Syntheses and Structural Analytical Studies of Two Co(II) Complexes Based on 1,4-Di(benzimidazole-1-yl)benzene

Two new Co(II) complexes of 1,4-di(benzimidazole-1-yl)benzene ligand (L) with the formulas [(CoLCl₂)(CHCl₃)(DMF)]_∞ (1) and [CoL(NO₃)₂]_∞ (2) have been synthesized by anion-directed self-assembly. Both complexes have been characterized by elemental analyses, IR, and X-ray single crystal diffraction. Complexes 1 and 2 exhibit 1D chain structures. In 1, Co(II) ions possess a distorted tetrahedral coordination environment composed of N₂Cl₂ donors from two L ligands and two chloride ions, while the Co(II) ions in 2 reveal a distorted octahedral structure defined by the N₂O₄ donors from two L ligands and two nitrate anions. These results illustrate that the anions play an important role in the self-assembly of metal–organic materials.     

First dicadmium(II) complex of tripodal amide ligand with one edge-sharing monocapped octahedral geometry

A new dicadmium(II) complex [Cd₂(L)₂(H₂O)₂](NO₃)₄ · 8H₂O (1) with the tripodal amide ligand L (tris[3-aza-2-oxo-4-(2-pyridyl)butyl]amine) was synthesized and structurally characterized. Complex 1 is revealed as a dinuclear 2:2 (Cd:L) complex, in which each cadmium(II) ion is hepta-coordinated with the coordination surrounding of distorted monocapped octahedral geometry. Two cadmium(II) ions are dibridged by two carbonyl μ-O atoms forming a Cd₂(μ-O)₂ parallelogram-type moiety. Interestingly, the dinuclear coordination sphere can be seen as resulting from the fusion of two distorted monocapped octahedral [Cd(L)(H₂O)]²⁺ units through sharing one edge originated from the two carbonyl μ-O atoms as a first example. Comparative NMR, IR and FAB-mass data of 1 are also discussed.     

Eight-coordination in nitrato manganese(II) complexes with tetradentate di-Schiff bases derived from 2-pyridyl ketones: preparation,characterization and catalytic activity for alkene epoxidation

The reactions of Mn(NO₃)₂·6H₂O with the tetradentate Schiff bases N,N′-bis[1-(pyridin-2-yl)ethylidene]ethane-1,2-diamine (L_A) and N,N′-bis[1-(pyridin-2-yl)benzylidene]ethane-1,2-diamine (L_B) afforded the novel eight-coordinate complexes [Mn(NO₃)₂(L_A)] (1) and [Mn(NO₃)₂(L_B)] (2), which have a distorted dodecahedral coordination geometry. The catalytic activity of 1 and 2 for alkene epoxidation is reported and discussed.     

One-pot synthesis of molecular dumbbell, [AgL(μ-bpy)AgL]2+ (L = S2O2-macrocycle; bpy = 4,4′-bipyridine)

One-pot reaction of S₂O₂-macrocyclic ligand L with AgClO₄ together with 4,4′-bipyridine (bpy) afforded a unique dumbbell-shaped complex 1, [(AgL)₂(μ-bpy)](ClO₄)₂. The macrocyclic dinuclear silver(I) complex 1 was structurally characterized by X-ray crystallography and MALDI-TOF-MS spectrometry. The crystal structure of 1 shows the silver(I) in a distorted square pyramidal environment formed by two sulfur and two oxygen donors from L and one nitrogen donor from bpy. Comparative NMR studies suggest the existence of the complex 1 in solution.     

Synthesis and characterization of nickel(II) and copper(II) complexes with a tetramethyltetraaza macrocycle containing 2-pyridylmethyl pendant arms

The complexes [Ni(L²)](ClO₄)₂·H₂O (1) and [Cu(L²)]Cl₂·4H₂O (2) have been synthesized and characterized by X-ray crystallography, electronic absorption and cyclic voltammetry. The crystal structure of 1 reveals a distorted octahedral geometry with four nitrogen atoms of the macrocycle and two nitrogen atoms of the pendant pyridylmethyl groups. The structure of 2 shows that the complex is centrosymmetric and the metal center has a tetragonally distorted octahedral environment. The electronic spectra and electrochemical behaviors of the complexes are significantly affected by the presence of the pendant arms.     

Syntheses and structures of a phenoxo-bridged copper(II) distorted cubane and related complexes with 2-hydroxy-N-(2-pyridylalkyl)benzamide ligands

Two new pyridylalkylamide ligands containing phenol groups appended to the amide, 2-hydroxy-N-(2-pyridylmethyl)benzamide (HL^PhOH) and 2-hydroxy-N-(2-pyridylethyl)benzamide (HL^PhOH′), were synthesized. Copper(II) complexes of these ligands were synthesized and characterized by X-ray crystallography, ESI-MS, FTIR, UV/Vis, and EPR spectroscopy. When basic Et₃N was used to deprotonate the ligands, tetracopper(II) [Cu₄(L^PhO)₄] (1) or dicopper(II) [Cu₂(L^PhO′)₂(CH₃OH)₂] (3) were formed. When base was not used, mononuclear [Cu(HL^PhOH)₂Cl₂] (2) resulted. Complex 1 possesses a distorted cubane-like structure, with the ligands bridging via the phenoxo oxygen atoms, and the copper atoms possessing a distorted square planar geometry. The ligands in dimeric complex 3 also bridge between copper(II) atoms via the phenoxo oxygen atoms, and the copper atoms are square pyramidal. Monomeric 2 is a tetragonally distorted six-coordinate species with pyridyl N atoms and chloride ligands in the equatorial plane, and long interactions with the amide carbonyl O atoms in the axial positions.     

Synthesis, Crystal Structures and Fluorescence Properties of Two One-Dimensional Cadmium(II) Coordination Polymers Containing Flexible Bis(benzimidazole) Ligands

Two one-dimensional Cd(II) coordination polymers constructed by ribbon-like molecules, {[Cd(L₁)₂(NO₃)]·NO₃} _n (1) (L₁ = 1,3-bis(5,6-dimethylbenzimidazol-1-yl)benzene) and [Cd(L₂)₂(NO₃)₂] _n (2) (L₂ = 1,3-bis(benzimidazol-1-yl)benzene) have been obtained through assembly of the two structurally similar flexible bis(benzimidazole)-based ligands and cadmium nitrate tetrahydrate. The cadmium(II) centers display different coordination environments with trigonal-bipyramidal geometry in 1, and a octahedral geometry in 2. Weak C–H···O interactions in 1 result in a two-dimensional supramolecular layer; two π–π interactions are present in 2 forming a three-dimensional supramolecular network structure. The solid state fluorescence properties of 1 and 2 were investigated.     

Two uranyl–organic frameworks with pyridinecarboxylate ligands. A novel heterometallic uranyl–copper(II) complex with a cation–cation interaction

Reaction of uranyl nitrate with pyridine-2-carboxylic acid (HL¹) under hydrothermal conditions gives the complex [(UO₂)₃(L¹)₄(NO₃)₂], 1, which differs from the previously reported molecular complex, obtained at room temperature, by the absence of water, coordinated and free, and the extended carboxylate bridging. Although the trimetallic basic unit is similar in both cases, 1 crystallizes as a two-dimensional assembly. A heterometallic complex results from the reaction of uranyl nitrate and copper(II) trifluoromethanesulfonate with nicotinic acid (pyridine-3-carboxylic acid, HL²), [UO₂Cu(L²)₂(NO₃)₂], 2, in which copper nicotinate two-dimensional subunits are bridged by uranyl nitrate groups to give a three-dimensional framework. The copper atom environment geometry is elongated octahedral, with one of the axial donors being a uranyl oxo group (cation–cation interaction).     

Copper(II) and cadmium(II) complexes with an imide tethered imidazole and a copper(II) coordination polymer through ring opening reaction

The reactions of 2-(3-(1H-imidazol-1-yl)propyl)isoindoline-1,3-dione (L) with copper (II) chloride or copper(II) nitrate resulted in mononuclear complexes [CuL₄Cl₂]·12H₂O (1) or [CuL₄(H₂O)NO₃]NO₃·2H₂O (2) respectively; whereas the copper(II) acetate reacted with L to give a three dimensional coordination polymer {[Cu(L′)₂]·4H₂O}n (3), (where L′ = 2-(3-(1H-imidazol-1-yl)propylcarbamoyl)benzoate). The reaction of cadmium(II) acetate with L led to the formation of a seven-coordinated complex [CdL₃(O₂CCH₃)₂]·2H₂O (4).     

Solvothermal in situ formation of a hexanuclear copper(I) complex with 2-thiolate-N,N′-dimethylnicotinamide

Solvothermal reaction of 2-mercaptonicotinic acid (HL¹) with copper(II) nitrate in DMF/methanol medium leads to the production of a novel hexanuclear complex [Cu(L²)]₆ · (H₂O)₂ (1), in which in situ formation of an anionic ligand 2-thiolate-N,N′-dimethylnicotinamide (L²) and reduction of copper(II) to copper(I) are observed. X-ray single-crystal structure of 1 reveals that each copper(I) center adopts a trigonal geometry provided by two thiolate and one pyridyl groups from three separated L² ligands. As a result, six copper(I) ions are interconnected by six μ₃–L² bridges to afford a hexanuclear cluster, in which the octahedral Cu₆ core is stabilized by significant cuprophilic interactions.     

Mono- and dinuclear silver(I) complexes of benzene- and pyridine-bearing 20-membered thiaoxaaza macrocycles

Two 20-membered penta- and hexadentate macrocycles containing one or two pyridine subunits, namely [20]aneNO₂S₂ (L¹) and [20]aneN₂O₂S₂ (L²), have been synthesized. Reaction of L¹ with silver(I) nitrate afforded a unique 2:2 (M:L) disilver(I) complex [μ₂-Ag₂(L¹)₂](NO₃)₂ (1) in which two four-coordinate Ag atoms bridge two ligands to form a cyclic dimer. In contrast, an endo-dentate 1:1 monosilver(I) complexes [AgL²]X; [X = ClO₄ (2) or PF₆ (3)] which show isomorphous structures were obtained from the reactions of L² with silver(I) salts.     

Complexation and electrochemical study of 1,5-diselena[5]ferrocenophane: X-ray crystal structures of 1,5-diselena[5]ferrocenophane,and silver,mercury complexes

The silver(I) and mercury(II) complexes of 1,5-diselena[5]ferrocenophane (L) have been synthesized. The X-ray crystal structures of L, [AgL₂]PF₆ and [HgI₂L] are reported. The small cavity of the macrocyclic ligand means that the ring must undergo a conformational change to allow coordination, and there is no significant through-space interaction M?Fe in any of the complexes. Electrochemical studies showed that no electronic communication between ferrocenylene groups was observed in the silver complex where the through-bond Fe···Fe distances are in the range 13.10 (3)–13.27(3) Å.     

Interaction of copper(II) with N-substituted bis(2-pyridylmethyl)amine derivatives: New discrete and 1-D polymeric complex systems — The latter displaying ferromagnetic behaviour

Interaction of copper(II) with the N-substituted bis(2-pyridylmethyl)amine derivatives, (R)-N¹,N¹-bis(pyridine-2-ylmethyl)butane-1,2-diamine (L¹) and (R)-2-(bis(pyridin-2-ylmethyl)amino)butan-1-ol (L²), has led to isolation of optically active [Cu(L¹)Cl]PF₆ (1) and [Cu(L²)Cl]ClO₄ (2), respectively. The X-ray structures of (1) and (2) show that the copper is bound to all four heteroatoms of the respective ligands as well as to a chlorine atom in a distorted square pyramidal arrangement in which the three nitrogens of L¹ or L² occupy three positions of each basal plane while the fourth position is occupied by the chloro ligand; apical sites in each case are filled by the amine donor from the NH₂-substituted butane arm in L¹ or the (protonated) alcohol oxygen of the 2-aminobutane-1-ol substituent in L². To a first approximation the coordination geometry in 2 is distorted square pyramidal; however, the remaining (axial) site on each copper centre is involved in a long contact (2.96 Å) with a bound chloro ligand from an adjacent complex which connects individual complex units in a zigzag 1-D polymeric chain, so that the coordination geometry could also be seen as pseudo-octahedral. A temperature-dependent magnetic study revealed the presence of ferromagnetic exchange coupling between copper centres in the chain reflecting the orthogonal structure between the chloro-bridged copper(II) ions; in contrast, and as expected, the discrete complex 1 is magnetically dilute.     

1-(Pyridin-2-ylmethyl)-2-(3-(1-(pyridin-2-ylmethyl)benzimidazol-2-yl) propyl) benzimidazole and its copper(II) complex as a new fluorescent sensor for dopamine (4-(2-aminoethyl)benzene-1,2-diol)

A new ligand 1-(pyridin-2-ylmethyl)-2-(3-(1-(pyridin-2-ylmethyl)benzimidazol-2-yl) propyl) benzimidazole (L) and its Cu(II) complex (1) have been synthesized and characterized spectroscopically and structurally. The Cu(II) ion is coordinated by two nitrogen atoms of benzimidazole groups, two oxygen atoms of the nitrate anions and one oxygen atom of a water molecule forming distorted trigonal bipyramidal geometry. The ligand and its complex have been utilized as a fluorescent sensor for 4-(2-aminoethyl)benzene-1,2-diol. A plot of F₀/F − F₀ vs 1/Conc (4-(2-aminoethyl)benzene-1,2-diol) at a selected wavelength of 306 nm with (L) that shows a straight line behavior, supports the validity of the assumption of 1:1 complex formation and the association constant of (L) with 4-(2-aminoethyl)benzene-1,2-diol is calculated to be 9868 M^− 1. Sensor (L) is found to be selective for 4-(2-aminoethyl)benzene-1,2-diol over aromatic amines, phenols, amino catechol (L-3,4-dihydroxyphenylalanine) and 4,6-ditertiarybutyl benzene-1,2-diol.     

Syntheses,characterizations, antitumor activities and cell apoptosis induction of Cu(II), Zn(II) and Cd(II) complexes with hydrazone Schiff base derived from isonicotinohydrazide

Three novel complexes, [Cu₄(L)₄Cl₄]·H₂O (1), Zn(L)₂ (2) and Cd(L)₂ (3), based on HL (where HL = 2-acetylpyridine isonicotinohydrazone) were synthesized and characterized by X-ray diffraction analyses. In the tetranuclear complex 1, each copper(II) ion with a distorted square-planar coordination geometry is five-coordinated by one chloride anion, one ON₂ donor set and one 4-pyridine nitrogen atom from another adjacent actylhydrazone ligand. However, the central ions in complexes 2 and 3 possess distorted octahedral coordination geometry, surrounded by two ON₂ donor sets. In addition, all the complexes have excellent antitumor activity towards human lung cancer (A549) and human gastric cancer (SGC7901 and BGC823) cell lines. Furthermore, cell apoptosis induced by complex 1 was detected through TUNEL and Annexin V/PI staining with flow cytometric analysis and western blotting analysis.     

Polymeric coordination system of [Ag2(NO3)2L]n [L = 1,4-bis((cyclohexylthio)acetyl)piperazine] that exhibits supramolecular isomerism with 2D and 3D frameworks

Depending on the solvents used for crystallization, silver nitrate and the flexible dithioether-type ligand incorporating piperazine diamide [L: 1,4-bis((cyclohexylthio)acetyl)piperazine] readily formed two distinct types of 2D (1) and 3D (2) coordination polymers with identical formula [Ag₂(NO₃)₂L]_n. The preparation and structural characterisation of 1 and 2 are reported as an example for the supramolecular isomerism.     

Novel Ag(I) complexes with propeller-like structure of tripodal ligand: syntheses and structures of two- and three-coordinate silver (I) complexes

Two mononuclear Ag(I) complexes, [Ag(tbsb)](NO₃)·DMF (1) and [Ag(tbsb)](NO₃)·4.5H₂O (2) {tbsb=1,3,5-tris(2-benzimidazol)sulfanylmethyl)-2,4,6-trimethylbenzene}, have been synthesized by self-assembly reaction of AgNO₃ with tbsb and characterized structurally. The silver atoms of both the complexes are coordinated by the imine nitrogen atoms from a tripodal ligand (tbsb) to form two- and three-coordinate structures, respectively. Complex 1 presents the first example of silver (I) compound of the tripodal ligand possessing propeller-like structure.     

Synthesis, crystal structure and luminescent properties of a thiocyanato bridged two-dimensional heteronuclear polymeric complex of cadmium(II) and copper(II)

A novel heteronuclear polymeric complex Cd(SCN)₃Cu(en)₂NO₃ (1) (en = ethylenediamine) has been synthesized and structurally characterized. The Cd(II) atom is surrounded by three S atoms and three N atoms from four 1,3-μ-SCN⁻ and two 1,1,3-μ-SCN⁻ to attain a distorted octahedral coordination geometry. Six Cd(II) centers are linked by twelve thiocyanato bridges to form hexagonal metallocyclic unit [Cd₆(SCN)₁₂] and extend a 2D network. Moreover, a 1,1,3-μ-SCN⁻ links two cadmium and one copper metal atoms. The luminescent properties of 1 in the solid state were investigated.     

Synthesis,Characterization and Properties of Four 3-D Supramolecular Architectures Assembled by Ni(II), Co(II), Zn(II), Cu(II) and 4-Nitro-1,3-benzenedicarboxylic Acid

Four new complexes M(NO₂–HBDC)₂(H₂O)₄·2H₂O [M = Ni (1), Co (2) and Zn (3)] and [Cu(NO₂–BDC)(H₂O)₃]₂ (4) (NO₂–H₂BDC = 4-nitro-1,3-benzenedicarboxylic acid) were prepared under hydrothermal conditions and were determined by single-crystal X-ray diffraction. X-ray structural analysis reveals that hydrogen bonds among the coordination water molecules and carboxyl oxygen atoms in complexes 1–3 bridge molecules forming an infinite chain, which is further interconnected to form a 3-D framework by a novel infinite 1-D metal–water chain containing the cyclic uudd water tetramer. In complex 4, Two five-coordinated Cu atoms are interlinked by NO₂–BDC ligands and coordinated water molecules to form a 3-D framework via hydrogen bonds and π···π stacking interactions. The elemental analysis, IR spectra, UV–vis and thermogravimetric analysis of complexes 1–4 were examined. The photoluminescence properties of complex 3 and temperature-dependent magnetic susceptibility for complex 4 were also studied.     

A fluorescent chemosensor for Zn2 + based on 3,8-bis(4-methoxyphenyl)-1,10-phenanthroline

3,8-Bis(4-methoxyphenyl)-1,10-phenanthroline (L) has been found to show high sensitivity toward Zn^2 + than other competitive metal ions, where Zn^2 +-selective chelation-enhanced fluorescence response at 461 nm is attributed to the formation of a 1:1 metal–ligand complex. In addition, two single-crystal structures of ligand L have been included with the same metal and ligand ratio of 1:1, namely one mononuclear Zn(II) complex [Zn(L)Cl₂] (1) and one 1D Cd(II) coordination polymer [Cd(L)(NO₃)₂]_n (2).