12H12]2– anion. The first example of a mixed-ligand binuclear cadmium(II) complex [Cd(bpa)2[μ-B12H12]]2 with the dodecahydro-closo-dodecaborate anion coordinated through a multicenter M−H(B) bond has been obtained and structurally characterized.

Isomerization of Binuclear Cadmium Carboxylate Complexes [Cd2L2(O2CR)4

Isomerization of Binuclear Cadmium Carboxylate Complexes [Cd2L2(O2CR)4

A Mixed Ligands Strategy Based Luminescent Binuclear Cadmium(II) Coordination Polymer as Chemo-sensor in the Detection of Nitrofurantoin Antibiotic in Water

Guided by mixed ligands strategy, a novel binuclear cadmium(II) coordination polymer, {[Cd2(HDDB)(m-bib)(H2O)2]·1.5H2O·DMF}n (1) [H5DDB = 3,5-di(2′,4′-dicarboxylphenyl)benozoic acid, m-bib = 1,3-bis(imidazol-1-yl)benzene], was constructed under solvothermal condition and then was further characterized by X-ray crystallography, IR, EA, TG, and PXRD. Structure analysis shows 1 displaying a new (3,4)-c {6.82}4{62.84} sheet when HDDB4− ligands and the [Cd2(COO)2] SBUs were simplified into 3-connected and 4-connected nodes. And further fluorescence analysis revealed that 1 showing outstanding performances as efficient chemo-sensor in the detection of NFT antibiotic in aqueous solution with low LOD, high selectivity, high sensitivity, and strong anti-interference. Besides, the mechanisms of luminescence quenching were explored from the viewpoints of inner filter effects (IFE) and the photo-induced electron transfer (PET), implied by the optical spectroscopy and quantum chemical calculation. Based on the mixed ligands strategy, a 2D binuclear Cd(II)CP was constructed and can be act as efficient chemo-sensor in the detection of NFT antibiotic in aqueous solution.

Synthesis, structural, spectral studies, and DFT calculations of a series of mixed ligand complexes of a tridentate N, N, S pyrazole based aldimine and 2,2′-bipyridine. The first example of structurally characterized dimeric cadmium(II) adduct with unusual μ2-Osulfonamido bridges

Refluxing of equimolar amounts of 2,2′-bipyridine (bipy) and N, N, S-tridentate basic form of the Schiff base N-[2-[[3-methyl-1-phenyl-5-thioxo-pyrazole-4-ylidenemethyl]amino]phenyl]-4-methylbenzenesulfonamide (H2L) with corresponding metal acetate hydrate (Cu, Ni, Zn, Cd) in acetonitrile-methanol solution (1:1) give rise to the formation of mononuclear mixed ligand complexes with a common formula [M(L)bipy]·(CH3CN) (M=Cu(II), Ni(II), Zn(II)) (1–3) and binuclear cadmium(II) heteroleptic compound with the composition [Cd2(L)2(bipy)2]·(CH3CN)2(CH3OH)2 (4). All compounds were characterized by C, H, N elemental analysis, FT-IR, 1H NMR, and magnetic measurements. The structures of the ligand H2L and complexes 1, 3 and 4 were determined by X-ray single-crystal diffraction. The metal center in 1, 3 is surrounded with imine and amide nitrogen, sulfur of thiol group of H2L and two nitrogen of 2,2′-bipy employing as the auxiliary ligand. The crystal structure of binuclear cadmium complex reveals unexpected μ2-O sulfonamido bridges. The time-dependent density functional theory (TD-DFT) calculations have been performed to explore the assignment and the nature of the bands in experimental UV–vis absorption spectra of adducts 1–4.

A Binuclear Cadmium(II) Cluster Based on π···π Stacking and Halogen···Halogen Interactions: Synthesis, Crystal Analysis and Fluorescent Properties

An interseting binuclear complex [Cd2(tcpa)4(bipy)2] (1) has been hydrothermally synthesized with 3, 5, 6-trichloropyridine phenoxy acetatic acid (Htcpa) and 2, 2′-bipyridine (bipy) coligands. The X-ray single-crystal diffraction analysis shows that the CdII center is situated on unusual triangular prismatic geometry formed by two pyridyl nitrogen atoms of a bipy molecule and four carboxyl oxygen atoms of four different tcpa− ligands. The four tcpa− anions play as bis-monodentate linkers and connect two CdII ions together to form the dimer structure of 1. 1 is further assembled into a 2D layer by the co-effects of π···π stacking and Cl···Cl halogen bonds interactions. Moreover, 1 exhibits intense solid-state luminescence emissions centered at 442 nm at room temperature, which mainly originates from the intraligand π → π* transitions of tcpa−. The CCDC number of 1 is 1,935,091.

Synthesis, spectral and structure analysis of mono and binuclear cadmium and mercury complexes

Three mono and binuclear cadmium and mercury complexes of 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine (dppt) formulated as Cd(dppt)2X2 (X = Br, I) (complexes: 1 and 2) and Hg2(dppt)2Cl2(complex: 3) were synthesized and characterized by physical and spectral (IR, 1H and 13C NMR) analyses. Moreover, structural analyses of these complexes were investigated by single crystal X-ray diffraction method. The complex 1 and 2 crystallize in the orthorhombic crystal system with space groups of Pna21, and Pbca respectively while the complex 3 crystallizes in monoclinic crystal system with space group P21/n. In all the complexes, the dppt ligand is coordinated via its N atoms of pyridyl and triazine rings to metal ion. In each cadmium complex, in addition to two bonded dppt ligands, the coordination sphere is completed by two halide anions and therefore the geometry around metal can be described as distorted octahedral. In spite of mononuclear cadmium complexes, the mercury compound is found as a centro-symmetric dimer complex including two Hg-Cl-Hg bridges, a terminal chloride and a dppt ligand on each mercury center. In this way, a distorted square pyramidal structure can be defined for the geometry around each mercury center.

Coordination capabilities of metal ions and steric features of organic ligands affecting formation of mono- or binuclear zinc(II) and cadmium(II) pivalates

Reactions between zinc(II) or cadmium(II) pivalates and 2,2′-bipyridine, various substituted 1,10-phenanthroline derivatives or 2,2′:6′,2″-terpyridine have resulted in ten mono- and binuclear complexes with general formula [M(piv)2L] or [Cd2(piv)4L2], where piv is the pivalate anion, L is N,N′- or N,N′,N″-donor ligand, and M = Zn(II), Cd(II). Molecular and crystal structures as well as optical properties of the obtained homometallic complexes are reported and discussed. Preferable formation of binuclear cadmium compounds depending on type of the ligand are studied and clearly explained by means of DFT calculations.

Crystal structure, DNA interaction and thermal analysis data of two new antimicrobial active binuclear cadmium and mercury complexes

Two new binuclear Schiff base complexes with the general formula [CdLBr(μ-Br)]2 (1) and [Hg2L(μ-I)2I2] (2) were prepared by the reaction of 2,2-dimethyl-N,N'- bis-(3-phenyl-allylidene)-propane-1,3-diamine (L), CdBr2 and HgI2. The crystal structure of two complexes was determined by X-ray crystallography. The common structures for four-coordinated compounds are square planar or the tetrahedral geometries, which is evaluated by the Houser angular index (τ4). In [CdLBr(μ-Br)]2 (1), each cadmium center is five-coordinated by two iminic nitrogen atoms from Schiff base ligand, two μ2-bridging bromide anions and one terminal coordinating bromide anion. The metal center in this centrosymmetric dimer has a distorted square-pyramidal geometry. [Hg2L(μ-I)2I2] (2) consists of two four-coordinated mercury centers with different coordination spheres (HgN2I2 for Hg1 and HgI4 for Hg2). The TG/DTG diagrams showed that both complexes were completely decomposed under a nitrogen atmosphere. Furthermore, antibacterial activities of compounds have been screened against various bacteria and fungi by Disk diffusion method. Mercury complex inhibited the growth of the microorganisms more efficient than cadmium complex. DNA cleavage potential of compounds was evaluated by agarose gel electrophoresis method. Finally, nano-structure cadmium complex was sono-chemically synthesized and applied as precursor for preparation of cadmium oxide nanoparticles.

An unusual 8-connected self-penetrating metal–organic framework based on binuclear cadmium clusters

A novel metal–organic framework based on binuclear cadmium clusters has been synthesized and characterized, which represents a new kind of 8-connected uninodal network topology presently known for self-penetrating systems.

Synthesis and crystal structures of two coordination polymers and a binuclear cadmium(II) complex containing 3- and 4-aminobenzoate ligands.

Due to their wide range of coordination modes and versatile conformations when binding to metal atoms, multicarboxylate ligands are of interest in the design of metal-organic frameworks (MOFs). Three Cd(II) complexes, namely catena-poly[diammonium [[chloridocadmium(II)]-di-μ-chlorido-[chloridocadmium(II)]-bis(μ-3-aminobenzoato)-κ(3)N:O,O';κ(3)O,O':N]], {(NH4)[CdCl2(C7H6NO2)]}n, (I), catena-poly[[[aquacadmium(II)]-bis(μ-4-aminobenzoato)-κ(3)N:O,O';κ(3)O,O':N] monohydrate], {[Cd(C7H6NO2)2(H2O)]·H2O}n, (II), and di-μ-acetato-κ(4)O:O'-bis[(4-aminobenzoato-κ(2)O,O')(2,2'-bipyridine-κ(2)N,N')cadmium(II)], [Cd2(CH3COO)2(C7H6NO2)2(C10H8N2)2], (III), with different stuctural forms are reported. Complex (I) has a one-dimensional ladder structure, with strong N-H···O and weak N-H···Cl hydrogen bonds linking the cations and anions in the three-dimensional supramolecular structure. Complex (II) has a one-dimensional chain structure. Extensive O-H···O and N-H···O hydrogen bonds between the anionic ligands and the solvent water molecules and π-π stacking interactions between the centroids of the benzene rings lead to the three-dimensional supramolecular structure. Complex (III) is a binuclear molecule which is extended into a three-dimensional supramolecular structure via strong N-H···O and weak C-H···O hydrogen bonds.

Two Novel Self-Assembly CdII Coordination Polymers: Single-or Double 1D Chain Controlled by Ratio Change in Solvent and Their Photoluminescence Property

Two novel coordination polymers of [Cd(NIPH)(imH)2H2O]n·nH2O (1) and [Cd(NIPH)(imH)(CH3CH2O)]n (2) (H2NIPH = 5-nitroisophthalic, imH = 1H-imidazole) were successfully synthesized by controlling the ratio of reaction solvents and characterized by element analysis, FT-IR, TG analysis, single crystal X-ray diffraction. Complex 1 exhibits a zigzag-like chain pattern containing mononuclear cadmium building blocks, while complex 2 shows a ladder-like double chain pattern with binuclear cadmium building blocks. Both of the two complexes show high thermal stability. In addition, the photoluminescence properties of the two complexes have been studied in this work.

Luminescent properties, internal hydrogen bonds and π–π interactions of Cd(II), Zn(II), Co(II) complexes based on 2,8-di(pyridin-4-yl)dibenzothiophene and dicarboxylate ligands

Based on a V-shaped N-containing ligand [2,8-di(pyridin-4-yl)dibenzothiophene, DPDBT], three new coordination polymers with different dimensionality, namely, {[Cd2(DPDBT)2(DCPS)2(H2O)](H2O)}n (1), {[Zn(DPDBT)2(5-OH-bdc)]}n (2) and {[Co(DPDBT)2(H2O)4](hfipbb)}n (3), [H2DCPS=4,4′-dicarboxydiphenyl sulfone, 5-OH-H2bdc=5-hydroxyisophthalic acid, H2hfipbb=4,4′-(Hexafluoroisopropylidene)bis(benzoic acid)], have been synthesized under solvothermal conditions. Complex 1 exhibits a 2D structure with two different kinds of binuclear cadmium cluster units. The formation from 0D, 1D, 2D→3D structures with hydrogen bonds and π–π interactions in 1–3 were investigated in details. In addition, luminescent properties of 1, 2 and related free ligands in the solid state have also been studied.

Binding forms of gold(III) from solutions by cadmium diethyl dithiocarbamate: Thermal behavior and role of secondary interactions in the supramolecular self-assembly of polymeric complexes ([Au{S2CN(C2H5)2}2][AuCl4]) n and [Au{S2CN(C2H5)2}Cl2] n

The chemisorption interaction between the binuclear cadmium diethyl dithiocarbamate (EDtc), [Cd2{S2CN(C2H5)2}4], (chemisorbent I) and AuCl3 solutions in 2 M HCl results in the formation of polymeric gold(III) complexes: ([Au{S2CN(C2H5)2}2][AuCl4]) n (II) and [Au{S2CN(C2H5)2}Cl2] n (III) with the same Au : EDtc : Cl ratio (1 : 1 : 2). The alternating centrosymmetric cations and anions of complex II are structurally self-assembled to form linear polymeric chains: the gold atom in [Au{S2CN(C2H5)2}2]+ forms secondary Au(1)⋯Cl(1) bonds (3.7784 A) with two neighboring [AuCl4]− anions. This binding is additionally strengthened by secondary S(1)⋯Cl(1) interactions (3.4993 A). The mixed-ligand complex III comprises two structurally non-equivalent molecules [Au{S2CN(C2H5)2}Cl2]: A—Au(1) and B—Au(2), each being in contact with two nearest neighbors through pairs of unsymmetrical secondary bonds: Au(1)⋯S(1)a/b 3.4361/3.6329; and Au(2)⋯S(4)c/d 3.4340/3.6398 A. At the supramolecular level, this gives rise to independent zigzag-like polymeric chains, (⋯A⋯A⋯A⋯) n and (⋯B⋯B⋯B⋯) n along which antiparallel isomeric molecules of III alternate. The chemisorption capacity of cadmium diethyl dithiocarbamate calculated from the gold(III) binding reaction is 963.2 mg of gold per 1 g of the sorbent. The recovery conditions for the bound gold were elucidated by simultaneous thermal analysis of II and III. The DSC curves reflect different sets of heat effects, because thermolysis occurs for complex molecules (III) or for cations and anions (II). Nevertheless, the patterns of experimental TG curves are similar despite different structures of the complexes. The final product of thermal transformations is reduced gold.

Adduct formation of cadmium(II) N,N-cyclo-hexamethylenedithiocarbamate, [Cd2{S2CN(CH2)6}4], with morpholine: Synthesis, molecular structure, and thermal behavior of a crystalline adduct cis-[Cd{NH(CH2)4O}2{S2CN(CH2)6}2

The reaction of [Cd2{S2CN(CH2)6}4] (I) with morpholine gives a crystalline adduct of cadmium N,N-cyclo-hexamethylenedithiocarbamate [Cd{NH(CH2)4O}2{S2CN(CH2)6}2] (II), whose coordination sphere includes two molecules of the donor base. The structural organization and thermal behavior of II is studied by X-ray diffraction analysis and simultaneous thermal analysis in comparison with the original binuclear cadmium complex I. The central cadmium atom (coordination number 6) coordinates two morpholine molecules and two structurally equivalent S,S’-anisobidentate ligands HmDtc to form a chromophore [CdN2S4] with the structure of a distorted octahedron. The thermal destruction of II proceeds in two stages and includes consecutive steps of dissociation of the Cd-N bonds followed by the desorption of morpholine and thermolysis of the dithiocarbamate moiety of the adduct to form CdS as the final product. The structure of binuclear [Cd2{S2CN(CH2)6}4] is refined for a correct refinement of the geometric characteristics of compounds I and II.

Solvothermal syntheses, crystal structures and photoluminescent properties of four coordination polymers with pamoic acid and pyridine mixed ligands

Four new mixed-ligand coordination polymers, namely [Co1/2(pam)1/2·(py)2·(H2O)2]n (1), [Ni1/2(pam)1/2·(py)2·(H2O)2]n (2), [Zn1/2(pam)1/2·(py)2]n (3), and [Cd(pam)(py)2]n (4) (H2pam=pamoic acid, py=pyridine) have been synthesized under hydro(solvo)thermal conditions. X-ray single crystal structure analysis shows that 1 and 2 are isomorphic and possess a linear chain. 3 is also a linear chain without coordinated water molecules in the structure. 4 is an unusual 2D structure constructed by a binuclear cadmium building block. It appears that the chelate ligands and metal ions of the larger size favor the formation of high-dimensional structures, whereas those of the smaller size favor the formation of low-dimensional structures in the present system. The solid-state fluorescence spectra of 3, 4 and free pamoic acid show that 3 and 4 exhibit a greatly enhanced emission compared to free pamoic acid ligand.

Auxiliary ligand-directed synthesis of a series of Cd(ii)/Co(ii) coordination polymers with methylenebis(3,5-dimethylpyrazole): syntheses, crystal structures, and properties

Using a flexible methylenebis(3,5-dimethylpyrazole) ligand (H2MDP) with different aromatic carboxylate ligands, six new complexes {[Cd(H2MDP)(OPh)](H2O)}n (1), {[Cd(H2MDP)(MPh)](H2O)(1/10)}n (2), {[Cd(H2MDP)(PPh)](H2O)(3/2)}n (3), {[Co(H2MDP)(OPh)](H2O)2}n (4), {Co(H2MDP)(MPh)}n (5), {Co(H2MDP)(HBTC)}n (6) (H2OPh = phthalic acid, H2MPh = isophthalic acid, H2PPh = terephthalic acid, H3BTC = benzene-1,3,5-tricarboxylic acid) have been isolated under hydrothermal conditions. The crystal structure analyses reveal that complexes 1 and 4 feature two-dimensional undulated sheets with 4(4)·6(2) topology. Both complexes 2 and 3 contain M2L2-type metallocyclic motifs composed of two H2MDP ligands and two metal atoms, while complex 2 features a two-dimensional 4(4)·6(2) network constructed from binuclear cadmium units as four connected nodes, and complex 3 shows a two-dimensional network with 6(3)-hcb topology. Complex 5 affords a one-dimensional chain structure, and complex 6 shows a two-dimensional (4,4) network further connected into a 3D supramolecular structure connected by intermolecular hydrogen bonds and by π-π interactions. In addition, the luminescent properties of complexes 2 and 3 as well as the magnetic properties of 4 and 5 were studied.

Two Distinct 2D Cd(II)/Zn(II) Networks Based on Flexible 1,2-Phenylenediacetate and N-donor Co-Ligand: Synthesis, Structure, and Fluorescent Properties

Two novel Cd(II)/Zn(II) compounds based on flexible benzene dicarboxylate and N-donor auxiliary ligands, formulated as [Cd(phda)(dpe)]n (1) and [Zn(phda)(acpy)(H2O)]n (2), have been synthesized by the hydrothermal reaction and characterized by single-crystal X-ray diffraction, elemental analysis, IR, and fluorescent spectra (phda = 1,2-phenylenediacetate, dpe = 1,2-di(4-pyridyl)-ethylene, and acpy = 4-acetylpyridine). Complex 1 displays 2D bilayer network featuring phda-bridged binuclear cadmium (II) ribbon-like chain further pillared by dpe ligand, whereas complex 2 exhibits 2D thick-layer with {4.82}-fes topology featuring phda-bridging carboxylate layer constructed by the alternate opposite helix chain. In addition, luminescent properties of the both complexes are also investigated.