Hydrothermal syntheses, crystal structures and characterizations of three new copper coordination polymers

Three new copper complexes, [Cu^IICu^I(ip)(ipH)(4,4′-bipy)_3/2]_n (1), [Cu(ip)(4,4′-bipy)]_n · 3nH₂O (2), and [Cu(ipH)₂(4,4′-bipy)]_n (3), have been hydrothermally synthesized by the reaction of Cu(NO₃)₂ · 3H₂O with isophthalic acid (ipH₂) and 4,4′-bipyridine (4,4′-bipy) under different reaction conditions. Complex 1, a mixed-valence copper(I,II) complex, exhibits a 2-D interpenetrating grid framework, in which five-coordinated Cu^II and three-coordinated Cu^I environments are established. The oxidation states of center Cu atoms have been confirmed by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance spectra (EPR). Complex 2 features a 2-D box-like bilayer architecture, in which Cu^II atoms are linked by ip ligands to form a 1-D double-chain and the resulting chains are further strutted by the 4,4′-bipy ligands. In complex 3, two bridging 4,4′-bipy ligands and two terminal ipH ligands confine the Cu^II center in a square plane coordination geometry. The whole molecule of 3 was arranged into a 1-D linear chain structure. Additionally, the thermogravimetric analyses (TGA) for complexes 1-3 are also discussed in this paper.     

Hybrid organic-inorganic assemblies built up from saturated heteropolyoxoanions and copper coordination polymers with mixed 4,4′-bipyridine and 2,2′-bipyridine ligands

Three new organic-inorganic hybrid compounds [Cu^I(2,2′-bipy)(4,4′-bipy)_0.5]₂[Cu^I(2,2′-bipy)(4,4′-Hbipy)][Cu^I(4,4′-bipy)]₂[P₂W₁₈O₆₂] · 3H₂O (1), [Cu^I(2,2′-bipy)(4,4′-bipy)_0.5]₂[Cu^I(4,4′-bipy)]₂[PW₁₂O₄₀] · 0.25H₂O (2), and[Cu^I(4,4′-bipy)]₃[PMo₁₂O₄₀] · en · 3H₂O (3) (2,2′- bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine), have been hydrothermally synthesized. Compound 1 represents the first 1D ladderlike structure formed by Dawson-type polyoxoanion [P₂W₁₈O₆₂]⁶⁻ and coordination polymer with mixed 4,4′-bipy and 2,2′-bipy ligands. The novel structure of 2 is composed of 1D hybrid zigzag chains linked by chains into a 3D framework. In compound 3, the [PMo₁₂O₄₀]³⁻ clusters are hung on chains to form a new 1D chain.     

Two new organic-inorganic hybrid materials based on the polyoxotungstoaluminates

Two new organic-inorganic hybrid compounds, {[Cu(2,2′-bipy)₂]₂(Hbpy)[α-AlW₁₂O₄₀]}·H₂O (1) and {[H₂en][Cu^I(4,4′-bipy)]₃(α-AlW₁₂O₄₀)}·4H₂O (2) (2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine, py = pyridine, en = ethylene dimine) based on Keggin-type α-[AlW₁₂O₄₀]⁵⁻ polyoxoaions and transition-metal organoamine subunits, have been hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy, thermal gravimetric analysis (TG), and single-crystal X-ray diffraction. In addition, the electrochemical properties and photocatalytic activity of compound 1 were studied. The structural analysis reveals that 1 shows a 1D infinite chain structure constructed from [α-AlW₁₂O₄₀]⁵⁻ polyoxoanions and {[Cu^II(2,2′-bipy)₂][Cu^II(2,2′-bipy)(py)]}⁴⁺ fragments, in which the remarkable aspect is that [α-AlW₁₂O₄₀]⁵⁻ polyoxoanion is modified in a fascinating symmetrical mode. Compound 2 displays an unprecedented 2D extended structure constructed from [α-AlW₁₂O₄₀]⁵⁻ polyoxoanions and 4,4′-bipy-Cu^I-4,4′-bipy linear chains, in which three - chain belts formed by three linear chains arranged Cu parallel connect alternately with [α-AlW₁₂O₄₀]⁵⁻ polyoxoanions. As far as we know, compounds 1 and 2 represent the first 1D and 2D extended hybrid materials constructed from 3d transition metals and polyoxotungstoaluminates linked through covalent bonds.     

Syntheses and characterizations of four mixed-ligand hydrogen bonding supramolecular architectures with different structural motifs

The reactions of 4-aminobenzoic acid (4-abaH), 4,4′-bipyridine (4,4′-bipy) and transitional metal ions (Zn^II, Mn^II and Cu^II) gave rise to four supramolecular architectures, namely, [(4-abaH)₂(4,4′-bipy)] (1), {[Zn₂(4,4′-bipy)₂(4-aba)₄] (H₂O)₅}_n (2), {[Mn(4,4′-bipy)₂(H₂O)₄] (4-aba)Br(H₂O)₃} (3) and {[Cu₂(4,4′-bipy)₃(H₂O)₂(4-aba)₂](NO₃)₂(H₂O)₄}_n (4). Their crystal structures were determined by X-ray diffraction and show different structural motifs. 1 is a one-dimensional hydrogen bonding ladder constructed by 4-abaH and 4,4′-bipy. In 2, 4,4′-bipy bridges Zn(4-aba)₂ units forming a one-dimensional zigzag chain, which is extended into a three-dimensional framework by crystalline water molecules through hydrogen bonding interactions. Three-dimensional network of 3 is constructed by mononuclear [Mn(4,4′-bipy)₂(H₂O)₄]²⁺ cations, neutral crystalline water molecules, and 4-aba and Br⁻ anions through extensive hydrogen bonding and π-π interactions. However, one-dimensional ladder formed by 4,4′-bipy and Cu(4-aba) units in 4 is extended into a three-dimensional architecture through interpenetration of the lateral 4-aba arms into squares of the adjacent Cu-(4,4′-bipy) ladders and extensive hydrogen bonding interactions.     

Construction of one-, two- and three-dimensional Cu(I) polymeric architectures containing bis(diphenylphosphino)acetylene and 4,4′-bipyridine linking ligands

One-dimensional {[Cu₂(dppa)₂(4,4′-bipy)(CH₃CN)₂](BF₄)₂ · 2CH₃CN}_n (1), two-dimensional {[Cu₂(dppa)(4,4′-bipy)₂(CH₃CN)₂](BF₄)₂ · 4CH₂Cl₂ · 4H₂O}_n (2) and three-dimensional {[Cu₂(dppa)(4,4′-bipy)₃](BF₄)₂ · 2CH₂Cl₂ · 3CH₃CN · 3H₂O}_n (3) polymeric complexes have been prepared by self-assembly of [Cu(MeCN)₄]BF₄, Ph₂PCCPPh₂ (dppa) and 4,4′-bipyridine (4,4′-bipy) in a 2:2:1, 1:1:1 and 2:2:3 molar ratio, respectively. The structures of 1-3, determined by an X-ray diffraction study, reveal a linear spring-like architecture for 1, a planar honeycomb grid for 2 and an interlocked adamantoid network for 3.     

Copper(II) complexes with monocarboxylate ligands bearing different substituent groups: Synthesis and spectroscopic studies

In our continuing efforts to explore the effects of substituent groups of ligands in the formation of supramolecular coordination structures, seven new Cu^II complexes formulated as [Cu₂(L¹)₄(DMF)₂] (1), {[Cu₂(L¹)₄(Hmta)](H₂O)_0.75}_∞ (2), [Cu₂(L²)₄(2,2′-bipy)₂] (3), [Cu₂(L³)₄(H₂O)₂] (4), [Cu₂(L³)₄(Hmta)]_∞ (5), [Cu₂(L³)₄(Dabco)]_∞ (6) and [Cu₂(L³)₄(Pz)]_∞ (7) with three monocarboxylate ligands bearing different substituent groups HL¹-HL³ (HL¹ = phenanthrene-9-carboxylic acid, HL² = 2-phenylquinoline-4-carboxylic acid, HL³ = adamantane-1-carboxylic acid, Hmta = hexamethylenetetramine, 2,2′-bipy = 2,2′-bipyridine, Dabco = 1,4-diazabicyclo[2.2.2] octane and Pz = pyrazine), have been prepared and characterized by X-ray diffraction. In 1, 2 and 4-7, each Cu^II ion is octahedrally coordinated, and carboxylate acid acts as a syn-syn bridging bidentate ligand. While each Cu^II ion in 3 is penta-coordinated in a distorted square-pyramidal geometry. 1 and 4 both show a dinuclear paddle-wheel block, while 2, 5, 6 and 7 all exhibit an alternated 1D chain structure between dinuclear paddle-wheel units of the tetracarboxylate type Cu₂-(RCO₂)₄ and the bridging auxiliary ligands Hmta, Dabco and Pz. Furthermore, 3 has a carboxylic unidentate and μ_1,1-oxo bridging dinuclear structure with the chelating auxiliary ligand 2,2′-bipy. Moreover, complexes 1-6 were characterized by electron paramagnetic resonance (EPR) spectroscopy.     

A new 3D transition-metal complex-templated framework based on Wells-Dawson polyoxometalate and copper(I)-pyrazine moieties

A new Wells-Dawson polyoxometalate-based compound, [Cu^II(2,2′-bipy)₂(H₂O)]₃[Cu^I₆(pz)₆(P₂W₁₈O₆₂)₂] (2,2′-bipy = 2,2′-bipyridine, pz = pyrizine) (1), has been hydrothermally synthesized and characterized by routine physical methods. Compound 1 exhibits a [Cu^II(2,2′-bipy)₂(H₂O)]²⁺ complex-templated 3D (3,4)-connected framework with the topology of (6³)(6²8⁴), which is built up by the cross-linking of porous P₂W₁₈-Cu layers and Cu^I-pz chains with Cu2 atoms as intersections. The transition-metal complex cation [Cu^II(2,2′-bipy)₂(H₂O)]²⁺ acts not only as a template locating in the voids of inorganic layers, but also as a charge-balance complex to make the 3D structure more steady. The electrochemistry property of compound 1 has also been discussed.     

In situ 5-sulfosalicylate decarboxylation or dimethylformamide hydrolysis generating supramolecular assembly architectures

Six transition-metal complexes, {[Co(4,4′-bipy)(H₂O)₄](Hbs)₂ · 3H₂O}_n (1), [Mn(4,4′-bipy)₂(H₂O)₄](Hbs)₂ · 2H₂O (2), {[Mn(HCOO)(H₂O)₂(4,4′-bipy)]₂[Mn(4,4′-bipy)(Hssal)₂(H₂O)₂]}_n (3), [Cd(4,4′-bipy)₂(H₂O)₄](Hbs)₂ · 2H₂O (4), {[Cd₃(CH₃COO)₄(4,4′-bipy)₄](Hbs)₂ · 10H₂O}_n (5), and {[Cd(HCOO)(H₂O)₂(4,4′-bipy)]₂[Cd(4,4′-bipy)(Hssal)₂(H₂O)₂]}_n (6), have been synthesized by hydrothermal or reflux synthetic method and characterized by single-crystal X-ray diffraction, IR, elemental analysis, thermogravimetric analysis and fluorescence analysis, where Hssal²⁻ is doubly deprotonated 5-sulfosalicylate, Hbs⁻ is 4-hydroxybenzenesulfonate and 4,4′-bipy is 4,4′-bipyridine. The structural analyses showed that all of the six complexes are cation-anion species containing in situ synthesized ligands, Hbs⁻ or HCOO⁻, and the former arises from the decarboxylation of 5-sulfosalicylic acid under the hydrothermal conditions. The formate anions derived from the hydrolysis of DMF. A series of supramolecular compounds show that the structural diversity is strongly associated with their properties.     

Syntheses, structures, and magnetic properties of three Fe(II) complexes with reduced radical ligands

Three new Fe(II) complexes [Fe(HIM2py)₂(SCN)₂] (1), [Fe(HIM2py)₂(H₂O)₂](ClO₄)₂ · 2H₂O (2), and [Fe(HIM2py)₂(4,4-bipy)](ClO₄)₂ · 3CH₃CH₂OH (3) (4,4-bipy = 4,4′-bipyridine, HIM2py = 1-hydroxyl-2(2′-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole) have been synthesized and characterized structurally as well as magnetically. The X-ray analysis reveals that HIM2py ligands are coordinated to the metal ions as an unusual six-membered didentate chelate with the κ²N(py), O(HIM) mode. Fe(II) ions in complex 3 are bridged by 4,4-bipy, leading to a 1D chain structure. The magnetic behavior of complex 3 is investigated, showing weak antiferromagnetic 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.     

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).     

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.     

Synthesis, crystal structures, and fluorescence properties of six complexes with thiophene derivative carboxylic acid ligand

The crystallization of 2,3-dihydro-thieno[3,4-b][1,4] dioxine-5,7-dicarboxylic acid (H₂tddc) with divalent transitional metal (Co, Ni, Zn, Cd) or with tervalent lanthanide metal (Sm) and with mixed ligand 4,4′-bipyridine (4,4′-bipy) or 1,10-phenanthroline (1,10-phen) formed six new complexes: [Co(C₈H₄O₆S) · 3H₂O] (1), [Co(C₈H₄O₆)(1,10-phen)(H₂O)] · H₂O (2), [Ni(C₈H₄O₆S)(4,4′-bipy)(H₂O)] · 3H₂O (3) [Sm(C₈H₄O₆S)(NO₃)(H₂O)₄] · 2H₂O (4), [Zn(C₈H₄O₆S)(H₂O)₃] (5), and [Cd₂(C₈H₄O₆S)₂(4,4′-bipy)₂] (6). The structures of these six crystals have been characterized by single-crystal X-ray diffraction analyses, which revealed that complexes 1, 4, 5 are all one-dimensional chain structures and they self-assemble into three-dimensional super-molecules via the hydrogen bond interactions and π-π stacking interactions, 2 is also a one-dimensional chain structure but still self-assembles into one-dimensional double-chains, the complex 3 has two-dimensional undulating parallelogram grid structure extended along the bc-plane, the crystal of 6 is a 3D threefold interpenetration topology framework with 4⁶6³8 nodes. The photoluminescent properties of the H₂tddc ligand and the six compounds have been measured in the solid state at room temperature. Free ligand has no luminescence, while its complexes 1, 4, and 6 all exhibit intense photoluminescence which implies that these complexes may be excellent candidates for potential photoactive materials.     

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.     

Manganese(II) complexes with V-shaped sulfonyldibenzoate: The 3D structures with interpenetrated threefold or tetra-nuclear manganese(II) units

Five Mn^II-sdba coordination polymers with mono-, di-, tri-, tetra-nuclear cores based on the V-shaped 4,4′-dicarboxybiphenyl sulfone (H₂sdba) ligands: [Mn(sdba)(phen)₂(H₂O)]_n·3nH₂O (1), [Mn₂(sdba)₂(μ-H₂O)(py)₄]_n (2), [Mn₃(sdba)₂(Hsdba)₂(2,2′-bipy)₂]_n (3), [Mn₄(sdba)₄(4-mepy)₂(H₂O)₄]_n·2nH₂O (4) and [Mn₄(sdba)₄(bpp)₄(μ-H₂O)₂]_n·0.5nH₂O (5) (phen = 1,10-phenanthroline, 2,2′-bipy = 2,2′-bipyridine, 4-mepy = 4-picoline, bpp = 1,3-bi(pyridine-4-yl)propane) were hydrothermally synthesized and structurally characterized. The M-O-C metal clusters in above complexes act as SBUs, and the V-shaped sdba ligands link the SBUs to generate the novel frameworks. In complexes 1 and 3 their 1D chains are linked into the 2D planes through various hydrogen bonding. Complex 2 displays the 3D structure with interpenetrated threefold, while complexes 4 and 5 both exhibit the 3D structures with the tetra-nuclear Mn₄ units. The magnetic susceptibility studies in the 2-300 K range for these complexes reveal the existence of anti-ferromagnetic exchange interactions between the Mn^II ions.     

Aromatic N-oxide bridged copper(II) coordination polymers: Synthesis, characterization and magnetic properties

The complexes [Cu₂(o-NO₂-C₆H₄COO)₄(PNO)₂] (1), [Cu₂(C₆H₅COO)₄(2,2′-BPNO)]_n (2), [Cu₂(C₆H₅COO)₄(4,4′-BPNO)]_n (3), [Cu(p-OH-C₆H₄COO)₂(4,4′-BPNO)₂·H₂O]_n (4), (where PNO = pyridine N-oxide, 2,2′-BPNO = 2,2′-bipyridyl-N,N′-dioxide, 4,4′-BPNO = 4,4′-bipyridyl-N,N′-dioxide) are prepared and characterized and their magnetic properties are studied as a function of temperature. Complex 1 is a discrete dinuclear complex while complexes 2-4 are polymeric of which 2 and 3 have paddle wheel repeating units. Magnetic susceptibility measurements from polycrystalline samples of 1-4 revealed strong antiferromagnetic interactions within the {Cu₂}⁴⁺ paddle wheel units and no discernible interactions between the units. The complex 5, [Cu(NicoNO)₂·2H₂O]_n·4nH₂O, in which the bridging ligand to the adjacent copper(II) ions is nicotinate N-oxide (NicoNO) the transmitted interaction is very weakly antiferromagnetic.     

Synthesis, structural and spectroscopic characterization of mono- and binuclear copper(I) complexes with substituted diimine and phosphine ligands

The reaction of [Cu(CH₃CN)₄]BF₄, 6-(4-methoxyl)phenyl-2,2′-bipyridine (designated as MeO-CNN), and/or tricyclohexylphosphine (PCy₃) and diimine ligands derived from 4,4′-bipyridine gave four mono- and binuclear copper(I) complexes, [Cu(MeO-CNN)₂]BF₄ (1), [Cu₂(MeO-CNN)₂(PCy₃)₂(4,4′-bipy)](BF₄)₂ · 1.5CH₂Cl₂ (2) (bipy = bipyridine), [Cu₂(MeO-CNN)₂(PCy₃)₂(bpete)](BF₄)₂ · 4CH₂Cl₂ (3) (bpete = trans-1,2-bis(4-pyridyl)ethene) and [Cu₂(MeO-CNN)₂(PCy₃)₂(4,4′-azpy)] (BF₄)₂ · 1.5CH₂Cl₂ (4) (azpy = azobispyridine). Crystallographic studies of complexes 1-4 show that each copper(I) center adopts a pseudo-tetrahedral coordination geometry. Complexes 2-4 consists of -Cu(MeO-CNN)(PCy₃) units which are linked through 4,4′-bipy, bpete and 4,4′-azpy, respectively. The UV-Vis spectra of these four complexes all exhibit intense high-energy absorptions at λ_max < 340 nm and broad visible bands in a range of 430-550 nm, ascribed to intraligand (IL π → π^∗) transitions and metal-to-ligand charge-transfer (MLCT) transitions, respectively. The density functional theory calculation was used to interpret the absorption spectrum of 1, which further supports the assignment of MLCT character. The binuclear complexes 2 and 3 both display red solid-state emissions centred at 620 and 660 nm from metal-to-ligand charge-transfer excited state, respectively. Interestingly, the electron paramagnetic resonance (EPR) spectral measurements confirm copper(I) complexes oxidized to corresponding copper(II)-halide product upon excitation at 355 nm in dichloromethane solution.     

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.     

Synthesis, crystal structures and biological evaluation of water-soluble zinc complexes of zwitterionic carboxylates

Three water-soluble zinc complexes, [Zn(Cbp)₂Br₂] (1) (Cbp = N-(4-carboxybenzyl)pyridinium), {[Zn(BCbpy)₂(H₂O)₄]₃Br₆·2(BCbpy)·2(4,4′-bipy)} (2) (BCbpy = 1-(4-carboxybenzyl)-4,4′-bipyridinium) and {[Zn₄(Bpybc)₆(H₂O)₁₂](OH)₈·9H₂O}_2n (3) (Bpybc = 1,1′-bis(4-carboxybenzyl)-4,4′-bipyridinium), were synthesized and characterized by IR, elemental analysis and single-crystal X-ray crystallography. In complex 1, the central Zn atom adopts a distorted tetrahedral coordination geometry that is formed from two unidentate Cbp ligands and two Br atoms. For complex 2, the Zn atom in [Zn(BCbpy)₂(H₂O)₄]²⁺ is strongly coordinated by four water molecules and two N atoms from two BCbpy ligands, hence forming an octahedral geometry. In complex 3, each Bpybc ligand bridges two [Zn(H₂O)₃]²⁺ units through two terminal carboxylate groups in a monodentate coordination mode, thus forming a flowerlike two-dimensional network. Agarose gel electrophoresis (GE) and ethidium bromide (EB) displacement experiments indicated that complex 3 was capable of converting pBR322 DNA into open circular (OC) and linear forms, and exhibited high binding affinity toward calf-thymus DNA. MTT assay showed that complex 3 displayed inhibitory activities toward the proliferation of lung adenocarcinoma A549 and mouse sarcoma S-180 cells, with the IC₅₀ values being 27.3 and 48.8 μM, respectively.     

Diverse dimensionalities and structures in copper coordination polymers incorporating substituted aliphatic dicarboxylate ligands and 4,4′-bipyridine

Hydrothermal synthesis has afforded a series of divalent copper coordination polymers with substituted glutarate ligands and the rigid rod tether 4,4′-bipyridine (bpy): {[Cu(Hdmg)₂(bpy)]·H₂O}_n (1, dmg = 3,3-dimethylglutarate), {[Cu₂(dmg)(bpy)₂](ClO₄)]_n (2), [Cu₂(emg)₂(bpy)]_n (3, emg = 3-ethyl, 3-methylglutarate) and [Cu₂(cda)₂(bpy)]_n (4, cda = 1,1-cyclopentanediacetate). All materials were characterized by single-crystal X-ray diffraction. Compound 1 manifests μ₂-oxygen bridged [Cu₂(Hdmg)₄] “X”-patterns connected into a ribbon motif by bpy linkers. On the other hand, 2 possesses mixed-valence [Cu^ICu^IICu^IICu^I] tetrameric clusters bridged by dmg ligands and pillared into an 8-connected body-centered cubic (bcu) cationic lattice by bpy linkers. Compounds 3 and 4 are structurally very similar, displaying chain motifs with {Cu₂(CO₂)₄} paddlewheels connected by dicarboxylates, in turn conjoined into (4,4)-grid coordination polymer layers by bpy tethers. Variable temperature magnetic data indicate the presence of very strong antiferromagnetic coupling within the {Cu₂(CO₂)₄} paddlewheels in the latter two complexes, with g = 2.30(2) and J = −352(3) cm⁻¹ for 3 and g = 2.35(2) and J = −352(5) cm⁻¹ for 4. Significant structural contrasts are evident when compared to previously reported divalent copper/4,4′-bipyridine coordination polymers with unsubstituted or 2-methyl substituted glutarate ligands.