Hafnium(IV) complexes with Schiff bases

Summary Hafnium(IV) complexes have been prepared by the reactions of hafnium(IV) isopropoxide isopropanol with Schiff bases [bis(salicylaldehyde)hydrazine] (Sal-AH₂), (bis(o-hydroxyacetophenone)hydrazine] (Acp-AH₂), [bis(resacetophenone)hydrazine] (Res-AH₂), [bis(salicylaldehyde)ethylenediimine) (SaleneH₂), [bis(o-hydroxyacetophenone)ethylenediimine] (AcpeneH₂) and [bis(salicylaldehyde)o-phenylenediimine] (SalpheneH₂) (derived from salicylaldehyde,o-hydroxyacetophenone, resacetophenone and diamines) in appropriate molar ratios using benzene as solvent. The complexes [Hf(OPr-i)₂(SB)] and [Hf(SB)₂] (where SB^2– represents the dianion of the Schiff base) are reported. The complexes of Sal-A, Acp-A and Res-A are 5-and 6-coordinate while those of salene, acpene and salphene are 6-and 8-coordinate. The Schiff bases draw on Sal-A, Acp-A and Res-A are tridentate and salene, acpene and salphene are tetradentate. The mode of bonding through nitrogen and oxygen and the stereochemistry of the complexes are discussed in relation to the elemental analyses and spectra (electronic, infrared and nuclear magnetic resonance).     

Co(II), Ni(II), Cu(II) and Zn(II) complexes of aminothiazole‐derived Schiff base ligands: Synthesis,characterization, antibacterial and cytotoxicity evaluation,bovine serum albumin binding and density functional theory studies

Transition metal complexes of type M(L)₂(H₂O)_x were synthesized, where L is deprotonated Schiff base 2,4‐dihalo‐6‐(substituted thiazol‐2‐ylimino)methylphenol derived from the condensation of aminothiazole or its derivatives with 2‐hydroxy‐3‐halobenzaldehyde and M = Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ (x = 0 for Cu²⁺ and Zn²⁺; x = 2 for Co²⁺ and Ni²⁺). The synthesized Schiff bases and their metal complexes were thoroughly characterized using infrared, ¹H NMR, electronic and electron paramagnetic resonance spectroscopies, elemental analysis, molar conductance and magnetic susceptibility measurements, thermogravimetric analysis and scanning electron microscopy. The results reveal that the bidentate ligands form complexes having octahedral geometry around Co²⁺ and Ni²⁺ metal ions while the geometry around Cu²⁺ and Zn²⁺ metal ions is four‐coordinated. The geometries of newly synthesized Schiff bases and their metal complexes were fully optimized in Gaussian 09 using 6–31 + g(d,p) basis set. Fluorescence quenching data reveal that Zn(II) and Cu(II) complexes bind more strongly to bovine serum albumin in comparison to Co(II) and Ni(II) complexes. The ligands and their complexes were evaluated for in vitro antibacterial activity against Escherichia coli ATCC 25922 (Gram negative) and Staphylococcus aureus ATCC 29213 (Gram positive) and cytotoxicity against lever hepatocellular cell line HepG2.     

Effect of Heavy‐Atom (Br) at the Phenyl Rings of Schiff‐Base Ligands on the NIR Luminescence of their Bimetallic Zn‐Nd Complexes

Two heterobimetallic Zn‐Nd phenylene‐bridged Schiff‐base ligands complexes [ZnNd L¹ (Py)(NO₃)₃] ( 1 ) and [Zn L² Nd(Py)(NO₃)₃]·MeCN ( 2 ) (Py = pyridine, H₂L¹ = N,N′‐bis‐ (3‐methoxy‐salicylidene)phenylene‐1,2‐diamine, H₂L² = N,N′‐bis‐5‐bromo‐3‐methoxy‐salicylidene)phenylene‐1,2‐diamine) were obtained. Both 1 and 2 were structurally characterized by X‐ray crystallography, and their near‐infrared (NIR) luminescent properties were determined. For the two complexes, the occupation of pyridine at the axial position of 3d Zn²⁺ ions could effectively prevent luminescent quenching arising from OH‐, NH‐ or CH oscillators of the solvates around the 4f Nd³⁺ ions, and the heavy‐atom (Br) effect of the Schiff‐base ligands on their NIR luminescent properties is also discussed.     

The Coordination Chemistry of the Versatile Ligand Bis(2‐pyridylthio)methane

Bis(2‐pyridylthio)methane [bpytm, (pyS)₂CH₂] and complexes of this ligand with Zn^II, Hg^II, Cu^I, and Ag^I have been prepared and characterised by elemental analysis, by IR, Raman and ¹H and ¹³C NMR spectroscopy, and by X‐ray diffractometry. The ligand is N, N′‐didentate in the Zn^II complexes; N‐monodentate in one Hg^II complex and N, N′‐bis(monodentate) in the other; N‐mono‐N′, S‐didentate in the Cu^I complex; and N, S′‐bis(mono)‐N′, S‐didentate in the Ag^I complex. The structural parameters of the ligand in each coordination mode are compared with those of the free ligand and those of the triiodide salt of the protonated ligand.     

Synthesis and Crystal Structures of an Unexpected Tetranuclear Zinc(II) Complex and a Benzoquinone Compound Derived from ZnII‐ and CdII‐Promoted Reactivity of Schiff Base Ligands

An unexpected polyhydroxyl‐bridged tetranuclear Zn^II complex and a benzoquinone compound derived from metal‐ion promoted reactivity of Schiff base ligands were synthesized and characterized. The reaction of zinc(II) acetate dihydrate with oxime‐type Schiff base ligand HL¹ [HL¹ = 1‐(3‐((3,5‐dibromosalicylaldehyde)amino)phenyl)ethan‐1‐one O‐benzyl oxime] in methanol, acetone, and acetonitrile resulted in the chemoselective cleavage of the C=N bond of the Schiff base HL¹, and then the further addition of acetone to two salicylaldehyde molecules derived from cleavage of the C=N bond in situ α,α double aldol reaction promoted by Zn^II ions. The newly formed ligands H₄L² coordinate to four Zn^II ions forming a defect‐dicubane core structure [Zn^II₄(H₂L²)₂(μ₃‐OCH₃)₂(μ‐OCH₃)₂(CH₃OH)₂] ( 1 ) bridged exclusively by oxygen‐based ligands. The similar ligand HL³ [HL³ = 1‐(3‐((3,5‐dichlorosalicylaldehyde)amino)phenyl)ethan‐1‐one O‐benzyl oxime)] was employed to react with Cd^II acetate dihydrate under the same reaction conditions. No aldol addition occurred but a unexpected benzoquinone compound 2,5‐bis(((3‐(1‐((benzyloxy)imino)ethyl)phenyl)imino)methyl)‐1,4‐benzoquinone ( 2 ) formed. The results provided interesting insights into one‐pot routes involving in situ reactions act as a strategy for obtaining a variety of polymeric/polynuclear complexes which are inconvenient to obtain from directly presynthesizing the ligands.     

Assembled synthesis of luminescent mono/double‐layered 2D and 3D Zn (II)‐based coordination polymers tuned by flexible bis (pyridyl)propane‐1,2‐diamines and diverse organic dicarboxylates

Six mono/double‐layered 2D and three 3D coordination polymers were synthesized by a self‐assembly reaction of Zn (II) salts, organic dicarboxylic acids and L1/L2 ligands. These polymeric formulas are named as [Zn(L1)(C₄H₂O₄)_0.5 (H₂O)]_n·0.5n(C₄H₂O₄)·2nH₂O ( 1 ), [Zn₂(L2)(C₄H₂O₄)₂]_n·2nH₂O ( 2 ), [Zn(L1)(m‐BDC)]_n ( 3 ), [Zn₂(L2)(m‐BDC)₂]_n·2nH₂O ( 4 ), [Zn₃(L1)₂(p‐BDC)₃(H₂O)₄]_n·2nH₂O ( 5 ), [Zn₂(OH)(L2) (p‐BDC)_1.5]_n ( 6 ), [Zn₂(L1)(p‐BDC)₂]_n·5nH₂O ( 7 ), [Zn₂(L2)(p‐BDC)₂]_n·3nH₂O ( 8 ) and [Zn₂(L1)(C₄H₄O₄)_1.5(H₂O)]_n·n(ClO₄)·nH₂O ( 9 ) [L1 = N,N′‐bis (pyridin‐4‐ylmethyl)propane‐1,2‐diamine, L2 = N,N′‐bis (pyridin‐3‐ylmethyl)propane‐1,2‐ diamine, m‐BDC^2? = m‐benzene dicarboxylate, p‐BDC^2? = p‐benzene dicarboxylate]. Meanwhile, these polymers have been characterized by elemental analysis, infrared, thermogravimetry (TG), photoluminescence, powder and single‐crystal X‐ray diffraction. Polymers 1–6 present mono‐ and double (4,4)‐layer motifs accomplished by L1/L2 ligands with diverse conformations and organic dicarboxylates, and the layer thickness locates in the range of 5.8–15.0 Å. In three 3D polymers, the L1 and L2 molecules adopt the same cis‐conformations and join adjacent Zn (II) cations together with p‐BDC^2? or succinate, giving rise to different binodal (4,4)‐c nets with (4.5².8³)(4.5³.7²) ( 7 ), pts ( 8 ) topology and twofold interpenetrated binodal (5,5)‐c nets with (3².4⁴.5².6²)(3.4³.5².6⁴) ( 9 ). Therefore, the diverse conformations of the two bis (pyridyl)‐propane‐1,2‐diamines and the feature of different organic dicarboxylate can effectively influence the architectures of these polymers. Powder X‐ray diffraction patterns demonstrate that these bulk solid polymers are pure phase. TG analyses indicate that these polymers have certain thermal stability. Luminescent investigation reveals that the emission maximum of these polymers varies from 402 to 449 nm in the solid state at room temperature. Moreover, 1 , 3 and 5–8 show average luminescence lifetimes from 8.81 to 16.30 ns.     

Coordination chemistry and biological activity of two tridentate ONS and NNS Schiff bases derived from S-benzyldithiocarbazate

Two tridentate Schiff bases having ONS and NNS donor sequences were prepared by condensing S-benzyldithiocarbazate (NH₂NHCSSCH₂Ph) (SBDTC) with pyridine-2-carboxaldehyde and salicylaldehyde, respectively. Complexes of these ligands with Ni^II, Zn^II, Cr^III, Co^II, Cu^II, and Sn^II were studied and characterized by elemental analyses and various physico-chemical techniques. Ni^II, Cu^II, Zn^II and Sn^II complexes were four-coordinate while the Cr^III, Sr^III and Co^III complexes were six-coordinate. The ONS Schiff base was moderately active against leukemia, while its zinc, antimony and cobalt complexes were strongly active against leukemic cells with DC₅₀ = 0.35–5.00.     

Aspartate‐Based CXCR4 Chemokine Receptor Binding of Cross‐Bridged Tetraazamacrocyclic Copper(II) and Zinc(II) Complexes

The CXCR4 chemokine receptor is implicated in a number of diseases including HIV infection and cancer development and metastasis. Previous studies have demonstrated that configurationally restricted bis‐tetraazamacrocyclic metal complexes are high‐affinity CXCR4 antagonists. Here, we present the synthesis of Cu²⁺ and Zn²⁺ acetate complexes of six cross‐bridged tetraazamacrocycles to mimic their coordination interaction with the aspartate side chains known to bind them to CXCR4. X‐ray crystal structures for three new Cu²⁺ acetate complexes and two new Zn²⁺ acetate complexes demonstrate metal‐ion‐dependent differences in the mode of binding the acetate ligand concomitantly with the requisite cis‐V‐configured cross‐bridged tetraazamacrocyle. Concurrent density functional theory molecular modelling studies produced an energetic rationale for the unexpected [Zn(OAc)(H₂O)]⁺ coordination motif present in all of the Zn²⁺ cross‐bridged tetraazamacrocycle crystal structures, which differs from the chelating acetate [Zn(OAc)]⁺ structures of known unbridged and side‐bridged tetraazamacrocyclic Zn²⁺‐containing CXCR4 antagonists.     

Complexes of a tridentate ONS Schiff base. Synthesis and biological properties

Several new complexes of a tridentate ONS Schiff base derived from the condensation of S-benzyldithiocarbazate with salicylaldehyde have been characterised by elemental analyses, molar conductivity measurements and by i.r. and electronic spectra. The Schiff base (HONSH) behaves as a dinegatively charged ligand coordinating through the thiolo sulphur, the azomethine nitrogen and the hydroxyl oxygen. It forms mono-ligand complexes: [M(ONS)X], [M=Ni^II, Cu^II, Cr^III, Sb^III, Zn^II, Zr^IV or U^VI with X = H₂O, Cl]. The ligand produced a bis-chelated complex of composition [Th(ONS)₂] with Th^IV. Square-planar structures are proposed for the Ni^II and Cu^II complexes. Antimicrobial tests indicate that the Schiff base and five of the metal complexes of Cu^II, Ni^II, U^VI, Zn^II and Sb^III are strongly active against bacteria. Ni^II and Sb^III complexes were the most effective against Pseudomonas aeruginosa (gram negative), while the Cu^II complex proved to be best against Bacillus cereus (gram positive bacteria). Antifungal activities were also noted with the Schiff base and the U^VI complex. These compounds showed positive results against Candida albicans fungi, however, none of them were effective against Aspergillus ochraceous fungi. The Schiff base and its zinc and antimony complexes are strongly active against leukemic cells (CD₅₀ = 2.3–4.3 μg cm⁻³) while the copper, uranium and thorium complexes are moderately active (CD₅₀ = 6.9–9.5 μg cm⁻³). The nickel, zirconium and chromium complexes were found to be inactive. This revised version was published online in June 2006 with corrections to the Cover Date.     

Trinuclear Cage‐Like ZnII Macrocyclic Complexes: Enantiomeric Recognition and Gas Adsorption Properties

Three zinc(II) ions in combination with two units of enantiopure [3+3] triphenolic Schiff‐base macrocycles 1 , 2 , 3 , or 4 form cage‐like chiral complexes. The formation of these complexes is accompanied by the enantioselective self‐recognition of chiral macrocyclic units. The X‐ray crystal structures of these trinuclear complexes show hollow metal–organic molecules. In some crystal forms, these barrel‐shaped complexes are arranged in a window‐to‐window fashion, which results in the formation of 1D channels and a combination of both intrinsic and extrinsic porosity. The microporous nature of the [Zn₃ 1 ₂] complex is reflected in its N₂, Ar, H₂, and CO₂ adsorption properties. The N₂ and Ar adsorption isotherms show pressure‐gating behavior, which is without precedent for any noncovalent porous material. A comparison of the structures of the [Zn₃ 1 ₂] and [Zn₃ 3 ₂] complexes with that of the free macrocycle H₃ 1 reveals a striking structural similarity. In H₃ 1 , two macrocyclic units are stitched together by hydrogen bonds to form a cage very similar to that formed by two macrocyclic units stitched together by Zn^II ions. This structural similarity is manifested also by the gas adsorption properties of the free H₃ 1 macrocycle. Recrystallization of [Zn₃ 1 ₂] in the presence of racemic 2‐butanol resulted in the enantioselective binding of (S)‐2‐butanol inside the cage through the coordination to one of the Zn^II ions.     

Assemblies of 1D and 2D Copper(II) Chiral Coordination Polymers by Salicylaldehyde Schiff Bases: Synthesis,Crystal Structures,and Magnetic Properties

Reaction of CuCl₂ · 2H₂O with chiral Schiff bases and sodium dicyanamide led to the formation of two chiral copper(II) coordination polymers, namely [Cu₄(L¹)₂(dca)₄]_n ( 1 ) and [Cu₂(L²)(μ‐Cl)(dca)(H₂O)]_n · nH₂O ( 2 ) {H₂L¹ = (1R, 3S)‐N′,N′′‐bis[salicylidene]‐1,3‐diamino‐ 1,2,2‐trimethylcyclopentane, H₂L² = (1R, 3S)‐N′,N′′‐bis[3‐ethoxysalicylidene]‐1,3‐diamino‐ 1,2,2‐trimethylcyclopentane, dca = dicyanamide}. Both complexes were structurally characterized by elemental analyses, IR spectroscopy and single‐crystal X‐ray diffraction. Complex 1 exhibits a two‐dimensional polymeric structure formed by single dca bridging tetranuclear Cu₄ units. Complex 2 displays a left‐handed helical chain structure constructed from Cu₂ dimers with single dca bridges. The chirality of 1 and 2 was confirmed by circular dichroism (CD) measurements in solution. Both complexes exhibit strong antiferromagnetic couplings with J = –308(4) cm^–1 for 1 and J = –123(1) cm^–1 for 2 in 2–300 K.     

Synthesis,characterization and biocidal studies of ruthenium(II) carbonyl complexes containing tetradentate Schiff bases

Stable ruthenium(II) complexes of Schiff bases have been prepared by reacting [RuHCl(CO)(PPh₃)₂(B)] (B = PPh₃, pyridine or piperidine) with bis(o-vanillin)ethylenediimine (valen), bis(o-vanillin)propylene-diimine (valpn), bis(o-vanillin)tetramethylenediimine (valtn), bis(o-vanillin)o-phenylenediimine (valphn), bis(salicylaldehyde)tetramethylenediimine (saltn) and bis(salicylaldehyde)o-phenylenediimine (salphn). These complexes have been characterised by elemental analyses, i.r., electronic, ¹H- and ³¹P{¹H}-n.m.r. spectral studies. In all the above reactions, the Schiff bases replace two molecules of Ph₃P, a hydride and a halide ion from the starting complexes, indicating that the Ru–N bonds present in the complexes containing heterocyclic nitrogen bases are stronger than the Ru–P bond to Ph₃P. The new complexes of the general formula [Ru(CO)(B)(L)] (B = PPh₃, py or pip; L = tetradentate Schiff bases) have been assigned an octahedral structure. Some of the Schiff bases and the new complexes have been tested against the pathogenic fungus Fusarium sp.     

Two ZnII‐based MOFs constructed with biphenyl‐2,2′,5,5′‐tetracarboxylic acid and flexible N‐donor ligands: syntheses,structures and properties

Two new Zn²⁺‐based metal–organic frameworks (MOFs) based on biphenyl‐2,2′,5,5′‐tetracarboxylic acid, i.e. H₄(o,m‐bpta), and N‐donor ligands, namely, poly[[(μ₄‐biphenyl‐2,2′,5,5′‐tetracarboxylato)bis{[1,3‐phenylenebis(methylene)]bis(1H‐imidazole)}dizinc(II)] dimethylformamide monosolvate dihydrate], {[Zn₂(C₁₆H₆O₈)(C₁₄H₁₄N₄)₂]·C₃H₇NO·2H₂O}_n or {[Zn₂(o,m‐bpta)(1,3‐bimb)₂]·C₃H₇NO·2H₂O}_n ( 1 ) {1,3‐bimb = [1,3‐phenylenebis(methylene)]bis(1H‐imidazole)}, and poly[[(μ₄‐biphenyl‐2,2′,5,5′‐tetracarboxylato)bis{[1,4‐phenylenebis(methylene)]bis(1H‐imidazole)}dizinc(II)] monohydrate], {[Zn₂(C₁₆H₆O₈)(C₁₄H₁₄N₄)₂]·H₂O}_n or {[Zn₂(o,m‐bpta)(1,4‐bimb)₂]·H₂O}_n ( 2 ) {1,4‐bimb = [1,4‐phenylenebis(methylene)]bis(1H‐imidazole)}, have been synthesized under solvothermal conditions. The complexes were characterized by IR spectroscopy, elemental analysis, single‐crystal X‐ray diffraction and powder X‐ray diffraction analysis. Structurally, the (o,m‐bpta)^4? ligands are fully deprotonated and combine with Zn²⁺ ions in μ₄‐coordination modes. Complex 1 is a (3,4)‐connected porous network with honeycomb‐like [Zn₂(o,m‐bpta)]_n sheets formed by 4‐connected (o,m‐bpta)^4? ligands. Complex 2 exhibits a (2,4)‐connected network formed by 4‐connected (o,m‐bpta)^4? ligands linking Zn²⁺ ions in left‐handed helical chains. The cis‐configured 1,3‐bimb and 1,4‐bimb ligands bridge Zn²⁺ ions to form multi‐membered [Zn₂(bimb)₂] loops. Optically, the complexes show strong fluorescence and display larger red shifts compared to free H₄(o,m‐bpta). Complex 2 shows ferroelectric properties due to crystallizing in the C_2v polar point group.     

Synthesis,structure, thermostability and luminescence properties of ZnII and CdII coordination polymers based on dimethysuccinate and flexible 1,4‐bis(imidazol‐1‐ylmethyl)benzene ligands

The design and synthesis of functional coordination polymers is motivated not only by their structural beauty but also by their potential applications. Zn^II and Cd^II coordination polymers are promising candidates for producing photoactive materials because these d¹⁰ metal ions not only possess a variety of coordination numbers and geometries, but also exhibit luminescence properties when bound to functional ligands. It is difficult to predict the final structure of such polymers because the assembly process is influenced by many subtle factors. Bis(imidazol‐1‐yl)‐substituted alkane/benzene molecules are good bridging ligands because their flexibility allows them to bend and rotate when they coordinate to metal centres. Two new Zn^II and Cd^II coordination polymers based on mixed ligands, namely, poly[[μ₂‐1,4‐bis(imidazol‐1‐ylmethyl)benzene‐κ²N³:N^3′]bis(μ₃‐2,2‐dimethylbutanoato‐κ³O¹:O⁴:O^4′)dizinc(II)], [Zn₂(C₆H₈O₄)₂(C₁₄H₁₄N₄)]_n, and poly[[μ₂‐1,4‐bis(imidazol‐1‐ylmethyl)benzene‐κ²N³:N^3′]bis(μ₃‐2,2‐dimethylbutanoato‐κ⁵O¹,O^1′:O⁴,O^4′:O⁴)dicadmium(II)], [Cd₂(C₆H₈O₄)₂(C₁₄H₁₄N₄)]_n, have been synthesized under hydrothermal conditions and characterized by single‐crystal X‐ray diffraction, elemental analysis, IR spectroscopy and thermogravimetric analysis. Both complexes crystallize in the monoclinic space group C2/c with similar unit‐cell parameters and feature two‐dimensional structures formed by the interconnection of S‐shaped Zn(Cd)–2,2‐dimethylsuccinate chains with 1,4‐bis(imidazol‐1‐ylmethyl)benzene bridges. However, the Cd^II and Zn^II centres have different coordination numbers and the 2,2‐dimethylsuccinate ligands display different coordination modes. Both complexes exhibit a blue photoluminescence in the solid state at room temperature.     

Hyperbranch‐polyethyleniminated functional polymers. I. Synthesis,characterization of novel ABA type of dumbbell‐like polyethyleniminated polyoxypropylenediamines,and their complexing properties with copper(II) ions in aqueous solution

Novel ABA‐type dumbbell‐like water‐soluble copolymers [D230(EI)₄, D400(EI)₄, and D400(EI)₈] were synthesized by introducing ethylenimine (EI) groups into both sides of polyoxypropylenediamines via a simple in situ ethylamination of polyoxypropylenediamine with 2‐chloroethylamine hydrochloride. The structures of the resultant polymers were identified by Fourier transform infrared spectroscopy and ¹H NMR. The percentages of primary, secondary, and tertiary amine present were determined by the potentiometric titration method after treatments with the appropriate chemicals of salicylaldehyde and acetic anhydride. The surface tension and solubilizing behavior of pyrene in the presence of these polymers in aqueous medium were also investigated, and the efficiency to reduce the surface tension and solubilizing behavior of pyrene depends on the attachments of EI to polymer backbone. The chelating properties of these polymers were examined quantitatively by ultraviolet–visible (UV–vis) spectroscopy in the presence of Cu²⁺ ions in aqueous solution, and continuous variation analysis revealed that the most stable complex is formed at the normality ratio of [N]/[Cu²⁺] = 3.0. UV–vis spectroscopy and transmission electron microscopy were used to evaluate the dumbbell‐like water‐soluble copolymer, D400(EI)₈, as a stabilizer for preparing colloidal noble metal nanoparticles (Au and Pt) in aqueous solution. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1360–1370, 2003     

A new nano‐sized mononuclear Cu (II) complex with N,N‐donor Schiff base ligands: sonochemical synthesis,characterization, molecular modeling and biological activity

A new, simple Cu²⁺ nano‐structure Schiff base complex in methanol medium has been synthesized by the ultrasonic method. Structure of the compound was confirmed by FT‐IR, GC‐Mass and other spectroscopic techniques. The copper oxide (CuO) was achieved from the copper nano‐structure Schiff base complex as the raw material after calcination for 3 hr at 600 °C. According to results Cu²⁺ gives a complex with mole ratio 1:2 of metal to ligand (ML₂) with Schiff base which a distorted square planer is the most probable geometry for it. The calculations results from XRD patterns propose the nano‐sized complexes. The SEM images show morphology of both the copper complex and the CuO powder were plate‐like. The metal chelates of Cu²⁺ in two states of bulk and nano have been screened for their in vitro antibacterial activity against four bacteria, gram‐positive (Staphylococcus aureus) and gram‐negative (Escherichia coli) and three strains of fungus (Aspergillus flavus). The nano metal chelates were shown to possess more antibacterial activity than the bulk chelate. Finally, the empirical parameters of Schiff base compounds showed a good agreement with theoretical ones.     

Syntheses,Crystal Structures,and Antibacterial Activities of Four Schiff Base Complexes of Copper and Zinc

Four Schiff base complexes, [Cu₂(L1)₂(μ‐NCS)₂] ( 1 ), [Cu₂(L2)₂(μ‐N₃)₂] ( 2 ), Cu[Cu(CH₃COO)(L3)]₂ ( 3 ), and [Zn{Zn(C₃H₄N₂)(L3)}₂(NO₃)](NO₃) ( 4 ) (where L1 = 2‐[(pyridin‐2‐ylmethylimino)methyl]phenol, L2 = 1‐[(pyridin‐2‐ylmethylimino)methyl]naphthalen‐2‐ol, and L3 = bis(salicylidene)‐1, 3‐propanediamine), were synthesized and characterized by elemental analyses, infrared spectroscopy, and single crystal X‐ray determinations. Both 1 and 2 are structurally similar di‐nuclear complexes, which are located at crystallographic inversion centers (with the center of the central Cu₂N₂ ring). In 1 , each copper atom has a slightly distorted square pyramidal configuration, coordinated by two nitrogen atoms and one oxygen atom from L1 and another two terminal nitrogen atoms from two bridging thiocyanate anions. The Cu···Cu separation is 3.466(3) Å. The structure of 2 is similar to that of 1 , with Cu···Cu separation of 3.368(2) Å. Both 3 and 4 are linear tri‐nuclear complexes. In 3 , the central Cu²⁺ ion is located on an inversion centre and has a distorted octahedral coordination involving four bridging O atoms from two Schiff base ligands (L3) in the equatorial plane and one O atom from each bridging acetate group in the axial positions. The coordination around the terminal Cu²⁺ ions is irregular‐square pyramidal, with two O and two N atoms of L3 in the basal plane and one O atom from an acetate group in the apical position. The acetate bridges linking the central and terminal Cu²⁺ ions are mutually trans. The Cu···Cu separation is 3.009(3) Å. In 4 , the coordination configuration of the central and the terminal zinc atoms are similar to that of the 3 , with Zn···Zn separation of 3.153(4) Å. The three Schiff bases and the corresponding three copper complexes exhibit good antibacterial properties, while the zinc complex 4 has nearly no.     

A New Luminescent Ruthenium(II) Polypyridine‐derived Dipicolylamine Complex as a Sensor for Cu2+ Ions

A chemo‐sensor [Ru(bpy)₂(bpy‐DPF)](PF₆)₂ ( 1 ) (bpy=2,2′‐bipyridine, bpy‐DPF=2,2′‐bipyridyl‐4,4′‐bis(N,N‐di(2‐picolyl))formylamide) for Cu²⁺ using di(2‐picolyl)amine (DPA) as the recognition group and a ruthenium(II) complex as the reporting group was synthesized and characterized successfully. It demonstrates a high selectivity and efficient signaling behavior only for Cu²⁺ with obvious red‐shifted MLCT (metal‐to‐ligand charge transfer transitions) absorptions and dramatic fluorescence quenching compared with Zn²⁺ and other metal ions.     

[62]Tetradecaphyrin and Its Mono‐ and Bis‐ZnII Complexes

A coiled structure of meso‐pentafluorophenyl‐substituted [62]tetradecaphyrin 1 was revealed by X‐ray structural analysis. Synthetic protocols were devised to form mono‐ and bis‐Zn^II complexes, 1 Zn and 1 Zn₂ , selectively. The former displayed a trigonal‐bipyramidal pentacoordinated Zn^II ion as a rare case and a cyclic voltammogram exhibiting eleven reversible redox waves. The latter showed a Ci‐symmetric structure with modest Hückel aromaticity owing to a 62 π‐electronic circuit as the largest aromatic molecule to date.     

Synthesis and crystal structure of the dinuclear copper(II) Schiff base complex μ‐hydroxido‐μ‐chlorido‐bis{[bis(trans‐2‐nitrocinnamaldehyde)ethylenediamine]chloridocopper(II)} dichloromethane sesquisolvate

Transition metal complexes of Schiff base ligands have been shown to have particular application in catalysis and magnetism. The chemistry of copper complexes is of interest owing to their importance in biological and industrial processes. The reaction of copper(I) chloride with the bidentate Schiff base N,N′‐bis(trans‐2‐nitrocinnamaldehyde)ethylenediamine {Nca₂en, systematic name: (1E,1′E,2E,2′E)‐N,N′‐(ethane‐1,2‐diyl)bis[3‐(2‐nitrophenyl)prop‐2‐en‐1‐imine]} in a 1:1 molar ratio in dichloromethane without exclusion of air or moisture resulted in the formation of the title complex μ‐chlorido‐μ‐hydroxido‐bis(chlorido{(1E,1′E,2E,2′E)‐N,N′‐(ethane‐1,2‐diyl)bis[3‐(2‐nitrophenyl)prop‐2‐en‐1‐imine]‐κ²N,N′}copper(II)) dichloromethane sesquisolvate, [Cu₂Cl₃(OH)(C₂₀H₁₈N₄O₄)₂]·1.5CH₂Cl₂. The dinuclear complex has a folded four‐membered ring in an unsymmetrical Cu₂OCl₃ core in which the approximate trigonal bipyramidal coordination displays different angular distortions in the equatorial planes of the two Cu^II atoms; the chloride bridge is asymmetric, but the hydroxide bridge is symmetric. The chelate rings of the two Nca₂en ligands have different conformations, leading to a more marked bowing of one of the ligands compared with the other. This is the first reported dinuclear complex, and the first five‐coordinate complex, of the Nca₂en Schiff base ligand. Molecules of the dimer are associated in pairs by ring‐stacking interactions supported by C—H…Cl interactions with solvent molecules; a further ring‐stacking interaction exists between the two Schiff base ligands of each molecule.