Influence of anions on copper(II) complexes of a flexible bis-pyridyltrazole ligand: identification of a discrete water–chloride cluster [(H<Subscript>2</Subscript>O)<Subscript>10</Subscript>(Cl)<Subscript>8</Subscript>]<Superscript>8−</Superscript>

Three Cu(II) complexes, [Cu(H₂L)(ClO₄)₂] (1), [Cu(H₂L)_0.5(µ-SO₄)(H₂O)]·H₂O (2) and [{Cu(H₂L)(H₂O)}{Cu(H₂L)(Cl)]Cl₃·4H₂O (3), with a flexible ligand 1,2-bis(5-(pyridine-2-yl)-1,2,4-triazole-3-yl)ethane (H₂L) were synthesized from various Cu(II) salts. X-ray crystal structure analysis reveals that the H₂L ligand demonstrates different coordination modes in each of these complexes. Complex 1 shows a mononuclear structure with ClO₄ ^? anions weakly coordinated to the metal center, which is further extended into a 1-D assembly through hydrogen bonds. Complex 2 is a polymeric species in which the dinuclear units [Cu₂(H₂L)(H₂O)₂] are linked through SO₄ ^2? anions to form 1-D chains, which are further associated into a 2-D assembly through a self-assembled decameric water cluster. Complex 3 features an interesting 3-D coordination architecture assembled through extensive hydrogen interactions between chloride anions and water molecules. Notably, a unique discrete water–chloride cluster [(H₂O)₁₀(Cl)₈]^8? built around a chair-like water–chloride octameric core is identified in the crystal matrix of complex 3. The choice of counteranion plays a key role in the diverse structures of these complexes. The spectroscopic properties of the complexes have also been investigated.     

Zn(II) and Cd(II) metal–organic frameworks (MOFs) constructed from a symmetric triangular semirigid multicarboxylate ligand: Synthesis,structures and luminescent properties

Three transition metal coordination polymers [Zn₂(H₂L)(2,2′-bpy)₂(H₂O)]_n∙2nH₂O (1), [Zn₂(H₂L)(2,2′-bpy)₂]_n (2), and [Cd₂(H₂L)(2,2′- bpy)₂(H₂O)₂]_n∙2nH₂O (3), have been assembled from a semirigid triangular multicarboxylate ligand 3,3′,3″-(1,3,5-phenylenetri(oxy))triphthalic acid (H₆L) with the help of 2,2′-bipyridine (2,2′-bpy) ligand. X-ray single crystal diffraction analysis reveals that complex 1 crystallizes in the space group of Pī and displays a one-dimensional (1D) ladder chain structure constructed from 2,2′-bpy ligand and H₂L ligand, which stacks together in an -ABCABC- motif, featuring a mutually embedded chained structure. In complex 2, the H₂L ligands bridge the adjacent Zn(II) atoms into a complicated ribbon chain along the b axis. There is π–π stacking interaction between the chains, which results in the formation of a 2D supramolecular structure. Complex 3 also exhibits a 1D ladder-like chain. The different molecular structures for complexes 1 and 2 formed from the same H₆L and Zn(NO₃)₂∙6H₂O in different metal-to-ligand ratios in the presence of NaOH, reveals the influence of metal–ligand ratio on the structure of the coordination polymer. In contrast, a series of same reaction using Cd(NO₃)₂∙4H₂O as a starting material instead of Zn(NO₃)₂∙6H₂O only led to the formation of 3, illustrating the fact organic ligands display different coordination preferences at different metal ions. In addition, the thermal and luminescent properties of complexes 1–3 were also investigated.     

Versatility of copper(II) coordination compounds with 2,3-bis(2-pyridyl)pyrazine mediated by temperature,solvents and anions choice

Tuning reaction temperatures as well as the variation in starting copper salts and solvents led to the formation of a new series of Cu(II) coordination compounds with 2,3-bis(2-pyridyl)pyrazine (dpp): a mononuclear [Cu(acac)(dpp)(NO₃)] (1) complex, two dinuclear [Cu₂(acac)₂(dpp)(NO₃)(H₂O)]NO₃ (2) and [Cu₂(Hdpp)₂(ox)(Cl)₂(H₂O)₂]Cl₂·6(H₂O) (4) complexes, and four coordination polymers {[Cu₄(dpp)₂(ox)(Cl)₆]}_n (3), {[Cu₄(dpp)₂(ox)(NO₃)₆(H₂O)₂]∙1.2(H₂O)}_n (5), {[Cu(dpp)(NO₃)](NO₃)·(H₂O)}_n (6) and {[Cu(dpp)(SO₄)(H₂O)₂]}_n (7), where acac⁻ = acetylacetonate, ox²⁻ = oxalate. Remarkably, the treatment of Cu(II) chloride dihydrate with dpp in methanol solution led to an unusual in situ condensation of dpp with acac⁻ to produce [Cu₂(acdpp)₂(Cl)₄]·2(MeOH) (8). The structure of 1 consists of neutral, mononuclear [Cu(acac)(dpp)(NO₃)] units with acac⁻ and dpp acting as bidentate ligands. In 2, the dpp ligand coordinates in a bis-chelating mode to two Cu(II) ions and bridges them into a dimeric entity, whereas an oxalate linker joins [Cu(Hdpp)(Cl)₂(H₂O)]⁺ units into a dimer in 4. Compounds 3, 5, 6 and 7 are 1D chain coordination polymers, which incorporate two symmetry independent metal centers and different bridging ligands: Hdpp⁺ as a protonated cationic or dpp as a neutral chelating ligand and oxalate, Cl⁻ anions or sulfate di-anions as bridging ligands. Magnetic studies were performed on samples 1 and 2, and the analysis reveals a very weak magnetic exchange coupling mediated via the dpp ligand.     

Treatment effects and mechanisms of Cu(II) coordination polymer in hypotension after anesthesia

A Cu(II) coordination polymer (CP) (that is, [Cu₂(OH)(H₂O)₂(cbca)·2H₂O]_n (1)) has been obtained with the reaction between Cu(II) salt and 4′-(1-carboxyethoxy)-[1,1′-biphenyl]-3,5-dicarboxylic acid (H₃cbca), a semi-rigid tricarboxylic acid ligand under the hydrothermal reaction condition. Prevention activity of the new compound on hypotension after anesthesia surgery was evaluated and the related mechanism was researched at the same time. The noninvasive blood pressure monitor was firstly conducted to measure the blood pressure of the animal after compound treatment. Besides, the real time RT-PCR assay was also used to determine theα receptor relative expression on vascular endothelial cells after compound treatment.     

A series of novel 1D coordination polymers constructed from metal–quinolone complex fragments linked by aromatic dicarboxylate ligands

Self-assembly of quinolones with metal salts in the presence of aromatic dicarboxylate ligands affords a series of novel 1D metal–quinolone complexes, namely [Mn(Hppa)(oba)]·3H₂O (1), [Co(Hppa)(oba)]·3.25H₂O (2), [Zn(Hppa)(sdba)]·1.5H₂O (3), [Mn(Hcf)(bpda)(H₂O)]·2H₂O (4), [Mn(Hppa)₂(bpdc)] (5) and [Mn(Hlome)₂(bpdc)]·4H₂O (6) (Hppa = Pipemidic acid, Hcf = ciprofloxacin, Hlome = lomefloxacin). The structures of compounds 1–3 consist of novel polymeric chains spanning two different directions, which display an intriguing 1D → 3D inclined polycatenation of supramolecular ladders. Compound 4 exhibits a chain compound formed from the interconnection of [Mn₂(Hcf)₂(μ-CO₂)₂] dimers with bpda ligands. Compounds 5 and 6 are similar chain compounds constructed from [Mn(Hppa)₂] (or [Mn(Hlome)₂]) fragments linked by bpdc ligands. The magnetic properties of 4 have been studied, which indicate the existence of antiferromagnetic interactions. Furthermore, the luminescent properties of compound 3 are discussed.     

Four Complexes with the Rigid Ligand 1,4‐Bis(1H‐imidazol‐4‐yl)benzene and Varied Carboxylate Ligands

Four metal‐organic coordination polymers [Co₂(L)₃(nipa)₂]·6H₂O ( 1 ), [Cd(L)(nipa)]·3H₂O ( 2 ), [Co(L) (Hoxba)₂] ( 3 ) and [Ni₂(L)₂(oxba)₂(H₂O)]·1.5L·3H₂O ( 4 ) were synthesized by reactions of the corresponding metal(II) salts with the rigid ligand 1,4‐bis(1H‐imidazol‐4‐yl)benzene (L) and different derivatives of 5‐nitroisophthalic acid (H₂nipa) and 4,4′‐oxybis(benzoic acid) (H₂oxba), respectively. The structures of the complexes were characterized by elemental analysis, FT‐IR spectroscopy and single‐crystal X‐ray diffraction. Complexes 1 and 3 have the same one‐dimensional (1D) chain while 2 is a 6‐connected twofold interpenetrating three‐dimensional (3D) network with α ‐Po 4¹²·6³ topology based on the binuclear Cd^II subunits. Compound 4 features a puckered two‐dimensional (2D) (4,4) network, and the large voids of the packing 2D nets have accommodated the uncoordinated L guest molecules. An abundant of N–H···O, O–H···O and C–H···O hydrogen bonding interactions exist in complexes 1–4 , which contributes to stabilize the crystal structure and extend the low‐dimensional entities into high‐dimensional frameworks. Lastly, the photoluminiscent properties of compounds 2 were also investigated.     

Four transition metal complexes constructed with mixed mercaptotetrazole and 4,4′-bipyridine ligands

Based on 5-mercapto-1H-tetrazole-1-methanesulfonic acid disodium salt (Na₂mtms) and 4,4′-bipyridine (bpy) as ligands, four new transition metal complexes, namely {[Cd₂(mtms)(bpy)₂(OAc)₂]·H₂O} _n (1), {[Cd(mtms)(bpy)₂(H₂O)₂]₂·bpy·4H₂O} _n (2), {[Zn₂(μ ₂-OH)(mtms)(bpy)₃(H₂O)]·ClO₄·H₂O} _n (3), and {[Co(mtms)₂(bpy)(H₂O)₂]·[Co(bpy)₂(H₂O)₄]·H₂O} _n (4), have been synthesized and characterized by single-crystal X-ray diffraction. Complex 1 features a pillared-layer coordination architecture linked by acetate, mtms, and bridging bpy ligands. Complex 2 has a 1D polymeric structure with [Cd(mtms)(bpy)₂(H₂O)₂] as the repeating unit; these infinite chains are further connected into a 3D supramolecular framework through π–π stacking of bpy ligands. In complex 3, the mtms ligand combined with μ ₂-OH bridges two Zn atoms to form a dimer structure, which is different from that of complex 2. Complex 4 shows a 3D supramolecular network containing infinite [Co(mtms)₂(bpy)(H₂O)₂]^2? anionic chains and free [Co(bpy)₂(H₂O)₄]²⁺ cationic components. The luminescence properties of 1 and 2 and the electrochemical properties of 3 are reported.     

Four novel linear trinuclear assemblies containing bridging triazole ligands. Crystal structure,magnetic, semiconducting and fluorescent properties

Four homotrinuclear linear coordination compounds with bridging ligand of (m-phenol)-1,2,4-triazole, [Mn₃(L)₆(H₂O)₆](ClO₄)₆ (1), [Ni₃(L)₆(H₂O)₆](BF₄)₆·4DMF (2), [Cd₃(L)₆(H₂O)₆](ClO₄)₆· 2H₂O·2DMF·2EtOH (3), [Zn₃(L)₈(H₂O)₄](BF₄)₄(SiF₆)·2EtOH·12H₂O (4), have been synthesized and structurally determined. The structures consist of three metal ions in linear arrangements, linked to each other by two pairs of three N1, N2 bridging triazole ligands. The negative value of J suggests that antiferromagnetic interaction exists in 1. Green fluorescence of 2 and 4 with emissions at 518 nm for 2 and 524 for 4 is possibly assigned to LMCT. The energy gaps of the compounds 2 and 4 are 1.82 and 1.97 eV, respectively, which suggests that the two materials behave as semiconductors.     

Synthesis,structures and electrochemical properties of two novel metal–organic coordination complexes based on trimesic acid (H3BTC) and 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (BPO)

Two novel metal–organic coordination complexes [Cu(HBTC)(BPO)]·H₂O (1) and [Co₃(BTC)₂(BPO)₃(H₂O)₂]·5.25H₂O (2), have been synthesized from hydrothermal reaction of metal chloride with the mixed ligands 1,3,5-benzenetricarboxylate (H₃BTC) and bent dipyridyl based ligand 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (BPO), and structurally characterized by elemental analyses, IR, TG and single-crystal X-ray diffraction analysis. The results reveal that each dinuclear Cu^II unit is bridged by two kinds of different ligands (H₃BTC and BPO) to form one-dimensional (1-D) chain structure in complex 1. The adjacent chains for 1 are further linked by π–π stacking interactions and hydrogen bonding interactions to form a three-dimensional (3-D) supramolecular framework. Complex 2 possesses a 3-D network composed of three different cobalt(II) centers [carboxylate-bridged dinuclear cobalt units and mononuclear cobalt ion] and bridging ligands BTC and BPO, which presents the first example of 3-D coordination polymer constructed from the BPO ligands simultaneously showing three different coordination modes. Moreover, the electrochemical behaviors of the two complexes bulk-modified carbon paste electrodes (1-CPE and 2-CPE) have been reported.     

Synthesis, crystal structure, spectroscopic and photoluminescence studies of manganese(II), cobalt(II), cadmium(II), zinc(II) and copper(II) complexes with a pyrazole derived Schiff base ligand

Varying coordination modes of the Schiff base ligand H₂L [5-methyl-1-H-pyrazole-3-carboxylic acid (1-pyridin-2-yl-ethylidene)-hydrazide] towards different metal centers are reported with the syntheses and characterization of four mononuclear Mn(II), Co(II), Cd(II) and Zn(II) complexes, [Mn(H₂L)(H₂O)₂](ClO₄)₂(MeOH) (1), [Co(H₂L)(NCS)₂] (2), [Cd(H₂L)(H₂O)₂](ClO₄)₂ (3) and [Zn(H₂L)(H₂O)₂](ClO₄)₂ (4), and a binuclear Cu(II) complex, [Cu₂(L)₂](ClO₄)₂ (5). In the complexes 1-4 the neutral ligand serves as a 3N,2O donor where the pyridine ring N, two azomethine N and two carbohydrazine oxygen atoms are coordinatively active, leaving the pyrazole-N atoms inactive. In the case of complex 5, each ligand molecule behaves as a 4N,O donor utilizing the pyridine N, one azomethine N, the nitrogen atom proximal to the azomethine of the remaining pendant arm and one pyrazole-N atom to one metal center and the carbohydrazide oxygen atom to the second metal center. The complexes 1-4 are pentagonal bipyramidal in geometry. In each case, the ligand molecule spans the equatorial plane while the apical positions are occupied by water molecules in 1, 3 and 4 and two N bonded thiocyanate ions in 2. In complex 5, the two Cu(II) centers have almost square pyramidal geometry (τ = 0.05 for Cu1 and 0.013 for Cu2). Four N atoms from a ligand molecule form the basal plane and the carbohydrazide oxygen atom of a second ligand molecule sits in the apex of the square pyramid. All the complexes have been X-ray crystallographically characterized. The Zn(II) and Cd(II) complexes show considerable fluorescence emission while the remaining complexes and the ligand molecule are fluorescent silent.     

Synthesis and spectroscopic studies of 2,5-hexanedione bis(isonicotinylhydrazone) and its first raw transition metal complexes

New VO²⁺, Mn²⁺, Co²⁺, Ni²⁺ Cu²⁺ and Zn²⁺ complexes of 2,5-hexanedione bis(isonicotinylhydrazone) [H₂L] have been synthesized and characterized. The analyses confirmed the formulae: [VO(L)]·H₂O, [Mn₂(H₂L)Cl₂(H₂O)₆]Cl₂, [Co(L)(H₂O)₂]·2H₂O, [Ni(HL)(OAc)]·H₂O, [Cu(L)(H₂O)₂]·2H₂O, [Cu(L)]·2H₂O and [Zn(L)(H₂O)₂]. The formulae of [Ni(HL)(OAc)]·H₂O, [Zn(L)(H₂O)₂] and [Mn₂(H₂L)Cl₂(H₂O)₆]Cl₂, are supported by mass spectra. The molecular modeling of H₂L is drawn and showed intramolecular hydrogen bonding. The ligand releases two protons during reaction from the two amide groups (NHCO) and behaves as a binegative tetradentate (N₂O₂); good evidence comes from the ¹H NMR spectrum of [Zn(L)(H₂O)₂]. The ligand has a buffering range 10–12 and pK's of 4.62, 7.78 and 9.45. The magnetic moments and electronic spectra of all complexes provide a square-planar for [Cu(L)]·2H₂O, square-pyramidal for [VO(L)]·H₂O and octahedral for the rest. The ESR spectra support the mononuclear geometry for [VO(L)]·H₂O and [Cu(L)(H₂O)₂]·2H₂O. The thermal decomposition of the complexes revealed the outer and inner solvents where the end product in most cases is metal oxide.     

Two new coordination host frameworks for the inclusion of 4-amino-benzophenone guest molecules

The synthesis and structural characterization of novel organometallic coordination polymers are reported. The reaction of Cd(NO₃)₂ and 4,4′-bipy in CH₃OH/H₂O gave a 2D coordination network formulated as {[Cd(4,4′-bpy)₂·(H₂O)₂](NO₃)₂·4H₂O}¹⁰, which was used to capture an organic guest species (4-amino-benezopheone, C₁₃H₁₁NO (3)) to obtain {[Cd(4,4′-bpy)₂(NO₃)(H₂O)]·NO₃·(C₁₃H₁₁NO)₂} (1). Using L (L=4,4′-trimethylenedipyridine) instead of 4,4′-bipy, {[Cd(L)₂(H₂O)₂]·2H₂O·2NO₃·C₁₃H₁₁NO} (2) was synthesized, which has an interesting configuration.     

Complexes derived from the copper(II) perchlorate/maleamic acid/2,2′-bipyridine and copper(II) perchlorate/maleic acid/2,2′-bipyridine reaction systems: Synthetic,reactivity, structural and spectroscopic studies

A systematic investigation of the reactions of Cu(ClO₄)₂ · 6H₂O with maleamic acid (H₂L) in the presence of 2,2′-bipyridine (bpy) has been carried out. The chemical and structural identity of the products depends on the solvent, the absence or presence of external hydroxides in the reaction mixture and the molar ratio of the reactants. Various reaction schemes have led to the isolation of the complexes [Cu₂(HL)₂(bpy)₂(H₂O)₂](ClO₄)₂ (1), [Cu₂(HL)₂(bpy)₂(H₂O)₂](ClO₄)₂ · 2H₂O (1 · 2H₂O), [Cu(L′′)(bpy)]_n · 2nH₂O (2 · 2nH₂O), [Cu₂(L′′)(bpy)₂(H₂O)₂]_n(ClO₄)_2n · 0.5nH₂O (3 · 0.5nH₂O), [Cu₂(L′′)₂(bpy)₂] · 2MeOH (5 · 2MeOH), [Cu₂(L′)₂(bpy)₂(ClO₄)₂] (6) and [Cu(ClO₄)₂(bpy)(MeCN)₂] (7b), where L′′^2? and L′^? are the maleate(?2) and monomethyl maleate(?1) ligands, respectively. The HL^? ion has been transformed to L′′^2? and L′^? in the known compounds 2 · 2nH₂O and 6, respectively, via metal ion-assisted processes involving hydrolysis (2 · 2nH₂O) and methanolysis (6) of the primary amide group. The reaction that leads to 6 takes place through the formation of the mononuclear complex [Cu(ClO₄)₂(bpy)(MeOH)₂] (7a), whose structure was assigned on the basis of its spectral similarity with the structurally characterized complex 7b. The structures of the cations in 1 and 1 · 2H₂O consists of two Cu^II atoms bridged by the carboxylate groups of the two HL^? ligands, each exhibiting the less common η² coordination mode; a chelating bpy molecule and a H₂O ligand complete square pyramidal coordination at each metal centre. The structure of the dinuclear repeating unit in the 1D coordination polymer 3 · 0.5nH₂O consists of two Cu^II atoms bridged by two syn,syn η¹:η¹:μ₂ carboxylate groups belonging to two L′′^2? ions; each ligand bridged two neighboring [Cu^II,II₂] units thus promoting the formation of a helical chain. The structure of the dinuclear molecule of complex 5 · 2MeOH consists of two Cu^II atoms bridged by two η² carboxylate groups from two L′′^2? ligands; the second carboxylate group of each maleate(?2) ligand is monodentately coordinated to Cu^II, creating a remarkable seven-membered chelating ring. The L′^? ion behaves as a carboxylate-type ligand in 6, with the carboxylate group being in the familiar syn,syn η¹:η¹:μ₂ coordination mode; a chelating bpy molecule and a coordinated ClO₄^? complete five-coordination at each Cu^II centre. The crystal structures of the complexes are stabilized by various H-bonding patterns. Characteristic IR bands of the complexes are discussed in terms of the known structures and the coordination modes of the ligands.     

Synthesis,characterization, electrochemical behavior and antioxidant activity of new copper(II) coordination compounds with curcumin derivatives

Five new copper(II) coordination compounds were prepared by template synthesis, using curcumin, 2-hydrazinobenzothiazole and metal salt (copper chloride, bromide, acetate and nitrate) in 1:2:1 and 1:2:2 molar ratio. The complexes were characterized by elemental and thermogravimetric analysis, IR, UV–Vis and mass spectroscopic methods and cyclic voltammetric studies. On the basis of physico-chemical measurements the following formulae have been assigned to the complexes: [Cu(H₂L)(H₂O)₂]Cl₂·H₂O, [CuL]·H₂O, [Cu(H₂L)(H₂O)Br]Br·5H₂O, [Cu₂L(H₂O)₄](NO₃)₂·2H₂O and [Cu₂(H₂L)(NO₃)₄]·H₂O, where H₂L is the hydrazone ligand formed in the reaction conditions. Metal complexes were tested for antioxidant activity by photochemiluminescence and this activity was quantified by comparison with TROLOX®, as standard. The results show that all complexes are more potent antioxidant agents than curcumin.     

Mono- and dinuclear vanadium complexes with the pentadentate schiff base 2,6-diacetylpyridine bis(nicotinylhydrazone): Synthesis and structures

A reaction between VOSO₄, 2,6-diacetylpyridine, and nicotinohydrazide in a molar ratio of 1: 1: 2 afforded two complexes differing in both color and crystal shape as well as in chemical composition and molecular structure. The compositions and structures of the vanadium complexes were determined by IR spectroscopy and X-ray diffraction (CIF files CCDC_nos. 1411235 (I) and 1411236 (II)). These complexes can be formulated as [V ₂ ^II (H₂L)₂](NO₃)₄ ? H₂O (I) and [V^IV(=O)(H₂L)(SO₄)] ? 5H₂O (II), where H₂L is 2,6-diacetylpyridine bis(nicotinylhydrazone). Complex I consists of centrosymmetric dinuclear complex cations [V₂(H₂L)₂]⁴⁺, NO ₃ ^- anions, and crystal water molecules in a ratio of 1: 4: 1; complex II is built from molecular V(IV) complexes and crystal water molecules in a ratio of 1: 5. The coordination polyhedron of the metal atom in I is a tetragonal pyramid made up of the electron-donating atoms N₃O₂ of two ligands H₂L. The coordination polyhedron of the metal atom in II is a pentagonal bipyramid made up of the electron-donating atoms N₃O₂ of one neutral five-coordinate ligand H₂L and two O atoms coming from the oxo ligand and the SO ₄ ^2- anion coordinated in a monodentate fashion.     

Synthesis,characterization and biological activity of triaminoxime and its metal complexes

Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes of multifunctional triaminoxime have been synthesized and characterized by elemental analyses, IR, UV–Vis spectra, magnetic moments, ¹H- and ¹³C-NMR spectra for ligand and its Ni(II) complex, mass spectra, molar conductances, thermal analyses (DTA, DTG and TG) and ESR measurements. The IR spectral data show that the ligand is bi-basic or tri-basic tetradentate towards the metals. Molar conductances in DMF indicate that the complexes are non-electrolytes. The ESR spectra of solid copper(II) complexes [(HL)(Cu)₂(Cl)₂] · 2H₂O (2) and [(L)(Cu)₃(OH)₃(H₂O)₆] · 7H₂O (6) show axial symmetry of a d _{x²???y ²} ground state; however, [(HL)(Co)] (4) shows an axial type with d _Z ² ground state and manganese(II) complex [(L)(Mn)₃(OH)₃(H₂O)6] · 4H₂O (10) shows an isotropic type. The biological activity of the ligand and its metal complexes are discussed.     

Polycarboxylate-assisted assembly of cobalt(II) metal–organic coordination polymers from a “V”-shaped tri-pyridyl-bis-amide ligand

The aim of this study was to explore the influence of the position and angles of carboxyl groups of polycarboxylates on constructing coordination polymers. Three Co(II) metal–organic coordination polymers based on a tri-pyridyl-bis-amide ligand, namely [Co(L)(1,2-BDC)(H₂O)₂]·2H₂O (1), [Co(L)(1,4-BDC)(H₂O)₂]·2H₂O (2) and [Co(L)₂(BTEC)_0.5]·H₂O (3) (L = N,N′-bis(pyridine-3-yl)pyridine-2,6-dicarboxamide, 1,2-H₂BDC = 1,2-benzenedicarboxylic acid, 1,4-H₂BDC = 1,4-benzenedicarboxylic acid, H₄BTEC = 1,2,4,5-benzenetetracarboxylic acid), have been obtained by tuning the auxiliary polycarboxylate ligands. Structural analyses reveal that complexes 1–3 display diverse structures. Complex 1 displays a meso-helical chain linked by L ligands, which is further extended into a three-dimensional supramolecular framework through hydrogen-bonding interactions. The 1,2-BDC with a chelating coordination mode only acts as the hydrogen bond acceptor. In complex 2, the 1,4-BDC anions connect adjacent Co(II) atoms to form a linear chain, which is connected by hydrogen-bonding interactions to construct a 3D supramolecular network. Complex 3 exhibits a chain, which is composed of left-/right-handed Co-L helical chains and Co-BTEC linear chain. The 1D chains are ultimately extended into a two-dimensional supramolecular network by hydrogen-bonding interactions. Moreover, the thermal stability and the fluorescent properties of the title complexes and the electrochemical behaviors of a bulk-modified carbon paste electrode with complex 2 have been investigated at room temperature.     

Multifunctional Gas Adsorption and Photocatalytic Degradation Based on a Porous Metal-Organic Framework Material

The reaction of Cu(NO₃)₂ · 3H₂O with rigid ligand 4'-(1H-tetrazol-5-yl)-[1,1'-biphenyl]-3,5-dicarboxylic acid (H₃L) gave a new metal-organic framework of [Cu₂(μ₃-OH)(L)(H₂O)₂] _n (I) (CIF file CCDC no. 1533273). Complex I has a truncated cuboctahedra that was connected by trigonal Cu₃O(N₄CR)₃ trimers using each tetrazolate (N₄CR) moiety and shows a overall 3D nnt net with (6.8²)₆(8³)₂(6².8⁴)₃ topology. The properties of gas adsorption and the degradation of the methyl violet have been examined.     

Synthesis,crystal structure,and luminescent properties of metal complexes bearing 2,6-pyridine-diacylhydrazide ligands: supramolecular assemblies via intermolecular interactions

Four metal complexes of N,N′-bis(salicyl)-2,6-pyridine-dicarbohydrazide ligand (H₆L), [Co^II(H₄L)(H₂O)₂]·2DMF (1), [Zn^II(H₄L)(H₂O)₂]·2DMF (2), [Cd^II(H₄L)(Py)₂]·DMF·Py (3), and [Co^IICo₂^III(H₄L)₄(H₂O)₄]·DMF·H₂O (4), were synthesized and characterized by elemental analysis, IR, and single-crystal X-ray diffraction analysis. Structural studies revealed that complexes 1–3 present discrete mononuclear structures and complex 4 displays a centrosymmetric mixed-valence trinuclear structure. All four complexes are further extended into interesting two- or three-dimensional supramolecular frameworks. The luminescent properties of 2 and 3 were studied, which show emissions with maxima at 485 nm upon excitation at 396 nm for 2 and 476 nm upon excitation at 397 nm for 3, respectively.