1,4-Di(1,2,3,4-tetrazol-2-yl)butane as a precursor of new 2D and 3D coordination polymers of Cu(II)

A series of new coordination polymers of Cu(II) have been prepared in a reaction between copper(II) perchlorate or tetrafluoroborate salt and a novel ligand 1,4-di(1,2,3,4-tetrazol-2-yl)butane (bbtz). The compounds were characterised by an elemental analysis, TG measurements, IR, EPR and UV-Vis spectroscopy. Crystal structures of bbtz and five complexes of Cu(II) were determined by a single crystal X-ray diffraction measurement performed at 100 K. The composition and architecture of the obtained complexes strongly depend on the reaction conditions especially on the kind of solvent. Investigated complexes are composed of polymeric macrocations and non-coordinated anions. In all cases the bbtz molecules act as the bidentate ligand coordinated to metal(II) ions via N4, N4^′ nitrogen atoms from tetrazole rings. The complexes {[Cu(bbtz)₂(MeOH)₂]X₂}_∞ (X=ClO₄⁻, BF₄⁻) crystallise from methanol as 2D coordination polymers. In these compounds central metal ions are coplanar linked by molecules of bbtz and a coordination sphere is completed by axially coordinated solvent molecules. The complexes {[Cu(bbtz)₃]X₂}_∞ (X=ClO₄⁻, BF₄⁻) were synthesised in EtOH/H₂O solvent system and posses a common network topology. In this group of complexes each central atom is linked by ligand molecules to six other in plane arranged central atoms resulting in 2D networks. Reactions between Cu(II) salts and bbtz performed in absolute ethanol resulted in the formation of the next type of product. In {[Cu(bbtz)₃](ClO₄)₂·2EtOH}_∞ neighboured copper(II) ions are linked by ligand molecules in the three directions what leads to the formation of 3D net. A crystal of this complex is composed of two mutually interpenetrated 3D networks.     

Preparation and properties of mono, homo- and heterobinuclear complexes with a new heptadentate Schiff base ligand

A new heptadentate Schiff base, containing an inner N₃O₂ and an outer O₂O₂ site, has been obtained by the reaction of 3-formylsalicylic acid and diethylenetriamine. By reaction of this ligand with copper(II), nickel(II) or uranyl(VI) salts, mononuclear and dinuclear complexes have been synthesized. The mononuclear complexes can act as ligands towards a second metal ion giving rise to homodinuclear or heterodinuclear complexes. The enlargement of the inner coordination chamber allows the synthesis of dinuclear uranyl(VI) species, impossible to obtain with the inner N₂O₂ site of the ligands previously employed. The equatorial pentacoordination of the UO₂²⁺ group in the outer O₂O₂ chamber is reached with the coordination of a solvent molecule to the central metal ion. The electrochemical behaviour of some complexes prepared is also reported.     

Copper(I) halide complexes from cis-1,2-bis(diphenylphosphino) ethylene and some heterocyclic thiones

Reaction of copper(I) chloride or bromide with equimolar amounts of the diphos ligand cis-1,2-bis(diphenylphosphino)ethylene (dppet) and a heterocyclic thione (L) in acetonitrile/methanol solvent afforded mononuclear complexes of the type [CuX(dppet)(L)] with the diphosphine ligand acting as a chelating ligand. However, the same reaction carried out at higher temperatures proceeds, in some cases, with exclusion of the phosphine ligand from the coordination sphere leading to double-S-bridged dimers. In contrast, copper(I) iodide under the same conditions gave the thione-free dimeric compound [CuI(dppet)]₂ which contains double-bridging iodine atoms. A notable exception was for the reaction with 5-methyl-1,3,4-thiadiazole-2-thione (mtdztH) which, under the same conditions, gave rise to the unexpected, simultaneous formation of the monomer [CuI(dppet)(CH₃CN)] as well as the above mentioned dimeric [CuI(dppet)]₂. Furthermore treatment [CuX(dppet)(L)] with two equivalents of triphenylphosphine was found to cause replacement of the diphos ligand, while substitution of the chlorine atom under HCl elimination and formation of [Cu(dppet)(mftztH)₂] occured in the unique case of treating [CuCl(dppet)(mftztH)] with one additional equivalent of the same thione ligand. The structures of one representative for each of the above mentioned types of complexes, namely [CuBr(dppet)(mftztH)], [Cu(dppet)(mftztH)₂], [Cu(μ-I)(dppet)]₂ · [CuI(dppet)(CH₃CN)] and [CuBr{μ-S(pymtH)}(pymtH)]₂ have been established by single-crystal X-ray diffraction.     

Solution equilibria and structural characterisation of the palladium(II) and mixed metal complexes of peptides containing methionyl residues

Palladium(II) complexes of the peptides GlyMet, GlyMetGly and GlyGlyMet containing methionyl residues were studied by potentiometric and 1H NMR spectroscopic methods. The coordination of terminal amino and deprotonated amide nitrogen and thioether sulfur donor atoms was suggested in the mono complexes of GlyMet and GlyMetGly. The fourth coordination site of these complexes can be occupied by solvent molecule, chloride or hydroxide ions or by another ligand molecule in the bis or mixed ligand complexes. The second ligand coordinates monodentately via the thioether function in acidic media and the amino group under neutral or basic conditions. The stoichiometry of the major species formed in the palladium(II)-GlyGlyMet system is [PdH(-2) L]- and this is coordinated by the amino, two-amide and the thioether donor functions. Thioether bridged mixed metal complexes formed in the reaction of [Pd(dien)]2+ and [Cu(GlyMetH(-1))] or [Ni(GlyMetGlyH(-2))]- also have been detected by spectroscopic techniques.     

Superoxidedismutase-mimetic copper(II) complexes containing saccharinate and 4-aminopyridine/4-cyanopyridine

Two copper(II) complexes, [Cu(sac)₂(4-cypy)₂(H₂O)], 1 and [Cu(sac)₂(4-Ampy)₂(H₂O)], 2 (4-cypy: 4-cyanopyridine; 4-Ampy: 4-aminopyridine) were prepared. Physicochemical properties of the complexes were studied by spectroscopic (solution UV–vis, diffuse reflectance and IR) techniques. Structural X-ray diffraction data could be obtained only for [Cu(sac)₂(4-cypy)₂(H₂O)] that it crystallized in the tetragonal space group P4cc with a=b=15.313(1), c=13.240(1) Å, and Z=4 molecules per unit cell. The complex was cited on a crystallographic C₂-axis with the Cu(II) ion in a square–pyramidal environment, coordinated at the pyramid basis to the nitrogen atom of two saccharine anions [d(Cu–N)=2.011(3) Å] and the pyridine N-atom of two 4-cyanopyridine ligands [d(Cu–N)=2.038(4) Å]. The coordination was completed by a water molecule at the pyramid apex [d(Cu–Ow)=2.189(5) Å]. Elemental and spectroscopic analyses revealed an O-saccharinate coordination mode for complex 2 and a square–pyramidal structure. Only complex 2 retained its structure in methanolic solution. However, both complexes were able to catalyze the dismutation of superoxide anion (O₂^?) (pH 7.5) at micromolar concentrations. Therefore, these complexes behaved as useful SOD-mimetic compounds.     

Conformational flexibility of 2,6-bis(pyrazol-1-ylmethyl)pyridine (L) in [(L)Co(H2O)3]Cl2 and [(L)Ni(H2O)2Cl]Cl·H2O. Molecular structures and non-covalent interactions

Using a non-planar tridentate ligand 2,6-bis(pyrazol-1-ylmethyl)pyridine (L⁵) two new coordination complexes [(L⁵)Co^II(H₂O)₃]Cl₂ (1) and [(L⁵)Ni^II(H₂O)₂Cl]Cl·H₂O (2) have been synthesized and structurally characterized. Complex 1 has N₃O₃ distorted octahedral environment around Co^II with coordination by L⁵ (two pyrazole and a pyridine nitrogen in a facial mode) and three water molecules. Complex 2 has N₃O₂Cl distorted octahedral geometry around Ni^II with meridional L⁵ coordination, two water molecules, and a Cl⁻ ion. Analysis of the crystal packing diagram reveals the involvement of solvent (water as metal-coordinated and as solvent of crystallization) and counteranion (Cl⁻) to play significant roles in generating 1D chains, involving O-H···Cl, and O-H···O interactions.     

Formation of coordination polymer and molecular complex of 4,4′-bipyridyl-N,N′-dioxide of manganese and zinc

A 1D-coordination polymer [{Mn₃(C₆H₅COO)₆(BPNO)₂(MeOH)₂}(MeOH)₂]_n (1) having benzoate as the anionic ligand and 4,4′-bipyridyl-N,N′-dioxide (BPNO) as bridging ligand is synthesized by reacting benzoic acid with manganese(II) acetate tetrahydrate followed by reaction with 4,4′-bipyridyl-N N′-dioxide. The bridging bidentate BPNO ligands in this coordination polymer along with the benzoate bridges hold the repeated units. The chain like structure in one dimension by benzoate bridges are connected to each other through the μ³-η²:η¹ bridges of BPNO ligands. This coordination polymer can be transformed to a molecular complex [Mn(H₂O)₆](C₆H₅COO)_2.4BPNO (2). In this complex the BPNO remains outside the coordination sphere but they are hydrogen bonded to water molecules to form self assembled structure. The reaction of 3,5-pyrazoledicarboxylic acid (L₁H2) and BPNO with manganese(II) acetate or zinc(II) acetate led to molecular complexes with composition [M₂(L₁)₂(H₂O)₆].BPNO·xH₂O {where M = Mn(II) (3), Zn(II)(4)}. These molecular complexes of BPNO are characterised by X-ray crystallography. The complexes 3-4 are binuclear carboxylate complexes having M₂O₂ core formed from carboxylate ligands with two metal ions.     

Succinate bridged dimeric Cu(II) system containing sandwiched non-coordinating succinate dianion: Crystal structure, spectroscopic and thermal studies of [(phen)2Cu(μ-L)Cu(phen)2]L · 12.5H2O (H2L = succinic acid; phen = 1,10-phenanthroline)

A mixed ligand and dimeric Cu^II complex [(phen)₂Cu(μ-L)Cu(phen)₂]L · 12.5H₂O (H₂L = succinic acid) containing bridging succinate moiety and also non-coordinated succinate dianion was prepared from polymeric Cu(II) succinate by nucleophilic reaction with o-phenanthroline (phen) followed by depolymerization. The dimeric product was characterized by crystallographic, spectroscopic and thermoanalytical studies. The complex crystallizes in triclinic crystal system and is composed of succinate bridged [(phen)₂Cu(μ-L)Cu(phen)₂]²⁺ complex cations, non-coordinated succinate anions and hydrogen bonded water molecules. Within the dimeric cationic unit, each of the Cu atoms is octahedrally coordinated by four N atoms of both phen ligands and both O atoms of a carboxylate moiety of the bridging succinate group in chelating form. Through intermolecular π-π stacking interactions, the complex cations form positively charged 2-D layers, between which the non-coordinating succinate anions and water molecules are sandwiched. Both the electronic and EPR studies indicate that the dimeric complex undergoes partial dissociation in solution state to exist in two structural forms. The kinetic and thermodynamic parameters involved in three stage thermal decompositions of the dimeric complex could also be evaluated using Coats-Redfern method.     

Synthesis and kinetic studies of new bipyridyl platinum(II) phenoxide complexes by phase transfer catalysis: Crystal structure of [(bipy)Pt(OC6H4-4-OMe)2]

The synthesis of new platinum bipy (bipy = 2,2′-bipyridyl) complexes containing phenoxide ligands is reported, together with kinetic studies of their oxidative addition reactions with MeI to produce phenoxo platinum(IV) complexes. Complexes of the form [(bipy)Pt(OC₆H₄-4-X)₂] (X = OCH₃, CH₃, H, Br, Cl) are prepared by the reaction of the chloro complex [(bipy)PtCl₂] with substituted phenols and KOH in a two phase system of water and chloroform in the presence of benzyl triphenylphosphonium chloride. Platinum(IV) complexes are formed by oxidative addition of MeI to the platinum(II) complexes obtained. The complexes are characterized by elemental analysis, UV-Vis, IR, mass spectrometry and ¹H and ¹³C NMR spectroscopy.The reaction of methyl iodide with [(bipy)Pt(OC₆H₄-4-OMe)₂] to give [(bipy)PtMe(I)(OC₆H₄-4-OMe)₂] follows the rate law rate = k₂[(bipy)Pt(OC₆H₄-4-OMe)₂][MeI]. The values of k₂ increase with increasing polarity of the solvent, suggesting a polar transition state for the reaction.     

Synthesis and characterization of 2-quinoxalinol Schiff-base metal complexes

The reaction of uranyl acetate with (2,2′-(1E,1′E)-(2-benzyl-3-hydroxyquinoxaline-6,7-diyl)bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene) diphenol) (H₂L1) at room temperature in methanol and chloroform yields the UO₂L1 complex. Crystals were grown through solvent diffusion of the ligand-metal complex in dimethyl formamide with diethyl ether to prepare: UO₂L1 · DMF (1). Complexes with 2,2′-(1E,1′E)-(2-benzyl-3-hydroxyquinoxaline-6,7-diyl)bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)dibenzene-1,4-diol (H₂L2) and 2,2′-(1E,1′E)-(2-hydroxy-3-isopropylquinoxaline-6,7-diyl)bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)diphenol (H₂L3) were also prepared, and crystals of the uranyl complexes (UO₂L2 · DMF (2) and (3)) grown from DMF/ether. A fourth complex UO₂L4 · H₂O (4) was prepared through layering a solution of the tetra-tert-butyl substituted 2-quinoxalinol salen ligand H₂L4 in acetone with an aqueous solution containing uranyl acetate. The complexes exhibit a symmetric core featuring a slightly distorted bicapped pentagonal geometry around the uranium center with two oxo-groups and two imine groups from the ligand chelating the ligand and the fifth site in the coordination plane of the ligand occupied by a solvent molecule. These compounds have been characterized using solution (NMR and UV-Vis) and solid-state (IR, X-ray crystallography) techniques. Complexes of H₂L4 with early transition metals; Mn²⁺, Co²⁺, Ni²⁺, and Cu²⁺ are also prepared and characterized for comparison of solution and spectroscopic characteristics.     

Diphosphines as bridging ligands in polymeric and dimeric thione-S-ligated Ag(I) nitrate complexes

Reactions of silver(I) nitrate with equimolar amounts of the diphos ligands 1,4-bis(diphenylphosphino)butane (dppb) or 1,2-bis(diphenylphosphino)ethane (dppe) and some heterocyclic thiones (L) in acetonitrile/methanol solvent afforded mixed-ligand complexes, the nature of which was found to be strongly influenced by the backbone length of the diphosphine ligand. The longer chained diphos ligand formed a series of dinuclear complexes of the type [Ag(dppb)(L)]₂(NO₃)₂ with both the diphosphine and thione ligands acting as bridging ligands between the two four-coordinate pseudo-tetrahedrally coordinated metal centers. In the unique case of L=4-methyl-5-trifluoromethyl-4H-1,2,4-triazoline-3(2H)-thione (mftztH), the reaction proceeded under exclusion of the thione ligand from the coordination sphere and coordination of the nitrate anions instead, leading to the diphosphine-doubly bridged dimeric compound [Ag(dppb)(NO₃)]₂. On the other hand, the complexes produced when using the short bite 1,2-bis(diphenylphosphino)ethane (dppe) turned out to be diphosphine-bridged cationic polymers of the type [Ag(dppe)(L)₂]_n(NO₃)_n. The structures of one representative for each of the two aforementioned series of complex compounds, namely [Ag(dppb)(py2SH)]₂(NO₃)₂ · 2H₂O and [Ag(dppe)(pymtH)₂]_n(NO₃)_n, have been established by single-crystal X-ray diffraction.     

Reversible photochromism of novel silver(I) coordination complexes with 1,2-bis(2′-methyl-5′-(2″-pyridyl)-3′-thienyl)perfluorocyclopentene in crystalline phase

Three novel silver(I) complexes with 1,2-bis(2-methyl-5′-(2″-pyridyl)-3′-thienyl)perfluorocyclopentene (BM-2-PTP) were synthesized by the reaction of Ag(CF₃SO₃) or Ag(CF₃COO) with BM-2-PTP in benzene at different temperatures. The structures of these metal complexes were revealed by X-ray crystallographic analyses and the correlation between crystal structures and photochromic performance was discussed. In complexes 1 and 2, silver(I) is three-coordinated to two nitrogens from distinct ligand molecules as well as one oxygen from anions to form a 1-D polymeric structure. On the other hand, complex 3 contains two crystallographic independent Ag(I) with different coordination environments, and the adjacent BM-2-PTP molecules are connected by Ag-CF₃CO₂-Ag chains to afford a 1-D double chain structure. The difference in structures of three complexes shows the interesting anionic effect on coordination and the subtleness of crystal engineering. It is noted that complex 3 underwent reversible photochromic reaction in crystalline state despite the unfavorable framework to the rotation of thiophene groups.     

Effect of metal coordination and intra-molecular H-bond on the acidity of phenolic proton in a set of structurally characterized octahedral Ni(II) complexes of l-histidine derivative

Four different mononuclear octahedral Ni(II) complexes with protonated and deprotonated form of the same ligand have been synthesized by controlling reaction conditions and structurally characterized. The complexes are [Ni(HL^l-his)(benzoate)(MeOH)] (1), [Ni(HL^l-his)(SCN)(MeOH)] (2), [Ni(HL^l-his)₂] (3) and [Ni(L^l-his)(imidazole)₂] (4) where H₂L^l-his is (S)-2-(2-hydroxybenzylamino)-3-(1H-imidazol-4-yl)-propionic acid. The ligand behaves as a monobasic tetradentate ligand in 1 and 2, monobasic tridentate ligand in 3 and dibasic tetradentate ligand in 4. Ni(II) coordinated phenolic proton of the ligand in the complexes 1-2 shows strong intra-molecular H-bonding with benzoate in 1 and lattice water in 2, whereas 3 shows intermolecular H-bonding between uncoordinated phenols with neighbouring carboxylate. The pH titration of the complexes revealed that metal coordination and H-bond in complexes 1 and 2 considerably lowers the acidity of ligand phenol (pK_a 6.8 and 7.0 respectively) compared to phenol (pK_a 10). The complex 4 does not show any proton loss due to the absence of phenolic proton. All the complexes show extensive H-bonded network in the crystals including narrow (7.8 × 5.2 Å) water filled one dimensional channel in 2.     

Effects of a derivative thiazoline/thiazolidine azine ligand and its cadmium complexes on phagocytic activity by human neutrophils

The complexes [CdCl₂(ATHTd)] (1) and [Cd(NO₃)₂(ATHTd)(H₂O)] (2) [ATHTd = N-(2-acetyl-2-thiazoline)-N′-(2-thiazolidin-2-one) azine] have been synthesized and characterized by a variety of physico-chemical techniques. X-ray data indicate that in 1 the coordination geometry around the metal ion can be considered a distorted square pyramid with cadmium(II) cation coordinated to one tridentate ATHTd ligand and two chloride ligands. In the case of 2, the coordination environment around Cd(II) atom approximates to a distorted pentagonal bipyramid with the cadmium atom bonded to one tridentate ATHTd ligand, one water molecule, one monodentate nitrate ligand and one bidentate nitrate ligand. The structure of ATHTd in the complexes presents an amino-2-thiazoline form instead of the iminothiazolidine one observed in free ATHTd. Likewise, the degree of rotation of the thiazoline rings around the C(1)-C(4) and C(6)-N(3) bonds has changed in complexes, which permit the coordination through thiazolinic nitrogen atoms. Besides, we study the phagocytic function in human neutrophils treated with ligand ATHTd, CdCl₂, Cd(NO₃)₂ and complexes 1 and 2. From the obtained results it can be concluded that the complexes 1 and 2 increase the phagocytic capacity of neutrophils with respect to Cd(II) salts and ATHTd.     

Synthesis and characterization of an N-coordinated amidate copper(II) complex of deprotonated N-(2,6-diisopropylphenyl)-2-(bis-(2-pyridylmethyl))aminoethanamide

The title ligand, N-(2,6-diisopropylphenyl)-2-(bis-(2-pyridylmethyl))aminoethanamide (DIPMAE-H), was prepared by a nucleophilic substitution reaction between N-(2,6-diisopropyl)phenyl-2-bromoethanamide and bis-(2-pyridylmethyl)amine. An analogous ligand (TBPMAE-H) in which the 2,6-diisopropylphenyl group was substituted for a tert-butyl group was also prepared in this manner. Then, [(DIPMAE-H)CuBr]⁺Br⁻ and [(TBPMAE-H)CuBr]⁺Br⁻ were prepared by heating one equivalent of ligand and CuBr₂ in CH₃CN. In both compounds the geometry about the copper center is square pyramidal with distortions due to the geometrical constraints of the ligand. The amide oxygen occupies the axial position, and the three amine nitrogens and the bromide ligand form the basal plane of the square pyramid. Pairs of complexes in the unit cell are associated via weak donation of a lone pair on the bromide ligand of one complex to the copper center of another (Cu?Br distances in the range of 3.3576-3.4022 Å).The title compound, (DIPMAE)CuBr, was prepared by deprotonation of [(DIPMAE-H)CuBr]⁺Br⁻ using NaH. The key feature of (DIPMAE)CuBr is the amidate group η¹- and N-coordinated to the copper center. The compound also exhibits distorted trigonal bipyramidal coordination geometry with the bromide and tertiary amine donors occupying the axial sites and the amidate and pyridyl donors occupying the equatorial positions. The copper atom is displaced from the trigonal plane towards the bromide donor apex due to the geometrical demands of the ligand.     

New acyclic and cyclie Schiff bases derived from 2,6-diformyl-4-chlorophenol and their interaction with uranyl(Vl), copper(II) and nickel(Il) ions

A new heptadentate compartmental ligand has been synthesized by condensation of 3-formylsalicylic acid and 1,5-diamino-3-thiapentane in methanol (H₄L_a). This Schiff base contains an inner N₂SO₂ and an outer O₂O₂ site and gives, by reaction with copper(II), nickel(II) and uranyl(VI) diacetate, mononuclear, homo- and heterobinuclear complexes. In the mononuclear copper and nickel complexes, the metal ion is in the inner N₂SO₂ site, while it is in the outer O₂O₂ for uranyl; a solvent molecule fills the fifth equatorial coordination position in this last complex. The physico-chemical properties of the compounds are discusscd on the basis of infrared, electronic and magnetic data and by comparison with the analogous complexes with the ligand obtained by reaction of 3- formylsalicylic acid and diethylenetriamine (H₄L_b). The mononuclear copper and the heterodinuclear copper-uranyl complexes show anomalously low magnetic moments.     

Reversed micelles to mimic the active site of metalloenzymes

The structure and reactivity of cobalt(II), nickel(II), and copper(II) halides have been investigated in 0.20 M CTAX (X = Cl, Br) |CHCl₃ reversed micelles. The former two metal ions adopt a tetrahedral configuration at low water concentrations in the micelle. The tetrahedral complexes are converted to octahedral aqua complexes by increasing the water concentration (solvochromism) or by lowering the temperature (thermochromism). Upon reaction with imidazole, the tetrahedral cobalt and nickel halide complexes also undergo a structural transformation into an octahedral configuration with imidazole coordination. At low water concentrations, copper halides form a polynuclear complex bridged by halide ions and these halogen bridges are easily broken upon addition of water or imidazole. The copper complexes produced by reaction with imidazole were deduced to be CuIm₂X₂ and CuIm₄X₂ at intermediate and high ligand concentrations, respectively. It was also found that the cupric ion in reversed micelles is readily reduced to the cuprous ion with 2-mercaptoethanol, and the cuprous ion is oxidized to the cupric ion by reaction with hydrogen peroxide.     

Reaction of methanol ligated manganese(II) silanethiolate with pyridine related ligands - Different structures of complexes with MnNO2S2 kernel

The reaction of [Mn{SSi(OBu^t)₃}₂(MeOH)₄] with pyridine and its three monosubstituted methyl derivatives leads to the formation of two distinct types of complexes, although both with the MnO₂NS₂ kernel. The first two compounds (with pyridine or 2-picoline) contain two silanethiolate ligands, heterocyclic base and two methanol molecules. In the second case (3- and 4-picoline) the role of O-donor and simultaneously S-donor ligand is fulfilled by tri-tert-butoxysilanethiolate rest which under favorable conditions can serve as a chelating agent.     

Uranyl(VI), copper(II) and nickel(II) complexes derived from a new compartmental ligand

A new heptadentate compartmental ligand has been synthesized by condensation of 3-formylsalicylic acid and 1,5-diamino-3-thiapentane in methanol (H₄L_a). This Schiff base contains an inner N₂SO₂ and an outer O₂O₂ site and gives, by reaction with copper(II), nickel(II) and uranyl(VI) diacetate, mononuclear, homo- and heterobinuclear complexes. In the mononuclear copper and nickel complexes, the metal ion is in the inner N₂SO₂ site, while it is in the outer O₂O₂ for uranyl; a solvent molecule fills the fifth equatorial coordination position in this last complex. The physico-chemical properties of the compounds are discusscd on the basis of infrared, electronic and magnetic data and by comparison with the analogous complexes with the ligand obtained by reaction of 3- formylsalicylic acid and diethylenetriamine (H₄L_b). The mononuclear copper and the heterodinuclear copper-uranyl complexes show anomalously low magnetic moments.     

Syntheses,structures and properties of three novel coordination polymers with a flexible asymmetrical bridging ligand

Three novel coordination polymers with different structural motifs, [Ag(pmtmb)]_n (1), [Cd(pmtmb)₂(H₂O)]_n (2) and [Cu(pmtmb)₂]_n (3), have been synthesized with a flexible asymmetrical bridging ligand, 4-(2-pyrimidylthiomethyl)benzoic acid (Hpmtmb). X-ray diffraction analyses show that 1 is a 2D layer containing unusual zigzag Ag chains based on mixed ligand-supported and ligand-unsupported Ag–Ag interactions, 2 is a necklace structure that further linked through hydrogen bonding to form a 2D sheet, and 3 is a 3D compact framework full assembled from 1D centipede-like chains via π–π stacking interactions. Interestingly, the ligand pmtmb adopts different configurations and coordination modes in the solid structures of these complexes. Furthermore, three complexes exhibit remarkable thermal stability and the complexes 1 and 2 exhibit intense green and purple luminescence, respectively.