Hydrothermal synthesis, crystal structures and properties of new Fe, Co, Ni, and Zn complexes with 6-quinolinecarboxylate: Interplay of coordinative and noncovalent interactions

Reactions of Fe^II, Co^II, Ni^II, and Zn^II salts with 6-quinolinecarboxylic acid (HL) under the hydrothermal conditions afford three monomeric complexes [M(L)₂(H₂O)₄] (M = Fe^II for 1, Co^II for 2, and Ni^II for 3) and a 1-D polymeric species {[Zn(L)₂(H₂O)] · H₂O}_n (4). The crystal structures of the ligand HL and these four complexes have been determined by using the X-ray single-crystal diffraction technique. The results suggest that complexes 1-3 are isostructural, displaying novel 3-D pillar-layered networks through multiple intermolecular hydrogen bonds, whereas in coordination polymer 4, the 1-D comb-like coordination chains are extended to generate a hydrogen-bonded layer, which is further reinforced via aromatic stacking interactions. Solid-state properties such as thermal stability and fluorescence emission of the polymeric Zn^II complex 4 have also been investigated.     

Syntheses, crystal structures and magnetic properties of trinuclear and [3 × 1 + 1 × 2] pentanuclear complexes derived from a compartmental ligand: Role of solvent on nuclearity and number of components

Reaction of [Cu^IIL⊂(H₂O)] (H₂L = N,N′-ethylenebis(3-ethoxysalicylaldimine)) with nickel(II) perchlorate in 1:1 ratio in acetone produces the trinuclear compound [(Cu^IIL)₂Ni^II(H₂O)₂](ClO₄)₂ (1). On the other hand, on changing the solvent from acetone to methanol, reaction of the same reactants in same ratio produces the pentametallic compound [(Cu^IIL)₂Ni^II(H₂O)₂](ClO₄)₂·2[Cu^IIL⊂(H₂O)]·2MeOH (2A), which loses solvated methanol molecules immediately after its isolation to form [(Cu^IIL)₂Ni^II(H₂O)₂](ClO₄)₂·2[Cu^IIL⊂(H₂O)] (2B). Clearly, formation of 1 versus 2A and 2B is solvent dependent. Crystal structures of 1 and 2A have been determined. Interestingly, compound 2A is a [3 × 1 + 1 × 2] cocrystal. The cryomagnetic profiles of 1 and 2B indicate that the two pairs of copper(II)···nickel(II) ions in the trinuclear cores in both the complexes are coupled by almost identical moderate antiferromagnetic interaction (J = −22.8 cm⁻¹ for 1 and −26.0 cm⁻¹ for 2B).     

Metal-regulated assemblies of Cu, Ni, and Zn complexes with isoquinoline-3-carboxylate displaying diverse supramolecular networks

Three distinct coordination complexes, viz. {[Cu(μ-L)₂] · (H₂O)₄}_n (1), [Ni(L)₂(CH₃OH)₂] (2), and [Zn(L)₂(H₂O)₂] · (H₂O)₂ (3), have been prepared by the reactions of metal nitrates with isoquinoline-3-carboxylic acid (HL). X-ray single-crystal diffraction suggests that 1 is a 1D chain coordination polymer in which the Cu^II ions are connected by carboxylates, whereas complexes 2 and 3 represent discrete mononuclear species. In all the cases, the coordination entities are further organized via hydrogen-bonding interactions to generate multifarious supramolecular networks. Remarkably, a well-resolved 1D water morphology is observed for the first time in the crystalline lattice of 1 along [1 0 0], which consists of edge-sharing tetrameric subunits and stabilized by the metal-organic host surroundings.     

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.     

Oxime-functionalized diazamesocyclic derivates and their metal complexes: Effect of the ligand backbones and anions on the generation of novel monomeric and mono-μ-Cl dimeric Cu complexes

Two oxime-functionalized diazamesocyclic derivates, namely, N,N′-bis(acetophenoneoxime)-1,4-diazacycloheptane (H₂L¹) and N,N′-bis(acetophenonoxime)-1,5-diazacyclooctane (H₂L²), have been prepared and characterized. Both ligands (obtained in the hydrochloride form) can form stable metal complexes with Cu^II and Ni^II salts, the crystal structures of which were determined by X-ray diffraction technique. The reactions of H₂L¹ with Cu(ClO₄)₂ and Ni(ClO₄)₂ afford a penta-coordinated mononuclear complex [Cu(H₂L¹)Cl] · ClO₄ (1) and a four-coordinated monomeric [Ni(HL¹)] · ClO₄ (2), in which the ligand is monodeprotonated. The ligand H₂L² also forms a quite similar mononuclear [Ni(HL²)] · ClO₄ complex with Ni(ClO₄)₂, according to our previous work. However, reactions of different Cu^II salts [Cu(ClO₄)₂, CuCl₂ and Cu(NO₃)₂ for 3, and CuSO₄ for 4] with H₂L² in the presence of NaClO₄ yield two unusual mono-μ-Cl dinuclear Cu^II complexes [Cu₂(HL²)₂Cl] · (ClO₄) (3), and [Cu₂(H₂L²)(HL²)Cl] · (ClO₄)₂ · (H₂O)(4). These results indicate that the resultant Cu^II complexes (1, 3 and 4) are sensitive to the backbones of diazamesocycles and even auxiliary anions.     

Construction of a series of 0D, 2D and 3D inorganic-organic hybrid coordination polymers based on octamolybdate and 2-(2-pyridyl)imidazole and its derivative

Four octamolybdate-based compounds, that is, Cu^II₂(L¹)₄(Mo₈O₂₆) (1), Cu^II₂(HL²)₄(Mo₈O₂₆)₂ (2), [Cu^IIL²(H₂O)(Mo₈O₂₆)_0.5]·2H₂O (3) and [Cu^IIL²(H₂O)(Mo₈O₂₆)_0.5]·2H₂O (4) (L¹ = 2-(2-pyridyl)imidazole, L² = 2-(1-(pyridine-3-ylmethyl)-1H-imidazol-2-yl)pyridine), have been hydrothermally synthesized via changing the reaction conditions and structurally characterized by single-crystal X-ray diffraction. With L¹ ligand, we obtained compound 1, which is a 0D molecule and extends to a 3D supramolecular structure via hydrogen-bonding interactions. By using L² instead of L¹ ligand, compound 2 comes into being which is as well a discrete molecule and further extended to a 3D supramolecular structure by hydrogen bonds. Intriguingly, compounds 3 and 4 are supramolecular isomers: the former is a 2D 4-connected network and the latter is a 3D (3,4)-connected framework. The measurements of diffuse reflectance for compounds 1-4 indicate that they are potential wide gap semiconductors.     

Syntheses, structures and magnetic properties of tetranuclear and trinuclear nickel(II) complexes with β-diketone-functionalized pyridinecarboxylate ligand

The new β-diketone-functionalized pyridinecarboxylate ligand 2-(3-oxo-3-phenyl-propionyl)-6-pyridinecarboxylic acid (H₂L) has been synthesized and fully characterized. Its tetranuclear and trinuclear nickel(II) coordination compounds [Ni₄L₄(DMF)(H₂O)₃]·2.5DMF·3H₂O (1) and [Ni₃L₂(OAc)₂(DMF)₂ (H₂O)₂]·DMF·H₂O (2) have also been synthesized and characterized by single crystal X-ray diffraction. Compound 1 has a [2 × 2] molecular grid structure and 2 is a trinuclear structure. The magnetic properties study of 1 and 2 revealed the intramolecular antiferromagnetic exchange coupling between the Ni(II) ions exists.     

Making 3d-4f hexanuclear clusters from heterotrinuclear cationic building blocks

The syntheses and crystal structures of two new hexanuclear complexes are reported: [{(LCu^II(ONO₂))(LCu^II(H₂O))Nd^III}₂(μ-C₂O₄)](NO₃)₂ · 6H₂O (1) and [{(LNi^II(H₂O))(N(CN)₂)}₂Pr^III}₂(ONO₂)](OH) · 2H₂O · 3CH₃CN (2) (L is the dianion of the Schiff-base resulted from the 2:1 condensation of 3-methoxysalyciladehyde with 1,3-propanediamine). Compounds 1 and 2 were obtained by connecting heterotrinuclear cationic complexes [{LM^II}₂Ln^III]³⁺ with oxalato or nitrato linkers. The structure of the complex cation in 1 shows two almost linear trinuclear [Cu₂Nd] moieties which are linked by a bis-chelating oxalato bridge between the neodymium ions. The hexanuclear cationic moiety in 2 is built up of two heterotrinuclear [Ni₂Pr] units that are linked by a nitrato group bridging two praseodymium(III) ions. The spectroscopic (FTIR, UV-Vis) and magnetic properties of 1 and 2 have been investigated.     

Coordination polymers of manganese(II) and cobalt(II) of a flexible tetradentate pyridine amide ligand: 1D zigzag network and non-covalent interactions

Synthesis and crystal structure of two coordination polymers of composition [Mn^II(H₂bpbn)_1.5][ClO₄]₂ · 2MeOH · 2H₂O (1) and [Co^II(H₂bpbn)(H₂O)₂]Cl₂ · H₂O (2) [H₂bpbn = N,N′-bis(2-pyridinecarboxamido)-1,4-butane], formed from the reaction between [Mn(H₂O)₆][ClO₄]₂/CoCl₂ · 4H₂O with H₂bpbn in MeCN, are described. In 1 each Mn^II ion is surrounded by three pyridine amide units, providing three pyridine nitrogen and three amide oxygen donors. Each Mn^II center in 1 has distorted MnN₃O₃ coordination. In 2 each Co^II ion is coordinated by two pyridine amide moieties in the equatorial plane and two water molecules provide coordination in the axial positions. Thus, the metal center in 2 has trans-octahedral geometry. In both 1 and 2, the existence of 1D zigzag network structure has been revealed. Owing to π-π stacking of pyridine rings from adjacent layers 1 forms 2D network; 2 forms 2D and 3D network assemblies via N-H?Cl and O-H?Cl secondary interactions. Both the metal centers are high-spin.     

3D hydrogen bonded heteronuclear Co, Ni, Cu and Zn aqua complexes derived from dipicolinic acid

The heteronuclear water-soluble and air-stable compounds [M(H₂O)₅M′(dipic)₂] · mH₂O (M/M′ = Cu^II/Co^II (1), Cu^II/Ni^II (2), Cu^II/Zn^II (3), Zn^II/Co^II (4), Ni^II/Co^II (5), m = 2-3; H₂dipic = dipicolinic acid) have been prepared by self-assembly synthesis in aqueous solution at room temperature, and characterized by IR, UV-Vis and atomic absorption spectroscopies, elemental and X-ray diffraction single crystal (for 1 and 2) analyses. 1-5 represent the first examples of heteronuclear dipicolinate compounds with 3d metals. Extensive H-bonding interactions involving all aqua ligands, dipicolinate oxygens and lattice water molecules further stabilize the dimetallic units by linking them to form three-dimensional polymeric networks.     

Bioinspired FeIIICdII and FeIIIHgII complexes: synthesis, characterization and promiscuous catalytic activity evaluation

In this work we report on the synthesis, crystal structure, and physicochemical characterization of the novel dinuclear [Fe^IIICd^II(L)(μ-OAc)₂]ClO₄·0.5H₂O (1) complex containing the unsymmetrical ligand H₂L = 2-bis[{(2-pyridyl-methyl)-aminomethyl}-6-{(2-hydroxy-benzyl)-(2-pyridyl-methyl)}-aminomethyl]-4-methylphenol. Also, with this ligand, the tetranuclear [Fe₂^IIIHg₂^II(L)₂(OH)₂](ClO₄)₂·2CH₃OH (2) and [Fe^IIIHg^II(L)(μ-CO₃)Fe^IIIHg^II(L)](ClO₄)₂·H₂O (3) complexes were synthesized and fully characterized. It is demonstrated that the precursor [Fe^III₂Hg^II₂(L)₂(OH)₂](ClO₄)₂·2CH₃OH (2) can be converted to (3) by the fixation of atmospheric CO₂ since the crystal structure of the tetranuclear organometallic complex [Fe^IIIHg^II(L)(μ-CO₃)Fe^IIIHg^II(L)](ClO₄)₂·H₂O (3) with an unprecedented {Fe^III(μ-O_phenoxo)₂(μ-CO₃)Fe^III} core was obtained through X-ray crystallography. In the reaction 2 → 3 a nucleophilic attack of a Fe^III-bound hydroxo group on the CO₂ molecule is proposed. In addition, it is also demonstrated that complex (3) can regenerate complex (2) in aqueous/MeOH/NaOH solution. Magnetochemical studies reveal that the Fe^III centers in 3 are antiferromagnetically coupled (J = − 7.2 cm^− 1) and that the Fe^III-OR-Fe^III angle has no noticeable influence in the exchange coupling. Phosphatase-like activity studies in the hydrolysis of the model substrate bis(2,4-dinitrophenyl) phosphate (2,4-bdnpp) by 1 and 2 show Michaelis-Menten behavior with 1 being ~ 2.5 times more active than 2. In combination with k_H/k_D isotope effects, the kinetic studies suggest a mechanism in which a terminal Fe^III-bound hydroxide is the hydrolysis-initiating nucleophilic catalyst for 1 and 2. Based on the crystal structures of 1 and 3, it is assumed that the relatively long Fe^III…Hg^II distance could be responsible for the lower catalytic effectiveness of 2.     

Novel Cu, Co and Pb supramolecular networks of pyridine-2,6-dicarboxylate (pydc) in cooperation with a bent dipyridyl spacer via coordinative, hydrogen-bonding and aromatic stacking interactions

Reaction of M(OAc)₂ (M^II = Cu^II for 1, Co^II for 2, and Pb^II for 3) with pyridine-2,6-dicarboxylic acid (H₂pydc) in presence of a dipyridyl spacer 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (bpo) affords three novel metal-organic supramolecular networks [Cu₂(bpo)(pydc)₂(H₂O)₃] · 2.75H₂O(1), [Co(bpo)(pydc)(H₂O)₂] · (H₂O) (2) and [Pb(pydc)]_n (3), which have been structurally determined by single-crystal X-ray diffraction. The dimeric Cu-pydc coordination framework bridged by a bpo spacer in 1 is hydrogen-bonded to four others to result in a two-dimensional (2-D) sheet array. The neutral monomeric molecules in 2 have an ordered 3-D stacking stabilized via hydrogen bonds and significant π-π interactions in the lattice, possessing large porous channels with the inclusion of guest solvates. In coordination polymer 3, the Pb^II ion takes the unusual distorted capped trigonal prismatic geometry (PbNO₆) and each pydc dianion binds to four Pb^II centres to form a 2-D infinite network. The thermal stabilities of these complexes have also been investigated.     

Two forms of a copper(II) complex of 3-phenyl-5-(2-pyridyl)-4-(4-pyridyl)-4H-1,2,4-triazole: a six-coordinate monomer versus a five-coordinate polymer

The reaction of the new bidirectional ligand 3-phenyl-5-(2-pyridyl)-4-(4-pyridyl)-4H-1,2,4-triazole (pyppt) with Cu(ClO₄)₂ · 6H₂O in a 2:1 molar ratio in EtOH affords the complex [Cu^II(pyppt)₂(ClO₄)₂] · H₂O (1) as a microcrystalline turquoise solid. Recrystallisation of complex 1 from MeCN by vapour diffusion of Et₂O gives blue crystals of the monomeric octahedral complex [Cu^II(pyppt)₂(ClO₄)₂] · MeCN (2). In contrast, addition of EtOH to a solution of complex 1 in MeCN followed by slow evaporation yields blue crystals of the five-coordinate polymeric complex {[Cu^II(pyppt)₂](ClO₄)₂ · EtOH}_∞ (3). The structures of both complexes have been determined by single crystal X-ray diffraction.     

Three new multidimensional organic-inorganic hybrids based on polyoxometalates and copper coordination polymers with 4,4′-bipyridine ligands

Three new organic-inorganic hybrid materials with 4,4′-bipy ligands and copper cations as linkers, [Cu^II(H₂O)(4,4′-bipy)₂][Cu^II(H₂O)(4,4′-bpy)₂]₂H[Cu^IIP₈Mo₁₂O₆₂H₁₂] · 5H₂O (1), [Cu^I(4,4′-bipy)][Cu^II(4,4′-bipy)]₂ (BW₁₂O₄₀) · (4,4′-bipy) · 2H₂O (2) and [Cu^I (4,4′-bipy)]₃ (PMo₁₂O₄₀) · (pip) · 2H₂O (3) (pip = piperazine; 4,4′-bipy = 4,4′-bipyridine), have been hydrothermally synthesized. The single X-ray structural analysis reveals that the structure of 1 is constructed from [Cu(H₂O)(4,4′-bipy)₂] complexes into a novel, three-dimensional supermolecular network with 1-D channels in which Cu[P₄Mo₆]₂ dimer clusters reside. To the best of our knowledge, compound 1 is the first complex in which the [P₄Mo₆] clusters have been used as a non-coordinating anionic template for the construction of a novel, three-dimensional supermolecular network. Compound 2 is constructed from the six-supported [BW₁₂O₄₀]⁵⁻ polyoxoanions and [Cu^I(4,4′-bipy)] and [Cu^II(4,4′-bipy)] groups into a novel, 3-D network. Compound 3 exhibits unusual 3-D supramolecular frameworks, which are constructed from tetrasupporting [PMo₁₂O₄₀]³⁻ clusters and [Cu^I (4,4′-bipy)_n] coordination polymer chains. The electrochemical properties of 2 and 3 have been investigated in detail.     

Synthesis and characterization of cobalt(II)-salicylate complexes derived from N4-donor ligands: Stabilization of a hexameric water cluster in the lattice host of a cobalt(III)-salicylate complex

The syntheses and structural characterization of four cobalt(II)-salicylate complexes, [(TPA)Co^II(HSA)](ClO₄) (1), [(isoBPMEN)Co^II(HSA)](BPh₄) (2), [(TPzA)Co^II(HSA)](ClO₄) (3) and [(6Me₃TPA)Co^II(HSA)](BPh₄) (4) [TPA = tris(2-pyridylmethyl)amine, isoBPMEN = N¹,N¹-dimethyl-N²,N²-bis(2-pyridylmethyl)ethane-1,2-diamine, TPzA = tris((3,5-dimethyl-1H-pyrazole-1-yl)methyl)amine and 6Me₃TPA = tris(6-methyl-2-pyridylmethyl)amine] are described. While 2, 3 and 4 are unreactive towards dioxygen, 1 reacts slowly with molecular oxygen to a cobalt(III)-salicylate complex, [(TPA)Co^III(SA)](ClO₄) (1a). Two different crystalline forms, 1a and 1a·4H₂O were isolated depending upon the condition of oxidation and crystallization. The solid-state structures of cobalt(III)-salicylate unit in both 1a and 1a·4H₂O show a six-coordinate distorted octahedral coordination geometry at the cobalt(III) center ligated by the tetradentate ligand (TPA) where the dianionic salicylate (SA) binds in a bidentate fashion through one carboxylate and one phenolate oxygen. The hydrated form 1a·4H₂O reveals a hexameric water cluster formation in the inorganic lattice host. The complex cation and the perchlorate counterion are involved in stabilizing the (H₂O)₆ cluster in a rare ‘pentamer planar+1’ conformation. A one-dimensional water tape consisting of edge-shared water hexamers is observed. The water tape represents a subunit of ice structure.     

Four coordination polymers constructed from a multicarboxylate ligand and metal centers various from Ba, Cu, Zn to Gd: Syntheses, crystal structures and properties

Hydrothermal reactions between H₄ODPA (2,2′,3,3′-oxydiphthalic acid) and metal ion salts of Ba²⁺, Cu²⁺, Zn²⁺ and Gd³⁺ afford four novel coordination polymers [Ba(H₂ODPA)(H₂O)₄] · H₂O (1), [Cu₂(ODPA)(H₂O)₃] · H₂O (2), Zn₂(ODPA)(H₂O)₂ (3) and [Gd(HODPA)(H₂O)_3.5] · H₂O (4), accordingly. These polymers show great differences in regard to their structures and properties originated from the variation of size and coordination geometry of the metal ions. Compound 1 presents puckered achiral layer structure with (4.8²) topology with helices, 2 has a 6³ topology with copper tetramer as SBUs, 3 has chiral layer with two kinds of helices built up from Zn-binuclear “paddle-wheel” like SBUs, and 4 features a simple 1D helix with opposite chirality. Compound 3 shows obvious fluorescent emissions upon excitation. Compound 2 shows ferromagnetic interactions between Cu^II centers bridged by carboxylate groups, whereas compound 4 presents weak ferromagnetic interaction between Gd^III ions.     

3D hydrogen bonded metal-organic frameworks constructed from [M(H2O)6][M′(dipicolinate)2] · mH2O (M/M′ = Zn/Ni or Ni/Ni). Identification of intercalated acyclic (H2O)6/(H2O)10 clusters

New heterodinuclear Zn^II/Ni^II (1) and homodinuclear Ni^II/Ni^II (2) water-soluble and air stable compounds of general formula [M(H₂O)₆][M′(dipic)₂] · mH₂O have been easily prepared by self-assembly of the corresponding metal(II) nitrates with dipicolinic acid (H₂dipic) in water solution at room temperature.  The compounds have been characterized by IR, UV/Vis and atomic absorption spectroscopies, elemental and X-ray single crystal diffraction (for 1 · 4H₂O and 2 · 5H₂O) analyses.  3D infinite polymeric networks are formed via extensive hydrogen bonding interactions involving all coordinated and crystallization water molecules, and all dipicolinate oxygens, thus contributing to additional stabilization of dimeric units, metal-organic chains and 2D layers.  In 1 · 4H₂O, the latter represent a rectangular-grid 2D framework with multiple channels if viewed along the c crystallographic axis, while in 2 · 5H₂O intercalated crystallization water molecules are associated to form acyclic nonplanar hexameric water clusters and water dimers which occupy voids in the host metal-organic matrix, with a structure stabilizing effect via host-guest interactions.  The hexameric cluster extends to the larger (H₂O)₁₀ one with an unusual geometry (acyclic helical octamer with two pendent water molecules) by taking into account the hydrogen bonds to water ligands in [Ni(H₂O)₆]²⁺.  The obtained Zn/Ni compound 1 relates to the recently reported family of heterodimetallic complexes [M(H₂O)₅M′(dipic)₂] · mH₂O (M/M′ = Cu/Co, Cu/Ni, Cu/Zn, Zn/Co, Ni/Co, m = 2, 3), what now allows to establish the orders of the metal affinity towards the formation of chelates with dipicolinic acid (Co^II > Ni^II > Zn^II > Cu^II) or aqua species (Co^II < Ni^II < Zn^II < Cu^II).     

Supramolecular architectures built of triangular molybdenum(IV) heterometallic clusters encapsulating novel water clusters

The hydrothermal reaction of the dimolybdenum(V) Na₂[Mo₂O₃S(HNTA)₂] · 6H₂O (1) and the lanthanide(III) ion yield the neutral trimolybdenum(IV) heterometalic cluster, [(H₂O)₈NdMo₃O₃S(HNTA)₂(NTA)] · 7H₂O (2) (NTA = nitrilotriacetato ligand). The addition reaction of Ag⁺ and [Mo₃O₄(C₂O₄)₃(H₂O)₃]²⁻ affords the anionic heterometallic cluster in N(C₂H₅)₄[Ag(H₂O)₃Mo₃O₄(C₂O₄)₃(H₂O)₃] · 5H₂O (3). The H-bonded self-assemblies of the resulting asymmetric and larger heterometallic clusters form the 2D layered structure and 3D supramolecular open framework in 2 and 3, respectively, with larger pores to be stabilized by water clusters. These water clusters appear as (H₂O)₄ and (H₂O)₁₈ in 2 and (H₂O)₂₂ in 3.     

Binuclear copper and zinc complexes based on polypyridyl ligand 2,3,5,6-tetra(2-pyridyl)pyrazine (tppz): Synthesis, spectral and structural characterization

The reaction of MCl₂ · 2H₂O (M = Cu, Zn) with 2,3,5,6-tetra(2-pyridyl)pyrazine (tppz) (referred hereafter as L) in 2:1 molar ratio in acetonitrile at room temperature afforded binuclear complexes [M₂(κ³-L)Cl₄] [Cu (1), Zn (2)] where the ligand is bis-tridentate manner. The complexes have been characterized by elemental analyses, FAB-MS, IR, EPR, NMR and electronic spectral studies. Solid state structures of both the [Cu₂(κ³-L)Cl₄] · 5H₂O (1), [Zn₂(κ³-L)Cl₄] · H₂O (2) have been determined by single crystal X-ray analyses. A well-resolved uudd cyclic water tetramer and water monomer were reported in the crystal host of [Cu₂(κ³-L)Cl₄] · 5H₂O (1) and [Zn₂(κ³-L)Cl₄] · H₂O (2) showing the contribution of the water cluster to the stability of the crystal host 1 and 2.     

Synthesis, structures and conductivity properties of silver 3-sulfobenzoate coordination polymers

Four coordination polymers based on Ag^I/3-sulfobenzoate/N-donor ligands, [Ag₂Na₂(3-sb)₂(H₂O)₇]_n (1), {[Ag₂(3-sb)(apy)]·(H₂O)}_n (2), {[Ag₂(4,4′-bipy)₂(H₂O)₃]·[Ag₂(4,4′-bipy)₂(H₂O)₂]·2(3-sb)·4(H₂O)}_n (3) and {[Ag(3-sb)(bpe)(H₂O)][Ag(bpe)(H₂O)]·3(H₂O)}_n (4) where 3-sb is 3-sulfobenzoate, apy is 2-aminopyridine, bipy is 4,4′-bipyridine and bpe is 1,2-bis(4-pyridyl)ethylene, were prepared and characterized, and their fluorescence and electric conductivity properties were studied. Complex 1 is a 3D architecture in which 3-sb ligands exhibit μ₄-κ¹(O1,O2-Ag): κ¹(O3,O5-Na) trans-trans coordination mode. The molecular structure of 2 is a 2D layer. Complexes 3 and 4 are cation-anion species and 1D polymers. In these complexes hydrogen bonds provide additional assembly forces, giving 3D hydrogen bonding networks for 1 and 3, and 2D layers for 2 and 4. Abundant weak interactions, such as Ag-Ag interactions in 1-3, Ag-π interactions in 1-4, π-π interactions in 1, 3-4, and C-H···π interactions in 3-4, also can be found. The weak interactions are strongly related to the fluorescence and electric conductivity properties, providing the way for understanding the relationship between structures and properties.