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The reactions of ReI3, Se, and KCN with Sb2O3 or Bi2O3 at elevated temperature led to the formation of two new tetrahedral clusters with mixed-ligand cluster cores {Re4Se3Sb}7+ and {Re4Se3Bi}7+. Th...

We report the synthesis of two isoreticular, mixed-ligand metal–organic frameworks (MOFs), [Cd(μ2-mia)(μ2-bpe)]n·n(DMF)0.5·n(H2O)0.5 (1) and [Cd(μ2-nia)(μ2-bpee)]n·nDMF (2), where mia = 5-methoxyis...

Mixed-ligand Cu(I) complexes have attracted attention as alternatives to the noble- and/or rare-metal complexes, because of their remarkable photofunctions. To develop mixed-ligand Cu(I) complexes with rich photofunctions, an investigation of a suitable combination of ligands has captured more and more research interests. Herein, we report the first examples of emissive heteroleptic diphosphine-disulfide Cu(I) complexes combined with diphosphine ligands. The systematic study using a series of diphosphine ligands revealed that large π-conjugated bridging moieties between the two P atoms in the diphosphine ligands result in higher light-emission performance. When the diphosphine ligand was (

A new metal–organic framework was prepared based on a mixed ligand system of the designed nitrogen-rich 3,6-bis(2-methylimidazole)pyrimidine (b2mpm) and benzophenone 4,4′-dicarboxylic acid (H2bpndc...

Advancement of the synthesis and control of the self-assembly process of new high-nucleus silver clusters with desired structures is important for both the material sciences and the many applications. Herein, three new silver clusters, 20-, 22-, and 8-nucleus, based on alkynyl ligands were constructed and their structures were confirmed by single-crystal X-ray diffraction, powder X-ray diffraction, elemental analyses, and Fourier-transform infrared spectroscopy (FT-IR). For the first time, the trivalent tetrahedron anion of AsO

Effective sequestration of harmful organic pollutants from wastewater has been a persistent concern in the interest of environmental and ecological protection from pollution and hazards. Currently, common water treatment technologies such as adsorption, coagulation, and membranes are expensive and not greatly effective. A new class of organic and inorganic composite metal-organic frameworks (MOFs) has emerged as an essential class of materials for numerous applications, including photocatalytic degradation of organic pollutants. Herein, we present a nanosize mixed-ligand MOF (nMLM) which was successfully synthesized by reacting a Zr metal source with a mixture of pyrene and porphyrin building units and further utilized as photocatalyst in the photodegradation of rhodamine B (RhB). The nMLM MOF showed excellent photocatalytic efficiency, which was due to the complementary absorption and sequential energy and electron transfer properties of its building blocks, pyrene and porphyrin. We also propose herein a possible mechanism of the photocatalytic function of the material.

A mixed-ligand system provides an alternative route to tune the structures and properties of metal–organic compounds by introducing functional organic or inorganic coligands. In this work, five new uranyl-based polyrotaxane compounds incorporating a sulfate or oxalate coligand have been hydrothermally synthesized via a mixed-ligand method. Based on C6BPCA@CB6 (C6BPCA = 1,1′-(hexane-1,6-diyl)bis(4-(carbonyl)pyridin-1-ium), CB6 = cucurbit[6]uril) ligand, UPS1 (UO2(L)0.5(SO4)(H2O)·2H2O, L = C6BPCA@CB6) is formed by the alteration of initial aqueous solution pH to a higher acidity. The resulting 2D uranyl polyrotaxane sheet structure of UPS1 is based on uranyl-sulfate ribbons connected by the C6BPCA@CB6 pseudorotaxane linkers. By using oxalate ligand instead of sulfate, four oxalate-containing uranyl polyrotaxane compounds, UPO1–UPO4, have been acquired by tuning reaction pH and ligand concentration: UPO1 (UO2(L)0.5(C2O4)0.5(NO3)·3H2O) in one-dimensional chain was obtained at a low pH value range (1.47–1.89) ...

Two new mixed ligand coordination polymers (CPs) that are sulfonic group functionalized, namely, {[Cd(bpe)0.5(5-sip)(H2O)]·4H2O(bpeH2)0.5}n (1) and {[Cd1.5(bte)(5-sip)(H2O)3]·3H2O}n (2) [where 5-si...

Heterometallic single-source precursors for the Pb/Fe = 1:1 oxide materials, PbFe(β-dik)4 (β-dik = hexafluoroacetylacetonate (hfac, 1), acetylacetonate (acac, 2), and trifluoroacetylacetonate (tfac, 4)), have been isolated by three different solid-state synthetic methods. The crystal structures of heterometallic diketonates 1, 2, and 4 were found to contain polymeric chains built on alternating [Fe(β-dik)2] and [Pb(β-dik)2] units that are held together by bridging M-O interactions. Heterometallic precursors are highly volatile, but soluble only in coordinating solvents, in which they dissociate into solvated homometallic fragments. In order to design the heterometallic precursor with a proper metal/metal ratio and with a discrete molecular structure, we used a combination of two different diketonate ligands. Heteroleptic complex Pb2Fe2(hfac)6(acac)2 (5) has been obtained by optimized stoichiometric reaction of an addition of homo-Fe(acac)2 to heterometallic Pb2Fe(hfac)6 (3) diketonate that can be run in solution on a high scale. The combination of two ligands with electron-withdrawing and electron-donating groups allows changing the connectivity pattern within the heterometallic assembly and yields the precursor with a discrete tetranuclear structure. In accord with its molecular structure, heteroleptic complex 5 is soluble even in noncoordinating solvents and was found to retain its heterometallic structure in solution. Thermal decomposition of heterometallic precursors in air at 750 °C resulted in the target Pb2Fe2O5 oxide, a prospective multiferroic material. Prolonging the annealing time or increasing the decomposition temperature leads to another phase-pure lead-iron oxide PbFe12O19 that is a representative of the important family of magnetic hexaferrites.

A novel ligand-exchange route for the synthesis of amidinate-containing compounds of aluminum is explored. Syntheses of three new compounds, MeC(NiPr)2AlEt2 (4), EtC(NiPr)2AlMe2 (5), and (Me2NC(NiPr)2)2AlH (6), are presented. These mixed-ligand compounds are difficult to make in high yields by the more traditional routes of carbodiimide insertion or salt metathesis. The thermal reactivities of these compounds and their parent homoleptic compounds [MeC(NiPr)2]3Al (1), [Me2NC(NiPr)2](3)Al (2), and [EtC(NiPr)2]3Al (3) are explored in detail and analyzed with respect to their utility as potential atomic-layer-deposition precursors for aluminum-containing films. The major mechanism of thermal decomposition is found to be carbodiimide deinsertion to form aluminum alkyls or amides. Because of their thermal characteristics, both compounds 3 and 5 hold promise for use as precursors.

Three new mixed ligand Cu(II)N2O2 complexes, namely, [Cu(II)(2-A-6-MBT)2(m-NB)2] (1), [Cu(II)(2-ABT)2(m-NB)2] (2), and [Cu(II)(2-ABT)2(o-NB)2] (3), (2-A-6-MBT = 2-amino-6-methoxybenzothiazole, m-NB = m-nitrobenzoate, 2-ABT = 2-aminobenzothiazole, and o-NB = o-nitrobenzoate), have been prepared by the biomimetic synthesis strategy, and their structures were determined by X-ray crystallography studies and spectral methods. These complexes exhibited the effective superoxide dismutase (SOD) activity and catecholase activity. On the basis of the experimental data and computational studies, the structure-activity relationship for these complexes was investigated. The results reveal that electron-accepting abilities of these complexes and coordination geometries have significant effects on the SOD activity and catecholase activity. Then, we found that 1 and 2 exerted potent intracellular antioxidant capacity in the model of H2O2-induced oxidative stress based on HeLa cervical cancer cells, which were screened out by the cytotoxicity assays of different kinds of cells. Furthermore, 1-3 showed the favorable biocompatibility in two different biological models: Saccharomyces cerevisiae and human vascular endothelial cells. These biological experimental data are indicative of the promising application potential of these complexes in biology and pharmacology.

Metal-center-driven spontaneous resolution of a chiral coordination polymer, [Ni(SDB)(BIX)](n) (1), from achiral precursors has been probed by single-crystal X-ray diffraction and circular dichroism spectroscopy. Enantiomorphs 1P and 1M showed a parallel interpenetrated 2D → 3D chiral framework with (8(2).10) topology. Switching of the metal center under the same reaction parameters resulted in isostructural achiral and noninterpenetrating (4,4) grid-type sql networks [M(SDB)(BIX)](n), where M = Co(II), Zn(II), and Cd(II) for 2-4, respectively.

A 2D flexible metal-organic porous solid, {[Ni(1,3-adc)(bpp)(H2O)2](H2O)(EtOH)}n (1), has been synthesized using flexible organic linkers. The desolvated framework, {[Ni(1,3-adc)(bpp)]}n (1'), undergoes structural contraction and exhibits double-step hysteretic adsorption for CO2, H2O, and MeOH and single-step gate-opening behavior with EtOH. These observations are correlated with the effect of the polarity and window dimension of the pore to the corresponding adsorbate molecules.

The reaction of Zn(NO3)2 x 6H2O, various dicarboxylic acids, and either 4,4'-bipyridine or N,N'-di(4-pyridyl)-1,4,5,8-naphthalenetetracarboxydiimide produces a family of anisotropic, mixed-ligand, open-framework compounds featuring paddle-wheel-type coordination of Zn(II) pairs in two dimensions and pyridyl ligand pillaring in the third. Despite 2-fold interpenetration, the compounds contain channels of molecular dimensions and several are permanently microporous, displaying high internal surface areas.

The synthesis and crystal structures of two new NLO-active coordination polymers, [Zn(2-pc)(4-pc)] and [Cd(2-pc)(4-pc)(H(2)O)]xN(2)H(4) (2-pc = 2-pyridine carboxylate, 4-pc = 4-pyridine carboxylate), bridged by in situ generated mixed ligands under solvothermal treatment is described.

The addition of dipyridylamine to bis(3-cyano-2,4-pentanedionato)copper(II), Cu(NC-acac)(2), induces changes in the mode of interaction and the conformation of the NC-acac(-) anion. The structure of the resulting binuclear compound was determined from a single microcrystal (monoclinic, space group P2(1), a = 7.894(7) Å, b = 25.550(24) Å, c = 11.661(13) Å, beta = 106.10(8) degrees, Z = 2, R(1) = 0.0564, (w)R(2) = 0.1197). In the addition compound {[Cu(NC-acac)dipyamH](NC-acac)}(2) when the NC-acac(-) acts as a chelating and bridging ligand, it assumes the commonly observed U(Z,Z) conformation, while behavior as weakly N-coordinated unidentate counteranion imposes the rarely encountered S(Z,E) conformation. In the [Cu(NC-acac)dipyamH](NC-acac)] entities one of the copper(II) centers is a 4 + 2 Jahn-Teller complex while the other is a square-based pyramid.

A new series of oxo-centered acetate-bridged triruthenium comlexes having two redox-active N-methyl-4,4‘-bipyridinium ions (mbpy+) have been prepared, and their reversible multistep and multielectron electrochemical properties are reported: [RuIII2RuII(μ3-O)(μ-CH3CO2)6(mbpy+)2(CO)]2+ and [RuIII3(μ3-O)(μ-CH3CO2)6(mbpy+)2(L)]3+ (L = H2O, pyrazine (pz), pyridine (py), imidazole (Him), and 4-(dimethylamino)pyridine (dmap)). Among these series, the CO complex, [RuIII2RuII(μ3-O)(μ-CH3CO2)6(mbpy+)2(CO)](ClO4)2·2DMF (1b·2DMF) was structurally characterized by X-ray crystallography. 1b·2DMF crystallizes in the monoclinic space group P21/m (No. 11) with a = 8.740(6) A, b = 32.269(6) A, c = 10.276(4) A, β = 103.37(5)°, V = 2820(2) A3, Z = 2, dcalcd = 1.636 g cm-3, and R = 0.071 (Rw = 0.074) for 5277 independent reflections (|Fo| > 3σ(|Fo|). The (CO)Ru···Ru distance (3.410(2) A) is appreciably longer than the other Ru···Ru distance (3.276(2) A), indicating that the trinuclear core is in the valence-trapped RuIII2RuI...

The synthesis and crystallographic characterization of three oxovanadium(IV) complexes as solvates are reported: (a) [{HB(Me 2 pz) 3 }VOCl(Me 2 pzH)].2MeCN (I.2MeCN), (b) [{HB(Me 2 pz) 3 }VO(benzoate)(Me 2 pzH)].0.4toluene (II-0.4toluene), and (c) [{HB(Me 2 pz) 3 }VO(μ-malonate)VO(Me 2 pzH){HB(Me 2 pz) 3 }]-2toluene (III.2toluene), where Me 2 pz=3,5-dimethylpyrazolyl.

A reversible crystal-to-crystal transformation of a new 2D lead(II) coordination polymer with the ligand 4-pyridinecarboxylic acid (4-Hpyc), [Pb(4-pyc)(Br)(H(2)O)](n) (1) to [Pb(4-pyc)(Br)](n) (2) by de- and rehydration, has been observed, and the structures of 1 and 2 have been determined by single-crystal X-ray diffraction. The thermal stabilities of compounds 1 and 2 were studied by thermal gravimetric and differential thermal analyses. Powder X-ray diffraction experiments showed that the structural transformation occurs in the batch powder samples and leads to monophasic products.

The mononuclear mixed ligand copper(II) complexes of the type [Cu(L-tyr)(diimine)](ClO(4)), where tyr is L-tyrosine and diimine is 2,2'-bipyridine (bpy) (1), 1,10-phenanthroline (phen) (2), 5,6-dimethyl-1,10-phenanthroline (5,6-dmp) (3), and dipyrido[3,2-d:2',3'-f]quinoxaline (dpq) (4), have been isolated and characterized by analytical and spectral methods. In the X-ray crystal structure 3 Cu(II) possesses a distorted square pyramidal coordination geometry with the two nitrogen atoms of 5,6-dmp ligand and the amine nitrogen and carboxylate oxygen atoms of L-tyrosine located at the equatorial sites and the coordinated water molecule present in the apical position. The electronic absorption and electron paramagnetic resonance (EPR) spectral parameters reveal that the complexes retain their square-based geometries even in solution. All of the complexes display a ligand field band in the visible region (600-700 nm) in Tris-HCl/NaCl buffer (5:50 mM) at pH 7.2 and also axial EPR spectra in acetonitrile at 77 K with g(parallel)g(perpendicular) indicating a d(x(2)-y(2)) ground state. The g(parallel) and A(parallel) values of 2.230 and (170-180) x 10(-4) cm(-1), respectively, conform to a square-based CuN(3)O coordination chromophore, which is consistent with the X-ray crystal structure of 3. The interaction of the complexes with calf thymus DNA (CT DNA) has been explored by using physical methods to propose modes of DNA binding of the complexes. Absorption (K(b)) and emission spectral studies and viscosity measurements indicate that 4 interacts with DNA more strongly than all of the other complexes through partial intercalation of the extended planar ring of dpq with DNA base stack. Interestingly, complex 3 exhibits a DNA binding affinity that is higher than that of 2, which suggests the involvement of 5,6-dimethyl groups on the phen ring in hydrophobic interaction with DNA surface. In contrast with the increase in relative viscosities of DNA bound to 2-4, the viscosity of DNA bound to 1 decreases, indicating the shortening of the DNA chain length by means of the formation of kinks or bends. All complexes exhibit effective DNA (pUC19 DNA) cleavage at 100 microM complex concentrations, and the order of DNA cleavage ability varies as 3241. Interestingly, 3 exhibits a DNA cleavage rate constant that is higher than that of the other complexes only at 100 microM concentration, whereas 4 exhibits the highest cleavage rate constant at 80 microM complex concentration. The oxidative DNA cleavage follows the order 4321. Mechanistic studies reveal that the DNA cleavage pathway involves hydroxyl radicals. Interestingly, only 4 displays efficient photonuclease activity upon irradiation with 365 nm light, which occurs through double-strand DNA breaks involving hydroxyl radicals. Furthermore, cytotoxicity studies on the nonsmall lung cancer (H-460) cell line show that the IC(50) values of 2-4 are more or less equal to cisplatin for the same cell line, indicating that they have the potential to act as very effective anticancer drugs in a time-dependent manner. The study of cytological changes reveals the higher induction of apoptosis and mitotic catastrophe for 4 and 3, respectively. The alkaline single-cell gel electrophoresis (comet assay), DNA laddering, and AO/EB and Hoechst 33258 staining assays have also been employed in finding the extent of DNA damage. Flow cytometry analysis shows an increase in the percentage of cells with apoptotic morphological features in the sub-G(0)/G(1) phase for 4, whereas it shows mitotic catastrophe for 3.

The reaction of Cu(hfac) 2 with hydroxylamines RLH (RLH=1-hydroxy-2,2,5,5-tetramethyl-4-R-3-imidazoline; R=Me, Et, i-Pr, Ph) in inert atmosphere on heating gives rise to the partial reduction of Cu(II) to Cu(I) and yields mixed-ligand mixed-valent complexes of the composition Cu 2 (hfac) 3 (RL) 2

The electrochemistry and spectroelectrochemistry of a novel series of mixed-ligand diruthenium compounds were examined. The investigated compounds having the formula Ru(2)(CH(3)CO(2))(x)(Fap)(4-x)Cl where x = 1-3 and Fap is 2-(2-fluoroanilino)pyridinate anion were made from the reaction of Ru(2)(CH(3)CO(2))(4)Cl with 2-(2-fluoroanilino)pyridine (HFap) in refluxing methanol. The previously characterized Ru(2)(Fap)(4)Cl as well as the three newly isolated compounds represented as Ru(2)(CH(3)CO(2))(Fap)(3)Cl (1), Ru(2)(CH(3)CO(2))(2)(Fap)(2)Cl (2), and Ru(2)(CH(3)CO(2))(3)(Fap)Cl (3) possess three unpaired electrons with a Ru(2)(5+) dimetal core. Complexes 1 and 2 have well-defined Ru(2)(5+/4+) and Ru(2)(5+/6+) redox couples in CH(2)Cl(2), but 3 exhibits a more complicated electrochemical behavior due to equilibria involving association or dissociation of the anionic chloride axial ligand on the initial and oxidized or reduced forms of the compound. The E(1/2) values for the Ru(2)(5+/4+) and Ru(2)(5+/6+) processes vary linearly with the number of CH(3)CO(2)(-) bridging ligands on Ru(2)(CH(3)CO(2))(x)(Fap)(4-x)Cl and plots of reversible half-wave potentials vs the number of acetate groups follow linear free energy relationships with the largest substituent effect being observed for the oxidation. The major UV-visible band of the examined compounds in their neutral Ru(2)(5+) form is located between 550 and 800 nm in CH(2)Cl(2) and also varies linearly with the number of CH(3)CO(2)(-) ligands on Ru(2)(CH(3)CO(2))(x)(Fap)(4-x)Cl. The electronic spectra of the singly oxidized and singly reduced forms of each diruthenium species were characterized by UV-visible spectroelectrochemistry in CH(2)Cl(2).

Four complexes of the ligand 1,12-diazaperylene (DAP) have been prepared, [Ru(bpy)n(DAP)(3-n)]2+ where n = 0-2 and [Ru(DAP)3]2+. The [Ru(DAP)3]2+ complex was characterized by X-ray analysis and was found to exhibit the expected propeller-like structure with significant intermolecular pi-stacking interactions. The three Ru(II) complexes showed self-consistent optoelectronic properties with similar ligand-centered pi-pi* absorptions in the range of 333-468 nm and MLCT bands associated with the DAP which increased in intensity and decreased in energy as the number of DAP ligands varied from 1 to 3. Hypochromicity and viscosity changes were observed that were consistent with DAP intercalation into DNA, and binding constants were measured in the range of 1.4-1.6 x 10(6) M(-1) for the mixed ligand complexes. Furthermore, the complex [Ru(bpy)2(DAP)]2+ was found to photocleave plasmid DNA upon irradiation with visible light.

A tetranuclear mixed ligand copper(II) complex of a pyrazole containing Schiff base and a hydroxyhexahydropyrimidylpyrazole and copper(II) and nickel(II) complexes of the Schiff base having N-donor atoms have been investigated. A 2 equiv amount of 5-methyl-3-formylpyrazole (MPA) and 2 equiv of 1,3-diamino-2-propanol (1,3-DAP) on reaction with 1 equiv of copper(II) nitrate produce an unusual tetranuclear mixed ligand complex [Cu4(L1)2(L2)2(NO3)2] (1), where H2L1 = 1,3-bis(5-methyl-3-formylpyrazolylmethinimino)propane-2-ol and HL2 = 5-methyl-3-(5-hydroxyhexahydro-2-pyrimidyl)pyrazole. In contrast, a similar reaction with nickel(II) nitrate leads to the formation of a hygroscopic intractable material. On the other hand, the reaction involving 2 equiv of MPA and 1 equiv each of 1,3-DAP and various copper(II) salts gives rise to two types of products, viz. [Cu(T3-porphyrinogen)(H2O)]X2 (X = ClO4, NO3, BF4 (2)) (T3-porphyrinogen = 1,6,11,16-tetraza-5,10,15,20-tetrahydroxy-2,7,12,17-tetramethylporphyrinogen) and [Cu(H2L1)X]X x H2O (X = Cl (3), Br (4)). The same reaction carried out with nickel(II) salts also produces two types of compounds [Ni(H2L1)(H2O)2]X2 [X = ClO4 (5), NO3 (6), BF4 (7)] and [Ni(H2L1)X2] x H2O [X = Cl (8), Br (9)]. Among the above species 1, 3, and 5 are crystallographically characterized. In 1, all four copper atoms are in distorted square pyramidal geometry with N4O chromophore around two terminal copper atoms and N5 chromophore around two inner copper atoms. In 3, the copper atom is also in distorted square pyramidal geometry with N4Cl chromophore. The nickel atom in 5 is in a distorted octahedral geometry with N4O2 chromophore, where the metal atom is slightly pulled toward one of the axial coordinated water molecules. Variable-temperature (300 to 2 K) magnetic susceptibility measurements have been carried out for complex 1. The separations between the metal centers, viz., Cu(1)...Cu(2), Cu(2)...Cu(2)A, and Cu(2)A...Cu(1)A are 3.858, 3.89, and 3.858 A, respectively. The overall magnetic behavior is consistent with strong antiferromagnetic interactions between the spin centers. The exchange coupling constants between Cu(1)...Cu(2) and Cu(2)...Cu(2A) centers have turned out to be -305.3 and -400.7 cm(-1), respectively, resulting in a S = 1/2 ground state. The complexes are further characterized by UV-vis, IR, electron paramagnetic resonance, and electrochemical studies.

Self-recognition in the transition-metal-mediated self-assembly of some 2-D polygons is presented. Prolonged heating of two or three organoplatinum reagents with 4,4'-dipyridyl in aqueous acetone results in the predominant formation of a rectangle, triangle, and/or square. All mixtures are characterized with NMR and electrospray ionization mass spectrometry (ESIMS). Despite the potential for ill-defined oligomeric products, these mixed ligand systems prefer to self-assemble into discrete species.

Efficient syntheses are reported for incorporating trimetal units of the type M(3)(dpa)(4)(2+) (M = Cr, Co, Ni, and dpa = 2,2'-dipyridylamide) into polyalkynyl assemblies to give the prototypical bis-phenylacetylide complexes M(3)(dpa)(4)(CCPh)(2). Reactions of M(3)(dpa)(4)Cl(2) with LiCCPh have led only to mixtures of products which cocrystallize forming materials of the composition M(3)(dpa)(4)(CCPh)(x)()Cl(2)(-)(x)(). Here we report that acetonitrile complexes [M(3)(dpa)(4)(NCCH(3))(2)](PF(6))(2) react cleanly with LiCCPh in MeCN to afford the desired target molecules in 40-60% yield and in excellent purity. Isolation of the mixed ligand complex [Co(3)(dpa)(4)(NCCH(3))(CCPh)]PF(6) has been accomplished, which suggests that these reactions are stepwise and that it will be possible to synthesize mixed acetylide complexes (i.e., M(3)(dpa)(4)(CCR)(CCR')) via this method.

The mononuclear gadolinium mixed-ligand complex [Gd(CF3CO2)3(phen)2(H2O)] has been prepared and structurally characterized by X-ray crystallography. Two complex molecules are doubly bridged by H bonds between carboxylate and aqua ligands with a Gd−Gd separation of 7.16(1) A. Magnetic susceptibility and EPR measurements showed weak magnetic exchange coupling of the 3D type.

In the absence of added solvent, B 4 Cl 4 and BBr 3 , present in a 1:5 mole ratio, generated B 4 BrCl 3 in approximately 13% yield after 800 h at 95 o C. Repeated exposure of B 4 Cl 4 to fresh aliquots of BBr 3 and pentane at 95 o C did ultimately (2200 h) form B 4 Br 4 and the mixed ligand species B 4 Br 3 Cl, B 4 Br 2 Cl 2 , and B 4 BrCl 3 , but the quantities provided were small

Etude de la complexation d'ions metalliques avec l'EDTA, l'EGTA et F − au moyen de la spectrometrie RMN 1 H

A series of 22 mixed-ligand complexes of the general formula TcOL(1)L(2), where L(1)H(2) are N-substituted bis(2-mercaptoethyl)amine ligands, [SN(R)S], and L(2)H are monodentate thiols as coligand, is reported. The complexes were prepared by the ligand exchange method using Tc-gluconate as precursor and equimolar quantities of the two ligands. In all cases the syn stereoisomer was formed in high yield and isolated as a crystalline product. In four cases HPLC analysis demonstrated the presence of the anti stereoisomer in the reaction mixture. Although the yield was less than 1%, one anti isomer, 4a, was successfully isolated as brown crystals. The isolated complexes were characterized by spectroscopic methods and elemental analysis. The formation of the two diastereomers, syn and anti, was expected due to the configuration of the nitrogen substituent (R) with respect to the central TcO core. The X-ray crystallography showed that the coordination geometry of the syn isomers 9, 11, and 18 is trigonal bipyramidal while for the anti isomer 4a it is distorted square pyramidal. This is the first documentation of syn/anti isomerism in N-substituted TcO[SN(R)S][S] mixed-ligand complexes.

A new type of lanthanide-Group(10) transition metal mixed ligand complex is produced in the redox reaction of YbCl2 with K2[Pd(CN)4]·H2O in DMF. This complex consists of a cationic, chainlike array...

Extraction de La, Pr, Eu et Yb sous forme LnP 3 avec PH=phenyl-1 methyl-3 acyl-4 pyrazolone-5 seul ou en combinaison avec phenanthroline-1,10,oxyde de trioctylphosphine, chlorure de methyltrioctylammonium

Der uberwiegende Teil der Titelkomplexe (I) wurde durch Oxidation von Co(II)-Salzen mit uberschussigem H2O2 in Gegenwart von N-(2-pyridylmethyl)-L-aspartat und dem Anion der jeweiligen Aminosaure dargestellt.

Oxidation of Ni/sup II/(CN)/sub 4//sup 2/minus// in aqueous solution gives trans-Ni/sup III/(CN)/sub 4/(H/sub 2/O)/sub 2//sup /minus//, which has labile axial water molecules that are readily replaced by other ligands. Electron paramagnetic resonance (EPR) spectra of frozen aqueous solutions indicate a variety of tetragonally elongated complexes with two equivalent axial donors, where an increase in g/sub av/ values (CN/sup /minus// < NH/sub 3/ < imidazole < N/sub 3//sup /minus// < pyridine < CH/sub 3/CN < Cl/sup /minus// < NCO/sup /minus// < H/sub 2/O) reflects a decrease in axial donor strength. Not all these complexes form in aqueous solution at room temperature, but five-line EPR spectra are seen for bis complexes of NH/sub 3/, imidazole, and pyridine. At 25/degree/C the values for the stepwise stability constants with pyridine are K/sub 1/ /approx equal/ 1 /times/ 10/sup 5/ M/sup /minus/1/ and K/sub 2/ /approx equal/ 4 /times/ 10/sup 2/ M/sup /minus/1/. Excess cyanide gives Ni/sup III/(CN)/sub 6//sup 3/minus//, which has temperature-dependent EPR spectra in frozen aqueous solutions (/minus/220 to /minus/35/degree/C) due to dynamic Jahn-Teller distortions. Studies with /sup 13/CN/sup /minus// confirm the presence of six cyanides around Ni(III). The reduction potential for Ni/sup III/(CN)/sub 4/(H/sub 2/O)/sub 2//sup /minus// is 1.15 V (vs NHE).more » The complex decomposes with a first-order rate constant of 4.0 /times/ 10/sup /minus/4/ s/sup /minus/1/ (pH 1-3, 25.0/degree/C, /mu/ = 0.1, /Delta/H/double dagger/ = 108 kJ mol/sup /minus/1/, /Delta/S/double dagger/ = 51 J mol/sup /minus/1/ K/sup /minus/1/). Base greatly accelerates this redox decomposition (k/sub obsd/ = 0.45 s/sup /minus/1/, /minus/log (H/sup +/) = 11.5, 25.0/degree/C, /mu/ = 0.1, /Delta/H/double dagger/ = 95 kJ mol/sup /minus/1/, /Delta/S/double dagger/ = 69 J mol/sup /minus/1/ K/sup /minus/1/). 38 refs., 7 figs., 9 tabs.« less