Chloro Bridges Research Articles

C-Cl Bond Activation at Rotated vs Unrotated Dinuclear Site Related to [FeFe]-Hydrogenases.

The novel dinuclear complex related to the [FeFe]-hydrogenases active site, [Fe2(μ-pdt)(κ2-dmpe)2(CO)2] (1), is highly reactive toward chlorinated compounds CHxCl4-x (x = 1, 2) affording selectively terminal or bridging chloro diiron isomers through a C-Cl bond activation. DFT calculations suggest a cooperative mechanism involving a formal concerted regioselective chloronium transfer depending on the unrotated or rotated conformation of two isomers of 1.

The role of methyl and benzyl substituted dithiocarbazate of 2-acetyl pyridine for the formation of bridged dimeric and unbridged monomeric copper(II) complexes and catecholase mimetic activity of the complexes

Monomeric [Cu(L1)Cl] (1) and dimeric [Cu(L2)Cl]2 (2) copper(II) complexes, where HL1 = methyl-2-(1-(pyridine-2-yl)ethylidene)-hydrazine-1-carbodithioate and HL2 = benzyl-2-(1-(pyridine-2-yl)ethylidene)hydrazine-1-carbodithioate, have been synthesized and characterized by X-ray crystallography, TGA and spectral methods. Complex 1 crystallizes in a space group P21/n and adopts a square planar environment surrounding the Cu ion, and complex 2 is a triclinic crystal system with space group Pī. Complex 2 is a centrosymmetric dimer where each copper atom forms two chloro bridges and completes five coordination with the tridentate NNS donor. Density functional calculations demonstrate that chloro-unbridged structure of 1 is favored by London dispersion between its layers. It is noticed that the layers are usually packed closely in the solid phase, such attractive interactions are sterically hindered between the layers of 2.Due to the presence of large phenyl group that extendfrom one layer to the other, the layers cannot slide on top of each other. This leads to the chloro-bridged structure of 2 stabilized by electrostatic interactions between Cu and Cl atoms located at different layers. Both complexes exhibit prominent catecholase activity in methanol following the oxidation of 3,5-di-tert-butyl catechol (DTBC) to the corresponding quinone. Based on the observed turn over frequency of 1 (25.19 h−1) and 2 (10.76 h−1), the monomeric complex demonstrates more catechol mimetic oxidation than the dimer. A plausible mechanism of catecholase activity has been discussed.

A linear tetranuclear Cu(II) complex exhibiting both ferro and antiferromagnetic couplings: Synthesis, characterization and magneto-structural studies

The pyrimidinyl hydrazone ligand OC{NHNC(Me)(pm)}2 (pm = 2-pyrimidinyl) (L3H2) has two potentially protic H atoms and multiple donor atoms. The reaction of L3H2 with CuCl2·2H2O yielded the tetranuclear complex [Cu4(L3H)2Cl6(CH3OH)2] (1). Structural studies on 1 reveal the molecule is located about a crystallographic inversion centre, affording two crystallographically independent Cu(II) centres with the two symmetry equivalent [Cu2(L3H)Cl3CH3OH] units connected via µ2-Cl bridges to generate a linear tetranuclear copper complex. The ligand is singly deprotonated (L3H−) and twisted around the diazine NN′ bond, affording an N3 donor set for the Cu1 centre and an N2O donor set for the Cu2 centre. The Cu1 ion is five coordinate with an [N3] donor set from the L3H− ligand and the remaining two sites occupied by Cl− anions. The Cu2 ion is six coordinate with the L3H− ligand offering a mer [N2O] donor set, with the three remaining sites occupied by two Cl− anions and a MeOH molecule. Magnetic studies reveal the presence of strong antiferromagnetic interactions via the diazine bridge linking the Cu1 and Cu2 ions and moderate ferromagnetic interactions via the chloro bridges located about the inversion centre, connecting the Cu2 and Cu2i ions.

A New Mixed-Valence Mn(II)Mn(III) Compound With Catalase and Superoxide Dismutase Activities.

The synthesis, X-ray molecular structure, physico-chemical characterization and dual antioxidant activity (catalase and superoxide dismutase) of a new polymeric mixed valence Mn(III)Mn(II) complex, containing the ligand H2BPClNOL (N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)[(3-chloro)(2-hydroxy)] propylamine) is described. The monomeric unit is composed of a dinuclear Mn(II)Mn(III) moiety, [Mn(III)(μ-HBPClNOL)(μ-BPClNOL)Mn(II)(Cl)](ClO4)·2H2O, 1, in which the Mn ions are connected by two different bridging groups provided by two molecules of the ligand H2BPClNOL, a phenoxide and an alkoxide group. In the solid state, this mixed valence dinuclear unit is connected to its neighbors through chloro bridges. Magnetic measurements indicated the presence of ferromagnetic [J = +0.076(13) cm−1] and antiferromagnetic [J = −5.224(13) cm−1] interactions. The compound promotes O dismutation in aqueous solution (IC50 = 0.370 μmol dm−3, kcat = 3.6x106 M−1 s−1). EPR studies revealed that a high-valent Mn(III)-O-Mn(IV) species is involved in the superoxide dismutation catalytic cycle. Complex 1 shows catalase activity only in the presence of a base, e.g., piperazine or triethylamine. Kinetic studies were carried out in the presence of piperazine and employing two different methods, resulting in kcat values of 0.58 ± 0.03 s−1 (detection of O2 production employing a Clark electrode) and 2.59 ± 0.12 s−1 (H2O2 consuption recorded via UV-Vis). EPR and ESI-(+)-MS studies indicate that piperazine induces the oxidation of 1, resulting in the formation of the catalytically active Mn(III)-O-Mn(IV) species.

Bis(μ-chloro) bridged 1D CuI and CuII coordination polymer complex and mononuclear CuII complex: Synthesis, crystal structure and biological properties

A novel one-dimensional coordination polymer containing Cu(I)Cu(II) core with chloro bridge on Cu(I) and ligand bridge on Cu(II) ions (1) and a mononuclear Cu(II) complex (2) have been synthesized from the reactions of 3- and 4-methoxy-3-quinolin-3-ylimino-methyl-2-phenol with [CuCl2(PPh3)2]. The ligands and the complexes have been characterized by spectral and analytical methods. In addition, the structures of both the ligands and the copper complexes were confirmed by single crystal X-ray diffraction studies. In both complexes, the phenolic oxygen and azomethine nitrogen atom of the ligand coordinate to the copper ions in a monobasic bidentate manner resulting in an approximately square planar geometry around the copper ion. In the polymeric complex, the N atom of the quinoline ring is coordinated to Cu(I) in addition to the phenolic oxygen and azomethine nitrogen atom coordinating to Cu(II) ion, thus bridging Cu(I) and Cu(II) ions in the complex. The interactions of the compounds with calf thymus DNA (CT-DNA) have been followed by absorption and emission titration methods, which revealed that the compounds interact with CT-DNA through intercalation. Further, the interactions of the compounds with bovine serum albumin (BSA) were also investigated using UV–visible, fluorescence spectroscopic methods. The results indicated that complex 1 exhibited a stronger binding to CT-DNA and BSA than the free ligands and complex 2. In addition, the in vitro cytotoxicity experiment showed that complexes 1 and 2 exhibit potent cytotoxic properties against PANC-1and Hela cells. Moreover, while complex 1 showed prominent cytotoxic activity against both PANC-1 and Hela cells with IC50 of 17.91 and 11.67 μM, complex 2 showed moderate cytotoxic activities with IC50 of 25.13 and 16.41 μM in PANC-1 and Hela cells. Further, apoptosis was confirmed by fluorescence image using EB/AO reagent.

Synthesis, characterization and DNA binding investigations on 1D polymeric copper(II) complexes of 1-amidino-O-alkylurea (alkyl = methyl, ethyl or propyl) having both dicyanamido and chloro bridges

Three new copper(II) complexes, [(CuL)2Cl{N(CN)2}3]n, where L = 1-amidino-O-methylurea (1), 1-amidino-O-ethylurea (2), or 1-amidino-O-propylurea (3), have been synthesized and characterized. The single crystal X-ray structure of 2 and X-ray powder diffraction analysis on 1 and 3 show that they crystallize in the monoclinic system. The neutral dinuclear entity of 2 contains a crystallographic 2-fold axis passing through the amido nitrogen of a bridging dicyanamido ligand. The dinuclear units are bridged by weak Cu … Cl interactions through the axial position of both copper ions to form a 1D polymer. The interaction of 1–3 with calf-thymus DNA (CT-DNA) has been explored by using absorption, emission, thermal denaturation, cyclic voltammetric studies, and viscosity experiments. The complexes bind to CT-DNA by non-intercalative mode and the order of binding ability is 1 > 2 > 3.

Structural insights into the coordination and selective extraction of copper(II) by tertiary amine ligands derived from 2-aminomethylpyridine

To develop selective ligands for the separation of copper(II), nickel(II) and cobalt(II), the solvent extraction and coordination chemistry of a bidentate chelating ligand, N,N-dioctyl-2-aminomethylpyridine (AMPO), and a tridentate chelating ligand, tert-butyl 2-(N-octyl-2-picolyamino)acetate (AMPA), were investigated. The ligands exhibit excellent extraction ability and high selectivity towards copper(II) over nickel(II) and cobalt(II) in the simulated electrolysis anolytes. Two novel copper(II) complexes, [Cu2(AMPO)2Cl4] (1) and [Cu(AMPA)Cl2] (2), were synthesized and fully characterized. The solid-state structures of the complexes 1 and 2 were established by single crystal X-ray diffraction. The results show that the complex 1 consists of isolated dinuclear molecules unit with two bridging chloro ligands and the geometry around Cu(II) displays a slightly distorted square pyramid, and the complex 2 is also best described as a slightly distorted square pyramid in reasonable approximation distance. The stoichiometric ratios and association constants of the copper(II) complexes with AMPO and AMPA were also determined in CH3OH/H2O mixtures by UV−Vis spectrometry, respectively. The interactions between the ligands and the metal ions (Cu2+, Ni2+ and Co2+) were correspondingly evaluated by X-ray photoelectron spectroscopy (XPS) and electrospray ionization-mass spectrometry (ESI-MS), and the results reveal that AMPO can be correspondingly coordinated through tertiary amine N atom and pyridine N atom with the three metal ions of copper(II), nickel(II) and cobalt(II), and AMPA can be coordinated through tertiary amine N atom, pyridine N atom and the carbonyl O atom only with copper(II) not with nickel(II) or cobalt(II). All the results indicate that AMPA could be a better candidate for the deep removal of copper(II) from the nickel or cobalt electrolysis anolyte.

2,5‐Norbornadiene C–C Coupling Reactions Mediated by Iridium Complexes

The treatment of [{Ir(µ‐Cl)(cod)}2] (cod = 1,5‐cyclooctadiene) with 2,5‐norbornadiene (nbd) in the presence of triethylphosphane under an atmosphere of ammonia afforded the cation complex [Ir(κC,κC‐C21H24)(NH3)3(PEt3)]Cl (1a) and complex [Ir(κC,κC‐C21H24)Cl(NH3)2(PEt3)] (1b), the structures of which include a novel seven‐membered iridacycle formed by three half‐coupled nbd molecules. The formation of the metallacycle has been found to occur through several steps. First, the nbd displaces the cod in [{Ir(µ‐Cl)(cod)}2] to give the IrIII chloro‐bridged complex [{Ir(κC,κC‐C14H16)(µ‐Cl)(η4‐C7H8)}2] (2), which bears a η4‐C=C‐coordinated nbd and a five‐membered iridacycle formed by two half‐coupled nbd moieties. Further reaction with PEt3 induces the C–C coupling between the iridacycle and the coordinated nbd to give the chloro‐bridged complex [{Ir(κC,κC‐C21H24)(µ‐Cl)(PEt3)}2] (4). Finally, 4 reacts with gaseous ammonia to split the chloro bridges and form species 1a and 1b. Also, complex 2 was found to react with several donor ligands to afford the corresponding mononuclear adducts [Ir(κC,κC‐C14H16)Cl(η4‐C7H8)(L)] [L = py (5), NH3 (6), PMe2Ph (7), tBuNC (8)]. The X‐ray molecular structures of 5, 7 and 8 show the presence of a five‐membered iridacycle, but their stereochemistries differ by virtue of the relative locations of the respective added ligand.

Synthesis and structural characterization of two cationic dinuclear cymene-ruthenium(II) complexes with thiolato and chloro bridges

Treatment of [(p-cymene)RuCl2]2 with HSp-Tol or HSCH2Ph in the presence of K[PF6] gave the cationic dinuclear cymene–ruthenium(II) complexes [(p-cymene)2Ru2(μ-Cl)(μ-Sp-Tol)2][PF6] (1) and [(p-cymene)2Ru2(μ-Cl)(μ-SCH2Ph)2][PF6] (2), respectively, which have been characterized by IR, NMR spectroscopies and mass spectrometry along with microanalyses. Their crystal structures were determined by single-crystal X-ray diffraction analyses. The structures of the cationic complexes contain the unusual pseudo-trigonal-bipyramidal Ru2S2Cl framework without a ruthenium–ruthenium single bond. The two p-cymene–ruthenium units are held together by two bridging thiolates and one bridging chloride.

C-H Activation in Primary 3-Phenylpropylamines: Synthesis of Seven-Membered Palladacycles through Orthometalation. Stoichiometric Preparation of Benzazepinones and Catalytic Synthesis of Ureas.

The dimeric cyclometalated complexes [Pd2{κ(2)C,N-C6H4CH2CH2C(R)(Me)NH2-2}2(μ-Cl)2] (R = Me (1a), H (1b)) are prepared by reacting 1,1-dimethyl-3-phenylpropylammonium or 1-methyl-3-phenylpropylammonium triflate with Pd(OAc)2 in a 1:1 molar ratio and subsequent treatment with excess NaCl. The mononuclear derivatives [Pd{κ(2)C,N-C6H4CH2CH2C(R)(Me)NH2-2}Cl(L)] (L = PPh3, R = Me (3a), H (3b); L = 4-picoline (4-pic), R = Me (4a), H (4b)) were prepared from 1a,b by splitting the chloro bridges with the neutral ligands L. A conformational analysis of the mononuclear palladacycles in solution has been carried out. Insertion of CO takes place into the Pd-C bond of complexes 1a,b, affording Pd(0) and the tetrahydro-benzazepinone 5a or 5b, which possesses potential pharmacological interest. Additionally, the triflate salt A or B undergoes catalytic carbonylation with CO to afford the corresponding N,N'-dialkylurea, using Pd(OAc)2/Cu(OAc)2, in boiling acetonitrile. The crystal structures of 3a·(1)/2H2O, 3b, 4b·CHCl3, and 5a were determined by X-ray diffraction studies.

Cadmium(II)-N-Ethylimidazole Coordination Polymer via Different Coordination Environment and Chloro Bridges: Synthesis, X-ray Structure, Spectroscopic and Thermal Analysis

A novel coordination polymer [Cd2(μ-Cl)4(Neim)3]n (1) (Neim = N-ethylimidazole) was synthesized and structurally characterized by means of elemental analysis, thermal analysis, FT-IR spectrum and single-crystal X-ray diffraction. There are two different cadmium centers in 1. One of these metal centers has octahedral geometry, while the other has square pyramidal geometry. Two Neim ligands are coordinated to the Cd(II) ion in octahedral geometry while one Neim ligand is coordinated to the Cd(II) ion in square pyramidal geometry. Relatively weak C–H···Cl interactions between N-ethylimidazole molecules and chloro ions in the complex play an important role in the construction of a three-dimensional supramolecular framework. Complex 1 exhibits photoluminescence emission in solid state at room temperature.

Dipalladium Complexes with Bridging Monoalkyl or Monophenyl Silyl Ligands in the Solid State and in Solution

HexSiH3, PhSiH3, and PhSiClH2 reacted with [Pd(PCy3)2] to yield dipalladium complexes with bridging silyl ligands: [{Pd(PCy3)}2(μ-HSiXR)2] (1, R = Hex, X = H; 2, R = Ph, X = H; 3, R = Ph, X = Cl). The X-ray crystallographic results displayed a typical bis(silyl)-bridged dinuclear structure with an anti conformation of the substituents on the Si atom in the solid state. Temperature-dependent NMR spectroscopic analyses of 1 and 2 revealed a dynamic syn–anti isomerization of the complex via exchange of the bridging and nonbridging Si–H hydrogens in solution. Complex 3 with bridging chloro(phenyl)silyl ligands did not show such a dynamic behavior.

Synthesis and structural studies of cyclopalladated complexes of secondary benzylamines

Di-nuclear cyclopalladated acetato-bridged complexes derived from secondary benzylamines, [Pd2{(C,N)-C6H4CH2NH(R)}2(μ-OAc)2] (R = Et (1), R = t-Bu (2)) were obtained by refluxing of corresponding benzylamines and Pd(OAc)2 in a 1:1 M ratio. Complex 1 was also prepared by heating the bis-amine complex [Pd(OAc)2(PhCH2NH(Et))2] (3) in toluene at 60 °C. Complex 3 reacted with an excess of NaCl to give [Pd(Cl)2(PhCH2NH(Et))2] (4). Metathetical reaction of 1 and 2 with an excess of NaCl or NaBr afforded the corresponding dimers [Pd2{(C,N)-C6H4CH2NH(R)}2(μ-X)2] (X = Cl, R = Et (5); X = Cl, R = t-Bu (6); X = Br, R = t-Bu (7)). The cationic complex [Pd(C,N)-C6H4CH2NH(Et)(phen)]BF4 (8) can be obtained by reacting chloro bridge dimer 5 with AgBF4 and 1,10-phenanthroline (phen). Neutral ligands split the halide bridges in 6 and 7 to give monomeric complexes [Pd(C,N)-C6H4CH2NH(t-Bu)X(L)] (X = Cl, L = PPh3 (9); X = Br, L = Me3Py (10)). Complexes 1–10 were fully characterized by elemental analysis, IR and NMR spectroscopies. In addition, the crystal structures of 2, 3, 4, 8, 9 and 10 were determined by single-crystal X-ray diffraction analysis. In all these structures, the palladium atom shows a distorted or slightly distorted square-planar geometry.

Dinuclear ortho-metallated palladium(II) azobenzene complexes with acetato and chloro bridges: Influence of polar substituents on the mesomorphic properties

The synthesis, characterization and mesomorphic properties of a new series of acetate and chloro-bridged dinuclear orthopalladated complexes derived from azobenzene with terminal groups of hexadecyloxy moiety at one end and different polar groups (Me, Cl, F, NO2, CN) at the other end are described. The mesomorphic properties of both the ligands and complexes were investigated by polarizing optical microscopy and X-ray studies to understand the effect of polar group in the nature of mesophase produced. Among the complexes, all chloro-bridged complexes predominantly exhibited SmA phase. However the rare phenomenon of observing mesomorphism in acetato-bridged palladium (II) complexes due its typical open book shape had been realized in substituted acetato-bridged complexes with fluoro and cyano substituents in the ligands. Nitro and cyano substituted ligands only exhibited monotropic Smectic A phase. Model molecular arrangement based on X-ray studies is presented.

Selective Dialkylation of a Doubly Linked Dicyclopentadiene Ligand and the Ensuing Ruthenium Complexes

The selective alkylation (Me or tert-butyl) of a doubly linked dicyclopentadiene ligand is presented. The reaction of (C5H3(t-Bu))2(CMe2)2 (4a,b), the di-tert-butyl-substituted ligand, with RuCl3·3H2O in MeOH at 140 °C for 15 min, followed by heating in CHCl3, gave the chloro-bridged complex cis-{(η5-C5H2(t-Bu))2(CMe2)2}Ru2(μ-Cl)2Cl2 (5) in 28% yield. Reduction of 5 with Zn in MeCN gave the chloro-bridged tetrakis(acetonitrile) complex cis-[{(η5-C5H2(t-Bu))2(CMe2)2}Ru2(MeCN)4(μ-Cl)]+ (6) in 62% yield. Addition of AgOTf to 6 in MeCN removed the bridging chloro ligand and gave [cis-{(η5-C5H2(t-Bu))2(CMe2)2}Ru2(MeCN)6][OTf]2 (7) in 38% yield. The X-ray crystal structures of 5 and 6 are reported.

Syntheses, Crystal Structures, and Magnetic Properties of μ‐O/μ‐Cl Bridged Dinuclear Manganese(II) and Copper(II) Complexes with Schiff base Ligand HL [HL = 2‐(benzothiazol‐2‐yl‐hydrazonomethyl)‐6‐methoxyphenol

AbstractA novel versatile multidentate ligand 2‐(benzothiazol‐2‐yl‐hydrazonomethyl)‐6‐methoxyphenol (HL), was obtained from a condensation reaction between 2‐hydrazino benzothiazole and o‐vanillin. The reactions of HL with CuCl2·2H2O/Mn(ClO4)2·6H2O generated two novel dinuclear compounds Cu2L(μ‐Cl)Cl2(CH3OH)2 (1) and Mn2L3(ClO4)(CH3CH2OH)3 (2). The crystal structures of 1 and 2 were determined by X‐ray diffraction studies. The two copper atoms in complex 1 are connected by a L– anion and a single chloro bridge with a Cu···Cu separation of 3.2729(4) Å. In complex 2, the two manganese atoms are held together by two L– anion bridges and the Mn···Mn separation amounts to 3.3433(7) Å. As expected, variable‐temperature magnetic susceptibility measurements of complex 1 showed strong antiferromagnetic intramolecular coupling between the copper(II) atoms with J = –102.2 cm–1, and evidenced for complex 2 weak antiferromagnetic coupling with J = –1.68 cm–1.

Group 6 Complexes with Iron and Zinc Heterometals: Understanding the Structural, Spectroscopic, and Electrochemical Properties of a Complete Series of MM···M′ Compounds

Binuclear quadruply bonded complexes Cr(2)(dpa)(4) (1, dpa = 2,2'-dipyridylamide), Mo(2)(dpa)(4) (2), and W(2)(dpa)(4) (3) react with anhydrous FeCl(2), yielding heterometallic compounds CrCrFe(dpa)(4)Cl(2) (4), MoMoFe(dpa)(4)Cl(2) (5), and WWFe(dpa)(4)Cl(2) (6). These molecules are structurally similar, having a linear M≡M···Fe chain that is axially capped by chloride ions and is equatorially supported by the helically twisted dpa ligands. A structurally related zinc analog, CrCrZn(dpa)(4)Cl(2) (7), can be prepared upon metalation of 1 with ZnCl(2). This reaction also persistently produces a 2:1 adduct of ZnCl(2) with 1, [Cr(2)(dpa)(4)](ZnCl(2))(2) (8), which is in equilibrium with 7 and has the two zinc ions bound externally to the Cr(2) core and axial bridging chloro ligands attached to each Cr ion. The sole isolable product of the addition of ZnCl(2) to 3 is a 1:1 adduct, [W(2)(dpa)(4)]ZnCl(2) (9). The structurally related chain complexes 4, 5, 6, and 7 are characterized by X-ray crystallography, UV-vis spectroscopy, cyclic voltammetry, and (57)Fe Mössbauer spectroscopy for the iron complexes in order to gain insights into the nature of heterometallic interactions, electronic excited states, and redox properties of these compounds, which have implications for all other M≡M···M' molecules. Additionally, NMR spectroscopy has been used to gain insight into the mechanism of the metalation of 1 by Zn(II).

Dinuclear ortho-Metallated Palladium(II) Complexes with Acetato and Chloro Bridges as Liquid Crystals

In this article we present the preparation and the investigation of the liquid crystal properties of a series of dinuclear acetato- and chloro-bridged ortho-metallated Pd(II) complexes bearing six alkoxy peripheral chains in the molecule. Their structures were assigned based on elemental analysis, Infrared (IR), and 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, whereas the thermal behavior was investigated by polarizing optical microscopy and differential scanning calorimetry. All these complexes show mesomorphic behavior with smectic A phases being displayed. The acetato complexes exhibit a monotropic smectic A phase with transition temperatures from the isotropic state depending on the alkyl chain lengths, whereas the chloro complexes decompose on melting from the crystalline state to an SmA phase.

Metallomacrocycle or coordination polymer: Spacer-directed self-assembly of transition-metal complexes based on flexible bis(benzotriazole) ligands

Three structurally related flexible bis(benzotriazole) ligands, 1,2-bis(benzotriazol-1-yl)ethane (L11), 1,5-bis(benzotriazol-1-yl)-3-oxapentane (L22) and 1,8-bis(benzotriazol-1-yl)-3,6-dioxaoctane (L33), have been synthesized. They were reacted with AgNO3 and CuCl2·2H2O at room temperature, resulting in the formation of six novel complexes: {[AgL11(NO3)(CH3CN)]}n (1), [Ag2(L22)3](NO3)2 (2), {[Ag2(L33)2(NO3)2]}n (3), {[CuL11Cl2]}n (4), [Cu2(L22)2Cl4] (5), and [Cu2(L33)2Cl4(DMF)2] (6). All complexes have been characterized by X-ray diffraction analysis. In 1 and 4, they exhibit similar coordination modes in which each ligand links two metal ions to form a 1D non-linear coordination polymeric chain. In 2, two AgI centers are close coupled by Ag⋯Ag interaction and three bridging ligands to form a dinuclear cation. The structure of 3 reveals the dinuclear cluster units, formed by two ligands and two AgI ions, are linked by anions to self-assemble a 1D chain. Complex 5 is an isolated dinuclear structure, in which ligands and bridging chloro ligands act as the organic clips to bridge two CuII centres. But in 6, a pair of ligands takes on the conformation to connect two metal ions to form bimetallic a macrocyclic architecture. These results unequivocally indicate that the influence of flexible ligand spacers, which bring structural varieties for the same metal ion, is the key factor governing the molecular architectures. Moreover, the thermal stability of 1–3 and 4–6 in the solid state has also been compared.

Use of a Reduced Schiff-Base Ligand to Prepare Novel Chloro-Bridged Chains of Rare Cu(II) Trinuclear Complexes with Mixed Azido/Oxo and Chloro/Oxo Bridges

Two mixed bridged one-dimensional (1D) polynuclear complexes, [Cu(3)L(2)(mu(1,1)-N(3))(2)(mu-Cl)Cl](n) (1) and {[Cu(3)L(2)(mu-Cl)(3)Cl].0.46CH(3)OH}(n) (2), have been synthesized using the tridentate reduced Schiff-base ligand HL (2-[(2-dimethylamino-ethylamino)-methyl]-phenol). The complexes have been characterized by X-ray structural analyses and variable-temperature magnetic susceptibility measurements. In both complexes the basic trinuclear angular units are joined together by weak chloro bridges to form a 1D chain. The trinuclear structure of 1 is composed of two terminal square planar [Cu(L)(mu(1,1)-N(3))] units connected by a central Cu(II) atom through bridging nitrogen atoms of end-on azido ligands and the phenoxo oxygen atom of the tridentate ligand. These four coordinating atoms along with a chloride ion form a distorted trigonal bipyramidal geometry around the central Cu(II). The structure of 2 is similar; the only difference being a Cl bridge replacing the mu(1,1)-N(3) bridge in the trinuclear unit. The magnetic properties of both trinuclear complexes can be very well reproduced with a simple linear symmetrical trimer model (H = -JS(i)S(i+1)) with only one intracluster exchange coupling (J) including a weak intertrimer interaction (j) reproduced with the molecular field approximation. This model provides very satisfactory fits for both complexes in the whole temperature range with the following parameters: g = 2.136(3), J = -93.9(3) cm(-1) and zj = -0.90(3) cm(-1) (z = 2) for 1 and g = 2.073(7), J = -44.9(4) cm(-1) and zJ' = -1.26(6) cm(-1) (z = 2) for 2.