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1.
Three new Cu(II) complexes with ethyl bis(2-pyridylmethyl)amino-2-propionate (Etdpa), or bis(2-pyridylmethyl)amino-2-propionate (Adpa), were synthesized and characterized by physico-chemical and spectroscopic methods. The X-ray crystal structure of [(Adpa)CuCl] shows that the copper(II) atom is coordinated by three N atoms, one oxygen atom from the ligand (Adpa) and one chloride anion, forming a trigonal bipyramidal geometry. The spectrophotometric and fluorescence titration data indicate that the interaction of square pyramidal [(Etdpa)CuCl2] with ct-DNA is weak, but the trigonal bipyramidal complexes [(Adpa)Cu(H2O)](ClO4) and [(Adpa)CuCl] interact with ct-DNA with the mode of intercalation. The inhibition activities of the three new copper(II) complexes on the four cancer cells (Mcf-7, Eca-109, A549, and Hela) are in the order: [(Adpa)Cu(H2O)](ClO4) > [(Adpa)CuCl] > [(Etdpa)CuCl2], which correlates with their DNA-binding properties. The results show that the substituents introduced on the secondary amino nitrogen atom of dpa have great contribution to the antitumor activities of these copper(II) complexes. It is also found that the coordination of copper(II) ions with AdpaH can decrease the toxicity of AdpaH. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

2.
The copper(II) complex [Cu(L)(dppz)](ClO4)2 (1) having a tripodal ligand ferrocenylmethylbis(2-pyridylmethylamine) (L) with a pendant ferrocenyl unit and a planar NN-donor dipyrido-[3,2-a:2′,3′-c]-phenazine (dppz) base is prepared and its DNA binding and cleavage properties studied. The complex is redox active showing cyclic voltammetric responses at 0.52 and –0.01 V vs. SCE due to Fe(III)/Fe(II) and Cu(II)/Cu(I) couples, respectively. The complex that binds to the major groove of DNA shows dual chemical nuclease activity involving both the metal centres. The complex displays efficient photo-induced DNA cleavage activity in visible laser light of 458 and 568 nm wavelengths forming cleavage active hydroxyl radicals. Significant DNA cleavage is also observed in red light of 647 nm within the photodynamic therapy (PDT) window.  相似文献   

3.
A novel series of 4,4′-bipyridine- and 1,2-bis(4-pyridyl)ethane-Cu(II) complexes were synthesized using a variety of amine ligands (DPA = di(2-pyridylmethyl)amine, Medpt = 3,3′-diamino-N-methyldipropylamine, Hbpca = bis(2-pyridylcarbonyl)amine, TPA = tris(2-pyridylmethyl)amine) and cyclen = 1,4,7,10-tetraazacyclododecane). Different complexes were obtained including mononuclear [Cu(cyclen)(4,4′-bipy)](ClO4)2 (1), dinuclear {[Cu(μ2-bpca)(4,4′-bipy)(H2O)]ClO4}2 (2), [Cu2(DPA)22-4,4′-bipy)(ClO4)4)]·H2O (3), [Cu2(cyclen)22-bpe)](ClO4)4 (4) and [Cu2(TPA)22-bpe)](ClO4)4 (5) and the 1-D polymer, {[Cu(Medpt)(μ2-4,4′-bipy)](ClO4)2}n (6). In the 16 samples, cooling up to 100 K produces only the expected, minor, changes in cell constants given no space group changes. Therefore, data for the 100 K structures are reported only. Single-crystal X-ray crystallography reveals the monodentate coordination of the 4,4′-bipy in 1 and 2, and the bridged nature of the di-pyridyl ligands in the dinuclear complexes 25 and in the polymeric complex 6. In this series, structures 36 consist of the 4,4′-bipy or bpe bridging the two Cu(II) centers, the coordination by the tri- or the tetra-N donors of the amine, and the ClO4? groups as counter ions in 46 complexes. In the complexes 36, the Cu···Cu distances across the bridged di-pyridyl ligands were found to be greater than 11 Å. The magnetic properties of complex 3 reveal no evidence for magnetic coupling between the two Cu(II) centers (J = ?0.58 cm?1).  相似文献   

4.
The new double-Schiff-base ligand H6ipa-bhea has been synthesized by condensation of a 4,6-diformylresorcinol derivative (ipa) with two equivalents of N,N-bis-(2-hydroxyethyl)ethylenediamine (bhea). Reaction with copper(II) perchlorate leads to the formation of two different products depending on the reaction conditions. The directed synthesis of either a mononuclear or dinuclear copper(II) complex is reported. The reaction in methanol results in the formation of a dinuclear complex [Cu2(H4ipa-bhea)](ClO4)2 (1). Whereas in the presence of water as solvent for the reaction, one imine side chain of the ligand is hydrolyzed regenerating the formyl moiety with the mononuclear complex [Cu(H3hyforsa-bhea)]ClO4 · 2H2O (2) as final product. Subsequent reaction of complex 2 with N,N-bis-(pyridin-2-ylmethyl)ethylenediamine (unspenp) as additional amine component results in the formation of the mononuclear complex [Cu(Hhyforsa-unspenp)]ClO4 (3). All complexes are characterized by IR spectroscopy, elemental analysis and X-ray crystallography. Temperature-dependent magnetic measurements on the dinuclear complex indicate weak antiferromagnetic exchange interactions between the copper(II) ions with a coupling constant of J = ?16.4 cm?1. Density functional calculations have been used to evaluate the magnetic properties. The exchange coupling constant can be nicely reproduced with the use of the broken symmetry approach. The exchange pathway through the meta-phenylene-linkage is discussed in terms of a competitive spin-polarization and superexchange mechanism as well as geometrical changes at the copper(II) ions.  相似文献   

5.
Four new platinum(II) complexes [Pt(dpen)(bpy)](ClO4)2 ( 1 ) , [Pt(dpen)(phen)](ClO4)2 ( 2 ), [Pt(dpen)(dpq)](ClO4)2 ( 3 ) and [Pt(dpen)(dppz)](ClO4)2 ( 4 ) comprising of different N,N‐donor ligands, viz., 2,2′‐bipyridine (bpy), 1,l0‐phenanthroline (phen), dipyridoquinoxaline (dpq), dipyrido‐[3,2‐d:2¢,3¢‐f –phenazine] (dppz), and chiral ancillary ligand 1R,2R ‐1,2‐diphenylethylenediamine (dpen) have been synthesized and characterized. The interaction of these complexes 1–4 with calf‐thymus DNA (CT‐DNA) has been explored using absorption, circular dichroism spectral and cyclic voltammetric studies. The absorption spectrum of complex 4 with dppz ligand exhibits a major red shift with an overall hypochromic as well as a hyperchromic effect in the presence of DNA, other complexes ( 1 – 3 ) show only hypochromism. From these absorption spectral studies, the intercalative ability of the complexes follows the order as, 4  >  3  >  2  >  1 , which is further confirmed by CD and cyclic voltammetry measurements. CD spectral studies show that DNA becomes more A ‐like upon interaction with the complexes 1 & 2 but the complexes 3 & 4 bring about B ‐form to Z ‐ form DNA conformational transition. The DNA cleavage study of these Pt(II) complexes 1–4 carried out by gel electrophoresis revealed that complexes 1–4 can cleave super coiled (SC) pUC18 DNA efficiently into open circular form (form II) under hydrolytic and oxidative conditions.  相似文献   

6.
Two dinuclear molecule-bridged Cu(I) complexes, (μ-bpym)[Cu(PPh3)Cl]2 (1), [(μ-bpym)(CuL)2](ClO4)2·(CH3CN)2(H2O) (2) (bpym = 2,2′-bipyrimidine, L = (R)-(+)-2,2′-bis(diphenylphospho)-1,1′-dinaphthalene) have been synthesized and characterized. The molecular structures of the two new dinuclear compounds exhibit bridging of two copper(I) centers by the symmetrically bis-chelating bpym ligand. Intriguingly, compound 1 features a remarkable “intramolecular organic sandwich” configuration where the central 2,2′-bipyrimidine bridging ligand interacts in π/π/π fashion with two phenyl rings from the coligands above and below the central plane, while chiral compound 2 exhibits second-order nonlinear optical effect and temperature-dependent luminescence. Upon decreasing the temperature from 298 to 10 K, compound 2 shows a red light emission.  相似文献   

7.
Redox active mononuclear and binuclear copper(II) complexes have been prepared and structurally characterized. The complexes have planar N-donor heterocyclic bases like 1,10-phenanthroline (phen), dipyridoquinoxaline (dpq) and dipyridophenazine (dppz) ligands that are suitable for intercalation to B-DNA. Complexes studied for nuclease activity have the formulations [Cu(dpq)2(H2O)] (ClO4)2.H2O (1), [CuL(H2O)2(μ-ox)](ClO4)2 (L = bpy,2; phen,3; dpq,4; and dppz,5) and [Cu(L)(salgly)] (L = bpy,6; phen,7; dpq,8; and dppz,9), where salgly is a tridentate Schiff base obtained from the condensation of glycine and salicylaldehyde. The dpq complexes are efficient DNA binding and cleavage active species. The dppz complexes show good binding ability but poor nuclease activity. The cleavage activity of thebis-dpq complex is significantly higher than thebis-phen complex of copper(II). The nuclease activity is found to be dependent on the intercalating nature of the complex and on the redox potential of the copper(II)/copper(I) couple. The ancillary ligand plays a significant role in binding and cleavage activity.  相似文献   

8.
A novel selective thiocyanate PVC membrane electrode based on bis-bebzoin-semitriethylenetetraamine binuclear copper(II) [Cu(II)2–BBSTA] as neutral carrier is reported, which displays an anti-Hofmeister selectivity sequence in following order: SCN > ClO4 > I >Sal >SO32− >NO3 > H2PO4 > Cl >NO2 > SO42−. The electrode exhibits Nernstian potential linear range to thiocyanate from 1.0 × 10−1 to 9.0 × 10−7 mol/l with a detection limit 7.0 × 10−7 mol/l and a slope of −57.0 mV/decade in pH 5.0 of phosphorate buffer solution at 25 °C. The response mechanism is discussed in view of the AC impedance technique and the UV spectroscopy technique. From comparison of potentiometric response characteristics between the binuclear metallic complex copper(II) [Cu(II)2–BBSTA] and mononuclear copper(II) metallic complex [Cu(II)–BBSDA], an enhanced response towards thiocyanate from the electrode based on binuclear metallic complex copper (II) [Cu(II)2–BBSTA] was observed. The electrode based on binuclear copper(II) compound was used to determine the thiocyanate content in waste water with satisfactory results.  相似文献   

9.
New copper(I) mixed-ligand complexes 14 of the formula Cu(N–N)PR3X, where N–N = 1,10-phenanthroline (phen), 2,2′-bipyridine (bpy), 5,5′-dimethyl-2,2′-bipyridine (5,5′dimbpy) and PR3 = tricyclohexylphosphine, tris(2-cyanoethyl)phosphine and isopropyldiphenylphosphine, have been synthesized. The complexes were characterized by EA, IR, NMR and single crystal X-ray diffraction. The solution fluorescence emission spectra were measured. The single crystal X-ray analysis showed that the copper(I) ion is four-coordinate with a distorted tetrahedral geometry. The complexes catalyze the formation of diphenylacetylene from the coupling of halobenzene with phenylacetylene. The complex Cu(5,5′-dimethylbpy)P{(cyhexyl)3}I showed the highest catalytic activity. At room temperature all four complexes exhibit, in dichloromethane, emission maxima in the 329–344 nm range, corresponding to intra-ligand excited states.  相似文献   

10.
《Polyhedron》2007,26(9-11):1849-1858
Three compounds composed of phenazine and copper chloride have been prepared and studied by infrared spectroscopy, X-ray diffraction, and variable temperature magnetization. The compounds synthesized and studied are: Cu(phenazine)Cl2 (1), (phenazinium)2CuCl4 · H2O (2), and [Cu(phenazine)Cl2 · H2O]2 (3). Compounds 1 and 2 are described as antiferromagnetic Heisenberg chains with exchange constants ∣J∣/kB = 33.8 K and 8.6 K, respectively.  相似文献   

11.
New bimetallic complex salts corresponding to the formulation [Ni(L)][MCl4] have been synthesized by the facile reaction between [Ni(L)](ClO4)2 and [MCl2(PPh3)2] in high yields {where M = Co(II), Zn(II), Hg(II) and L = 3,7-bis(2-aminoethyl)-1,3,5,7-tetraazabicyclo(3.3.1)nonane}. The complexes were characterized by IR, electronic spectra, TGA/DSC, magnetic moment and conductivity measurements. The X-ray crystal structure for [Ni(L)][CoCl4] clearly establishes the cationic–anionic interaction. It crystallizes in the space group P1 with unit cell dimensions a = 7.1740(15) Å, b = 8.1583(16) Å and c = 8.3102(16) Å. A square-planar geometry is evident for the [Ni(L)]2+ cation while the anion is found to be tetrahedral. A two-step thermolytic pattern is observed in the pyrolysis of the bimetallic complex salts.  相似文献   

12.
Two new copper(II) complexes, [Cu2(L1)2](ClO4)2 (1) and [Cu(L2)(ClO4)] (2), of the highly unsymmetrical tetradentate (N3O) Schiff base ligands HL1 and HL2 (where HL1 = N-(2-hydroxyacetophenone)-bis-3-aminopropylamine and HL2 = N-(salicyldehydine)-bis-3-aminopropylamine) have been synthesised using a template method. Their single crystal X-ray structures show that in complex 1 two independent copper(II) centers are doubly bridged through phenoxo-O atoms (O1A and O1B) of the two ligands and each copper atom is five-coordinated with a distorted square pyramidal geometry. The asymmetric unit of complex 2 consists of two crystallographically independent N-(salicylidene)-bis(aminopropyl)amine-copper(II) molecules, A and B, with similar square pyramidal geometries. Cryomagnetic susceptibility measurements (5–300 K) on complex 1 reveal a distinct antiferromagnetic interaction with J = ?23.6 cm?1, which is substantiated by a DFT calculation (J = ?27.6 cm?1) using the B3LYP functional. Complex 1, immobilized over highly ordered hexagonal mesoporous silica, shows moderate catalytic activity for the epoxidation of cyclohexene and styrene in the presence of TBHP as an oxidant.  相似文献   

13.
This review summarizes structural parameters for forty five Cu44-O)(η-X)6(L4) tetramers. There are four types of structurally equal core units, CuCl3ON, CuCl3OO, CuCl3OCl and CuBr3ON. There are also tetramers which contain structurally unequal core units: CuCl3ON (x2) and CuCl2BrON (x2); CuCl3ON (x1), CuCl2BrON (x2) and CuCl3OCl (x1). There is a tendency for an elongated Cu?Cu separation as well as Cu–L bond distances with increase of the covalent radius of the coordinating atom(s). Tetrahedral distortion around oxygen atom (OCu4) increases in the order: 1.67° (CuCl3OCl) < 2.10° (CuCl3ON) < 2.11° (CuCl3OO′) < 2.27° (CuBr3ON). The mean Cu–Cl–Cu bridge angle of 80.5° is about 4.0° more open than that of a Cu–Br–Cu (76.5°). The cluster Cu16O4Br7Cl17(4-Mepy)16 (4-Mepy = 4-methylpyridine) contains four crystallographically independent tetramers: Cu4OBrCl5(4-Mepy)4 (1), Cu4OBrCl5(4-Mepy)4 (2) Cu4OBr2Cl4(4-Mepy)4 (3) and Cu4OBr3Cl3(4-Mepy)4 (4), which is a unique example of stereoisomerism. There are other examples which exist in two isomeric forms. Another contains two or even four crystallographically independent tetramers within the same crystal, differing mostly by degree of distortion and is an examples of distortion isomerism. Pairs of Cu4OCl6(n-Meim)4 (n-Meim = n-methylimidazole) (n = 1 or 2) are examples of ligand isomerism.  相似文献   

14.
Summary Four new trinuclear copper(II) complexes, [Cu(phen)-(NBzIm)] (ClO4) (1), [Cu(bpy)(NBzIm)](ClO4) (2), [Cu-(Me2-bpy)(NBzIm)](Ac)·1/2H2O (3) and [Cu(Me2-bpy)-(Im)](ClO4)·1/2H2O (4) (phen = 1, 10-phenanthroline, bpy = 2,2-bipyridine, NBzIm = 6-nitrobenzimidazolate ion, Im=imidazolate ion) have been prepared and characterized by variable temperature magnetic susceptibility measurements. A weak antiferromagnetic spin exchange interaction operates between copper(II) ions, exchange integrals evaluated as J =-23.82 cm-1 for (1); and J=-21.91 cm-1 for (2).  相似文献   

15.
Two substituted N-acylthioureas and the respective Ni(II) and Cu(II) complexes were synthesized, namely: N,N-di-n-butyl-N′-thenoylthiourea (Hnbtu); N,N-di-iso-butyl-N′-thenoylthiourea (Hibtu); bis[N,N-di-n-butyl-N′-thenoylthioureato]nickel(II), [Ni(nbtu)2]; bis[N,N-di-n-butyl-N′-thenoylthioureato]copper(II), [Cu(nbtu)2]; bis[N,N-di-iso-butyl-N′-thenoylthioureato]nickel(II), [Ni(ibtu)2]; bis[N,N-di-iso-butyl-N′-thenoylthioureato]copper(II), [Cu(ibtu)2]. The standard (p° = 0.1 MPa) molar enthalpies of formation and sublimation of the two N-acylthioureas were measured, at T = 298.15 K, by rotating-bomb combustion calorimetry and Calvet microcalorimetry, respectively. The standard (p° = 0.1 MPa) molar enthalpies of formation of the Ni(II) and Cu(II) complexes were determined, at T = 298.15 K, by high precision solution–reaction calorimetry. From the results obtained, the enthalpies of hypothetical metal–ligand and metal–metal exchange reactions, in the gaseous phase, were derived, thus allowing a discussion of the gaseous phase energetic difference between the complexation of Ni(II) and Cu(II) to 1,3-ligand systems with (S,O) ligator atoms.  相似文献   

16.
The heterometallic photoinitiated electron collector [{(phen)2Ru(dpp)}2RhBr2](PF6)5 (phen = 1,10-phenanthroline, dpp = 2,3-bis(2-pyridyl)pyrazine) has been synthesized and studied by spectroscopic, photophysical, electrochemical, and photochemical techniques. Substitution of chloride with bromide in the previously reported [{(phen)2Ru(dpp)}2RhCl2](PF6)5 complex presents a new photoinitiated electron collector which can assist in understanding the functioning of our supramolecular systems [{(TL)2Ru(BL)}2RhX2](PF6)5 (TL = terminal ligand, BL = bridging ligand, X = halide) in the photoinitiated electron collection and generation of hydrogen through the reduction of water and a detailed comparison is presented. Both the bromide and chloride analogues of these supramolecular complexes contain low energy, emissive metal-to-ligand charge transfer (3MLCT) excited states that populate lower lying metal-to-metal charge transfer (3MMCT) excited states. The electrochemistry of these complexes showed an impact on the reduction of the central RhIII upon halide substitution with the bromide analogue [(phen)2Ru(dpp)}2RhBr2](PF6)5 having a slightly lower reduction potential than the corresponding chloride counterpart. The more positive reduction of RhIII to generate the RhI species in the bromide analogue impacts the photocatalytic properties upon photolysis in the presence of a sacrificial electron donor. The trimetallic complex [{(phen)2Ru(dpp)}2RhBr2](PF6)5 generates hydrogen through the reduction of water with higher yields than the chloride [{(phen)2Ru(dpp)}2RhCl2](PF6)5 analogue under the same conditions. Despite the longer lived 3MLCT state of both [(TL)2Ru(dpp)]2+ and [{(TL)2Ru}2(dpp)]4+ when TL = phen vs. bpy (bpy = 2,2′-bipyridine), the phen trimetallics with X = Cl? or Br? do not display longer lived 3MLCT states and show lower H2 yields than the analogous bpy trimetallic systems.  相似文献   

17.
The reaction of Cu(ClO4)2·6H2O with dimethylglyoxime (H2dmg) in a 1:1 mole ratio in aqueous methanol at room temperature affords the dinuclear complex [Cu2(μ-Hdmg)4] (1). Reaction of 1 with [Cu(bpy)(H2O)2](ClO4)2 (bpy = 2,2′-bipyridine) in a 1:1 mole ratio in aqueous methanol at room temperature yields the tetranuclear complex [Cu4(μ-Hdmg)2(μ-dmg)2(bpy)2(H2O)2](ClO4)2 (2). The direct reaction of Cu(ClO4)2·6H2O with H2dmg and bpy in a 2:2:1 mole ratio in aqueous methanol at room temperature also yields 2 quantitatively. The complexes 1 and 2 were structurally characterized by X-ray crystallography. Unlike the binding in Ni/Co-dmg, two different types of N?O bridging modes during the oxime based metallacycle formation and stacking of square planar units have been identified in these complexes. The neutral dinuclear complex 1 has CuN4O coordination spheres and complex 2 consists of a dicationic [Cu4(μ-Hdmg)2(μ-dmg)2(bpy)2(H2O)2]2+ unit and two uncoordinated ClO4? anions having CuN4O and CuN2O3 coordination spheres. The two copper(II) ions are at a distance of 3.846(8) Å in 1 for the trans out of plane link and at 3.419(10) and 3.684(10) Å in 2 for the trans out of plane and cis in plane arrangements, respectively. The average Cu–Noxime distances are 1.953 and 1.935 Å, respectively. The average basal and apical Cu?Ooxime distances are 1.945, 2.295 and 2.429 Å. The UV–Vis spectra of 2 is similar to the spectrum of the reaction mixture of 1 and [Cu(bpy)(H2O)2]2+. Variable temperature magnetic properties measurement shows that the interaction between the paramagnetic copper centers in complex 1 is antiferromagnetic in nature. The EPR spectra of frozen solution of the complexes at 77 K consist of axially symmetric fine-structure transitions (ΔMS = 1) and half-field signals (ΔMS = 2) at ca. 1600 G, suggesting the presence of appreciable Cu–Cu interactions.  相似文献   

18.
Abstract

Two mononuclear heteroleptic copper complexes, [Cu(±trans-dach)(bpy)](ClO4)2 1a and [Cu(±trans-dach)(phen)](ClO4)2 2a [dach?=?1,2-diaminocyclohexane, bpy?=?2,2′-bipyridine and phen?=?1,10-phenanthroline], were synthesized and analyzed by CHN analysis, electronic absorption, FT-IR spectroscopy, EPR, and SXRD. The molecular structures of 1a and 2a showed octahedral geometry around Cu(II). Both complexes interacted with phosphoesters and DNA. Their binding affinities with diphenylphosphate, di n-butylphosphate, trimethylphosphate, and triphenylphosphate were studied by UV–vis spectroscopy. For understanding the stereochemical role of dach ligand toward DNA interaction, enantiopure DACH complexes [Cu(R,R-trans-dach(bpy)](ClO4)2 1b, [Cu(S,S-trans-dach)(bpy)](ClO4)2 1c, [Cu(cis-dach)(bpy)](ClO4)2 1d, [Cu(R,R-trans-dach)(phen)](ClO4)2 2b, [Cu(S,S-trans-dach)(phen)](ClO4)2 2c, and [Cu(cis-dach)(phen)](ClO4)2 2d were synthesized and analyzed. All complexes interacted with calf thymus-DNA (CT-DNA) as studied by UV–vis spectroscopy. The nature of binding to CT-DNA was groove/electrostatic as supported by circular dichroism, cyclic voltammetry, and docking studies. Complexes were able to cleave plasmid DNA at 12.5 µM (1ad) and 6 µM (2ad), where 2d showed 64% Form II and 36% Form III. The in vitro cytotoxic studies of two different cancer cell lines showed inhibition with low IC50 value in comparison to reference control (cisplatin). These complexes are efficient in inducing apoptosis in cancer cells, making them viable for potent anticancer activity.  相似文献   

19.
The syntheses and characterization of six copper(II) complexes of 2-benzoylpyridine benzhydrazone in the form of [Cu(BPB)2], [Cu(BPB)Cl]·H2O, [Cu(BPB)Br], [Cu2(BPB)2](ClO4)2·4H2O, [Cu(BPB)N3]·H2O, and [Cu(BPB)NCS]·H2O·CH3OH are reported. The analytical methods used for the characterization of complexes include partial elemental analyses, IR, electronic and EPR spectra, conductivity measurements, magnetic susceptibility measurements and single crystal X-ray diffraction. From the crystal structure, it is clear that the hydrazone adopts the E conformation about the azo bond to attach to the metal through the Npy–Nazo–O chelating system. In the EPR spectra of complexes in DMF at 77 K four hyperfine quartets in the parallel region could be resolved and a half field signal is observed at 1500 G for complex [Cu2(BPB)2](ClO4)2·4H2O in polycrystalline state at 298 K which gives evidence for its binuclear nature indicating a weak interaction between the two Cu(II) ions.  相似文献   

20.
In an effort to develop new tripodal N-heterocyclic carbene (NHC) ligands for small molecule activation, two new classes of tripodal NHC ligands TIMER and TIMENR have been synthesized. The carbon-anchored tris(carbene) ligand system TIMER (R = Me, t-Bu) forms bi- or polynuclear metal complexes. While the methyl derivative exclusively forms trinuclear 3:2 complexes [(TIMEMe)2M3]3+ with group 11 metal ions, the tert-butyl derivative yields a dinuclear 2:2 complex [(TIMEt-Bu)2Cu2]2+ with copper(I). The latter complex shows both “normal” and “abnormal” carbene binding modes and accordingly, is best formulated as a bis(carbene)alkenyl complex. The nitrogen-anchored tris(carbene) ligands TIMENR (R = alkyl, aryl) bind to a variety of first-row transition metal ions in 1:1 stoichiometry, affording monomeric complexes with a protected reactivity cavity at the coordinated metal center. Complexes of TIMENR with Cu(I)/(II), Ni(0)/(I), and Co(I)/(II)/(III) have been synthesized. The cobalt(I) complexes with the aryl-substituted TIMENR (R = mesityl, xylyl) ligands show great potential for small molecule activation. These complexes activate for instance dioxygen to form cobalt(III) peroxo complexes that, upon reaction with electrophilic organic substrates, transfer an oxygen atom. The cobalt(I) complexes are also precursors for terminal cobalt(III) imido complexes. These imido complexes were found to undergo unprecedented intra-molecular imido insertion reactions to form cobalt(II) imine species. The molecular and electronic structures of some representative metal NHC complexes as well as the nature of the metal–carbene bond of these metal NHC complexes was elucidated by X-ray and DFT computational methods and are discussed briefly. In contrast to the common assumption that NHCs are pure σ-donors, our studies revealed non-negligible and even significant π-backbonding in electron-rich metal NHC complexes.  相似文献   

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