Synthesis and properties of a redox active starburst ligand with three bispicorylamino groups and its trinuclear complexes

A starburst-shaped ligand, 4,4′4″-tris[N,N-bis(2-pyridylmethyl) aminomethyl] triphenylamine, and its palladium and copper trinuclear complexes were designed and prepared. NMR techniques, COSY and ROESY, were applied to the palladium complex to examine its conformation in solution. The palladium complex was found to prefer a folded conformation even at 75 °C, indicating the occurrence of strong intramolecular stacking interaction. CV measurements of the palladium complex showed reversible TTA/TTA⁺ redox couples. ETSF measurements showed that the corresponding radical pendant complex is very unstable. Molecular design rules for triarylamine-based spin bearing ligands are discussed.     

Synthesis and structure of a dinuclear copper complex of a bis(bidentate)triazenide ligand

The synthesis and characterization of a dinuclear copper(II) complex with a bis(bidentate) ligand is reported. The ligand is a functionalized 1,3-diaryl triazene substituted with carboxymethyl groups at the ortho positions of the aryl rings. Reaction of this ligand with Cu₂(OAc)₄·2H₂O resulted in the formation of the Cu₂(OAc)₃(triazenide) where the triazenide binds to each copper through one of the triazenide nitrogens and the carbonyl oxygen of the pendant esters. The structures of this dinuclear complex and of the ligand are reported.     

Synthesis,structure, redox property and ligand replacement reaction of ruthenium(II) complexes containing a terpyridyl ligand with a redox active moiety

Ruthenium(II) complexes bearing a redox-active tridentate ligand 4′-(2,5-dimethoxyphenyl)-2,2′:6′,2′′-terpyridine (tpyOMe), analogous to terpyridine, and 2,2′-bipyridine (bpy) were synthesized by the sequential replacement of Cl by CH₃CN and CO on the complex. The new ruthenium complexes were characterized by various methods including IR and NMR. The molecular structures of [Ru(tpyOMe)(bpy)(CH₃CN)]²⁺ and two kinds of [Ru(tpyOMe)(bpy)(CO)]²⁺ were determined by X-ray crystallography. The incorporation of monodentate ligands (Cl, CH₃CN and CO) regulated the energy levels of the MLCT transitions and the metal-centered redox potentials of the complexes. The kinetic data observed in this study indicates that the ligand replacement reaction of [Ru(tpyOMe)(bpy)Cl]⁺ to [Ru(tpyOMe)(bpy)(CH₃CN)]²⁺ proceeds by a solvent-assisted dissociation process.     

Efficient photocatalytic properties of a dinuclear iron complex with bis[2-hydroxybenzaldehyde]hydrazonate ligand

A novel photooxidative system for degrading toxic organic pollutants is reported. A new complex of Fe2L3(L = bis[2-hydroxybenzaldehyde]hydrazone) synthesized can efficiently activate hydrogen peroxide (H2O2) to oxidize and mineralize the target complexes rhodamine B (RhB) and methyl orange (MO) in aqueous media under ambient temperature and normal pressure and with visible light irradiation.     

Synthesis,crystal structure,electrochemical and magnetic properties of dinuclear complexes with strong electron-drawing groups in the diphenoxo-tetraaza macrocyclic ligand

Three symmetrical macrocyclic dinuclear complexes [M₂L(H₂O) _n ](ClO₄)₂ (M²⁺ = Cu²⁺, Ni²⁺, Mn²⁺ and n = 0, 2) have been synthesized by cyclocondensation between 2,6-diformyl-4-fluorophenol and 1,4-diaminobutane in the presence of M²⁺ cations. The crystal structure of [Cu₂L](ClO₄)₂ was determined by X-ray diffraction techniques. The electronic and magnetic properties of the complexes were studied by cyclic voltammetry and magnetic susceptibility. The results confirm that the complexes obtain electrons easily and there are very strong antiferromagnetic couplings between two copper(II) ions in [Cu₂L](ClO₄)₂. The strong electron-drawing groups of fluorine attached to the phenyl ring of a macrocyclic complex enhances the antiferromagnetic exchange of the complex and makes it more easily reduced than its analogs.     

Synthesis and luminescence properties of a kinetically stable dinuclear ytterbium complex with differentiated binding sites

The complex Yb2L contains two DO3A units separated by a phenol bridging group and gives time-resolved luminescence spectra in solution consistent with the presence of two types of binding site.     

Synthesis and structure of a chiral dinuclear palladium(0) complex with a 30-membered hexaolefinic macrocyclic ligand

Selective and efficient preparation of a new chiral dipalladium(0) complex with an olefinic macrocyclic ligand named (E,E,E,E,E,E)-1,6,11,16,21,26-hexakis[(4-methylphenyl)sulfonyl]-1,6,11,16,21,26-hexaazacyclotriaconta-3,8,13,18,23,28-hexaenedipalladium(0) (5) is reported. Dinuclear palladium(0) complex 5 has been fully characterized by means of NMR spectroscopy and X-ray diffraction analysis.     

Crystal structure and magnetic properties of dinuclear iron(III) complex with ONNO-donor ligand

A new dinuclear Fe(III) complex, [Fe(5-MeOL1)(OH)_0.86(CH₃O)_0.14]₂?2(CH₃OH), [H₂-5-MeOL1 = N,N′-bis(5-methoxy-2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine], 1 has been synthesized and characterized by single crystal structure analysis. The structure of 1 consists of two Fe(III) centers with one tetradentate schiff base ligand (N₂O₂) which are bridged by dihydroxo/dimethoxo groups to yield a Fe₂O₂ core. Complex 1 exhibits weak antiferromagnetic exchange interaction between Fe(III) ions with J = ?0.21 cm^–1.     

Synthesis and redox properties of crowded triarylphosphines possessing ferrocenyl groups

Crowded triarylphosphines possessing ferrocenyl groups [(4-ferrocenyl-2,6-diisopropylphenyl)(n)(2,4,6-triisopropylphenyl)(3-n)P (5a, n = 1; 5b, n = 2; 5c, n = 3)] were synthesized by the reaction of the corresponding arylcopper(I) reagents with the diarylchlorophosphines. Structures of the triarylphosphines were studied by 1H, 13C, and 31P NMR spectroscopies, and the characteristic patterns of the proton signals of the 2,6-isopropyl groups and upfielded 31P chemical shifts suggest structural similarities of the triarylphosphine moiety to the previously reported tris(2,4,6-triisopropylphenyl)phosphine (2). X-ray crystallography of 5c also revealed that the structure around the phosphorus is similar to that of 1, where the average bond angle and length around the phosphorus atom are 110.8 degrees and 1.854 A, respectively. According to the electrochemical measurements, phosphines 5a, 5b, and 5c are reversibly oxidized in two, three, and four steps, respectively, which suggests significant electronic interaction among the triarylphosphine and the ferrocene redox centers as well as weak interaction among the ferrocene redox centers. The EPR spectra obtained at cryogenic temperature after oxidation of phosphines 5a, 5b, and 5c are superpositions of those for the cation radicals of the crowded triarylphosphine and ferricinium. The solution spectra obtained at 293 K, which consist of two lines typical of the cation radical of the crowded triarylphosphines, become weaker as the number of the ferrocenyl groups increases and the cation radical of 5c does not show EPR signals. These findings suggest not only instability of the tetra(cation radical) of 5c but also the course of oxidation where the ferrocenyl groups in the periphery of the molecules are oxidized at first.     

Synthesis, crystal structure, spectroscopy and magnetic properties of a dinuclear Cu complex with 3,5-bis(2-pyridyl)pyrazole bridging ligand

A dinuclear Cu^II complex [Cu₂(bpp)₂(H₂O)₂](ClO₄)₂ (1) with 3,5-bis(2-pyridyl)pyrazole (Hbpp), has been synthesized and characterized by elemental analyses, thermal analysis, conductance, UV-vis and IR spectra. The crystal structure of 1, determined by X-ray diffraction technique, reveals that two centrosymmetric Cu^II centers are bridged by a pair of tetradentate anionic bpp ligands, adopting a square-pyramidal environment with the water ligand occupying the axial site. An interesting feature of this structure is the formation of a two-dimensional supramolecular network through O-H?O hydrogen bonds between the water moieties of the cationic [Cu₂(bpp)₂(H₂O)₂]²⁺ subunits and perchlorate anions. The magnetic properties of 1 have been investigated by variable-temperature magnetic susceptibility and EPR measurements. Very strong antiferromagnetic interaction between the Cu^II centers (with H=−JS₁S₂, J=−368.3 cm⁻¹) has been observed, and the magneto-structural correlations was analyzed.     

Synthesis and crystal structure of a new dinuclear manganese(II) complex of a macrocyclic ligand with multi-ligating pendant-arms

A new dinuclear manganese(II) macrocyclic complex has been synthesized by [2 + 2] Schiff-base condensation between sodium 2,6-diformyl-4-chlorophenolate with the reduced 1:1 Schiff base of tris(2-aminoethyl)amine (tren) and 2-acetylpyridine in the presence of Mn(ClO₄)₂ · 6H₂O. The crystal structure shows that each pendant-arm is bonded in a bidentate fashion to the adjacent metal atom and that both arms are on the same side of the macrocycle. One manganese(II) ion is seven-coordinate with a geometry of a capped distorted octahedron, while another manganese(II) ion is six-coordinate with a geometry of a distorted octahedron.     

Synthesis and crystal structure of the first dinuclear zinc complex containing 1,4,7-triazacyclononane and biological properties of the protonated ligand

Abstract

A new binuclear complex, [Zn₂L₂Cl₄]·2H₂O {L?=?N-aldehyde-N-(4-(benzyloxy)benzyl)-1,4,7triazacyclononane}, was synthesized and characterized by X-ray, elemental analysis, infrared and electronic spectroscopy, and mass spectrometry. The central ion is bridged by the L and lies in a tetrahedral configuration with Zn···Zn distance of 6.283 Å. The complex crystallizes in the triclinic space group Pī. ESI-MS of the complex indicates that the protonated ligand HL⁺ is the active species. The interaction of HL⁺ with calf thymus–DNA (CT–DNA) and bovine serum albumin (BSA) was studied by means of various spectroscopic methods, which revealed that HL⁺ could interact with CT–DNA through groove-binding mode and could quench the intrinsic fluorescence of BSA in a static quenching process. DNA–cleavage experiments indicate that HL⁺ exhibits efficient DNA–cleavage activity in the presence of H₂O₂, hydroxyl radical (HO^?) may serve as the major cleavage active species, and the pseudo-Michaelis–Menten kinetic parameters (K_cat, K_M, V_max); 2.47?h^?1, 2.70?×?10^?4 M and 6.68?×?10^?4 Mh^?1.     

Synthesis,crystal structure,and DNA cleavage activity of a dinuclear nickel(II) complex with a macrocyclic ligand

A new Ni(II) complex, namely [Ni₂(OAc)L]·ClO₄·H₂O, was synthesized by [2 + 2] cyclo-condensation between 2,6-diformyl-4-methylphenol and N,N-bis(3-aminopropyl)-4-methoxybenzylamine (amba) in the presence of nickel(II) and characterized by spectroscopy, elemental analysis, and X-ray single crystal diffraction. The interactions of the complex with DNA have been measured by spectroscopy and viscosity measurements. Absorption spectroscopic investigation reveals intercalative binding of the Ni(II) complex with DNA, with a binding constant of 2.6 × 10⁴ M⁻¹. Fluorescence spectroscopy shows that the Ni(II) complex can displace ethidium bromide and bind to DNA, with a quenching constant of 7.57 × 10³ M⁻¹. The appearance of increased CD bands near 245 and 275 nm gives evidence for effective complex DNA binding. The agarose gel electrophoresis studies show that the complex displays effective DNA cleavage activity in the absence of any external agents.     

Stacking interaction in crystals of a dinuclear rhodium complex with a bridging phenylborole ligand

Russian Chemical Bulletin -     

双核铕(Ⅲ)配合物的合成及选择性激发

成功地合成一种新的四齿配体2,5-二(4-((2-吡啶-1氢-苯并[d]嘧唑)甲基)苯基)-1,3,4-噁二唑(L),并且将该配体作为第二配体合成出双核Eu3+配合物[Eu(TTA)3]2L(TTA二2-噻吩三氟甲基乙酰丙酮),配合物[Eu(TTA)3]2L的结构用红外光谱,吸外-可见吸收光谱进行了充分表征.为了讨论配...     

Synthesis and photophysical properties of a fluorescent TREN-type ligand incorporating the coumarin chromophore and its zinc complex

A new, UV-excited fluorescent Zn²⁺ indicator was synthesized and the spectral profile of its free and Zn²⁺ bound forms were studied. The fluorescent properties of this probe are due to the 7-amino-4-methylcoumarin fluorophore, which is conjugated with the tris(2-aminoethyl)amine (TREN) that functions as the zinc-chelating moiety. The compound exhibits a Zn²⁺ dissociation constant of 18.0 μM. The fluorescence spectra of the probe showed a clear shift in excitation wavelength maxima upon Zn²⁺ binding, indicating its potential use as ratiometric Zn²⁺ indicator.     

Synthesis and crystal structure of a dinuclear praseodymium nitrate complex

Dinuclear supramolecular complex of praseodymium nitrate with an unsymmetrical tipodal ligand benzyl-N,N-bis[(2′-benzylaminoformyl)phenoxyl)ethyl]-amine (L), have been prepared. The X-ray single-crystal diffraction analysis indicates that this complex was crystallized in the monoclinic system, space group P2₁/c with parameters a = 16.736(3), b = 14.042(3), c = 19.782(4) Å, β = 101.823°, V = 4550.50(16) ų, Z = 4. The structure was refined to the final R ₁ = 0.0473. The complex units are linked by the intermolecular hydrogen bonds to form a three-dimensional (3D) netlike supramolecuar structure.     

Synthesis, structure and catalytic activity of an oxo-bridged dinuclear oxovanadium complex of an isonicotinohydrazide ligand

A mononuclear dioxo vanadium(V) complex of a hydrazone ONO donor ligand, [V^VO₂(L¹)] (1), was synthesized by the reaction of V₂O₅ and terephthalic acid with H₂L¹ in 1:1:1 mol ratio, while an oxo-bridged bis(vanadium(IV)oxo) complex, [μ ₂–O–{V^IVO(L²)}₂] (2), was synthesized by the treatment of isonicotinic acid hydrazide, salicylaldehyde and CoSO₄·7H₂O with bis(acetylacetonato)oxovanadium(IV) (H₂L¹ = isonicotinic acid(2-hydroxy-benzylidene)-hydrazide, H₂L² = isonicotinic acid (1-methyl-3-oxo-butylidene)-hydrazide). The complexes were characterized by elemental analyses and spectroscopic methods. The crystal structure of complex 2 was determined by X-ray analysis. The complexes were tested as catalysts for the oxidation of cycloalkenes and benzyl alcohol using H₂O₂ as terminal oxidant. Excellent selectivity was achieved in the oxidation of cyclohexene.     

Synthesis and magnetic properties of a highly conducting neutral nickel complex with a highly conjugated tetrathiafulvalenedithiolate ligand

A neutral nickel complex with the extended tetrathiafulvalene-4,5-dithiolate ligand benzotetrathiafulvalenedithiolate (btdt2-) is synthesized and characterized. From the structural analysis, the neighboring molecules in this complex are stacked in a different way compared to the previously reported single-component metal [Ni(tmdt)2]. The computational studies confirm that the difference in molecular packing results in the variance of conductivity.     

Synthesis,structure and electrochemical properties of a dioxomolybdenum(VI) complex with a ferrocene-containing ligand

Summary Bis[ferrocene aldehyde benzoylhydrazonato(1-)-N ¹,O]- dioxomolybdenum(VI) has been synthesized and characterized by x-ray diffraction and i.r.,¹H n.m.r. and electronic spectroscopies. The CH₂Cl₂/hexane solvate crystallizes in space group P2₁/n witha=11.149(6),b=20.463(8),c= 15.541(5) Å, =90.40(3)° andZ=4. The structure has been refined to R_w=0.049 based on 2886 independent reflections. The complex has distorted octahedral geometry with the two bidentate ligands coordinated through the oxygen and the azomethine nitrogen atoms. The MoO ₂ ²⁺ unit has the expectedcis geometry and the Mo-N bonds aretrans to the oxo-groups. The chelate rings are nearly planar but the cyclopentadienyl and phenyl rings are twisted out of the chelate rings. The electrochemical behaviour of the compound is also discussed: the two ferrocenyl groups appear to be independent with respect to oxidation and the molybdenum centre displays a nearly reversible one-electron reduction.