Design and syntheses of blue luminescent Cu(II) and Zn(II) polymeric complexes with 2-(2′-pyridyl)benzimidazole derivative ligand

The polymeric complexes of 4,4′-bis[2-(2′-pyridyl)benzimidazolyl]biphenyl (Bmbp) with Cu(II) (1), Zn(II) (2) and 1,3,5-tris[2-(2′-pyridyl)benzimidazolyl]benzene (Tmb) with Cu(II) (3), Zn(II) (4) were successfully synthesized and characterized by IR spectroscopy, elemental analysis, thermal analysis and conductivity measurements. The results indicate that the stoichiometry of these metal complexes is metal: Bmbp (or Tmb) = 1:1 for 1 and 2 (2:1 for 3 and 4). Ligands coordinated with metal ions to get a five-membered chelate ring and formed polymeric complexes with metal ion. Their luminescence properties were also studied by UV–vis and fluorescence spectra. At room temperature, complexes 1–4 emit blue luminescence from 419 to 483 nm in the solid state and purple/blue luminescence from 385 to 437 nm in DMF solution. Thermal properties measurement and analysis shows that they have good thermal stabilities.     

Microporous metal–organic frameworks constructed by Cu(I)/Zn(II), Tpt and 1,4-benzenedicarboxylate

Two novel metal–organic frameworks, [Cu(tpt)(bdc)_1/2]_n · nH₂O (1) and [Zn(tpt)(bdc)_1/2I]_n (2) (tpt = 2,4,6-tris(4-pyridyl)-1,3,5-triazine, H₂bdc = 1,4-benzenedicarboxylic acid), have been prepared by hydrothermal reactions. In complex 1, Cu(I) center is in a trigonal coordination environment with bidentate tpt coordinating Cu(I) atoms to form 1D zigzag chains, and bdc ligand links the zigzag chains to form a 2D layered structure. In complex 2, Zn(II) center is in a trigonal–pyramidal environment with bidentate tpt coordinating Zn(II) atoms to form zigzag chains, and bdc links the zigzag chains to form metal–organic framework which contains interesting hexagonal nano-channels.     

Diversity of carboxylate coordination in two novel zinc(II) cinnamate complexes

Two novel mixed-ligand zinc(II) complex compounds [Zn(cinn)₂(mpcm)]_n (1) and [Zn(p-HO-cinn)₂(nia)(H₂O)₂] · H₂O (2) (cinn = cinnamato, mpcm = methyl-3-pyridylcarbamate, nia = nicotinamide) were prepared and characterized by elemental analysis, infrared spectroscopy, single crystal X-ray diffraction and thermal analysis. Diverse modes of carboxylate coordination were found in the complexes. In 1 the cinnamate ligands coordinate as monodentate and bridging (syn–anti), respectively. The syn–anti carboxylate bridges connect the molecules of 1 to infinite polymeric helical chains. The structure of 2 is monomeric. One of the carboxylate oxygens of p-hydroxycinnamate is semi-coordinated (Zn–O = 2.549(2) Å).     

Synthesis,characterization and photoluminescence properties of copper(II)–azido/thiocyanato complexes with thiazolylazo dye and1,2-bis(diphenylphosphino)ethane

A series of copper(II) complexes of the formula [Cu(L)(dppe)(N₃)₂] (1a–3a) and [Cu(L)(dppe)(NCS)₂] (1b–3b) (where L = 4-(2′-thiazolylazo)chlorobenzene (L₁); 4-(2′-thiazolylazo)bromobenzene (L₂) and 4-(2′-thiazolylazo)iodobenzene (L₃); dppe = cis-1,2-bis(diphenylphosphino)ethane) has been prepared and characterized on the basis of their elemental analysis, molar conductance, magnetic moment, IR, UV–vis and ¹H NMR spectral studies. The electrochemical behaviour of the complexes showed that the redox responses of copper(II) complexes shifted to more negative potential in order of decrease in electron withdrawing nature of the substituent on the azo ligands. All the complexes exhibit intraligand (π→π*) fluorescence in blue-green region with high quantum yield in DMF solution.     

Initial use of 1-hydroxybenzotriazole in the chemistry of group 12 metals: An 1D zinc(II) coordination polymer and a mononuclear cadmium(II) complex containing the deprotonated ligand in a novel monodentate ligation mode

The chemistry of 1-hydroxybenzotriazole (btaOH) with the group 12 metal ions Zn(II) and Cd(II) resulted in the 1D coordination polymer [Zn(btaO)₂]_n (1) and the mononuclear complex [Cd(btaO)₂(H₂O)₄] · 3H₂O (2 · 3H₂O), respectively. Polymer 1 forms double-stranded chains which are further supported by weak C–H?O hydrogen bonds resulting in a pcu (primitive cubic) rod packing. The mononuclear complexes of 2 form undulating hydrogen bonded layers while the lattice water molecules form 1D hydrogen bonded tapes, comprising 4- and 6-membered rings, within the layers and bridge them to the third dimension. The thermal and optical properties of both compounds are presented. IR data are discussed in terms of the chemical composition of the compounds and the coordination mode of btaO^?.     

Intercalation of Ga3 +-salicylidene-amino acid Schiff base complexes into layered double hydroxides: Synthesis,characterization, acid resistant property,in vitro release kinetics and antimicrobial activity

This study is aimed to evaluate the potential application of a drug delivery system of Ga^3 + complexes in layered double hydroxide, i.e. [Ga(L)₂]⁻-LDH (L represents Schiff base ligands made up of salicylidene with glycine, alanine, tyrosine, phenylalanine, aspartic acid and glutamic acid for complexes 1–6, respectively). The successful intercalation of Ga^3 + complexes into Mg/Al-NO₃-LDH by delaminating/restacking method was proved by elemental analysis, XRD, FTIR spectra, UV–vis DR spectra, TG analysis and SEM measurements. A monolayer intercalation of 5 and 6, bilayer of 1 and 3 and trilayer of 2 and 4 in interlayer region of hybrids which have extended gallery height of 11.86–21.22 Å were deduced. Better acid resistance than the pristine complexes in wide pH range from 7 to 1 was revealed by UV–vis spectra. The cumulative release profile of Ga^3 + complexes from the hybrids in phosphate buffer (pH 7.4) following first-order kinetics via ion-exchange between guest anions and phosphate anions was established by UV–vis spectra. Antibacterial activity of hybrids with MIC values of 65–137 μmol/L against Pseudomonas aeruginosa was demonstrated by the broth twofold dilution method. These results suggest that LDH is a promising host material for carry and controlled delivery of biologically active Ga^3 + complexes.     

1-D networks formed by metal⋯sulfur van der Walls contacts: Novel tetrazole–thiolato Pd(II) and Pt(II) complexes

Pd(II)– and Pt(II)–azido complexes, [M(N₃)(PMe₃)₂(C–L)] {LH = 2-(2′)-thienyl pyridine; M = Pd (1), Pt(2)}, which contain σ-bonded heterocycles (L), were treated with aryl isothiocyanate (Me₂C₆H₃–NCS) to afford the corresponding Pd(II) and Pt(II) tetrazole–thiolato complexes, trans-{M[SCN₄(2,6-Me₂C₆H₃)](PMe₃)₂(C–L)} {M = Pd (3), Pt (4)}. Complexes 3 and 4 have a 1-D helical network formed by the intermolecular M?S van der Waals contacts.     

Synthesis and ion responsiveness of optically active polyacetylenes containing salicylidene Schiff-base moieties

Acetylenic monomers containing salicylidene Schiff-base groups (1a and 1b) as well as Schiff-base and hydroxy groups (1c) were synthesized and polymerized with [(nbd)RhCl]₂/Et₃N catalyst to afford the corresponding polymers 2a–c with high molecular weights (M_n = 2.6–7.2 × 10⁵) in high yields (75–97%). Polarimetric, circular dichroism (CD), and UV–vis spectroscopic analyses indicated that the polymers formed helical structures with a predominantly one-handed screw sense. The addition of metal ions to salicylidene Schiff-base-containing polymers 2a and 2b produced insoluble polymer/metal complexes through ionic cross-linking as a result of salicylaldimine–metal ion complexation. Polymers 2b and 2c underwent a helix–coil transition upon the addition of HSO₄⁻, whereas these polymers did not exhibit responsiveness to other anions, such as F⁻, Cl⁻, and Br⁻.     

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).     

Metal ions directed self-assembly based on rigid polycarboxylate ligand 5-tert-butyl isophthalic acid and flexible N-heterocyclic ligand 1,4-bis(2-methylimidazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene

Two new complexes {[Cd(bmimx)_0.5(tbip)(H₂O)] · H₂O}_n (1) and [Zn(bmimx)(tbip)]_n (2) (bmimx = 1,4-bis(2-methylimidazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene, H₂tbip = 5-tert-butyl isophthalic acid) based on mixed ligands have been hydrothermally synthesized by varying the metal ions. Structural analysis reveals that complex 1 displays a 2D layer structure with a 4⁴-sql topology; complex 2 exhibits a 3D 4-fold interpenetrated framework with sra topology. The structural differences between 1 and 2 indicate that metal ions have significant effects on the formation of the final architectures. In addition, the thermal stabilities and photoluminescent properties of the two complexes were also investigated.     

Synthesis,crystal structure and urease inhibitory activities of Schiff base metal complexes

Six new transition metal complexes (1–6) with Schiff base were synthesized and crystallographically characterized. Their urease inhibitory activities were evaluated. Three of them showed potent inhibitions against jack bean urease. Mn(II) complex (2) possessed the best jbU inhibitory activity with IC₅₀ of 8.30 ± 0.93 μM, which was much better than those of the corresponding ligand and control ion. The investigation on the stability constants and the structure-activity relationships of the complexes indicated that the complexes interacted with the enzyme in the whole complex forms rather than the free ions.     

Three platinum(II) complexes of 2-(methoxy-phenyl)-imidazo-[4,5-f]-[1,10] phenanthroline: cell apoptosis induction by sub-G1 phase cell cycle arrest and G-quadruplex binding properties

Three platinum(II) complexes, including 2-(2-methoxy-phenyl) imidazo [4,5-f]-[1,10] phenanthroline, 2-(3-methoxy-phenyl) imidazo [4,5-f]-[1,10] phenanthroline and 2-(4-methoxy-phenyl) imidazo [4,5-f]-[1,10] phenanthroline, were synthesised and structurally characterised. In complexes 1–3, the platinum centre adopts a four-coordinate square planar geometry. In the MTT assay, these complexes exhibited considerable cytotoxicities against the SPC-A-2, MGC80-3, BEL-7404 and HeLa human tumour cell lines, with IC₅₀ values in the range of 4.7 ± 0.8 to 23.3 ± 0.4 μM, and lower cytotoxicities towards the HL-7702 human normal liver cell line. By flow cytometry analyses, the HeLa cells treated with complexes 1–3 for 72 h exhibited DNA damage at the sub-G1 phase with a dose-dependent effect resulting in the blockage of cell cycle at sub-G1 phase, which might contribute to the cell apoptosis observed in HeLa cells. From the results of the CD, UV–vis and FID spectral analyses, complexes 1–3 showed good binding affinity with human telomeric G-quadruplex DNA. It suggested the potential inhibition on the telomerase activity, which should be a key antitumour mechanism for complexes 1–3. Furthermore, complex 1 with 2-substituted MOIP ligand, which may have lower steric hindrance for DNA intercalation, showed higher G-quadruplex DNA binding affinity than complexes 2 and 3. This was supported by the results from cell growth inhibition and cell apoptosis induction.     

Divalent cobalt,zinc, and copper coordination polymers based on a new bifunctional ligand: Syntheses,crystal structures,and properties

Three new coordination polymers, namely, [ML(H₂O)]_n (M = Co (1), Zn (2)) and [CuL(DMF)]_n (3), have been hydrothermally synthesized through the reaction of bifunctional ligand 5-((2-methyl-1H-imidazol-1-yl)methyl)benzene-1,3-dioic acid (H₂L) with divalent cobalt, zinc and copper salts, and structurally characterized by elemental analysis, IR and X-ray diffraction. Both complexes 1 and 2 are two-fold interpenetration 3D frameworks. Complex 3 exhibits (3,6)-connected framework with (4.6²)₂(4².6¹⁰.8³) topology. Furthermore, UV–vis absorption spectra and powder X-ray diffraction (PXRD) were investigated as well.     

Hydrothermal synthesis,crystal structure and strong blue fluorescence of a novel 3D coordination polymer containing copper and zinc centers linked by isonicotinic acid ligands

The first mixed metal Zn/Cu coordination polymer, [Zn₃Cu₂(IN)₈] (1) (HIN = isonicotinic acid) was synthesized under hydrothermal conditions. The three dimensional structure of 1 has a novel topological metal-organic framework, which is built up by Zn²⁺, Cu⁺ and ligands IN to generate an open-framework with an unusual helical [–Zn(Cu)-IN–]_n chains along the b axis. The very strong blue fluorescence for 1 can be observed in the solid state.     

Syntheses,characterizations, and redox behaviors of new self-assembled metal complexes with bridging ligands incorporating chalcogen sites

Three new complexes, [Zn(dbsf)₂(dmf)₂] · 5.5dmf (dbsf = 4,4′-sulfonyldibenzoate) (1β), [Cu(tdsa)(phen)₂] · 1.5EtOH (tdsa = 5,5′-thiodisalicylate, phen = 1,10-phenanthroline) (2), and [Cu(sdp)(phen) · Cu(Hsdp)(phen)(CH₃COO)] · 3EtOH (sdp = 4,4′-sulfonyldiphenolate) (3) were prepared and structurally characterized. Complex 1β shows a one-dimensional coordination framework constructed from bridges between Zn(II) centers with two ligands. Complex 2 is a monomeric complex, which assembles by π–π interactions. Complex 3 shows a unique two-dimensional coordination framework that is constructed from two Cu(II) centers, sdp, and Hsdp. The redox properties of these three complexes were characterized by solid-state cyclic voltammetry. Complexes 1β and 3 show irreversible reduction waves because of the reduction of their sulfone sites. Complex 2 shows an irreversible oxidation wave because of oxidation of the sulfide site.     

1D Zn(II) coordination polymer of arylhydrazone of 5,5-dimethylcyclohexane-1,3-dione as a pre-catalyst for the Henry reaction

Reaction of a new hydrazone of β-diketone, 5-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)isophthalic acid (H₃L), with zinc(II) nitrate hexahydrate in a mixture of DMF and water (1:1) under hydrothermal conditions affords the 1D coordination polymer [Zn(μ₃-HL)(H₂O)₂]_n ∙ nH₂O (1), where one of the carboxylic groups links two Zn(II) centers in a bridging bidentate (syn-syn-type) mode and the remaining one ligates a third metal cation in a monodentate fashion. It was characterized by IR and NMR spectroscopies, ESI-MS, elemental and single-crystal X-ray crystal structural analyses. 1 acts as an efficient pre-catalyst for the Henry reaction at 40 °C in aqueous medium, providing β-nitroalcohols with good yields (67–86%) and diastereoselectivities (syn:anti 77:23–69:31).     

Linear trinuclear manganese(II) complexes: crystal structures and magnetic properties

Two new trinuclear manganese(II) complexes, [Mn₃(O₂CCH(CH₃)₂)₆(N–N)₂] (N–N is 1,10′-phenanthroline (1) and 2,2′-bipyridine (2)) have been prepared and fully characterized. Single crystal X-ray diffraction analysis confirmed a linear arrangement of three Mn(II) centers bridged by six isobutyric carboxylate groups. The magnetic measurements showed that both complexes exhibit an S_T = 5/2 spin ground state induced by antiferromagnetic interactions between the Mn(II) sites: J/k_B = −2.31(2) and −2.67(2) K for 1 and 2, respectively.     

ESR,solid-state 31P MAS NMR,and UV–vis–NIR studies on linear CuI CuII CuI trinuclear species: Crystal structure of bis-μ-salicylato (2−)-1:2 κ4O; 2:3 κ4O-tetrakis (triphenylphosphine-1κ2P, 3κ2P)-tricopper(I,II, I), [(PPh3)2Cu]2(μ-o-OC6H4COO)2Cu

A novel neutral mixed-valence Cu(I)Cu(II)Cu(I) linear trinuclear copper metallomacrocycle [(PPh₃)₂Cu]₂[μ-o-OC₆H₄COO]₂Cu (3) has been synthesized and characterized. Compound 3 consists of two Cu(I) ions and one Cu(II) ion which are bridged by two salicylate (2^?) ligands, and the external copper(I) atoms are coordinated by four terminal triphenylphosphines. The essentially localized mixed-valence [Cu(I)Cu(II)Cu(I)] formulation for 3 was determined on the basis of X-ray crystallography, solid-state ³¹P MAS NMR, and ESR spectroscopy. The solid-state ³¹P MAS NMR spectra of 3 is reported, affording δ[P(2)] = ?1.7 ppm with ¹J[Cu(I), P] = 1330 Hz and δ[P(1)] = ?3.4 ppm with ¹J[Cu(I), P] = 1600 Hz. UV–vis–NIR spectral measurement demonstrates the Robin–Day class II behavior of the mixed-valence compound 3 with a weak copper–copper interaction.     

Synthesis,structure and near-infrared (NIR) luminescence of three solvent-induced pseudo-polymorphic complexes from a bimetallic Zn–Nd Schiff-base molecular unit

Three solvent-induced pseudo-polymorphic bimetallic Zn–Nd complexes [ZnNdL(OAc)(NO₃)₂(DMF)] · solvate (solvate: MeCN (1), THF (2), EtOH (3); H₂L = N,N′-bis(3-methoxy-salicylidene)phenylene-1,2-diamine) were obtained, and their solid NIR luminescence related to the packing structure from the intermolecular π–π interactions was discussed.     

1D helical ZnII metal–organic polymers: Syntheses,structures and fluorescent properties

Hydrothermal reactions of 1,1′-(1,5-pentanediyl)bis-1H-benzimidazole (pbbm) with ZnCl₂ afford two 1D helical metal–organic polymers {[ZnCl₂(pbbm)] · (H₂O)_1/8}_n (1) and {[Zn(pbbm)₂] · Cl₂ · (H₂O)_1/2}_n (2). Polymer 1 features a 1D single helical architecture, whereas 2 possesses a 1D cationic double helical chain framework. Photoluminescence investigations reveal that both of them display strong emissions in the solid state at room temperature, which could originate from a ligand-to-ligand charge-transfer (LLCT) transition, as confirmed by the molecular orbital (MO) calculations.