Oxotungsten(VI) complexes with amino(phenolate)alcoholate ligand

The reaction between tungsten(VI) complex [W(eg)₃] (eg = 1,2-ethanediolato dianion) and a phenolic ligand precursor 2,4-di-tert-butyl-6-(((2-hydroxyethyl)(methyl)amino)methyl)phenol (H₂L) affords a monomeric oxotungsten complex [WO(eg)(L)]. This complex reacts further with Me₃SiCl, which leads to the displacement of ethanediolato ligand from the complex unit and formation of cis- and trans-isomers of corresponding dichloro complex [WOCl₂(L)]. Identical dichloro complexes were also prepared by the reaction between H₂L and WOCl₄. Molecular structure of [WO(eg)(L)] was verified by X-ray crystallography.     

Synthesis,structural studies,and oxidation catalysis of the manganese(II), iron(II), and copper(II) complexes of a 2-pyridylmethyl pendant armed side-bridged cyclam

The first 2-pyridylmethyl pendant armed structurally reinforced cyclam ligand has been synthesized and successfully complexed to Mn^2 +, Fe^2 +, and Cu^2 + cations. X-ray crystal structures were obtained for the diprotonated ligand and its Cu^2 + complex demonstrating pentadentate binding of the ligand with trans-II configuration of the side-bridged cyclam ring, leaving a potential labile binding site cis to the pyridine donor for interaction of the complex with oxidants and/or substrates. The electronic properties of these complexes were determined by means of solid state magnetic moment, with a low value of μ = 3.10 μ_B for the Fe^2 + complex suggesting that it has a trigonal bipyramidal coordination geometry, matching the crystal structure of the Cu^2 + complex, while the μ = 5.52 μ_B value for the Mn^2 + complex suggests that it is high spin octahedral. Cyclic voltammetry in acetonitrile revealed reversible redox processes in all three complexes, suggesting that catalytic reactivity involving electron transfer processes are possible for these complexes. Screening for oxidation catalysis using hydrogen peroxide as the terminal oxidant identified the Fe^2 + complex as the oxidation catalysts most worthy of continued development.     

Nitrosyl cis-dichlorodiammine ruthenium complex with bridging H3O2− ligand

The ruthenium complex with bridging H₃O₂⁻ ligand was obtained and the crystal structure was determined. The compound cis-[{RuNO(NH₃)₂Cl₂}₂(μ₂-H₃O₂)]Cl crystallizes in the monoclinic space group P2₁/n with cell parameters a = 15.0651(5), b = 6.3624(2), c = 15.3813(6) Å, β = 94.9690(10)°, Z = 4 and R = 0.0185. The hydroxide hydrate anion is coordinated to the ruthenium atoms of the identical cis-{RuNO(NH₃)₂Cl₂} fragments. The protonation of the starting cis-[RuNO(NH₃)₂(NO₂)₂OH] complex leads to the required coordinated aqua/hydroxide ratio if the specific amount of hydrochloric acid is used. The DFT calculations confirm the formation of the dimer structure in the gas phase. However, the presence of water molecules dramatically reduces the dimerization efficiency.     

Hydrothermal synthesis and characterization of a 3D luminescent lead(II) framework containing 3D Pb–X–Pb linkage (X = O and Cl) tuned by cis- and trans-ligand conformations

Under hydrothermal conditions using cis-butenedioic acid (H₂L) and corresponding lead(II) salts, a three-dimensional (3D) lead(II) complex {[Pb₂(L)(μ₂-Cl)(μ₃-Cl)]}_n (1) containing 3D Pb–X–Pb (X = O and Cl) linkage has been isolated. 1 also represents a truly 3D hybrid luminescent lead(II) framework with I³O⁰ type connectivity. Further analysis reveals that cis- and trans-conformations of butenedioic acid ligand greatly affect the lead(II) framework structure. Solid-state fluorescence spectrum of 1 exhibits the maximum emission peak at 379 nm.     

Synthesis and characterization of formyl group containing N-monofunctionalized tetraazamacrocyclic ligand and its nickel(II) complex

New N-functionalized tetraaza macrocyclic ligand [N-{(2-hydroxy-3-formyl-5-bromo)benzyl}-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (L)] and its nickel(II) complex has been prepared and characterized. The X-ray structural analysis of [NiL](ClO₄) · H₂O showed that the geometry around nickel(II) ion is distorted trigonal bipyramid. Cyclic voltammetric studies of Ni(II) complex show one electron irreversible reduction at E_pc = −1.49 V and oxidation at E_pa = 1.12 V. Nickel(II) complex has a room temperature magnetic moment value of μ_eff = 3.35 B.M.     

An unexpected oxovanadium(IV) complex with in situ generated lactone ligand: Synthesis,crystal structure and DNA-binding property

A novel unexpected oxovanadium(IV) complex, [VO(L)(Phen)] (H₂L = 2-((2-hydroxynaphthalen-1-yl)-methyleneamino)-5-oxotetrahydrofuran-2-carboxylic acid, Phen = 1, 10-phenanthroline) (1), in which the L^2– is an unexpected in situ generated lactone Schiff base ligand from the precursor of K₂HL¹ (K₂HL¹ = potassium 2-(((2-hydroxynaphthalen-1-yl)methylene)amino)pentanedioate), has been synthesized and structurally characterized. The DNA binding properties of 1 with calf thymus DNA (CT-DNA) have been investigated by fluorescence and circular dichroism (CD) spectra, results indicate that 1 can bind to CT-DNA via an intercalative mode.     

A nitrogen rich Ni(II)–dithiolate system exhibiting acid–base behavior: Synthesis,supramolecular structure and spectroscopy of [Bu4N]2[NiII(ppdt)2] (ppdt = pyrido[2,3-b]pyrazine-2,3-dithiolate)

The compound [Bu₄N]₂[Ni(ppdt)₂] (1) (ppdt = pyrido[2,3-b]pyrazine-2,3-dithiolate) has been synthesized, starting from pyrido[2,3-b]pyrazine-2,3-dithiol, nickel chloride and tetrabutylammonium bromide in methanol. Compound 1 crystallizes in P2₁/c space group (monoclinic system). Its crystal structure is characterized by interesting C–H?S and C–H?N supramolecular weak interactions. Its solution state has been described with acid–base (protonation–deprotonation) behavior, that has rarely been investigated for a metal–dithiolene system. Compound 1 is first instance of a metal–dithiolene compound that has three ring nitrogen on each dithiolate ligand. The pH dependent changes in the charge-transfer absorption band are attributed to the protonation on an imine nitrogen of the ppdt ligand. The complex is electrochemically quasi-reversible with an oxidation potential of E_1/2 = +0.46 V vs. Ag/AgCl in methanol.     

The first crystallographically-characterised Cu(II) xanthate

The copper(II) xanthate Cu(S₂COEt)₂·TMEDA (1) (TMEDA = N,N-tetramethylethylenediamine) has been synthesised and is the first structurally-characterised xanthate of copper in the + 2 oxidation state. 1 has an octahedral cis, cis, cis-ligand arrangement about the metal, in which xanthate chelation is markedly asymmetric. Both bulk thermal decomposition and film growth by aerosol-assisted chemical vapour deposition (AACVD) using 1 as precursor lead to the formation of Cu₂S.     

New trinuclear dendritic complexes with [Ru(tpy)(bpy)X]n + (X = Cl,H2O; n = 1, 2) for enhanced water oxidation and light-driven alcohol oxidation

A symmetric trinuclear ruthenium complex with [Ru(tpy)(bpy)(Cl)]⁺ (tpy = 2,2′:6′,2″-terpyridine; bpy = 2,2′-bipyridine) connected by 2,4,5-trimethylbenzene was easily prepared. The complex showed effective chemical water oxidation and light-driven oxidation activity of alcohols to corresponding aldehydes in water. When Cl⁻ is replaced by H₂O, the resulting complex exhibited over a twofold increase in O₂ evolution activity compared with its parent complex. Moreover, compared with equimolar ruthenium amounts of the mononuclear complex with the H₂O ligand, the trinuclear ruthenium complex with the conjugated ligand motif also displayed a two time increase in water oxidation activity.     

Microwave-assisted and solvent-free peroxidative oxidation of 1-phenylethanol to acetophenone with a CuII–TEMPO catalytic system

The water-soluble copper(II) complex [Cu(H₂R)(HL)]∙H₂O (1) was prepared by reaction of copper(II) nitrate hydrate with (E)-2-(((1-hydroxynaphthalen-2-yl)methylene)amino) benzenesulfonic acid (H₂L) and diethanolamine (H₃R). It was characterized by IR and ESI-MS spectroscopies, elemental and X-ray crystal structural analyses. 1 shows a high catalytic activity for the solvent-free microwave (MW) assisted oxidation of 1-phenylethanol with tert-butylhydroperoxide, leading, in the presence of TEMPO, to yields up to 85% (TON = 850) in a remarkably short reaction time (15 min, with the corresponding TOF value of 3.40 × 10³ h^− 1) under low power (25 W) MW irradiation.     

One-dimensional supramolecular assembly of an Mn12 single molecule magnet by ligand interactions

A new Mn₁₂ complex was synthesized using ligand substitution reaction of Mn₁₂–OAc with 4-(thiophen-3-yl)benzoic acid and complex’s structural and magnetic properties were analysed. [Mn₁₂O₁₂(O₂CC₆H₄C₄H₃S)₁₆(H₂O)₃]·14CH₂Cl₂ (1) crystallized in the P2₁/c space group. Intermolecular π–π interactions between phenyl and thiophene rings of two adjacent Mn₁₂ molecules result in one-dimensional supramolecular assembly of 1 in the crystal. On the other hand, steric repulsion between the neighbouring molecules causes unusual ligand arrangement and coordination geometry of Mn(III) ion with five coordination. The ac magnetic study of 1 gives U_eff = 69.98 K and 1/τ₀ = 1.456 × 10⁸ s^?1 and dc reduced magnetization measurement gives S = 10, g = 1.95 and D = ?0.425 cm^?1 showing that outer ligand distortion has little effect on the magnetic properties.     

A Michael-type reaction between acrylato ions and ethylenediamine coordinated to Ni(II). Synthesis,crystal structure and magnetic properties of [Ni2(EDDP)2(H2O)2] · 2H2O (H2EDDP = ethylenediamine-N,N-dipropionic acid)

The reaction between NiCO₃ · Ni(OH)₂, acrylic acid and ethylenediamine in a 2:4:1 molar ratio affords the binuclear complex, [Ni₂(EDDP)₂(H₂O)₂] · 2H₂O 1. The organic ligand, EDDP^2? (the dianion of the ethylenediamine-N,N-dipropionic acid ligand), results from the addition of one amine group to the carbon–carbon double bonds of two acrylato ions. The crystal structure of 1 consists of neutral centrosymmetric entities, with the nickel ions connected by two carboxylato groups, each one acting as a monoatomic bridge. The intramolecular Ni?Ni distance is 3.212 Å. The metal ions exhibit an octahedral geometry. The cryomagnetic investigation of 1 reveals an antiferromagnetic coupling of the nickel(II) ions (J = ?21.8 cm^?1, H = ?JS_Ni1S_Ni2).     

Synthesis,structures and photocatalytic properties of a mononuclear copper complex with pyridine-carboxylato ligands

A mononuclear copper (II) complex with pyridine-carboxylate ligands, Cu(pc)₂·2H₂O (pcH = pyridine-2-carboxylic acid), and its initial ligand pyridine-2-amidoxine, have been prepared by a hydrothermal method. The structure of the complex has been characterized by X-ray crystallography. The complex was observed to be active in photo-catalyzing oxidation of Rhodamine B (RhB) and Methyl Orange (MO) in aqueous solution with hydrogen peroxide (H₂O₂).     

A chiral twofold interpenetrated diamond-like 3D In(III) coordination network with 4,4′,4″-phosphoryltribenzoate

A novel In(III) coordination complex, [In(ptc)(H₂O)]_n (H₃ptc = 4,4′,4″-phosphoryltribenzoic acid) (1), was synthesized under hydrothermal condition and characterized by single-crystal X-ray analysis, IR, X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) and solid-state photoluminescence. Complex 1 crystallizes in a chiral P2₁ space group, In(III) ions are eight-coordinated and the ligand exhibits a novel and unique tetrahedral coordination mode. The complex shows intense blue emission at 435 nm with the excitation of 330 nm.     

Room-temperature Suzuki–Miyaura coupling of aryl bromides with phenylboronic acid catalyzed by a palladium complex with an inexpensive nitrogen-containing bis(phosphinite) ligand

A palladium(II) complex with a known inexpensive and very easily synthesized nitrogen-containing bis(phosphinite) ligand has been prepared and characterized by spectroscopic and crystallographic studies. The ligand is bound to the metal in a P,P-bidentate coordination mode with a bite angle of 98.90°. This complex was found to be an efficient catalyst for room-temperature Suzuki–Miyaura coupling of a variety of aryl bromides with phenylboronic acid. At 0.1 mol% of palladium in DMF/K₃PO₄ for 24 h, the corresponding biaryls were obtained with 75–92% yields. Activated substrates displayed high yields even within minutes.     

The novel polymeric potassium complex with a new coordination mode of orotic acid [K(μ5-H2Or)(μ-H2O)]n: Synthesis and structural characterization

Novel polynuclear seven-coordinated potassium complex, [K(μ₅-H₂Or)(μ-H₂O)]_n(H₃Or = orotic acid), with the new coordination mode of orotic acid has been prepared and characterized by elemental analysis, FT-IR spectra, X-ray diffraction. The orotate ligand exhibits new coordination mode of μ₅-κO, O: κO′, O′: O″ for H₂Or⁻.     

A lead(II)-orotate coordination polymer with a new coordination mode: Synthesis,structure and luminescent property

A lead(II) orotate complex [Pb(HOr)(H₂O)]_n (1), (H₃Or = orotic acid) was synthesized under hydrothermal condition and characterized by X-ray diffraction, IR, solid-state photoluminescence and thermogravimetric analysis. Lead atom in 1 is in a holodirected eight-coordinated polyhedron and the orotate ligand exhibits a new and unique hexametallic coordination mode. The lead complex shows a 6,6-connected (4⁸, 6⁶, 8)(4¹³, 6²) topology. The complex exhibits photoluminescence at 546 nm (λ_ex = 350 nm).     

Self-assembly and guest binding of nickel(II) macrocyclic complex with pentyl groups and cis,cis-1,3,5-cyclohexanetricarboxylic acid

Reaction of the nickel(II) macrocyclic complex 1 including pendant pentyl groups in MeCN/H₂O mixed solvent with deprotonated cis,cis-1,3,5-cyclohexanetricarboxylic acid (CTC^3 −) resulted in two-dimensional (2-D) coordination polymer [Ni(C₁₈H₄₂N₆)]₃[C₆H₉(COO)₃]₂·6H₂O·6CH₃CN (2). The crystal structure of 2 indicates that each nickel(II) macrocyclic unit binds two CTC^3 − ions in trans position and each CTC^3 − ion coordinates three nickel(II) macrocyclic complexes to form a 2-D layer with hexagonal motif. The dried solid of 2 differentiates MeOH, EtOH, and PhOH in toluene solvent with the K_f values of 1.38, 2.11, and 6.68 M^− 1, respectively.     

Cobalt(II) complex containing two-ring scorpionate-like ligands formed in situ. Studies on the [Co0–1-hydroxymethyl-3,5-dimethylpyrazole–MoO3–NH4I] system

We report preparation and characterization of a novel complex cis–mer [Co(L)₂]I₂ CH₃OH (1) (L-N,N-bis(1-(3,5-dimethylpyrazolylmethyl)amine)) isolated from the [Co⁰–1-hydroxymethyl-3,5-dimethylpyrazole–MoO₃–NH₄I] system. A two-ring scorpionate ligand (L) was obtained in situ via redox and condensation processes. The catalytical properties of MoO₃ are responsible for the formation of this atypical scorpionate ligand. Compound (1) crystallizes in the orthorhombic space group Pna2₁ with a = 24.5578(14) Å, b = 13.8388(8) Å, c = 9.6072(7) Å, V = 3265.0(4) Å³ and Z = 4. The metal ion coordinates through six nitrogen atoms which belong to two tridentate ligands forming a deformed octahedron. The complex was characterized by IR, FIR, UV–VIS and magnetic investigations. The ligand was ranked in the spectrochemical series between imidazole and bipyridine. The crystal field splitting of tridentate N-donor L was found to be smaller in comparison to e.g. bidentate bipyridine.     

Two nickel coordination polymers with flexible ligand 1,3,5-tri(1,2,4-triazol-1-ylmethyl)-2,4,6-trimethylbenzene

The reaction of 1,3,5-tri(1,2,4-triazol-1-ylmethyl)-2,4,6-trimethylbenzene (ttmb) with Ni(II) salts yields two coordination polymers [Ni₃(ttmb)₂(H₂O)₆Cl₆](H₂O)₃ (1) and [Ni(ttmb)₂(H₂O)₂](NO₃)₂(H₂O)₄ (2). The flexible ligand ttmb shows the cis,cis,cis-conformation and a tri-monodentate coordination mode in 1. Each ttmb links three Ni(II) atoms to form an undulated (3, 4)-connected two-dimensional network. Each undulated two-dimensional network polycatenates other two identical networks, thus giving a rare (2D → 3D) parallel polycatenation network in 1. The ttmb ligand exhibits the cis,trans,trans-conformation and a two-monodentate coordination mode in 2. Each ttmb connects two Ni(II) atoms to construct a two-dimensional (4, 4) network in 2. The thermal stability of compounds 1 and 2 was studied.