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.     

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.     

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.     

Preferential azido bridging regulating the structural aspects in cobalt(III) and copper(II)-Schiff base complexes: Syntheses, magnetostructural correlations and catalytic studies

A tridentate NNO donor Schiff base ligand [(1Z,3E)-3-((pyridin-2-yl)methylimino)-1-phenylbut-1-en-1-ol = LH] in presence of azide ions coordinates with cobalt(II) and copper(II) ions giving rise to three new coordination complexes [Co₂(L)₂(μ_1,1-N₃)₂(N₃)₂] (1), [Cu₂(L)₂(μ_1,3-N₃)]·ClO₄ (2) and [(μ_1,1-N₃)₂Cu₅(μ-OL)₂(μ_1,1-N₃)₄(μ_1,1,1-N₃)₂]_n (3). The complexes have been characterized by elemental analysis, FT-IR, UV-Vis spectral studies, and single crystal X-ray diffraction studies. These complexes demonstrate that under different synthetic conditions the azide ions and the Schiff base ligand (LH) show different coordination modes with cobalt(II) and copper(II) ions, giving rise to unusual dinuclear and polynuclear species (1, 2 and 3) whose structural variations are discussed. Magneto-structural correlation for the very rare singly μ_1,3-N₃ bridged Cu^II-Schiff base dinuclear species (2) has been studied. In addition, the catalytic properties of 1 for alkene oxidation and the general catalase-like activity behavior of 2 have been discussed.     

Dinuclear copper(I) complexes containing diimine and phosphine ligands: Synthesis, copper-copper separation and photophysical properties

Dinuclear copper(I) complexes with bridging bis(dicyclohexylphosphino)methane (dcpm) or bis(diphenylphosphino)methane (dppm) and 2,2′-bipyridine or 2-[N-(2-pyridyl)methyl]amino-5,7-dimethyl-1,8-naphthyridine (L), [Cu₂(bpy)₂(dppm)₂](BF₄)₂ (1), [Cu₂(bpy)₂(dcpm)](BF₄)₂ (2), [Cu₂(L)(dppm)](BF₄)₂ (3) and [Cu₂(L)(dcpm)](BF₄)₂ (4) were prepared, and their structures were determined by X-ray crystal analysis. Two-, three-, and four-coordinate copper(I) centers are found in these complexes. Compounds 3 and 4 show close Cu^I?Cu^I separations of 2.664(3) and 2.674(1) Å, respectively, whereas an intramolecular copper-copper distance of 3.038 Å is found in 2 having only dcpm as an additional bridge. Powdered samples of 1, 3, and 4 display intense and long-lived phosphorescence with λ_max at 533, 575, and 585 nm at room temperature, respectively. In the solid state, 2 exhibits only a weak emission at 555 nm. The time-resolved absorption and emission spectra of these complexes were investigated. The difference in the emission properties among complexes 1-4 suggests that both Cu^I?Cu^I distances and coordination environment of the copper(I) centers affect the excited-state properties.     

Four copper(II) coordination polymers with a tetrachlorinated benzenedicarboxylate ligand: Solvent effect on diversiform supramolecular arrays

To further investigate the solvent effect on the structures of coordination polymers, a series of polymeric Cu^II complexes have been synthesized and characterized by single-crystal diffraction through combining of 2,3,5,6-tetrachloro-1,4-benzenedicarboxylic acid (H₂BDC-Cl₄) with Cu^II perchlorate. The products including {[Cu(BDC-Cl₄)(py)₃] · H₂O}_n (py = pyridine) (1), {[Cu(BDC-Cl₄)(dioxane)(H₂O)₂] · dioxane}_n (2), and {[Cu₂(BDC-Cl₄)₂(DMF)₄] · 2G}_n (G = MeOH in 3 and G = EtOH in 4) have been obtained in different mixed solvents systems. With the change of the solvent system from pyridine/H₂O (1:1) into dioxane/H₂O (1:1), the infinite 1-D Cu^II-BDC-Cl₄ chain motif in 1 is tuned into the 2-D (4,4) layered structure in 2 with the coordination of dioxanes to copper atoms. When the solvent system is changed into DMF/MeOH (1:1), then into DMF/EtOH (1:1), similar 1-D Cu^II-BDC-Cl₄ double chains are afforded in 3 and 4 with different solvents inclusion. Moreover, the judicious choice of binding-guests leads to numerous coordination geometries of Cu^II centers and final dissimilar supramolecular lattices of 1-4 from 1-D to 3-D via robust hydrogen-bonding interactions. The spectroscopic, thermal, and fluorescent properties of 1-4 have also been investigated.     

Imidazole derivatives of binuclear copper (II) and nickel (II) complexes incorporating bis(1,4,7-triazacyclononan-1-yl) ligands

A series of new binuclear copper (II) and nickel (II) complexes of the macrocyclic ligands bis(1,4,7-triazacyclononan-1-yl)butane (L^but) and bis(1,4,7-triazacyclononan-1-yl)-m-xylene (L^mx) have been synthesized: [Cu₂L^butBr₄] (1), [Cu₂L^but(imidazole)₂Br₂](ClO₄)₂ (2), [Cu₂L^mx(μ-OH)(imidazole)₂](ClO₄)₃ (3), [Cu₂L^but(imidazole)₄](ClO₄)₄ · H₂O (4), [Cu₂L^mx(imidazole)₄](ClO₄)₄ (5), [Ni₂ L^but(H₂O)₆](ClO₄)₄ · 2H₂O (6), [Ni₂L^but(imidazole)₆](ClO₄)₄ · 2H₂O (7) and [Ni₂L^mx (imidazole)₄(H₂O)₂](ClO₄)₄ · 3H₂O (8). Complexes 1, 2, 7 and 8 have been characterized by single crystal X-ray studies. In each of the complexes, the two tridentate 1,4,7-triazacyclononane rings of the ligand facially coordinate to separate metal centres. The distorted square-pyramidal coordination sphere of the copper (II) centres is completed by bromide anions in the case of 1 and/or monodentate imidazole ligands in complexes 2, 4 and 5. Complex 3 has been formulated as a monohydroxo-bridged complex featuring two terminal imidazole ligands. Complexes 6-8 feature distorted octahedral nickel (II) centres with water and/or monodentate imidazole ligands occupying the remaining coordination sites. Within the crystal structures, the ligands adopt trans conformations, with the two metal binding compartments widely separated, perhaps as a consequence of electrostatic repulsion between the cationic metal centres. The imidazole-bearing complexes may be viewed as simple models for the coordinative interaction of the binuclear complexes of bis (tacn) ligands with protein molecules bearing multiple surface-exposed histidine residues.     

Synthesis, structure and properties of unsymmetrical μ-alkoxo-dicopper(II) complexes: biological relevance to phosphodiester and DNA cleavage and cytotoxic activity

The unsymmetric dinucleating ligand N-(2-hydroxybenzyl)-N,N′,N′-tris(2-pyridylmethyl)-1,3-diaminopropan-2-ol (L = H₂btppnol) and the corresponding copper(II) complex [Cu₂(Hbtppnol)(μ-CH₃COO)](ClO₄)₂ (1) have been recently reported in part in a short communication [Inorg. Chem. Commum. 8 (1999) 334]. In this study, we investigated the ability of complex 1 to promote the hydrolysis of P-O phosphate diester bonds in bis(2,4-dinitrophenyl) phosphate (2,4-BDNPP) and the cleavage of genomic and plasmid DNA molecules. Reaction of 1 with excess of the diester 2,4-BDNPP, at pH 7.0, results in the formation of the monoester phosphate coordinated [Cu₂(Hbtppnol)(μ-((NO₂)₂-C₆H₃)PO₄)]ClO₄ (3) complex, which was also characterized by X-ray crystallography. In addition, the stable μ-phosphate complex [Cu₂(Hbtppnol)(μ-(NO₂-C₆H₄)PO₄)](ClO₄) (2) obtained from the reaction of 4-nitrophenyl phosphate with complex 1 was also characterized by X-ray crystallography, indicating that 1 is unable to cleave monoester-phosphate bonds. The kinetics for the promotion of bis(2,4-dinitrophenyl) phosphate (2,4-BDNPP) hydrolysis by complex 1 was investigated as a function of pH, catalyst concentration and substrate concentration. On the basis of kinetic and potentiometric studies, the deuterium isotope effect (k^H/k^D ∼ 1) and the X-ray structure of the monoester phosphate coordinated [Cu₂(Hbtppnol)(μ-((NO₂)₂-C₆H₃)PO₄)]ClO₄ (3) complex as the product of the reaction, we demonstrated that the aquo/hydroxo complex is the active species and the reaction occurs through the formation of a ternary complex in which one Cu^II binds the substrate and the second copper center has a terminal bound hydroxide to attack the phosphorus atom, at physiological pH. A rate enhancement factor of ∼100 was calculated relative to that measured for the uncatalyzed reaction under identical conditions. Complex 1 effectively promotes the cleavage of double-stranded genomic and plasmid DNA, at physiological pH, probably through a hydrolytic mechanism in agreement with that proposed for the reaction of 1 with 2,4-BDNPP. Finally, cytotoxic activity of 1 in a human small cell lung carcinoma cell line (GLC4) and its cisplatin resistant subline (GLC4/CDDP) was studied and the IC₅₀ values were determined.     

Bidentate guanidine ligands with ethylene spacer in copper-dioxygen chemistry: Structural characterization of bis(μ-hydroxo) dicopper complexes

The syntheses of the aliphatic bidentate guanidine-amine-hybrid ligands DMEGdmae (L1), TMGdmae (L2), TMGdeae (L3) and DPipGdmae (L4) as well as the reaction of their Cu(I) complexes with molecular oxygen (monitored by UV-Vis spectroscopy) are reported. The molecular structures of 10 bis(μ-hydroxo) dicopper complexes based on these ligands are described. The solid state structures of [Cu₂(μ-OH)₂(DMEGdmae)₂]X₂ (X⁻ = I⁻ (1), CF₃SO₃⁻ (2), SbF₆⁻ (3), PF₆⁻ (4)), [Cu₂(μ-OH)₂(TMGdmae)₂]X₂ (X⁻ = I⁻ (5), CF₃SO₃⁻ (6)), [Cu₂(μ-OH)₂(TMGdeae)₂]Cu₂I₄ (7) and [Cu₂(μ-OH)₂(DPipGdmae)₂]X₂ (X⁻ = CF₃SO₃⁻ (8), SbF₆⁻ (9), PF₆⁻ (10)) show a square-planar distorted coordination of the copper(II) ion. The bis(μ-hydroxo) dicopper complex 1 exhibits a Cu···Cu distance of 2.860(1) Å, which is one of the smallest observed for hydroxo-bridged copper compounds so far. The influence of the anion on the structure of the bis(μ-hydroxo) dicopper(II) unit is analyzed for the reported complexes and a literature overview with emphasis on the structural characteristics of the Cu₂O₂ moiety of bis(μ-hydroxo) dicopper(II) and bis(μ-oxo) dicopper(III) is given.     

Coordination chemistry of heterocycle-functionalized diazamesocycles: tuning the productive Ni complexes through altering the pendants of ligands

In order to further understand the coordination chemistry of diazamesocyclic systems, a series of mononuclear Ni^II complexes with 1,4-diazacycloheptane (DACH) functionalized by additional imidazole or pyridine donor pendants, including [NiL¹](ClO₄)₂ · H₂O (1), [NiL¹Cl](ClO₄) (2), [NiL²Cl](ClO₄) · CH₃OH (3), [NiL²Cl][NiL²](ClO₄)₃ (4) and [NiL³](ClO₄)₂ (5), where L¹ = 1,4-bis(N-1-methylimidazol-2-yl-methyl)-1,4-diazacycloheptane, L² = 1,4-bis(pyridyl-2-yl-methyl)-1,4-diazacycloheptane, and L³ = 1,4-bis-(imidazol-4-yl-methyl)-1,4-diazacycloheptane, have been prepared and characterized. A detailed study on the solid structures and solution spectra of these complexes indicates that tetradentate ligands L¹, L² and L³ would lead to new Ni^II complexes with different coordination environments in the solid states and solution. The N-methyl substituted imidazole functionalized ligand L¹ forms green compound 2 and yellow product 1; while the pyridine functionalized ligand L² affords red product 4 and green complex 3; the ligand L³ results in only one stable mononuclear Ni^II product 5. The solution behaviors of these interesting compounds were also investigated by UV-Vis technique.     

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.     

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.     

Synthesis and characterization of imidazolate-bridged polynuclear copper complexes

Copper(II) complexes of N4-donor ligands containing imidazole moieties, 4-[bis(1-methylimidazole-2-yl-methyl)aminomethyl]imidazole (Him-im₂) and 4-[bis(1-methylimidazole-2-yl-methyl)aminoethyl]imidazole (Hhis-im₂), were prepared, and [Cu(Him-im₂)Cl]ClO₄ (1) and [Cu(Hhis-im₂)Cl]ClO₄ (2) were structurally characterized by the X-ray diffraction method. Complexes 1 and 2 have a mononuclear structure with a coordinated chloride ion. The geometry of the Cu(II) center in 1 was found to be 5-coordinate trigonal-bipyramidal, whereas that of 2 was square-pyramidal. Complexes 1 and 2 showed different absorption and EPR spectra in MeOH, indicating that these compounds in solution maintain the structures revealed in the solid state. On the other hand, the reaction of Him-im₂ with Cu(ClO₄)₂ · 6H₂O under basic conditions gave a tetranuclear Cu(II) complex, [Cu₄(im-im₂)₄](ClO₄)₄ (3), whereas using the ligand Hhis-im₂ gave two kinds of polynuclear complexes [Cu₄(his-im₂)₄](ClO₄)₄ (4) and [Cu₆(his-im₂)₆](ClO₄)₆ (5) exhibiting discretely different structures. X-ray crystal structure analysis of the polynuclear complexes revealed their cyclic structures bridged by the imidazolate moiety. The geometry difference of the Cu(II) centers between 1 and 2 is thus concluded to determine the structures of tetranuclear complexes 3 and 4, respectively. Temperature dependent magnetic susceptibility measurements of complexes 3, 4, and 5 have shown an antiferromagnetic exchange interaction with a coupling constant of J = −32.5, −27.1 and −22.8 cm⁻¹, respectively.     

Mixed-ligand tris chelated complexes of Mo(IV) and W(IV): A comparative study

Two hitherto unknown mixed-ligand tris chelated complexes containing 2-aminothiophenolate, [Et₄N]₂[M^IV(NH-(C₆H₄)-S)(mnt)₂] (M = Mo, 1a; W, 2a) and two mixed-ligand tris chelate complex containing N,N-diethyldithiocarbamate, [Et₄N]₂[M^IV(Et₂NS₂)(mnt)₂] (M = Mo, 1b; W, 2b) have been synthesized and characterized structurally. Although these complexes are supposed to be quite similar to the well-known symmetric tris chelate complexes of maleonitriledithiolate (mnt), [Et₄N]₂[M^IV(mnt)₃] (M = Mo, 1c; W, 2c), but display both trigonal prismatic and distorted trigonal prismatic geometry in their crystal structure indicating the possibility of an equilibrium between these two structural possibilities in solution. Unlike extreme stability of 1b, 2b, 1c and 2c, both 1a and 2a are highly unstable in solution. In contrast to one reversible reduction in case of 1b and 2b, 1a and 2a exhibited no possible reduction up to −1.2 V and two sequential oxidation steps which have been further investigated with EPR study. Differences in stability and electrochemical behavior of 1a, 1b, 2a and 2b have been correlated with theoretical calculations at DFT level in comparison with long known 1c and 2c.     

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 and structures of heterobimetallic complexes derived from [Ga(edt)2] as a metalloligand (edt = SC2H4S): Potential precursors for ternary materials MGaS2 (M = Cu or Ag)

Metathesis reaction between equimolar amount of [Et₄N][GaCl₄] and Na₂edt in methanol resulted in the formation of the dichloro complex [Et₄N][Ga(edt)Cl₂] (1), whereas reaction of [Et₄N][GaCl₄] with two equivalents of Na₂edt in methanol gave the complex [Et₄N][Ga(edt)₂] (2) which can act as a metalloligand. Treatment of 2 with M(PPh₃)₂NO₃ in DMF/CH₂Cl₂ afforded the heterobimetallic complexes [Ga(edt)₂M-(PPh₃)₂] (M = Cu 3, Ag 4) in moderate yields. The structures of 1-4 were determined by single-crystal X-ray diffraction analyses. Both [Ga(edt)Cl₂]⁻ and [Ga(edt)₂]⁻ anions have a distorted tetrahedral geometry. The former consists of one five-membered ring formed by chelating dithiolate and two terminal chloride atoms while the latter consists of two five-membered rings formed by two the chelating dithiolates. Complexes 3 and 4 consist of metalloligand [Ga(edt)₂]⁻ anion chelated to [M(PPh₃)₂]⁺via the sulfur atoms. Both tetrahedrally coordinated Ga and Cu(Ag) atoms are bridged by two sulfur atoms, forming a planar “GaS₂M” (M = Cu, Ag) core. Thermogravimetry analysis revealed that heterobimetallic complexes 3 and 4 decomposed to give the corresponding ternary metal sulfide materials.     

Copper(II) chloride/1-methylbenzotriazole chemistry: influence of various synthetic parameters on the product identity, structural and magnetic characterization, and quantum-chemical studies

A systematic investigation of the CuCl₂/Mebta (Mebta = 1-methylbenzotriazole) reaction system is described, involving the determination of the influence of the Cu^II:Mebta ratio, the nature of solvent and the presence of counterions on the identity of the reaction products. As a consequence, complexes [Cu₂Cl₄(Mebta)₄] (1), [CuCl₂(Mebta)₂] (2), {[Cu₂Cl₄(Mebta)₂]}_n (3), [Cu₄OCl₆(Mebta)₄] · 0.25H₂O (4 · 0.25H₂O) and [Cu₂Cl₂(Mebta)₆](ClO₄)₂ (5) have been isolated and structurally characterized by single-crystal X-ray studies. Mebta behaves as a monodentate ligand binding through N(3). 1 is a dinuclear complex, the structure of 2 consists of discrete monomeric units, and that of 3 is composed of linear, well-separated polymeric chains of Cu^II atoms. The molecules of 4 · 0.25H₂O have a central μ₄-oxide ion surrounded tetrahedrally by four Cu^II atoms. In the cations of 5 the two Cu^II centres are asymmetrically bridged by two chloro ligands, with three Mebta molecules completing five coordination at each metal. Complexes were characterized by spectroscopic (IR, far-IR, solution UV/Vis) and thermal decomposition (TG, DTG, and DTA) techniques. Variable-temperature magnetic susceptibility data for 1, 3 and 5 showed intramolecular (1, 5) and intrachain (3) ferromagnetic exchange interactions. Estimates of the Jparameters, experimentally derived, were in close agreement with a new magneto-structural criterion developed by us, holding for bis(μ-chloro) copper(II) dimers. A comparison between the CuCl₂/Mebta and CuBr₂/Mebta systems is also presented.     

Complexes of N-thiophosphorylthioureas RNHC(S)NHP(S)(OiPr)2 (HL) (R = pyridin-2-yl, pyridin-3-yl, 6-amino-pyridin-2-yl) with copper(I): Crystal structures of Cu(PPh3)nL (n = 1, 2)

Reaction of the potassium salts of N-thiophosphorylated thioureas of common formula RNHC(S)NHP(S)(OiPr)₂ [R = pyridin-2-yl (HL^a), pyridin-3-yl (HL^b), 6-amino-pyridin-2-yl (HL^c)] with Cu(PPh₃)₃I in aqueous EtOH/CH₂Cl₂ leads to mononuclear [Cu(PPh₃)₂L^a,b-S,S′] (1, 2) and [Cu(PPh₃)L^c-S,S′] (3) complexes. Using copper(I) iodide instead of Cu(PPh₃)₃I, polynuclear complexes [Cu_n(L-S,S′)_n] (4-6) were obtained. The structures of these compounds were investigated by IR, ¹H, ³¹P{¹H} NMR spectroscopy, ES-MS and elemental analyses. The crystal structures of Cu(PPh₃)₂L^b (2) and Cu(PPh₃)L^c (3) were determined by single-crystal X-ray diffraction.     

Insertion reactions of organic anhydrides into the M-O bond of CuOBu and Sb(OMe)3

The synthesis and structural characterization of the copper salts [Cu₂(2-Boc-benzoate)₄(dme)₂] (1), [Cu(2-Boc-benzoate)₂(tmeda)] (2), [Cu₂(2-Boc-benzoate)₂(dppm)] (3), [Cu(2-Boc-nicotinate)(PPh₃)₂] (4), [Cu₂{2-Boc-5,6-anhydride-naphthylcarboxylate}₂(dppm)₂] (5) [dme = 1,2-dimethoxyethane, dppm = bis(diphenylphosphino)methane, tmeda = N,N′-tetramethylethylenediamine, Boc = tert-butoxycarbonyl] prove that cyclic organic anhydrides and dianhydrides readily insert into the Cu-O bond of [CuO^tBu] forming carboxylate ligands with ester functionalities in the ligand periphery. [Sb(CO₂Ph-o-CO₂Me)₂(OMe)(tmeda)] (6) was synthesised by insertion reaction of Sb(OMe)₃ with phthalic anhydride.     

Heterometal cubane-type WFe3S4 and related clusters trigonally symmetrized with hydrotris(3,5-dimethylpyrazolyl)borate

The scope of formation and structures of tungsten-iron-sulfur clusters has been explored using reactions based on [(Tp*)WS₃]¹⁻ (1) as the ultimate precursor. The reaction system 1/FeCl₂/NaSEt/S affords the cubane cluster [(Tp*)WFe₃S₄Cl₃]¹⁻ (2), which with NaSEt is converted to [(Tp*)WFe₃S₄(SEt)₃]¹⁻ (3).Clusters 2 and 3 contain the cubane [WFe₃(μ₃-S)₄]³⁺ core.Complex 1 with FeCl₂/NaSEt forms [(Tp*)WFe₂S₃Cl₂(SEt)]¹⁻ (4) with the cuboidal [WFe₂(μ₂-S)₂(μ₃-S)(μ₂-SR)]²⁺ core.Treatment of 2 with excess Et₃P yields the edge-bridged double [(Tp*)₂W₂Fe₆S₈(PEt₃)₄] (5) with the [W₂Fe₆(μ₃-S)₆(μ₄-S)₂] core. Reaction of 2 with excess leads a mixture of products, from which [(Tp*)₂W₂Fe₅S₉Na(SH)(MeCN)]³⁻(6) was identified.This cluster, as closely related [(Tp)₂Mo₂Fe₆S₉(SH)₂]³⁻, exhibits a core topology [W₂Fe₅Na(μ₂-S)₂(μ₃-S)₆(μ₆-S)] very similar to the P^N cluster of nitrogenase. All reactions were carried out in acetonitrile. The structures of 2-6 were established crystallographically as Et₄N⁺ salts. In the cubane series, substitution of tungsten for molybdenum decreases the [MFe₃S₄]^3+/2+ redox potential by ca. 0.20 V but has a negligible effect on electron distribution. This work expands the small set of previously known weak-field W-Fe-S clusters, demonstrates the existence of tungsten-containing edge-bridged double cubanes and clusters with the P^N core topology, and introduces a new cuboidal core structure as found in 4 (Tp = hydrotris(pyrazolyl)borate, Tp* = hydrotris(3,5-dimethylpyrazolyl)borate).