1-(Pyridin-2-ylmethyl)-2-(3-(1-(pyridin-2-ylmethyl)benzimidazol-2-yl) propyl) benzimidazole and its copper(II) complex as a new fluorescent sensor for dopamine (4-(2-aminoethyl)benzene-1,2-diol)

A new ligand 1-(pyridin-2-ylmethyl)-2-(3-(1-(pyridin-2-ylmethyl)benzimidazol-2-yl) propyl) benzimidazole (L) and its Cu(II) complex (1) have been synthesized and characterized spectroscopically and structurally. The Cu(II) ion is coordinated by two nitrogen atoms of benzimidazole groups, two oxygen atoms of the nitrate anions and one oxygen atom of a water molecule forming distorted trigonal bipyramidal geometry. The ligand and its complex have been utilized as a fluorescent sensor for 4-(2-aminoethyl)benzene-1,2-diol. A plot of F₀/F − F₀ vs 1/Conc (4-(2-aminoethyl)benzene-1,2-diol) at a selected wavelength of 306 nm with (L) that shows a straight line behavior, supports the validity of the assumption of 1:1 complex formation and the association constant of (L) with 4-(2-aminoethyl)benzene-1,2-diol is calculated to be 9868 M^− 1. Sensor (L) is found to be selective for 4-(2-aminoethyl)benzene-1,2-diol over aromatic amines, phenols, amino catechol (L-3,4-dihydroxyphenylalanine) and 4,6-ditertiarybutyl benzene-1,2-diol.     

Synthesis, structure and magnetic properties of the first copper(II) complex with an (E)-4-aryl-4-oxo-2-butenoato ligand

A new binuclear Cu(II) complex with an (E)-4-(2,4-diisopropylphenyl)-4-oxo-2-butenoato ligand (L) was successfully synthesized and characterized by elemental analysis and IR-spectroscopy. The structures of (E)-4-(2,4-diisopropylphenyl)-4-oxo-2-butenoic acid (HL), and the corresponding (tetrakis)-μ-[(E)-4-(2,4-diisopropylphenyl)-4-oxo-2-butenoato]-bis(ethanol)-copper(II) complex, [Cu₂L₄(C₂H₅OH)₂], were determined by single crystal X-ray analyses and are preliminarily discussed. This is the first complex of a transition metal with ligand L, as well as the first determined crystal structure of a metal complex with this type of ligand. Analysis of the magnetic susceptibility measurements of the isolated [Cu₂L₄(C₂H₅OH)₂] · H₂O complex shows the existence of a strong anti-ferromagnetic intradimer coupling, with an exchange integral value 2J of −260 cm⁻¹.     

Bis[4-(methylthio)phenylmethyleneaminophenyl] disulfide, 2-[4-(methylthio)phenyl]-2,3-dihydro-1,3-benzothiazole,and its nickel(II) and cobalt(II) complexes: Synthesis,adsorption on gold surface and electrochemical characterization

2-[4-(Methylthio)phenyl]-2,3-dihydro-1,3-benzothiazole (1) and bis[4-(methylthio)phenylmethylene-aminophenyl] disulfide (2) were synthesized. Novel coordination compounds of Ni(II) and Co(II) with 2-[4-(methylthio)phenylmethyleneamino]thiophenol, M(1)₂ (M=Co (3); M=Ni (4)), were prepared by reacting 1 with M(OAc)₂·6H₂O or MCl₂·6H₂O in EtOH solution. The structure of 2 was proved by X-ray crystallography. Electrochemical behavior of 1–4 in CH₃CN solution and at the surface of a gold electrode was studied by cyclic voltammetry. The modification of the electrode by ligand 1 and its complexes with Ni²⁺ and Co²⁺ is described in detail. Two procedures were used to obtain a self-assembled monolayer of a metal complex on the gold surface: the adsorption of prepared coordination compound 3 or 4 on the electrode and the initial modification of the electrode with ligand 1 followed by the formation of a coordination complex between the ligand adsorbed on the electrode and a metal salt occurring in solution. On the basis of the electrochemical data, it was found that the structure of complexes formed on the surface differs from that of the complexes produced in solution.     

Synthesis and Characterization of Some Triphenyltin(IV) Complexes from Sterically Crowded [((E)-1-{2-Hydroxy-5-[(E)-2-(aryl)-1-diazenyl]phenyl}methylidene)amino]acetate Ligands and Crystal Structure Analysis of a Tetrameric Triphenyltin(IV) Compound

Four new triphenyltin(IV) complexes containing [((E)-1-{2-hydroxy-5-[(E)-2-(aryl)-1-diazenyl]phenyl}methylidene)amino]acetate ligands (L) have been synthesized with formulations of Ph₃SnLH. They have been studied by multinuclear (¹H, ¹³C, ¹¹⁹Sn) NMR, ¹¹⁹Sn M?ssbauer and IR spectroscopy. A full characterization of one complex, Ph₃SnL¹H (1), was accomplished by single crystal X-ray crystallography, which revealed the compound to be a macrocyclic tetramer. In the tetramer, the five coordinate tin atoms have distorted trigonal bipyramidal geometries with the three phenyl groups occupying equatorial positions, while an oxygen atom of the carboxylate group of one L ligand and the oxide O-atom (formerly the hydroxy group) of a second L ligand in an apical positions. The carboxylate ligands bridge adjacent tin atoms and coordinate in the zwitterionic form with the phenolic proton moved to the nearby nitrogen atom. ¹¹⁹Sn NMR results indicate that the tetrameric structures of the complexes in the solid state, in which the tin atoms are five-coordinated, dissociate in solution to yield four coordinate monomeric species.     

A fluorescent chemosensor for Zn2 + based on 3,8-bis(4-methoxyphenyl)-1,10-phenanthroline

3,8-Bis(4-methoxyphenyl)-1,10-phenanthroline (L) has been found to show high sensitivity toward Zn^2 + than other competitive metal ions, where Zn^2 +-selective chelation-enhanced fluorescence response at 461 nm is attributed to the formation of a 1:1 metal–ligand complex. In addition, two single-crystal structures of ligand L have been included with the same metal and ligand ratio of 1:1, namely one mononuclear Zn(II) complex [Zn(L)Cl₂] (1) and one 1D Cd(II) coordination polymer [Cd(L)(NO₃)₂]_n (2).     

The C-substituted charge-compensated dicarbollide [7-SMe2-7,8-C2B9H10]−: Synthesis and room-temperature rearrangement of the iridium complex

The reaction of [7-SMe₂-7,8-C₂B₉H₁₀]⁻ with [(cod)IrCl]₂ at room temperature affords iridacarborane 1-cod-8-SMe₂-1,2,8-IrC₂B₉H₁₀. The metal insertion is accompanied by polyhedral rearrangement of the carborane ligand with migration of the substituted carbon atom from the metal bonded pentagonal face. The electronic factors rather than steric ones play the main role in the ligand rearrangement. According to DFT calculations the final iridacarborane is more stable by 6–7 kcal mol^− 1 than the transient pseudocloso-1-cod-2-SMe₂-1,2,3-IrC₂B₉H₁₀ complex. Structures of 7-SMe₂-7,8-C₂B₉H₁₁ and 2 were determined by X-ray diffraction.     

Synthesis and characterization of the dihydrosalpren ligand (H2L1) and of its trinuclear Ni(II) complex

The synthesis of the new unsymmetrical tetradendate Schiff ligand N-(2-hydroxybenzyl)-N′-(2-hydroxybenzylidene)-1,3-diaminopropane (H₂L¹) is reported. The ligand comprises two different coordination moieties: a rigid salicylaldimmine unit and a more flexible (2-hydroxybenzyl)-amino (hydrogenated salicylaldimmine) unit. The reaction of H₂L¹ with Ni(OAc)₂·4H₂O (1:1 molar ratio) leads to the spontaneous formation of a trinuclear complex with composition {[Ni(L¹)OH₂]₂(OAc)₂Ni}·2H₂O, characterized by X-ray crystallography, where two [Ni(L¹)] units act as O,O-bidentate chelate to a Ni(II) ion.     

A unique diruthenium(II,III) unit surrounded by tridentate ligands of N-(2-pyridyl)-2-oxy-5-chlorobenzylaminate

A new metal–metal bonded diruthenium(II, III) compound with a dianionic tridentate ligand, N-(2-pyridyl)-2-oxy-5-chlorobenzylaminate (5-Clsalpy²⁻), was synthesized and structurally characterized as Li₂(THF)₄Cl[Ru₂(5-Clsalpy)₃] (1). The 5-Clsalpy²⁻ ligand that acts as a bridging/chelating co-ligand afforded a unique coordination mode of [M–M bridging/equatorial-chelating] in addition to the “common” mode of [M–M bridging/axial-chelating] around the diruthenium unit of 1.     

Synthesis,spectral characterization,properties and structure of dinuclear rhenium complex containing bis[4-(2-pyridylmethyleneamino)phenyl]methane ligand

The synthesis, characterization, properties and crystal structure of {(bis[4-(2-pyridylmethyleneamino)phenyl]methane)[Re(CO)₃Br]₂} complex are reported. The ¹H NMR data for this complex shows downfield shift of the bis-diimine ligand protons upon coordination to the Re center. The molecular structure of the dinuclear rhenium(I) complex exhibits distorted octahedral geometries around the each metal center with one Br and facial arrangement of three CO and a cis-bonded diimine ligands. The bis-diimine ligand, twists via a half-turn around the metal–metal axis. Electrochemical investigation reveals two oxidation waves and two irreversible reduction waves.     

Pseudo-isomeric zinc/copper coordination polymers based on 3-(2-pyridyl)pyrazole-5-carboxylic acid

Reaction of 3-(2-pyridyl)pyrazole-5-carboxylic acid (H₂L) with Zn(II) or Cu(II) perchlorate yielded [ZnL]_n (1) and [CuL]_n (2) with similar composition. The ligand L^2 − adopts the same μ₃κ⁵ coordination mode. The Zn(II) and Cu(II) atom takes square pyramid coordination polyhedron with some discrepancy. Bigger difference in the dimeric secondary building blocks leads to distinct two-dimensional metal–organic frameworks. The Zn(II) complex fluoresces stronger than the free ligand. The Cu(II) polymer displays strong antiferromagnetic intra-dimer exchange and ferromagnetic inter-dimer exchange.     

Unusual dirhenium complexes containing the bis[2-(diphenylphosphino)phenyl]ether ligand including a terephthalate-bridged tetrarhenium compound

The synthesis, structures and reactivity of unsymmetrical multiply-bonded dirhenium(IV,II) and dirhenium(III,II) complexes that contain the bis[2-(diphenylphosphino)phenyl]ether ligand (L¹) are described, including the isolation and structural characterization of the novel terephthalate-bridged tetrarhenium complex [Re₂Cl₄(η³-L¹)]₂(μ-O₂CC₆H₄CO₂) in which there is weak electronic coupling between the pairs of dirhenium centers.     

KINETICS OF THE COMPLEXATION OF UO2(NO3)2 WITH TRIBUTYL PHOSPHATE (TBP) IN XYLENE#

ABSTRACT

The kinetics of ligand exchange between bulk solution TBP and uranyl nitrate bound TBP in o-xylene has been investigated by ³¹P dynamic NMR spectroscopy. First order ligand exchange rate constant, k, and the activation energy for the uranyl nitrate-TBP system were determined from plots of transverse relaxation rates (In (l/τ)) versus reciprocal temperature (1/T). Using the Eyring equation, the average values of activation enthalpy, δH^* (30.8±5.1 kJ-mole^?1), and activation entropy, δS^* (-109±19 J/mol-K) have been calculated. The negative entropy of activation value indicates an increase in order on proceeding from the reactants to the activated complex. Therefore, an associative mechanism may be proposed for the ligand exchange reaction between UO₂(NO₃)₂ TBP2 and TBP. Equilibration of the extractant phase with 1.0 M HC1 did not change the ligand exchange rate constants or the activation parameters appreciably. These results are discussed in comparison with previous reports on TBP exchange rates for this system.     

Hydrothermal syntheses and characterization of a series of mixed-ligand luminescent CdII frameworks with novel 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl) acetate ligand and benzenedicarboxylate isomers

Under similar hydrothermal synthetic conditions using a novel flexible ligand 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl)acetonitrile (PPAN), benzenedicarboxylate isomers (H₂pa = phthalate, H₂ip = isophthalate, and H₂tp = terephthalate) and Cadmium(II) acetate, three novel mixed-ligand Cd(II) coordination polymers {[Cd₂(PPAA)₂(μ-pa)(H₂O)]·2H₂O}_n (1), {[Cd₄(PPAA)₄ (μ₄-ip)₂]·2H₂O}_n (2) and {[Cd₂(PPAA)₂(μ-tp)]·2H₂O}_n (3) (PPAA⁻ = 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl) acetate) have been isolated, in 1–3 PPAN, and are also hydrolyzed into a novel PPAA⁻ ligand. Complex 1 is a 1D coordination polymer in which the tetra-nuclear [Cd₄(PPAA)₄]^4 + structural units are extended by tri-dentate μ-pa^2 − ligands. Complex 2 contains binuclear [Cd₂(PPAA)₂]^4 + structural units, which are extended by four tetra-dentate μ₄-ip^2 − ligands to link eight neighboring binuclear [Cd₂(PPAA)₂]^4 + units ultimately forming a 2D layered framework, while complex 3 contains 1D double chain containing [Cd(PPAA)]_n cation structural units, which are further extended by tetradentate μ-tp^2 − ligands to form a new 2D layered framework. All the complexes have been investigated by elemental analysis, FT-IR, thermal analysis and fluorescence characterization. The flexible coordination modes of PPAA⁻ are also briefly analyzed. The flexible coordination modes of PPAA⁻ and benzenedicarboxylate isomers also reveal great potential in the construction of these novel mixed-ligand luminescent frameworks with diverse structural motifs and unique functional properties.     

A new 2D HgII coordination polymer containing novel coordination mode of 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (bpo) ligand, [Hg(μ-bpo)2(N3)2]n: Spectroscopic,thermal, fluorescence and structural studies

A new two-dimensional Hg^II coordination polymer containing 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (bpo) and azide anions, [Hg(μ-bpo)₂(N₃)₂]_n, has been synthesized and characterized by elemental analysis, IR-, ¹H NMR-, ¹³C NMR spectroscopy and structurally determined by X-ray single-crystal diffraction. The thermal stability of compound [Hg(μ-bpo)₂(N₃)₂]_n was studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The single-crystal X-ray data shows that ligand bpo is bridged via one pyridyl nitrogen and one oxadiazole nitrogen atom, as a novel coordination mode of the ligand bpo. Furthermore, the ligand and complex are luminescent in the solid state, with emission maxima in the visible light region (λ_max = 470 nm for both bpo and [Hg(μ-bpo)₂(N₃)₂]_n).     

Redox properties of (1-(2-pyridylazo)-2-naphthol)copper(II) encapsulated in Y Zeolite

The electroactivity of zeolite-encapsulated redox-active transition metal complexes was explored for copper(II)-PAN (PAN = 1-(2-pyridylazo)-2-naphthol) complex encaged in the supercages of Y zeolite. Copper(II)-PAN complex and the zeolite boundary were investigated electrochemically by dispersion with a Nafion/water solution on carbon Toray as supporting electrode. Encapsulation was achieved by: (i) ion exchange of copper(II) in NaY zeolite and (ii) coordination of the intrazeolite metal ion with the PAN ligand using an L:copper(II) molar ratio of 2:1. The resulting materials were characterized by cyclic voltammetry in zeolite modified electrodes, surface analysis (XPS, SEM and XRD), spectroscopic methods (EPR and FTIR) and chemical analysis, which indicated that the copper(II)-PAN complex was effectively encapsulated inside the supercages of NaY, without any modification of the morphology and structure of the zeolite. The coordination geometry of Y-encapsulated copper(II)-PAN complex has been obtained with preferentially 1:1 stoichiometry analogous to the model complex, [CuCl(PAN)], by molecular simulations. For the cyclic voltammetry studies, the electrochemical behavior of free complex was compared with copper(II)-PAN complex encapsulated in Y zeolite. The results show evidence for electroactivity restricted to the boundary associated to the copper(II)-PAN complex.     

1,1′-Ferrocene dicarboxylic acid pyridin-4-yl ester: A new bidentate ligand in arene ruthenium chemistry

1,1′-Ferrocene dicarboxylic acid pyridin-4-yl ester (1) is prepared from 1,1′-ferrocene dicarbonyl chloride and 4-hydroxypyridine. This new bidentate ferrocenoyl ligand reacts with the monocationic complex [(η⁶-p-cymene)₂Ru₂(μ-OH)₃]⁺ to give the dicationic complex [(η⁶-p-cymene)₂Ru₂(μ-OH)₂(1,1′- (NC₅H₄–OOC)₂–Fc)]²⁺ (2) (Fc: C₅H₄–Fe–C₅H₄), isolated as a tetrafluoroborate salt. The single-crystal X-ray structure analysis of [2][BF₄]₂ reveals the ferrocenoyl pyridine ligand 1 to act as μ₂-η² chelating ligand in the dinuclear complex, having replaced a μ₂-η¹-hydroxo ligand.     

Initial use of 1,1′-oxalyldiimidazole for inorganic synthesis: Decomposition of the ligand as a means to the preparation of an imidazole- and oxalate(-2)-containing, 1D copper(II) complex

The use of 1,1′-oxalyldiimidazole, (im)COCO(im), for the synthesis of coordination complexes is explored for the first time. The [Cu₂(O₂CMe)₄(H₂O)₂]/(im)COCO(im) reaction system in 96% EtOH yields the new, 1D coordination polymer [Cu(ox)(Him)₂]_n (1), where Him is the neutral imidazole and ox^2? is the oxalate(-2) ligand. A mechanism for the hydrolytic decomposition of the ligand is proposed. Complex 1 comprises neutral, zigzag chains with the η¹:η¹:η¹:η¹:μ (2.1111 using Harris notation) ox^2? ligand bridging two neighboring Cu^II centers; two cis Him groups complete a Jahn–Teller distorted octahedral geometry at the metal. The dc, variable-temperature magnetic susceptibility data for the complex reveal antiferromagnetic Cu^II?Cu^II exchange interactions.     

Synthesis, X-ray structure and Hg, Se CP MAS NMR studies on the first tris(imidazolidine-2-selone) mercury complex: {Chloro-tris[N-methyl-2(3H)-imidazolidine-2- selone]mercury(II)}chloride

A novel cationic Hg(II) complex has been synthesized with N-methyl-imidazolidine-2-selone ligand. The tris(N-Methyl-imidazolidine-2-selone) mercury(II) complex, [(MeImSe)₃HgCl]⁺Cl⁻ (1), has been characterized by single crystal X-ray analysis and CP MAS ¹⁹⁹Hg and ⁷⁷Se NMR.     

2-(2′-乙酰氧基-5′-溴甲基苯基)-2H-苯并三唑的合成

2-(2′-羟基-5′-甲基苯基)-2H-苯并三唑(UV-P)经过羟基乙酰化、N-溴代丁二酰亚胺(NBS)溴代,合成了具有高反应活性的2-(2′-乙酰氧基-5′-溴甲基苯基)-2H-苯并三唑。为提高目标产物产率和反应效率,分别对溶剂、引发剂、反应温度、反应时间、反应物投料比和反应底物浓度进行了研究。得出较优合成条件为:氮气保护下,四氯化碳为溶剂,偶氮二异丁腈(AIBN)引发,NBS与2-(2′-乙酰氧基-5′-甲基苯基)-2H-苯并三唑摩尔比1∶1,回流反应1h。在上述条件下,2-(2′-乙酰氧基-5′-溴甲基苯基)-2H-苯并三唑产率为60%。产物经过IR、1HNMR、MS分析证明结构正确。     

Novel Hg and Mn supramolecular complexes with a versatile building block 5-(4-pyridyl)-1,3,4-oxadiazole-2-thiolate involving in situ ligand formation

Reaction of potassium N′-(pyridine-4-carbonyl)-hydrazinecarbodithioate ([K⁺(H₂L)⁻]) with Hg^II or Mn^II inorganic salt in the presence of 1,10-phenanthroline (phen) or 4,4′-bipyridine (bipy), yields complexes [Hg(pyt)₂(phen)] (1) and {[Mn(pyt)₂(H₂O)₂]·(bipy)·(H₂O)₂}_n (2), in which the pyt ligand (Hpyt = 5-(4-pyridyl)-1,3,4-oxadiazole-2-thiol) is obtained by in situ ligand formation from the acyclic precursor [K⁺(H₂L)⁻]. Single crystal X-ray diffraction suggests that the pyt anionic ligands in 1 and 2 behave as thiolate and thione isomers, respectively, and display S- and μ-N_pyridyl, N_oxadiazole-binding fashions. Complex 1 shows a 1-D fishbone-like supramolecular array via strong aromatic stacking interactions between the discrete mononuclear coordination motifs, whereas 2 has a 2-D layered host coordination framework with the inclusion of bipy and water guests in the cavities.