Polymeric Cadmium Research Articles

Synthesis, crystal structure, hirshfeld surface analysis, and computational studies of dimeric and polymeric cadmium complexes

In the current investigation, a new dimeric [Cd(DNBA)2(py)2]2 and a polymeric [Cd(DNBA)2(pyz)2]n cadmium complexes have been prepared by the reaction of 3,5-dinitrobenzoic acid (main ligand), nitrogen donor auxiliary ligands (pyridine and pyrazine), and Cd(II) sulphate in aqueous media. The crystal structures of the synthesized compounds were determined by single-crystal X-ray diffraction analysis. The crystal structures were investigated in terms of the coordination geometry, dihedral angles between various rings, and intermolecular interactions. The solid-state assembly was stabilized by various interatomic contacts, explored by Hirshfeld surface analysis. Void analysis was performed to predict the response of crystals to the applied stress. The optimized molecular geometries of the compounds were achieved utilizing the DFT approach along with the B3LYP functional/6–311G(d,p)/LANL2DZ basic set. MEP maps, molecular orbital theory, and quantum chemical parameters for the synthesized compounds were generated using the same level of theory.

A new N2O2-donor compartmental Schiff base ligand and its cadmium(II) complex: synthesis, mesogenic and photoluminescent properties

ABSTARCT A new mesomorphic compartmental [N2O2] donor Schiff base ligand [H2L] has been synthesized and one corresponding polymeric cadmium(II) complex of the type [Cd-L]n {H2L = 4,6-bis((E)-1-(octadecylimino)ethyl) benzene-1,3-diol} is prepared by direct reaction of metal ion with ligand. Both the ligand and its Cd-complex do exhibit mesomorphic properties. The IR spectrum of the ligand clearly reveals that the ligand acts as a bi-negative tetradentate donor through the two sets of phenolate oxygen and azomethine nitrogen. Mesomorphic behavior of these compounds are investigated with the help of polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). The organization of the ligand and complex molecules in the mesophase are investigated by X-ray diffraction techniques. The Schiff base ligand and its Cd-complex shows plastic columnar mesophase (Colp) at ∼82 and ∼86 °C, respectively. The polymeric Cd-complex is blue light emitter with a broad emission maximum at ∼475 nm on excitation at 380 nm.

Synthesis of polymeric CdS and its optical properties investigation

Producing of polymeric cadmium sulfide in polyvinyl alcohol matrix is reported. The result was achieved through solid state sulfurization of hybrid interpolymeric complex of polyvinyl alcohol with cadmium chloride. In this process CdS inherits polymeric chain structure of CdCl2 complexing with polyvinyl alcohol due to diffusion restriction. One-dimensional structure of CdS was verified by high degree of luminescence polarization and Raman spectra behavior. It was observed that Raman spectrum of produced material is similar to spectrum of polyacetylene. This similarity disappears at impurities addition. Appearance of Raman band at 228 cm-1 indicates formation of CdS chain structure. Resulting polyvinyl alcohol --- CdS system has a structure of Little's high temperature superconductor. Keywords: one-dimensional structures, inorganic polymers, conjugated polymers, hybrid polymeric complexes, polyvinyl alcohol, CdS.

Synthesis, structure and molecular Hirshfeld surface analysis of polymeric cadmium(II) complex involving tetradentate N3S-donor ligand and dicyanamide as bridging ligand

One new polymeric cadmium(II) complex {[Cd(bdmpe)(µ 1,5 -dca)]ClO 4 .CH 3 OH} n has been synthesized by the reaction of cadmium perchlorate with ligand N,N -bis((3,5-dimethyl- 1H -pyrazol-1-yl)methyl)-2- phenylthio)ethan-1-amine (bdmpe) in presence of dca (dicyanamide, N(CN) 2 - ) as bridging ligand in methanol and characterized by spectroscopic techniques. Single crystal X-ray diffraction study of the complex confirmed that it has polymeric 1D chain and each cadmium centre has distorted octahedral geometry with N 5 S coordination and is bonded through two terminal nitrile group of the dca ligand using m 1,5 coordination modes. Intermolecular interactions and packing modes of the compound are described by Hirshfeld surface analysis and two dimensional finger print plots.

Molecular and Polymeric Cadmium Nitrate Complexes with Bridging 3-Aminoquinoline: Synthesis, Structures, and Luminescence Properties

The reaction of Cd(NO3)2⋅4H2O with 3-aminoquinoline (3-Аq) affords the molecular and poly-meric complexes [Cd(NO3)2(H2O)(3-Аq)]⋅2MeCN (I) and {[Cd(NO3)2(3-Аq)2]⋅MeCN}n (II), respectively, depending on the ratio of the reagents and composition of the medium. Compounds I and II are studied by elemental analysis, X-ray structure analysis (CIF files CCDC nos. 2015059 (I) and 2015060 (II)), X-ray diffraction analysis, and luminescence investigation. In both cases, the environment of the cadmium atom is a pentagonal bipyramid. The 3-Аq molecules of dimer I are bridging ligands, and the monodentate mode of binding with Cd(II) along with the indicated function is observed in the polymer. Hydrogen bonds between the H atoms of the NH2 group and the N atom of the solvate MeCN molecule and the O atom of the NO3 group result in the formation of a three-dimensional supramolecular network, which is additionally strengthened by intermolecular stacking interactions between the aromatic fragments of 3-Аq of the adjacent molecules. Both compounds luminesce in the red spectral range. As compared to the spectrum of free 3-Аq, the shift of the emission bands of dimer I and polymer II in this range is 93 and 38 nm, respectively.

A novel one-dimensional coordination polymer of cadmium(II)/triazine extending by di-chloro and di-iodo bridges

A new triazine ligand salt, 2,2′,2″-(1,3,5-triazine-2,4,6-triyl)tris(hydrazin-1-ium) chloride [THT·(HCl)3], and the one-dimensional coordination polymer of cadmium, [Cd2( µ-THT)( µ-Cl)( µ-I)I2]·2(H2O), are prepared and characterized by elemental analysis, Fourier-transform infrared spectroscopy, 1H NMR spectroscopy, and single-crystal X-ray diffraction (for the cadmium polymer). X-ray analysis revealed that the polymeric backbone is extended alternatively by di-iodo and di-chloro bridges; this type of bridge is not observed previously between any metal atoms. There are two types of cadmium atoms in the polymer: cadmium of the polymeric chain and terminal cadmiums. The geometry around the first (CdN2Cl2I2) is octahedral, while the latter (CdN3I2) has an incline to square-pyramidal geometry. The triazine ligand of this structure also bridges two cadmium atoms and acts as an N3 donor toward the terminal cadmium atoms and as an N2 donor toward the cadmium atoms of the chain. In the crystal network of the cadmium polymer, the hydrogen bonds of N–H···X (X: O, N, I) form different hydrogen bond motifs, including [Formula: see text](8), [Formula: see text](10), [Formula: see text](14), [Formula: see text](18), [Formula: see text](20), [Formula: see text](24), [Formula: see text](28), and [Formula: see text](32).

Formation of New Unusual Cadmium Polymer with Bridging Thiocyanate Ions

The reaction of cadmium thiocyanate with 2-(methylamino)pyridine (2-Map) in an ethyl alcohol solution gave a new unusual coordination polymer [Cd2(NCS)4(2-Map)3]. The structure of the polymer was determined (CIF file CCDC no. 1917586). The crystals are triclinic, space group P$$\bar {1}$$. The polymer elementary unit is composed of binuclear [Cd2 (NCS)4(2-Map)3] moiety in which the Cd atoms are connected by μ-NCS bridges. The Cd(1) environment is completed to an octahedron (CdS2N4) via coordination of two pyridine nitrogen atoms of the 2-Map molecules in the apical positions. The Cd(2) coordination environment (CdS2N3) is a trigonal bipyramid supplemented by the pyridine nitrogen atom of the 2-Map molecule. The uncoordinated nitrogen atoms of the NH group are involved in the intrachain H-bonds with the NCS-group nitrogen atoms. The luminescence spectrum of the synthesized compounds was recorded.

Ionic nature of cadmium polymer plays decisive role in selective dye adsorption

A new coordination polymer {[Cd3(EGTA)(H2O)5]·(NO3)2}n1 was synthesized by using cadmium nitrate salt and flexible carboxylate EGTA (ethylene bis(oxyethylenenitrilo)tetraaceticacid) ligand under hydrothermal condition. The structure of 1 was characterized by FT-IR spectroscopy, elemental analysis and single crystal X-ray diffraction techniques. Complex 1 displayed 2D structure with uninodal 4-connected underlying net of a rare kgm topology with point symbol {32.62.72}. All three Cd(II) in the complex exhibited different geometrical configuration such as distorted square antiprism geometry, distorted trigonal pyramidal and distorted square pyramidal geometry. Additionally, TGA property of complex 1 was also studied. The anionic dyes (methyl orange and congo red) were studied to examine the potential of complex 1 for removal of dyes from aqueous solution. Interestingly, ionic nature of complex 1 played decisive role in removal of anionic dye within 15 min as two nitrate ion present in the lattice could influence the adsorption performance.

2D polymeric cadmium(II) complexes containing 1,3-imidazolidine-2-thione (Imt) ligand, [Cd(Imt)(H2O)2(SO4)]n and [Cd(Imt)2(N3)2

The present study aims at preparing and carrying out the structural investigation of two polymeric cadmium(II) complexes of imidazolidine-2-thione (Imt) based on sulfate or azide ions, [Cd(Imt)(H2O)2(SO4)]n (1) and [Cd(Imt)2(N3)2]n (2). The structures of the complexes were determined by single crystal X-ray analysis. Both compounds, 1 and 2 crystallize in the form of 2D coordination polymers and the cadmium(II) ion is six-coordinate having a distorted octahedral geometry in each compound. In 1, the metal ion is bonded to one sulfur atom of Imt and five oxygen atoms with two from water and three of bridging sulfate ions. In 2, the cadmium coordination sphere is completed by two Imt molecules binding through the sulfur atoms and four nitrogen atoms of bridging azide ions. The crystal structures are stabilized by intra and intermolecular hydrogen bonding interactions. The complexes were also characterized by IR and NMR spectroscopy and the spectroscopic data is consistent with the binding of the ligands.

A new two-dimensional polymeric cadmium(II) complex containing dicyanamide bridging ligands.

As part of an exploration of new coordination polymers, a cadmium-dicyanamide complex, namely poly[benzyltriethylammonium [tri-μ-dicyanamido-κ6N1:N5-cadmium(II)]], {(C13H22N)[Cd(C2N3)3]}n, has been synthesized by the reaction of benzyltriethylammonium bromide, cadmium nitrate tetrahydrate and sodium dicyanamide in aqueous solution, and characterized by single-crystal X-ray diffraction at room temperature. In the crystal structure, each CdII cation is coordinated by six nitrile N atoms from six anionic dicyanamide (dca) ligands to furnish a slightly distorted octahedral geometry. Neighbouring CdII cations are linked by dicyanamide bridges to construct a two-dimensional anionic layer coordination polymer. One amide N atom in the bridging dca ligand is disordered over two sites. The cations lie between the anionic frameworks and there are no hydrogen-bond interactions between the cations and anions. The organic cations are not involved in the formation of the supramolecular network.

A Rarely Seen Phenolato and Azido-Bridged Polymeric Cadmium(II) Complex Derived from 2-Bromo-6-[(2-isopropylaminoethylimino)methyl]phenol.

A rarely seen phenolato and azido-bridged polymeric cadmium(II) complex derived from the Schiff base ligand 2-bromo-6-[(2-isopropylaminoethylimino)methyl]phenol (HL) has been prepared and characterized by elemental analysis, IR spectroscopy, and single crystal X-ray diffraction. The Schiff base ligand coordinates to the Cd atom through the NNO donor set. The Cd atom is hexa-coordinated in an octahedral geometry. Adjacent two Cd atoms are bridged by two phenolato groups generating a dimer with Cd···Cd distance of 3.475(1) Å. The dimers are further linked via azido bridges forming 2D sheets parallel to the bc plane.

Luminescence properties of copper(I), zinc(II) and cadmium(II) coordination compounds with picoline ligands

Mononuclear coordination compounds of copper(I) – [Cu(PPh3)2(picoline)(NO3)], zinc(II) – [ZnCl2(picoline)2] (picoline=3– and 4–methylpyridine) and polymeric cadmium(II) – [CdCl2(β-picoline)2]n were prepared and their luminescence properties in solid state and acetonitrile solutions were determined. Single crystal X-ray crystallography revealed distorted tetrahedral geometry around the central ions of the compounds. The compounds exhibit green photoluminescence in solid state and in acetonitrile solutions. The emission of copper(I) compounds originated from metal-to-ligand charge transfer state combined with nitrato-to-picoline charge transfer state i.e. (1(M+X)LCT). The presence of nitrato ligand in the coordination sphere of copper(I) compounds quenches the emission. Luminescence of zinc(II) and cadmium(II) compounds results from chloride-to-picoline charge transfer state and the quantum efficiency in the case of the polymeric Cd(II) compound reaches 39%. The photoluminescence quantum yields of the mononuclear zinc(II) compounds vary from 10 to 16% depending on the conditions (solid state, solution).

New red-luminescent cadmium coordination polymers with 4-amino-2,1,3-benzothiadiazole

New polymeric cadmium complexes, α-[CdLCl2]n (1), [CdL2Cl2]n (2) and β-[CdLCl2]n (3) (L = 4-amino-2,1,3-benzothiadiazole), were obtained as products of the reaction of CdCl2 with L. The synthetic procedures allowing isolation of pure 1–3 were optimized. The structures of 1–3 were established by single-crystal X-ray diffraction and the compounds were characterized by UV–Vis and IR spectroscopy. In these compounds, L is either μ-bridging (1) or terminal (2 and 3). The UV–Vis spectra of the complexes in the solid state resemble that of free L. However, coordination of L leads to a significant shift of emission in photoluminescence spectra from yellow (free L) to red (1–3).

Mononuclear, tetranuclear and polymeric cadmium(II) complexes with the 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine ligand: Synthesis, crystal structure, spectroscopic and DFT studies

The reaction of 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (bptz) with the respective cadmium halides results in the formation of tetranuclear [Cd4(bptz)2(H2O)2(μ3-Cl)2(μ-Cl)2Cl4] (1), coordination polymer {[Cd(μ-bptz)Br2]·DMSO}n (2) and mononuclear [Cd(bptz)2I2] (3). To interpret the UV–vis spectra of the compounds measured in the solution phase and also the emission behavior of solid samples, the electronic structures and also electronic spectra of the compounds were studied, respectively, by DFT and TDDFT methods in the free gaseous and solid state. According to our calculations, the synthesized compounds 1, 2 and 3 have an indirect band gap of 1.405, 0.794 and 0.912eV, respectively. Based on the calculated electronic structures in the solid state, the excitation of the compounds at 450nm promotes electrons from bptz centered π states (valence bands, VBs) and also halide np states (VBs) to the bptz-π∗ states (conduction bands, CBs). Moreover, the solid compounds show a narrow emission band at 680 nm due to electron transitions from an excited bptz-π∗ state (CBs) to the top of the VBs. The compounds were also studied in the solution phase using the 1H NMR spectroscopy method. Also, thermogravimetric analysis (TGA) and differential thermal analysis (DTA) methods were used to determine the thermal stability of the prepared compounds.

Synthesis, characterization and luminescent properties of polymeric cadmium(II) bridged-thiocyanato and mononuclear thiocyanato-zinc(II) complexes of pyridine-N-oxide derivatives

The synthesis and structural characterization of six new d10 Cd(II) and Zn(II) thiocyanato complexes with pyridine-N-oxide compounds: the polymeric catena-[Cd(μ2-2-picoline-N-oxide)(μN,S-NCS)2] (1), catena-[Cd(μ2-3-picoline-N-oxide)(μN,S-NCS)2] (2), catena-[Cd(4-nitropyridine-N-oxide)2(μN,S-NCS)2] (3), the dinuclear [Cd(4-cyanopyridine-N-oxide)2(μN,S-NCS)(NCS)(H2O)]2 (4) and the mononuclear complexes [Zn(2-picoline-N-oxide)2(NCS)2(H2O)] (5) and [Zn(4-cyanopyridine-N-oxide)2(NCS)2(H2O)] (6) are reported. Single crystal X-ray crystallography revealed the 2D polymeric nature in complexes 1 and 2, the 1D chain in 3 and the dimeric structure in complex 4 with the doubly-bridged Cd(μN,S-NCS)2Cd moiety. Five-coordinate monomeric Zn(II) complexes were obtained in 5 and 6, where the thiocyanto ligands are acting as monodentate N-bonded. The emission spectral properties of the six complexes were investigated. Very strong enhancing fluorescence intensity was observed in complex 3.

Synthesis, crystal structure, and fluorescence property of a thiocyanato-bridged polymeric cadmium(II) complex derived from (1-pyridin-2-ylethylidene)pyridin-2-ylmethylamine

A new thiocyanato-bridged polymeric cadmium(II) complex with the Schiff base ligand (1-pyridin-2-ylethylidene)pyridin-2-ylmethylamine (L) derived from 2-acetylpyridine and 2-aminomethylpyridine has been prepared and characterized by elemental analyses, IR spectrum, and single crystal X-ray crystallographic determination. The complex crystallizes in the monoclinic space group P21/n with unit cell dimensions a = 8.904(2), b = 12.041(2), c = 15.550(3) A, β = 92.354(2)°, V = 1665.7(5) A3, Z = 4, R1 = 0.0523, and wR2 = 0.1274. The Schiff base ligand coordinates to the Cd atom through the three N atoms. The Cd atom of the complex is heptacoordinated by the Schiff base ligand in a tridentate fashion, one nitrate ligand in a bidentate fashion, and one N and one S atoms from two thiocyanate ligands. The overall coordination is pseudopentagonal bipyramidal geometry. The fluorescence property of the complex was investigated.

One-Dimensional Cadmium Polymers with Alternative di(EO/EE) and di(EO/EO/EO/EE) Bridged Azide Bonding Modes

Four new doubly bridged Cd(II)-azido complexes derived from sterically hindered NNN- and NN-donors were synthesized and structurally characterized. The tridentate amine ligands 2-methylquinolyl-2(ethyl-2-pyridyl)-methylamine (Meepmqa) and bis(2-methylypyridyl)methylamine (MeDPA) afforded the dinuclear complexes [Cd2(Meepmqa)2(μ1,3-N3)2(N3)2] (1) and [Cd2(MeDPA)2(μ1,1-N3)2(N3)2] (2) with di-EE- and di-EO-azido bridges, respectively. The N-substituted trialkyl ethylenediamine compounds N,N,N′-triethylethylenediamine (Et3en) and N,N,N′-trimethylethylenediamine (Me3en) resulted in the formation of 1D-polymeric chains {[Cd2(Et3en)2(μ1,1-N3)2(μ1,3-N3)2]}n (3) and {[Cd4(Me3en)4(μ1,1-N3)6(μ1,3-N3)2]}n (4) with alternative (di-EO/di-EE)- and di(EO/EO/EO/EE)-azido bonding modes. The IR asymmetric stretching vibration, νas(N3) of the azido ligands in these complexes and in related complexes, were analyzed in an attempt to predict the coordination bonding mode of the bridged azide. The fluorescence properties of the ligand Meepmqa and its complex 1 are reported. The Cd-complex 1 has increased fluorescence intensity compared to its free ligand. This was attributed to the strong Cd–N bond of the quinolyl group of Meepmqa and the nonflexibility of the corresponding five-membered chelate ring.

Assembly of three cadmium polymers from a newly designed imidazole multi-carboxylate ligand

Abstract Three coordination polymers, [Cd(p-CPhH2IDC)(H2O)]n (p-CPhH4IDC = 2-(4-carboxylphenyl)-1H-imidazole-4,5-dicarboxylic acid) (1), [Cd3(p-CPhHIDC)2(H2O)6]n (2), and {[Cd2(p-CPhIDC)(2,2′-bipy)2]·H2O}n (2,2′-bipy = 2,2′-bipyridine) (3), have been hydrothermally synthesized, and structurally characterized by elemental analyses, IR spectra, single-crystal X-ray diffraction, and further characterized by thermogravimetric and solid-state fluorescence determinations. Polymer 1 presents a 2D doubled-layer architecture containing 1D distorted quadrilateral open channels. Polymer 2 emerges a 1D zigzag chain constructed by parallelogram clusters. Polymer 3 exhibits a net-like layer structure constructed by two types of wavy chains. The coordination features of the ligand p-CPhH4IDC have been discussed as well.

Ligands containing pyridyl-carboxylate terminals and their discrete silver and polymeric cadmium compounds: (n-py)–CH[dbnd]N–C10H6–COOH (n = 2 (HL1), 3 (HL2)), [Ag(HL1)2](PF6), [Ag(HL1)2](NO3)(H2O), and [Cd(L2)2

Two potential linking ligands containing pyridyl-carboxylate terminals {(n-py)–CH=N–C10H6–COOH (n=2 (HL1), 3 (HL2)} were synthesized by Schiff-base condensation under solvothermal conditions in methanol. Molecules of ligand HL1 are connected by the intermolecular O–H⋯N hydrogen bonds to create a 1D zigzag network. Ligand HL1 reacted with AgPF6 and AgNO3 to produce discrete Ag(I) complexes [Ag(HL1)2](PF6) (1) and [Ag(HL1)2](NO3)(H2O) (2), respectively. Compounds 1 and 2 form a dimeric structure formed by the intermolecular O–H⋯O hydrogen bonds between two carboxylate terminals of two adjacent molecules. A 3D cadmium coordination polymer, [Cd(L2)2]∞ (3), was prepared from ligand HL2 and Cd(CH3COO)2·2H2O under solvothermal conditions. Ligand HL1 exhibited a red-shift on complex formation in its photoluminescence emission spectrum.

Hexagonal structured Zn(1−x)CdxO solid solution thin films: synthesis, characterization and applications in photoelectrochemical water splitting

Hexagonal nanostructured zinc–cadmium oxide [Zn(1−x)CdxO where x = 0.08, 0.15, and 0.17] solid solution thin films were deposited on FTO coated glass substrates from a common solution of zinc acetate and a newly developed polymeric cadmium precursor by an aerosol-assisted chemical vapour deposition (AACVD) technique. The polymeric cadmium precursor [Cd3(TFA)4(OAc)2(THF)4]n (1) was synthesized by the reaction of cadmium(II)acetate dihydrate with triflouroacetic acid in THF solution and characterized by melting point, microanalysis, FTIR, 1H-NMR, thermogravimetry (TG/DTG) and single crystal X-ray analysis. The deposited thin films were characterized by powder XRD, SEM, EDX and UV-visible spectrophotometry, and tested for photoelectrochemical (PEC) water splitting to hydrogen and oxygen. The effect of various thin film deposition parameters such as solvent type, temperature and electrolyte concentration on PEC properties has been investigated. The SEM analysis illustrated that the morphology of the films changes significantly with the change of the solvent. The films deposited from THF solution have a needle-like appearance scattered vertically on the FTO-coated glass substrate. An optical band gap of 2.40 eV has been estimated by UV-visible spectrophotometry. The current–voltage characterization proved that the nanocrystalline hexagonal structured Zn0.83Cd0.17O electrodes exhibit an n-type semiconducting behaviour and the photocurrent was found to be strongly dependent on the deposition solvent, deposition temperature and electrolyte concentration. The maximum photocurrent density of 0.23 mA cm−2 at 0.55 V vs. Ag/AgCl/3 M KCl (∼1.23 V vs. RHE) was obtained for the Zn0.83Cd0.17O photoelectrode deposited at 500 °C for 45 min from 0.5 M solution of (1) and Zn(CH3COO)2·2H2O in THF.