Synthesis, crystal structure and luminescent behaviour of coordination complexes of copper with bi- and tridentate amines and phosphonic acids

The synthesis and crystal structure of four new copper(I) and copper(II) supramolecular amine, and amine phosphonate, complexes is reported. Reaction of copper(I) with 2-,9-dimethyl-1-10-phenanthroline (dmp) produced a stable 4-coordinate Cu(I) species, [Cu^(I)(dmp)₂]Cl · MeOH · 5H₂O (2), i.e., the increased steric hindrance in the ‘bite’ area of dmp did not prevent interaction with the metal and provided protection against oxidation which was not possible for the phen analogue [R. Clarke, K. Latham, C. Rix, M. Hobday, J. White, CrystEngCommun. 7(3) (2005), 28-36]. Subsequent addition of phenylphosphonic acid to (2) produced two structures from alternative synthetic routes. An ‘in situ’ process yielded red block Cu(I) crystals, [Cu^(I)(dmp)₂] · [C₆H₅PO₃H₂ · C₆H₅PO₃H] (4), whilst recrystallisation of (2) prior to addition of the acid (‘stepwise’ process) produced a green, needle-like Cu(II) complex, [Cu^(II)(dmp) · (H₂O)₂ · C₆H₅PO₂(OH)] [C₆H₅PO₂(OH)] (3). However, addition of excess dmp during the ‘stepwise’ process forced the equilibrium towards product (4) and resulted in an optimum yield (99%). The structure of (4) was similar to the phen analogue, [Cu^(II)Cl(phen)₂] · [C₆H₅PO₂(OH) · C₆H₅PO(OH)₂] (1) [R. Clarke, K. Latham, C. Rix, M. Hobday, J. White, CrystEngCommun. 7(3) (2005), 28-36], but the presence of dmp exerted some influence on global packing, whilst (3) exists as a polymeric layered material. In contrast, reaction of copper(I) with di-2-pyridyl ketone (dpk), followed by phenylphosphonic acid produced purple/blue Cu(II) species, [Cu^(II)(dpk · H₂O)₂] Cl₂ · 4H₂O (5), and [Cu^(II)(dpk · H₂O)₂] · [C₆H₅PO₂(OH)₂ · C₆H₅PO(OH)₂] (6), respectively, i.e., in both cases oxidation of copper occurred. Solid-state luminescence was observed in (2) and (4). The latter showing a 5-fold enhancement in intensity.     

Copper(II) complexes with 2,2′-biimidazole. Preparation and crystal structure determination of a complex of stoichiometry Cu1.5Cl3(H2bim)2 (H2bim=2,2′-biimidazole)

By reacting 2,2′-biimidazole and copper(II) chloride in aqueous HCl we obtained the complex CuCl₂(H₂bim) as the main product and a compound with stoichiometry Cu_1.5Cl₃(H₂bim)₂ as a byproduct. The structure of the latter compound has been determined by X-ray analysis: monoclinic, a= 794.0(3), b=3146.8(6), c=722.9(4) pm, β= 114.2(1)°, space group P21/c. The compound actually contains two species, namely [Cu(H₂bim)₂]Cl₂ and [CuCl₂(H₂bim)] in a 1:2 molar ratio.     

Copper(II) complexes based on a new chelating 4-(3,5-diphenyl-1H-pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine ligand: Synthesis and crystal structures. Lone pair-π, C-H···π, π-π and C-H···A (A = N, Cl) non-covalent interactions

A new bidentate chelating pyrazolylpyrimidine ligand bearing a strong electron-donating substituent, i.e. 4-(3,5-diphenyl-1H-pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine (L) (Scheme 1), has been synthesized and used to obtain the copper(II) complexes by reaction with CuCl₂. The molar ratio Cu:L = 1:2 leads to isolation of a complex having CuL₂Cl₂ empirical formula, while the molar ratio Cu:L = 1:1 gives a complex with CuLCl₂ empirical formula. The crystal structure of L as well as the structures of both complexes were studied by single crystal X-ray diffraction. The crystal structure of CuL₂Cl₂ compound is formed by trans-[CuL₂Cl₂] mononuclear molecules. Surprisingly, in contrast to the previous compound having molecular structure, the crystal structure of CuLCl₂ consists of mononuclear [CuL₂Cl]⁺ complex cations and dinuclear [Cu₂Cl₆]²⁻ anions. Thus, formula of CuLCl₂ complex can be represented as [CuL₂Cl]₂[Cu₂Cl₆]. In both complexes molecules of L adopt bidentate chelating coordination mode through N² atom of pyrazole and N³ atom of pyrimidine rings forming five-membered CuN₃C metallocycles. Owing to C-H···N interactions and π-π-stacking L molecules form 2D network. In the structure of trans-[CuL₂Cl₂] there exist double lone pair(N(piperidine))-π(pyrimidine) interactions and C-H···Cl contacts resulting in the formation of 1D chains. Layered 2D structure of [CuL₂Cl]₂[Cu₂Cl₆] results from C-H···Cl, C-H···π and double lone pair(Cl([CuL₂Cl]⁺ complex cation)-π(pyrimidine) interactions.     

Synthesis, spectroscopic and structural characterization of some novel adducts of copper(II) salts with unidentate nitrogen bases

Syntheses, spectroscopic characterization and single crystal X-ray studies are reported for a number of complexes of copper(II) salts with simple monodentate nitrogen bases. The 1:4 adduct of copper(II) sulfate with 3,5-dimethylpyridine (m₂py) CuSO₄·4m₂py, takes the form [(O₃SO)Cu(m₂py)₄], the Cu-O vector of the square-pyramidal coordination environment being disposed on the 4-axis in tetragonal space group P4/n. The complex CuCO₃·Cu(NCS)₂·4py is a linear polymer, taking the form ?O·Cu(py)₂·O·C{O·Cu(py)₂(NCS)₂}·O·Cu(py)₂? (etc.), all atoms lying in the mirror plane of space group Pnma, excepting the pair of ‘py’ (pyridine) ligands disposed to either side. In Cu(OH)I·3/4I₂·2py·1/2MeCN ≡ [{(py)₂Cu(OH)}₄](I₃)₃I·2MeCN a novel cubanoid tetranuclear cation is found (2-symmetry). The EPR spectra of the above compounds show a trend in the anisotropy of the g-values that correlates well with the crystal structures. Obtained only in small quantities but supported by single crystal X-ray studies are the adduct of Cu(OH)Cl with pyrrolidine (pyrr), Cu(OH)Cl:pyrr (1:3), which takes the centrosymmetric binuclear form [(pyrr)₃Cu(μ-OH)₂Cu(pyrr)₃]Cl₂, the copper atom being disposed in a distorted trigonal bipyramidal array, and the adduct 3CuCl₂·CuO·4quin, [Cu₄Cl₆O(quin)₄]Cl₂, which contains the familiar Cu₄Cl₆O core with monodentate quinuclidine (quin) attached to the copper atoms; this compound crystallizes in the cubic space group .     

A new (8,3)-connected anionic 3-D open-framework based on paradodecatungstate and Cu linkers

The hydrothermal reaction of [H₂W₁₂O₄₂]¹⁰⁻ precursors and CuCl₂ in a CH₃COOK/CH₃COOH solution (pH 3.5) led to the isolation of a new compound, KNa₃[Cu(H₂O)₂{Cu(H₂O)₃}₂(H₂W₁₂O₄₂)] · 16H₂O (1). Compound 1 possesses a new anionic three-dimensional (3-D) open-framework based on the [H₂W₁₂O₄₂]¹⁰⁻ building blocks and Cu^II linkers. This anionic 3-D framework represents the first example of a (8,3)-connected structural topology in POM-based solid materials. The magnetic behavior of 1 exhibits weak antiferromagnetic interaction.     

Low-dimensional compounds containing cyano groups. XIX. Crystal structure, spectroscopic, thermal and magnetic properties of {[Cu(tn)2]3[Pt(CN)4]2}[Pt(CN)4] (tn = 1,3-diaminopropane) complex

Violet prismatic crystals of {[Cu(tn)₂]₃[Pt(CN)₄]₂}[Pt(CN)₄] (tn = 1,3-diaminopropane) were crystallized from the water-methanol solution containing CuCl₂·2H₂O, tn and K₂[Pt(CN)₄]·3H₂O. Prepared complex was characterized using elemental analysis, infrared and UV-Vis spectroscopy, magnetic measurement and thermal analysis. X-ray analysis revealed an ionic character of the complex containing mononuclear square planar [Pt(CN)₄]²⁻ complex anions and penta-nuclear [Cu(tn)₂-Pt(CN)₄-Cu(tn)₂-Pt(CN)₄-Cu(tn)₂]²⁺ complex cations. The inner Cu(II) atom of the complex cation is hexa-coordinated, whereas two crystallographically equivalent peripheral Cu(II) atoms are penta-coordinated in the shape of a deformed square pyramid. Four v(CN) absorption bands observed in the IR spectrum are in agreement with the higher number of crystallographically different cyano groups and a broad highly asymmetric band observed in the reflectance UV-Vis spectrum is consistent with the presence of both hexa- and penta-coordinated Cu(II) atoms in the structure. The temperature dependence of the inverse susceptibility suggests the presence of a weak antiferromagnetic exchange coupling between Cu(II) ions. The complex is stable up to 210 °C when its two-stage thermal decomposition starts.     

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.     

Syntheses, structures and properties of copper(II) complexes containing N-(2-hydroxybenzyl)-amino amide ligands

Four copper(II) complexes containing the reduced Schiff base ligands, namely, N-(2-hydroxybenzyl)-glycinamide (Hsglym) and N-(2-hydroxybenzyl)-l-alaninamide (Hsalam) have been synthesized and characterized. The crystal structures of [Cu₂(sglym)₂Cl₂] (1), [Cu₂(salam)₂(NO₃)₂] · H₂O (3), [Cu₂(salam)₂(NO₃)(H₂O)](NO₃) · 1.5H₂O (4), [Cu₂(salam)₂](ClO₄)₂ · 2H₂O (5) show that the Cu(II) atoms are bridged by two phenolato oxygen atoms in the dimers. The sglym ligand bonded to Cu(II) in facial manner while salam ligand prefers to bind to Cu(II) in meridonal geometry. Variable temperature magnetic studies of 3 showed it is antiferromagnetic. These Cu(II) complexes and [Cu₂(sglym)₂(NO₃)₂] (2), exhibit very small catecholase activity as compared to the corresponding complexes containing acid functional groups.     

Two novel hybrid compounds based on [MW12O40] (M = B, Al) heteropolyanions and copper coordination polymer with bpp ligands

Under hydrothermal condition, two novel organic-inorganic hybrid compounds, [Cu(bpp)][Cu_2.5(bpp)₃(Hbpp)]H_0.5[BW₁₂O₄₀]·1.5H₂O (1) and [Cu(en)₂(H₂O)]{[Cu(bpp)]₃[AlW₁₂O₄₀]}·H₂O (2) (bpp = 1,3-bis(4-pyridyl)propane; en = ethylenediamine), have been synthesized based on B/Al atom-centered Keggin-type polyoxometalates combined with Cu ions and bpp ligands. The two compounds are characterized through single-crystal X-ray diffraction analysis, elemental analyse, IR, UV and TG. For compound 1, as the nodes, the [BW₁₂O₄₀]⁵⁻ polyanions link to the [Cu_2.5(bpp)₃(Hbpp)]^3.5+ oligomers, leading to the formation of 1D helical chains which further attach to the macrocycles [Cu₂(bpp)₂]²⁺ via the Cu-O weak interaction to construct the 2D “wave-like” layers. For compound 2, the {[Cu(bpp)]₄[AlW₁₂O₄₀]₂} unit is obtained by the interaction between two Keggin-type [AlW₁₂O₄₀]⁵⁻ polyanions and one tetranuclear macrocycle composed by four [Cu(bpp)]⁺ complex cations. Furthermore, the units are sandwiched by two 1D “wave-like” polymeric chains resulting in a new 1D structure. In addition, the electrochemical properties and electrocatalytic activities of these two compounds have been studied in this paper.     

Synthesis and characterization of new oligomeric and polymeric complexes based on the [Cu(bpca)] unit [Hbpca = bis(2-pyridylcarbonyl)amine]

Five novel bpca-based Cu(II) polynuclear coordination compounds [Hbpca = bis(2-pyridylcarbonyl)amine] were prepared using the [Cu(bpca)(H₂O)₂](NO₃)·2H₂O (1) building block and characterized by single crystal X-ray diffraction. We have also isolated and characterized two new crystal forms of the starting species, with lower water contents. Three of the new products are dinuclear complexes obtained by reacting 1 with different rigid or flexible spacer ligands: [Cu₂(bpca)₂(H₂O)₂(bipy)](NO₃)₂·6H₂O (2) (bipy = 4,4′-bipyridine) and [Cu₂(bpca)₂(H₂O)₂(bpete)](NO₃)₂·xH₂O (3) [bpete = (E)-1,2-di(pyridin-4-yl)ethane] are linear dumbbell-like species with Cu?Cu separations of 11.075 and 13.275 Å, respectively. The third dinuclear compound, [Cu₂(bpca)₂(H₂O)₂(bpx)](NO₃)₂·8H₂O (4) [bpx = 1,4-bis((1H-pyrazol-1-yl)methyl)benzene], with the flexible bpx ligand, assumes an unusual S-shaped conformation and shows a quite shorter Cu?Cu contact of 6.869 Å only. We have also obtained a chiral 1D neutral polymeric complex, [Cu₃(bpca)₂(bipy)₃(NO₃)₄]·6H₂O (5), that shows a central linear -Cu-bipy-Cu- chain, with all these Cu atoms connected to two lateral [Cu(bpca)(NO₃)₂]⁻ groups on two opposite sides by means of bipy spacers. An unprecedented type of Cu(II) neutral trinuclear complex, [Cu₃(bpca)₂(H₂O)₂(NO₃)₂] (6), was obtained which has a centrosymmetric structure with two external [Cu(bpca)(NO₃)₂]⁻ units chelating on a central copper atom via the two pairs of carbonyl groups of the bpca ligands. The central metal is octahedral with two axial water molecules, while the two lateral Cu atoms are in square pyramidal geometry; the Cu?Cu separation is 5.205 Å. The magnetic properties of 6 have been rationalized through a ferromagnetic coupling between the central metal ion and the peripheral ones which are coupled by a smaller antiferromagnetic interaction. DFT calculations have been also performed in order to give a better insight into magnetic interactions.     

Syntheses and crystal structures of cyano-bridged cluster-metal layered coordination polymers [Cu(dien)]3[W4Te4(CN)12] · 9H2O and [Ni(en)(NH3)]3[W4Se4(CN)12] · 7.5H2O

Two new tetrahedral tungsten cyanide cluster compounds, [Cu(dien)]₃[W₄Te₄(CN)₁₂] · 9H₂O (1) (dien=diethylenetriamine) and [Ni(en)(NH₃)]₃[W₄Se₄(CN)₁₂] · 7.5H₂O (2) (en=ethylenediamine), were synthesized by treating aqueous solutions of the saltlike cluster compound K₆[W₄Te₄(CN)₁₂] · 5H₂O/K₆[W₄Se₄(CN)₁₂] · 6H₂O with copper(II)/nickel(II) chloride in aqueous ammonia containing dien/en. The cyano-bridged layered coordination polymeric compounds were characterized by single-crystal X-ray diffraction analysis: monoclinic, space group P2₁ for 1; trigonal, space group for 2. Structures of 1 and 2 consist of infinite neutral layers of cluster components {W₄Te₄(CN)₁₂}/{W₄Se₄(CN)₁₂} connected, one another by {Cu(dien)} or {Ni(en)(NH₃)} fragments, respectively.     

Zinc(II) and copper(II) 1D coordination polymeric complexes of a reduced Schiff base ligand

The reaction of Zn(ClO₄)₂ · 6H₂O and Cu(ClO₄)₂ · 6H₂O with H₃Sas (H₃Sas = N-(2-hydroxybenzyl)-L-aspartic acid in water afforded the complexes [Zn₆(Sas)₄(H₂O)₈]·5H₂O (1) and [Cu(HSas)(H₂O)] (2), respectively, which were characterized by infrared spectroscopy, elemental analysis, thermogravimetry and single-crystal X-ray crystallography. In 1, the pentanuclear clusters formed by four H₃Sas ligands and five Zn(II) metal ions are bridged by the “[Zn(H₂O)₄]²⁺” cations to form 1D polymeric chains. While in 2, the mononuclear [Cu(HSas)(H₂O)] repeating units form a 1D zigzag chain and further extended by strong intermolecular hydrogen bonds to form a 2D sheet. The different coordination geometries of Cu(II) and Zn(II) show significant influence on the polymeric structures.     

Coordination polymers built from Cu(II) and pyrazine-2,3,5,6-tetracarboxylate or pyridine-2,4,6-tricarboxylate: Structural and magnetic studies

Room temperature reaction of Cu(NO₃)₂ · 6H₂O and pyrazine-2,3,5,6-tetracarboxylic acid (ptecH₄) in the presence of pyridine (py) in water-methanol (1:1) mixture results in the formation of {[Cu₂(ptec) · (py)₂ · (H₂O)₃] · 4H₂O}_n (1). With pyridine-2,4,6-tricarboxylic acid (pytcH₃) and Cu(NO₃)₂ · 6H₂O, crystals of {[Cu(pytc)] · 1/2[Cu(H₂O)₆] · H₂O}_n (2) could be obtained hydrothermally at 180 °C. The structure of 1 consists of 2D polymeric sheets. These sheets are stacked on top of one another due to strong C-H?π interactions forming an overall 3D structure. The structure of 2, on the other hand, consists of twin-chain coordination polymers. The void spaces between two polymeric chains are occupied by [Cu(H₂O)₆]²⁺ ions which are H-bonded to the polymeric chains. The variable temperature magnetic measurements for 1 and 2 show weak antiferromagnetic interaction between Cu(II) centers. The EPR spectra of the compounds are consistent with their structures.     

Effect of copper-substitution on the structure and nuclearity of Cu(II)-pyrazolates: from trinuclear to tetra-, hexa- and polynuclear complexes

The influence of terminal ligands on the structure and nuclearity of copper(II)-pyrazolates has been investigated. Exchange of the chloride ligands of [Cu₃(μ₃-X)(μ-pz)₃Cl₃]ⁿ⁻ (X=O, OH; n=2, 1) or [Cu₃(μ₃-Cl)₂(μ-pz)₃Cl₃]²⁻ complexes for cyanate, acetate or bromide ligands maintains the integrity of the triangular species: PPN[Cu₃(μ₃-OH)(μ-pz)₃(NCO)₃], PPN[Cu₃(μ₃-OH)(μ-pz)₃(O₂CCH₃)₃(H₂O)] · H₂O, Bu₄N[Cu₃(μ₃-OH)(μ-pz)₃(O₂CCH₃)₃] · 3H₂O and (Bu₄N)₂[Cu₃(μ₃-Br)₂(μ-pz)₃Br₃] have been prepared and characterized by spectroscopic and X-ray diffraction techniques, respectively. In contrast, tetranuclear complexes (Bu₄N)₂[Cu₄(μ₃-OH)₂(μ-4-X-pz)₂(μ-O₂CPh)₂(O₂CPh)₄] (X=H, Cl, Br, NO₂) and the hexanuclear complex (Bu₄N)₂[Cu₆(μ₃-O)(μ₃-OH)(μ-4-NO₂-pz)₆(μ-O₂CPh)₃(O₂CPh)₂(H₂O)] · (CH₂Cl₂)_0.5 have been obtained on substitution for benzoate ligands. An attempt to partially substitute the chlorides for tert-butoxide ligands, also provided a tetranuclear complex, (Bu₄N)₂[Cu₄(μ-OH)₂(μ-pz)₄Cl₄], without incorporation of the incoming ligand. Similarly, removal of all chloride ions in the absence of an appropriate substituting ligand leads to higher nuclearity metallacycles [Cu(μ-OH)(μ-pz)]_n (n=6, 8, 9, 12, 14).     

A series of inorganic-organic hybrid compounds constructed from bis(undecatungstophosphate) lanthanates and copper-organic units

A series of inorganic-organic hybrid compounds built from bis(undecatungstophosphate) lanthanates and copper-complexes, namely, H₈[Cu(en)₂H₂O]₄[Cu(en)₂]{[Cu(en)₂][La(PW₁₁O₃₉)₂]}₂·18H₂O (1), H₆[Na₂(en)₂(H₂O)₅][Cu(en)₂H₂O]₄[Cu(en)₂]{[Cu(en)₂][Ce(PW₁₁O₃₉)₂]}₂·16H₂O (2), H₆[Na₂(en)₂(H₂O)₅][Cu(en)₂H₂O]₄[Cu(en)₂]{[Cu(en)₂][Pr(PW₁₁O₃₉)₂]}₂·18H₂O (3), H₆[Na₂(en)₂(H₂O)₄][Cu(en)₂H₂O]₄[Cu(en)₂]{[Cu(en)₂][Nd(PW₁₁O₃₉)₂]}₂·14H₂O (4), H₆[Na₂(en)₂(H₂O)₅][Cu(en)₂H₂O]₄[Cu(en)₂]{[Cu(en)₂][Sm(PW₁₁O₃₉)₂]}₂·20H₂O (5), and H₇[Cu(en)₂]₂[Sm(PW₁₁O₃₉)₂]·10H₂O (6) (where en = 1,2-ethylenediamine), have been prepared. In these compounds, two lacunary [PW₁₁O₃₉]⁷⁻ anions sandwich an eight-coordinated Ln(III) cation to yield [Ln(PW₁₁O₃₉)₂]¹¹⁻ anion in a twisted square anti-prismatic geometry, which is further bridged by [Cu(en)₂]²⁺ fragments to generate a 1D zigzag-like chain. In 1-6, the coordination bond interactions and weak interactions between adjacent 1D chains play an important role in the zigzagging distances and angles of different 1D chains. The magnetic studies indicate that antiferromagnetic interactions exist in compounds 1, 2 and 4.     

Self-assembly of four three-dimensional reduced molybdenum(V) phosphates decorated with transitional metal complexes

Four new three-dimensional materials built from reduced molybdenum(V) phosphates as building blocks and transitional metal (Co, Zn and Cd) complexes as linkers, (Hbpy)₂[Co(bpy)(H₂O)]₂[Co(H₂PO₄)₂ (HPO₄)₆(MoO₂)₁₂(OH)₆] (1), [Co(H₂O)₄]₂[Co(Hbpy)(H₂O)]₂[Co(bpy)][Co(HPO₄)₄(PO₄)₄(MoO₂)₁₂(OH)₆] · 6H₂O (2), Na₂[Zn(Hbpy)(H₂O)₂]₂[Zn(Hbpy)]₂[Zn(HPO₄)₂(PO₄)₆(MoO₂)₁₂(OH)₆] · 4H₂O (3), (H₂bpy)₂[Cd(bpy)(H₂O)]₂[Cd(bpy)(H₂O)₂]₂[Cd(HPO₄)₄(PO₄)₄(MoO₂)₁₂(OH)₆] · 2H₂O (4) (bpy = 4,4′-bipyridine), have been synthesized and characterized by elemental analyses, IR, TG, and single crystal X-ray diffraction. The 3-D framework of 1 is constructed from Co[P₄Mo₆]₂ dimers bonded together with [Co(bpy)]_n coordination polymer chains. In compound 2, the Co[P₄Mo₆]₂ dimers are linked by both [Co(bpy)] complex chains and the cobalt dimers to form a 3-D framework. Compounds 1 and 2 represent the first examples of reduced molybdenum(V) phosphates decorated with transition metal complexes chains. The 3-D framework of 3 is constructed from Zn[P₄Mo₆]₂ dimers bonded together with [Zn(bpy)] coordination complexes and [Zn(bpy)(H₂O)₂] complexes. In compound 4, the Cd[P₄Mo₆]₂ dimers are coordinated with [Cd(bpy)(H₂O)] and [Cd(bpy)(H₂O)₂] complexes to construct a 3-D structure. To our best knowledge, it is the first time that linear ligand 4,4′-bpy molecules have been grafted into the backbone of reduced molybdenum phosphates. Furthermore, the magnetic properties of compounds 1 and 2 are reported.     

Selective inclusion of DMF molecules within non-covalent cavity

[Me₄P]₄[Cu₄(mnt)₄]·2CH₃CN (1), [Me₄P]₄[Cu₄(mnt)₄]·2CH₃NO₂ (2), [Me₄P]₄[Cu₄(mnt)₄]·2DMF (3) and [Me₄P]₄[Cu₄(mnt)₄]·2C₃H₃N (4) (mnt = maleonitriledithiolate, [S₂C₂(CN)₂]²⁻) clusters are readily synthesized in several solvents like acetonitrile, nitromethane, N,N-dimethylformamide and acrylonitrile to provide respective solvent as guest within the non-covalent cavity of the cluster ion. The guest species is accommodated within non-covalent cavity that is generated by two adjacent {Cu₄(mnt)₄} cores bridging with tetramethylphosphonium cation through hydrogen bonding. These hydrogen bonds are not strong and when mixed solvents were used selective DMF binding takes place to yield only complex 3 over other complexes.     

New yttrium(III) and copper(II) coordination polymers with partially protonated cyclohexane-1,2,3,4,5,6-hexacarboxylato ligands: Synthesis, crystal structures and properties

Two coordination polymers, [Y(H₂O)₄(H₃chhc)]·6H₂O (1) and [Cu₅(H₂O)₁₀(Hchhc)₂]·4H₂O (2) with H₆chhc = cyclohexane-1,2,3,4,5,6-hexacarboxylic acid) represent rare examples of metal complexes with partially protonated cyclohexane-1,2,3,4,5,6-hexacarboxylato ligands. The [Y(H₂O)₄]³⁺ units in 1 are interlinked by the triprotonated (H₃chhc)³⁻ anions in a η⁵μ₄ bridging mode to form 2D (4³)₂(4⁶·6⁶·8³) topological networks, which are stacked along [0 1 0] direction in ···ABAB··· fashion with the lattice H₂O molecules sandwiched between layers. The pentameric [Cu₅(H₂O)₁₀]¹⁰⁺ units in 2 are bridged by monoprotonated (Hchhc)⁵⁻ anions in a η⁸μ₆ fashion to generate a 3D MOF of an unprecendented (4³)(4⁵·6⁷·8³) topology with the lattice H₂O molecules in channels. The temperature-dependent magnetic susceptibility data of 2 could be modeled to a combination of a linear chain of equally-spaced Cu(II) ions (J₁ = 1.86 cm⁻¹) with an isosceles triangular Cu₃ unit (J₂ = 5.86 cm⁻¹).     

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.     

Synthesis of copper(II) complexes with 3,5-bis(4,6-dimethylpyrimidin-2-yl)-4H-1,2,4-triazol-4-amine (L). Molecular and crystal structures of L and [Cu2L2Cl4]·2MeCN

A series of copper(II) complexes, i.e. Cu₂LCl₄, CuLCl₂·H₂O and [Cu₂L₂Cl₄]·2MeCN (8), based on a new potentially polytopic ligand, 3,5-bis(4,6-dimethylpyrimidin-2-yl)-4H-1,2,4-triazol-4-amine (3b, L), have been synthesized. The crystal structures of L and [Cu₂L₂Cl₄]·2MeCN were studied by X-ray single crystal analysis. The dinuclear compound [Cu₂L₂Cl₄]·2MeCN represents the first example of structurally characterized metal complexes with 3,5-di(pyrimidin-2-yl)-4H-1,2,4-triazol-4-amines. Both copper atoms have distorted tetragonal-pyramidal 3N + 2Cl environment. Surprisingly, in contrast to the complexes based on 3,5-di(pyridin-2-yl)-4H-1,2,4-triazol-4-amine (pyridinyl analog of L), the compound [Cu₂L₂Cl₄]·2MeCN adopts a dinuclear trans-(N′,N¹,N²)₂ double bridging binding mode which is due to tridentate coordination of two L molecules linking two copper atoms through N¹,N²-triazole and N′-pyrimidine atoms. It seems to be reasonable that it is methyl groups in pyrimidinyl moiety that obstruct the expected dinuclear (N′,N¹,N²,N″)₂ double bridging coordination being one of the most common for 4-substituted 3,5-di(pyridin-2-yl)-4H-1,2,4-triazoles and 3,5-di(pyridin-2-yl)-1,2,4-triazolates. Due to π-π stacking interactions, molecules of Cu₂L₂Cl₄ in the structure of [Cu₂L₂Cl₄]·2MeCN form 1D chains.