Synthesis,structure, and electrochemical behavior of a new dinuclear Rh(III) complex bridged by a bpp− ligand (bpp− = 3,5-bis(2-pyridyl)pyrazolate)

The new dinuclear rhodium complex [(Cp*RhCl)₂(bpp)](PF₆) ([1](PF₆), Cp* = pentamethylcyclopentadienyl, bpp = 3,5-bis(2-pyridyl)pyrazolate) was synthesized by the reaction of [Cp*RhCl₂]₂ with 3,5-bis(2-pyridyl)pyrazole (bppH). [1](PF₆) was characterized by ¹H- and ¹³C{¹H}-NMR spectroscopy and X-ray diffraction. The distance between the two Rh atoms in [1](PF₆) is 4.746(3) Å. A cyclic voltammogram of [1](PF₆) in acetonitrile shows three-step reduction peaks at E_pc = − 1.44, − 1.68 and − 1.88 V (vs. Fc⁺/Fc), which are assigned to the reduction of the two Rh(III) centers and the bpp⁻ ligand, respectively. [1](PF₆) catalyzes the reduction reaction of NAD⁺ (nicotinamide adenine dinucleotide) using HCO₂⁻ as a reductant.     

Ligand concentration and reaction time controlled successive substitution of chloro and η6-benzene of di-μ-chlorobis{η6-benzene)dichlororuthenium(II)} with selenated Schiff base: Formation of half sandwich Ru(II) complex highly active catalyst for oxidation of alcohols

Schiff base (L) synthesized by reacting 2-methylthiobenzeldehyde with 2-(phenylseleno)ethylamine on reaction with di-μ-chlorobis{η⁶-benzene)dichloro-ruthenium(II)}(a) forms two type of species: (i) [Ru(L)₂][PF₆]₂ (1) [L:a = 4:1 and reaction time ～8 h] and (ii) [Ru(η⁶-C₆H₆)(L)][PF₆]₂ (2) [L:a = 2:1 and reaction time ～1 h]. This is first example in which chloro as well benzene ring both are successively substituted by controlling metal:ligand ratio and duration of reaction. The geometry around Ru in complex 1 is distorted octahedral. The 2 has a pseudo-octahedral half sandwich “piano-stool” disposition of ligands around Ru. The Ru–Se distances are 2.4683(10)–2.5082(7) ?. The proton and carbon-13 NMR spectra of L and its both complexes 1 and 2 authenticate them. The 2 shows high catalytic activity for oxidation of primary and secondary alcohols both (TON upto 9.6 × 10⁴; TOF upto 4.80 × 10⁴ h^?1).     

Selective adenine/cytosine cations in one-dimensional coordination polymers of manganese (II) and copper (II) 2,3-pyridinedicarboxylates

One-dimensional coordination polymer {[1H,9H-ade]₂[MnL₂]?4H₂O}_n (1) and {[1H,3H-cyt]₂[CuL₂]?6H₂O}_n (2) (ade = adenine, cyt = cytosine, L = dianion of 2,3-pyridinedicarboxylic acid) are selectively synthesized and variable-temperature magnetic susceptibility measurements revealed weak antiferromagnetic interactions within the chains of 1 and 2 (J = ? 0.29 cm^? 1 for 1 and J = ?0.03 cm^? 1 for 2, according to the ? 2J_ijS_iS_j HDvV Hamiltonian formalism).     

Two new luminescent Cd(II)/Zn(II) metal–organic frameworks for exceptionally selective detection of picric acid explosives

Two new coordination polymers, {[Cd(BIDPT)(oba)]·0.5H₂O}_n (1) and {[Zn(BIDPT)(4,4′-sdb)]·2.25H₂O}_n (2) (BIDPT = 4,4′-bis(imidazol-l-yl)diphenyl thioether, H₂oba = 4,4′-oxydibenzoic acid, 4,4′-H₂sdb = 4,4′-sulfonyldibenzoic acid), have been solvothermally synthesized and characterized. Both 1 and 2 show 2-fold interpenetrating 3D frameworks with {6⁵ ∙ 8} cds and {6⁶} dia topology, respectively. These two coordination polymers show strong luminescence and their luminescence could be quenched by a series of nitro explosives. Importantly, they exhibit very highly sensitive and selective detection of picric acid compared to other nitro explosives.     

Reactions of benzene based half sandwich ruthenium(II) complex with 2,6-bis((phenylseleno)methyl)pyridine: Preferential substitution of ring resulting in a catalyst of high activity for oxidation of alcohols

[2,6-Bis((phenylseleno)methyl)pyridine] (L) a (Se, N, Se) pincer ligand synthesized by reacting PhSe^? (in situ generated) with 2,6-bis(chloromethyl)pyridine reacts with [{(η⁶-C₆H₆)RuCl(μ-Cl)}₂] (2:1 molar ratio) by preferential substitution of ring resulting in the first Ru-(Se, N, Se) pincer ligand complex, mer-[Ru(CH₃CN)₂Cl(L)][PF₆](1).H₂O. Similar reaction in 4:1 molar ratio results in mer-[Ru(L)₂][ClO₄]₂(2). The ¹H, ¹³C{¹H} and ⁷⁷Se{¹H} NMR spectra of L, 1 and 2 were found characteristic. The single crystal structures of 1 and 2 were studied by X-ray crystallography. The geometry of Ru in both the complexes is distorted octahedral. The Ru–Se distances are in the ranges 2.4412(16)–2.4522(16) and 2.4583(14)–2.4707(15) ? respectively for 1 and 2. The structural solutions from the crystal data in case of 2, due to inferior quality of its crystals, are suitable for supporting bonding mode of L with Ru(II) only. The 1 shows high catalytic activity for oxidation of primary and secondary alcohols (TON up to 9.7 × 10⁴).     

Three d10 coordination polymers based on rigid ligands with flexible functional groups: Syntheses,structures and luminescence

Three coordination polymers, namely, {[Zn(L)(BPY)]·DMF·H₂O}_n (1), {[Zn(L)(TPY)]·0.5H₂BDC·H₂O}_n (2), {[Cd(L)(H₂O)₂]·DMF}_n (3), have been synthesized based on a rigid linear carboxylate ligand (H₂L = 2′,5′-dimethoxy-[1,1′:4′,1″-terphenyl]-4,4″-dicarboxylic acid) and different lengths of pyridine ligands (TPY = 4,3′:5′,4″-terpyridine; BPY = 4,4′-bipyridine). These complexes have been characterized by single crystal X-ray diffraction, infrared spectroscopy, thermogravimetry, elemental analysis, and powder X-ray diffraction measurements. Complex 1 is a 6-connected 3-fold interpenetrating pcu net with point symbol {4¹² ∙ 6³}, 2 and 3 can be simplified as 4-connected sql nets with point symbol {4⁴ ∙ 6²}. In addition, their photoluminescent properties are also investigated in detail.     

Hydrothermal synthesis,crystal structure and electrochemical behavior of two new isomorphic layered vanadates: [M(dpa)V3O8.5] (M = Cu(II) 1 and Zn(II) 2; dpa = 2,2′-dipyridylamine)

Two new isomorphic vanadates, [M(dpa)V₃O_8.5] (M = Cu²⁺ 1, Zn²⁺ 2; dpa = 2,2′-dipyridylamine) have been synthesized hydrothermally. X-ray crystal analysis reveals that vanadates 1 and 2 exhibit a layered structure constructed from {V₃O_8.5}^2? layers inlaid with [M(dpa)]²⁺ subunits. The {V₃O_8.5}^2? layers consist of ribbon-like chains of edge sharing {VO₅} square pyramids bridged through {V₂O₇} fragments. Electrochemical measurement shows that lithium ions are reversibly intercalated and deintercalated in vanadate 1.     

Synthesis,structure and luminescent property of a new Zn(II) coordination polymer with isolated tetrahedral {Zn4O} clusters as building subunits

A new luminescent Zn(II) coordination polymer, namely [Zn₄(L)₂(μ₄-O)(H₂O)₂(DMF)]_n (1 H₃L = biphenyl-3,4,5-tricarboxylic acid, DMF = N,N′-dimethyl formamide) has been synthesized by combining the H₃L ligand with Zn(II) salts under solvothermal conditions. Single-crystal X-ray diffraction analysis reveals that 1 features μ₄-oxygen-bridged tetrahedral {Zn₄O} clusters as building subunits, which are further bridged by L^3 − ligands into a complicated three-dimensional (3D) architecture. Topological analysis reveals that it can be reduced into a (3, 6)-connected topological network with the schläfli symbol of {4 · 6²}₂{4² · 6⁹ · 8⁴}. In addition, the luminescent property of 1 was also investigated in the solid state at room temperature.     

Design,synthesis, structure and magnetic behavior of a high spin binuclear Fe(III) complex of N-(1-ethanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl) amine

The Mannich reaction of 2-aminoethanol, 2-tert-butyl-4-methylphenol, and formaldehyde at the ratio sets of 1:2:2 provided a new ligand, N-(1-ethanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine (H₃L). In the presence of base, H₃L reacted with FeCl₃·6H₂O to form a dinuclear Fe(III) complex [Fe₂L₂] 1. The value of μ_eff at room temperature (5.95 μ_B), is much less than the expected spin-only value (8.37 μ_B) of two high spin (hs) Fe³⁺ (S = 5/2) ions [μ = g[∑ ZS(S + 1)]^1/2], indicating there were strong interactions between Fe³⁺ ions. The effective magnetic moment (μ_eff) decreased abruptly with cooling to a minimum value of 0.1 μ_B at 2 K. It was worth noting that Fe³⁺ ions of 1 exhibited thermally induced quartet ? doublet spin transitions, and these transitions were abrupt. The magnetic behaviors of 1 denoted the occurrence of intramolecular anti-ferromagnetic interactions. J (? 13.58 cm^? 1) agrees with the result from Gorun–Lippard equation, ? J (cm^? 1) = Aexp(BP(Å) = 12.9).     

Syntheses,structures, and luminescent properties of zinc(II) complexes assembled with aromatic polycarboxylate and 1,3-bis(1,2,4-triazol-1-yl)propane

Three new coordination compounds, {[Zn(btrp)(ip)]?2H₂O}_n (1), {[Zn(btrp)(hip)]?2H₂O}_n (2), and {[Zn_1.5(btrp)(btc)(H₂O)]?H₂O}_n (3) (btrp = 1,3-bis(1,2,4-triazol-1-yl)propane, H₂ip = isophthalate, H₂hip = 5-hydroxy isophthalate, H₃btc = benzene-1,3,5-tricarboxylic acid) have been prepared via solvothermal method and characterized by single crystal X-ray diffraction and elemental analysis. 1 possesses 2D (4. 4) net framewok. 2 is also a 2D infinite layer framework, and the resulting 2D structure is interconnected by hydrogen-bond and π…π interactions to lead to a 3D supramolecular architecture. 3 exhibits a novel 2D framework with three nonequivalent points, {5.6²}{5².6}{5⁴.8²}. The fluorescence properties of 1–3 have been studied at room temperature.     

Synthesis,structures and properties of cobalt(II) and copper(I) complexes of 2,6-diamino-3-[(2-carboxymethyl)phenylazo]-pyridine

The reaction of methyl anthranilate, sodium nitrite, and 2,6-diamino-pyridine affords a new compound, 2,6-diamino-3-[(2-carboxymethyl) phenylazo]-pyridine (L), which has been characterized with X-ray crystallography and NMR spectrum. The reaction of L and CoCl₂? 6H₂O or Cu(ClO₄)₂? 6H₂O gives a dinuclear cobalt(II) complex [Co₂L₂Cl₃]Cl (1), and a copper(I) complex [CuL₂]ClO₄ (2),respectively. They are characterized by X-ray crystallography, X-ray photoelectron spectroscopy, NMR spectra, magnetic measurement and emission spectra. Magnetic behavior of 1 denotes the occurrence of intramolecular antiferromagnetic interactions (J = ? 141.8 cm^? 1). Complex 2 exhibits photoluminescence at 557 nm.     

Syntheses,crystal structures,and magnetic studies of two cobalt(II) coordination polymers based on concurrent ligand extension

An ether bridged tetracarboxylic acid ligand, 5-(3′,4′-Dicarboxylphenoxy)-isophthalic acid (H₄L) was used to construct two Co(II) coordination polymers in presence of different nitrogen donor ligands such as 4,4′-bipyridine (4,4′-bpy) and 4,4′-bis(pyrid-4-yl)biphenyl (bpbp). The products formed under hydrothermal conditions are formulated as [Co₂L(4,4′-bpy)₂(H₂O)₃]_n (1) and {[Co(bpbp)₂(H₂L)]·H₂O}_n (2). The compounds were characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analysis, and powder X-ray diffraction (PXRD) measurement. Compound 1 shows an intriguing (3,4,5)-connected 3D framework with a point symbol of (4² · 6² · 8²)(4² · 6⁵ · 8³)(6² · 8). Compound 2 is an unusual 3D supramolecular framework generated by the one-dimensional [Co(bpbp)(H₂L)]_n polymer chain. The magnetic properties of compounds 1 and 2 were examined, indicating antiferromagnetic interactions between the cobalt(II) ions in the temperature range of 2–300 K.     

Effects of salicylate derivate on the competing reaction of chromium(III) complex [Cr(III)(R-SA)(en)2]Cl with apoovotransferrin

Four novel Cr(III) complexes, Bis(ethylenediamine-κ²N,N′)(R-SA-κ²O,O′)chromium(III) chloride (H₂SA = salicylic acid, R = 5-F, 5-Cl, 5-Br, 4-CH₃ ethylenediamine = en) have been synthesized and three of them are determined by X-ray crystallography. The competition reaction with EDTA and apoovotransferrin (apoOTf) was monitored by UV–Visible (UV–vis) and fluorescence spectra at 37 °C. The reaction with EDTA is only a simple competitive process and no specific selectivity was observed (k_EDTA/F410 = 4.07 × 10^?3–4.37 × 10^?3 M^?1 s^? 1). While for the reaction with apoOTf, an instable intermediate species (R-SA)–Cr(III)–OTf forms (k_OTf/F336 = 1.70 × 10^? 1–2.08 × 10^?1 M^?1 s^? 1), where R-SA^2? act as the role of synergistic anion. The intermediate is instable and the R-SA^2? ligand will then be released with the rate constants of 1.17 × 10^? 1 (5-F-SA^2?) ≈ 1.01 × 10^? 1 (4-CH₃-SA^2?) > 3.19 × 10^? 2 (5-Cl-SA^2?) > 3.25 × 10^? 3 (5-Br-SA^2?) M^?1 s^? 1. The substitutive groups R on SA have positive influence on charge density of O donor atom, which directly affect the stability of the (R-SA)–Cr(III)–OTf intermediate.     

Construction of a new 3D Zn(II) coordination polymer with (4,6)-connected topology: Synthesis,structure and luminescence

A new coordination polymer of {[Zn₂(odpa)(IP)]·4H₂O}_n (1) (H₄odpa = 3,3′,4,4′-oxydiphthalic acid and IP = 1-H-imidazo[4,5-f][1,10]-phenanthroline), is reported. The 3D (4,6)-connected {4⁴∙6²∙8⁸∙12}{4⁴∙6²} topology net is formed by IP and odpa ligands in 1. Interestingly, the IP ligand acts as a tridentate mode and extends the resulting 3D feature. The luminescence study indicates that the title compound emits bright red fluorescence.     

Studies on interaction of Cr(III) polypyridyl complexes with DNA

Two chromium(III) complexes containing derivatives of 1,10-phenanthroline were synthesized and characterized using different spectroscopic methods. The interaction of the synthesized complexes with DNA was performed. From the absorption titration data, the binding constant for the complexes [Cr(imiphen)₂Cl₂]⁺ (1) and [Cr(furphen)₂Cl₂]⁺ (2) with DNA were found to be 5.69 ± 0.3 × 10⁴ M^− 1 for 1 and 3.7 ± 0.2 × 10⁴ M^− 1 for 2, respectively. The viscosity studies show that both the complexes bind to DNA in a partial intercalative mode. The results of competitive binding assay reveal that both complexes displace EB from DNA marginally. Gel electrophoresis data show that both the complexes 1 and 2 requires co-reagent to induce DNA cleavage but complex 2 exhibit better nuclease activity compared to complex 1. The results from this study describe the role of ligand structure in the binding and cleavage of DNA as furan based ligand exhibit better cleaving ability compared to imidazole moiety.     

DNA and copper (II) governed fluorescence tuning of phenanthroline possessing Ru(II) complex. Interplay of electrostatic interactions

Tuning of the fluorescence properties of [Ru (bpy) ₂ (L₁)] ^2 + (1) [L₁ = 2-(2-methoxyphenyl)-1H–imidazo [4, 5-f] Kumar et al. (2010), Rawle et al. (1992) phenanthroline] by DNA and/or Cu^2 + ion have been investigated. Fluorescence of 1 gets enhanced upon binding to DNA owing to electrostatic interactions. The binding constant of 8.4 × 10⁴ has been evaluated. Cu^2 + ions though unable to alter the fluorescence intensity of free 1 but successfully sequestrate the DNA bound 1, evidently decreasing its fluorescence intensity. The reversibility of the sequestration process was ascertained by the recovery of the quenched fluorescence intensity via introduction of equimolar EDTA to the buffer system of DNA bound 1 and Cu^2 +.     

A lamella 2D silver(I) coordination polymer constructed from in situ generated 2-mercaptobenzoic acid

The reaction of Ag₂O and 2,2′-dithiodibenzoic acid (dtba) under ultrasonic condition gave rise to a novel metal–organic coordination polymer [Ag₄(2-mba)₂·(H₂O)₂]_n (1) (2-H₂mba = 2-mercaptobenzoic acid) involving in situ generated 2-mba ligand. Complex 1 shows a lamella 2D structure with a 6³-hcb net which is comprised of fused Ag₆ hexagonal rings. Moreover, 1 exhibits photoluminescence maximized at 468 nm upon 330 nm excitation at room temperature, which may be assigned to a ligand-to-metal charge transfer (LMCT) transition. Semiconducting behavior was also measured at room temperature with σ value of 3.24 × 10^?5 S cm^?1.     

Syntheses,structures and properties of chiral Ln(III) coordination polymers based on (R)-4-(4-(1-carboxyethoxy)phenoxy)-3-fluorobenzoic acid

Two isomorphic chiral lanthanide coordination polymers (CCPs), namely, [Ln₂(cpfa)₃]_n {Ln = Yb Xu et al. (2011) and Lu Zheng et al. (2015) } {H₂cpfa = (R)-4-(4-(1-carboxyethoxy)phenoxy)-3-fluorobenzoic acid, have been synthesized under hydro(solvo)thermal conditions. Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by infrared spectra (IR), powder X-ray diffraction (PXRD), elemental analyses, thermogravimetric (TG) analyses and circular dichroism spectra (CD). Structure analysis reveals that CCPs 1 and 2 are isomorphic, crystallizing in Orthorhombic space group P2₁2₁2₁ and giving 3D rhombic framework. Further, CCP 1 show the strong NIR luminescence of Yb(III) ions, suggesting that [cpfa]^2 − is able to sensitize the luminescence of lanthanide ions efficiently. The two polymers also exhibit modest SHG efficiency indicating their potential application as optical materials. Thermogravimetric analyses show the remarkable thermal stabilities of the two lanthanide 3D frameworks up to 420 °C.     

One-dimensional macrocyclic zinc(II) coordination polymer containing an unusual bis-monodentate oxalate bridge

A new zinc(II) complex, {[Zn(L1)(oxalate)] · 3.5H₂O}_n (1) (L = 5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0^1,18.0^{7, 12}]docosane) has been prepared and characterized by single crystal X-ray structure determination. In 1 the rigidity and steric hindrance of the macrocycle L1 causes the bridging oxalate ligand to coordinate to the zinc(II) ions in an unusual twisted bis-monodentate coordination (1,1′-bicoordination) mode.     

The spin gap system by self-assembly of benzyl-4-ethylpyridinium and bis(maleonitriledithiolate)niclelate(III) anion

The self-assembly of [BzEtPy]⁺([BzEtPy]⁺ = benzyl-4-ethylpyridinium) cation and the [Ni(mnt)₂]^? (mnt^2? = maleonitriledithiolate) anion results in the forming of a new molecular solid [BzEtPy][Ni(mnt)₂](1), in which the anions and cations stack into columns and the Ni(III) ions form a 1D zigzag alternating chain through Ni···S and π···π interactions between [Ni(mnt)₂]^? anions with the Ni···Ni distances of 3.886 Å and 4.781 Å, and the four columns of cations create cubic-like large channel in which the [Ni(mnt)₂]^? columns are located. Magnetic susceptibility measurements show that 1 exhibits a spin gap transition around 90 K.