镧系元素配位化学新领域: 生理及更高pH下镧 系元素-羟基自组装多核配合物 研究

在生理及更高pH下以α-氨基酸或EDTA作为配体,抑制Ln(Ⅲ)水解得到了一类镧系元素-羟基自组装多核配合物。该类多核配合物以具有类立方烷结构的[Ln4(μ~3-OH)~4]^8^+为基本结构单元,可以单体{[Ln~4(μ~3-OH)~4]^8^+},共顶点的“环状四聚体”{[Ln~1~2(μ~3-OH)~1~6]^2^0^+}或“环状五聚体”{[Ln~1~5(μ~3-OH)~2~0]^2^5^+}的形式稳定存在。本文报道了该类配合物的合成、结构及性质,探讨了卤素离子对“环状四聚体”及“环状五聚体”形成的模板效应,并初步证明了类立方烷结构单体,“环状四聚体”及“环状五聚体”乃是生理及更高pH下镧系元素的稳定存在形式。同时还证明了直接水解镧系元素硝酸盐或高氯酸盐能得到一类以正八面体结构的[Ln~6(μ~6-O)(μ~3-OH)~8]^8^+]为骨架的多核配合物。磁性测定表明,室温下各配合物的类立方烷结构中的镧系离子间无明显磁交换。     

Coordination chemistry of amine bis(phenolate) titanium complexes: tuning complex type and structure by ligand modification

The coordination chemistry of titanium(IV) complexes of amine bis(phenolate) ligands was investigated by synthesizing various types of complexes and analyzing them specroscopically and structurally. Steric effects of tridentate [ONO]- and tetradentate [ONNO]-type ligands were studied by reacting the ligand precursors with titanium tetra(isopropoxide). [ONNO]-type ligands featuring an amine donor located on a pendant arm led to octahedral bis(isopropoxide) complexes, regardless of the steric bulk around the metal. Several such complexes having varying steric crowding were thus synthesized. On the other hand, steric effects were found to play a major role in determining the complex constitution when [ONO]-type ligands, featuring no side donor, were involved. Relatively sterically undemanding ligands led to octahedral bis(homoleptic) complexes, whereas increased steric bulk resulted in the formation of pentacoordinate bis(isopropoxide) complexes. These pentacoordinate complexes readily lead to bis(heteroleptic) complexes by reaction with nonsterically demanding [ONO]- and [ONNO]-type ligand precursors. In the latter case the sidearm nitrogen remains uncoordinated to the metal. The bis(isopropoxide) complexes of the [ONNO]-type ligands may also lead to bis(heteroleptic) complexes, however, these reactions are much slower.     

Preparation, UV-vis, IR, EPR and resonance Raman study of Fe, Ni, Co and Zn dioxolene complexes

An UV-vis, Raman, IR and EPR spectroscopic study was performed for the water soluble complexes of Fe(III), Ni(II), Co(II) and Zn(II) coordinated to dioxolene ligands derived from oxidized dopamine. The complexes were obtained and stabilized at neutral pH by the strong reducing agent sodium thiosulfate. Iron(III) stabilizes the ligand in catecholate form as [Fe(III)(Cat)2]1-, Cat=dopacatecholate, and the divalent metals as dopasemiquinone (SQ): [Ni(SQ)3]1-, [Co(SQ)3]1- and [Zn(SQ)3]1-. The resonance Raman spectra of the solid complexes as [CAT][Ni(SQ)3], [CTA][Co(SQ)3] and [CTA][Zn(SQ)3], CTA is the cetyltrimethylammonium, are very similar to the spectra of the complexes in solution, while the Fe(III) complex is a mixture of two iron complexes, with catecholate or dopasemiquinone ligands.     

Effect of Chelate Ring Size in Iron(II) Isothiocyanato Complexes with Tetradentate Tripyridyl‐alkylamine Ligands on Spin Crossover Properties

Iron(II) complexes of the type [Fe(L)(NCS)₂] with tetradentate ligands L are well known to show spin crossover properties. However, this behavior is quite sensitive in regard to small changes of the ligand system. Starting from the thoroughly investigated complex [Fe(tmpa)(NCS)₂] [tmpa = tris(2‐pyridylmethyl)amine, also abbreviated as tpa in the literature] we modified the ligand by increasing systematically the chelate ring sizes from 5 to 6 thus obtaining complexes [Fe(pmea)(NCS)₂], [Fe(pmap)(NCS)₂], and [Fe(tepa)(NCS)₂] [pmea = N,N‐bis[(2‐pyridyl)methyl]‐2‐(2‐pyridyl)ethylamine, pmap = N,N‐bis[2‐(2‐pyridyl)ethyl]‐(2‐pyridyl)methylamine, and tepa = tris[2‐(2‐pyridyl)ethyl]amine]. All complexes were structurally characterized and spin crossover properties were investigated using Mößbauer spectroscopy, magnetic measurements, and IR/Raman analyses. The results demonstrated that only the iron complexes with tmpa and pmea showed spin crossover properties, whereas the complexes with the ligands pmap and tepa only formed high spin complexes. Furthermore, DFT calculations supported these findings demonstrating again the strong influence of ligand environment. Herein the effect of increasing the chelate ring sizes in iron(II) isothiocyanato complexes with tetradentate tripyridyl‐alkylamine ligands is clearly demonstrated.     

Synthesis, structure and properties of ruthenium(II) complexes with quinolinedione derivatives as chelate ligands: Crystal structure of [Ru(CO)2Cl2(6-methoxybenzo[g]quinoline-5,10-dione)]

The reaction of the dimer complex [{Ru(CO)₃Cl₂}₂] with the ligands 4,6-dichloroquinoline-5,8-dione and 6-methoxybenzo[g]quinoline-5,10-dione in ethanol solution led to the neutral mononuclear complexes of general formula [Ru(CO)₂Cl₂(κ²-quinolinedione-N,O)]. The complexes were characterized by elemental analysis, IR and RMN spectroscopy, and the molecular structure of [Ru(CO)₂Cl₂(6-methoxybenzo[g]quinoline-5,10-dione)] was determined by single-crystal X-ray diffraction. The redox chemistry of ligands and complexes was investigated by cyclic voltammetry, and their potential antitumor activity was also evaluated.     

Modular approach to tridentate N,O,N' ligands using pyrazolylborate chemistry

Two anionic tridentate N,O,N' chelators, [pz(Ph)B(mu-pz)(mu-O)B(Ph)pz](-) (3(-)) and [pz(Ph)(Ph)B(mu-pz)(mu-O)B(Ph)pz(Ph)](-) (4(-)), as well as the corresponding complexes [Fe(3)(py)Cl], [Fe(3)Cl(2)] and [Cu(3)Cl], have been synthesised and structurally characterised by X-ray crystallography (pz: pyrazolyl, pz(Ph): 3-phenylpyrazolyl, py: pyridine). Since our synthesis approach takes advantage of the highly modular pyrazolylborate chemistry, inexpensive and relatively resistant N,O,N' ligands of varying steric demand are readily accessible. The complexes [Fe(3)(py)Cl] and [Fe(3)Cl(2)] possess a distorted trigonal-bipyramidal configuration with the pyrazolyl rings occupying equatorial positions and the oxygen donor being located at an apical position. The complex [Cu(3)Cl] crystallises as chloro-bridged dimers featuring Cu(II) ions with ligand environments that are intermediate between a square-planar and a trigonal-bipyramidal geometry.     

Die Reaktion von Eisen(III) mit Brenzkatechin-3,5-disulfonsäure (Tiron) und Äthylendiamintetraessigsäure

The Reaction of Iron(III) with Catechol-3,5-Disulphonic Acid (Tiron) and Ethylene Diamine-Tetracetic Acid In the system iron(III)-Tiron-EDTA a ternary chelate could be detected besides the well known complexes in a weak acid solution. By means of spectro-photometric measurements under various conditions (concentration of ligands) we found [FeHYL]^4? with λ_max = 555 nm und ε₅₅₅ = 2500 l · mol^?1 · cm^?1. The formation of the ternary chelate is an inner-complex reaction of displacing, in which donor atoms of the EDTA in FeY^? are replaced by Tiron. By graphic methods the equilibrium constants could be calculated from the measurements.     

Synthesis of star-shaped poly(epsilon-caprolactone) via'click' chemistry and 'supramolecular click' chemistry

The synthesis of star-shaped poly(epsilon-caprolactone) is described via azide-alkyne cycloaddition ('click' chemistry) and via self-assembly of polymeric ligands into [2 x 2] grid-like metal complexes ('supramolecular click' chemistry).     

Addressing lead toxicity: complexation of lead(II) with thiopyrone and hydroxypyridinethione O,S mixed chelators

The lead(II) ion is regarded as a serious environmental contaminant. A considerable need exists to develop selective ligands for remediation of this metal ion. Herein, the coordination chemistry of lead(II) is investigated with three O,S donor ligands: thiomaltol, 3-hydroxy-1-methyl-2(1H)-pyridinethione (3,2-HOPTO), and 3-hydroxy-1,2-dimethyl-4(1H)-pyridinethione (3,4-HOPTO). The X-ray structures of [Pb(thiomaltolato)(2)] and [Pb(3,4-HOPTO)(2)] have been solved, revealing the expected 4-coordinate geometries. Electronic spectra have been obtained for the lead(II) complexes with all three ligands. Preliminary solution studies show that the thiomaltol ligand binds lead(II) preferentially over magnesium(II) and calcium(II); however, [Pb(thiomaltolato)(2)] is not stable in the presence of 1 equiv of EDTA. Tetradentate ligands derived from these O,S chelators are expected to generate higher affinity ligands for lead(II) sequestration.     

Asymmetric Borohydride Reduction of Acetophenone Catalyzed by Chiral Salen-Co(Ⅱ) Complex Using Sodium Borohydride

Development of efficient catalytic asymmetric reactions is the most challenging task in current synthetic chemistry; much effort has been devoted to create the chiral metal complexes of asymmetric catalysis. In the last two decades' many brand-new ligands had been synthesized and their combination with various metal ions has been applied in asymmetric catalysis. However, most ligands have only narrow applications and their use is limited to some reactions. Exceptionally, a few ligands and their metal complexes such as binaphthol, semicollin,and binap show wide applicability. Chiral salen ligand is one of such ligands and their metal complexes are now used as the catalysts for a variety of asymmetric reactions such as epoxidation^[1], aziridination^[2], cyclopropanation^[3], Diels-Alder reaction^[4], asymmetric transfer hydrogenation of aromatic ketones^[5] and kinetic resolution of racemic epoxides^[6] and so on.     

Pnictogen-thiacrown complexes with Pt(II) and Pd(II)

Platinum(II) and palladium(II) complexes of the trithiacrown [9]aneS(3) containing a range of Group 15 donors are reviewed. These complexes have the general formula [M([9]aneS(3))(L(2))](n+) where L represents at least one Group 15 donor. Complexes involving pnictogens, with the exception of bismuth, are observed. The complexes generally have an elongated square pyramidal geometry with a long distance interaction to the third sulphur of the [9]aneS(3) which forms the apex of the square pyramid. This axial metal-sulphur distance is quite sensitive to the donor properties of L. Poorer donors such as Sb and As ligands show short axial distances whereas the better N donor ligands show longer distances. Pt(II) complexes of the formula [Pt([9]aneS(3))(EPh(3))(2)](2+) (E = P, As, Sb) show a considerable distortion towards a trigonal bipyramidal geometry due to intramolecular π-π interactions. Over seventy of these types of complexes have been crystallographically characterized and are discussed in this article. Other unique features of the complexes, including NMR spectroscopy, redox chemistry, and electronic spectroscopy, are also discussed.     

Spectral characteristics, DNA-binding and cytotoxicity of two functional Ru(II) mixed-ligand complexes

Two functional Ru(II) mixed-ligand complexes, [Ru(phen)(2)(ttbd)](2+) (1) (ttbd = 4-(6-propenyl-pyrido[3,2-a]phenzain-10-yl-benzene-1,2-diamine, phen = 1,10-phenanthroline) and [Ru(bpy)(2)(ttbd)](2+) (2) (bpy = 2,2'-bipyridine), have been synthesized and characterized. The spectral characteristics of complexes 1 and 2 were investigated using fluorescence spectroscopy and revealed that both complexes were very sensitive to solvent polarity and oxygen molecules in nonaqueous solvents. The binding properties of the two complexes towards calf thymus DNA (CT-DNA) were investigated with different spectrophotometric methods, viscosity measurements and quantum chemistry calculations, indicating that both complexes could enantioselectively bind to CT-DNA by means of intercalation, but with different binding strengths and discrimination. On the other hand, the cytotoxicity of both complexes have been evaluated by MTT assays and Giemsa staining experiments. The main results reveal that the hydrophobicity and surface area of the ancillary ligands have a significant effect on their DNA binding behavior and both complexes are likely to be useful for optically probing nonaqueous and oxygen-free environments.     

Synthesis of new metal-free 1,2,4,5,9,10,12,13-octaaza[16]annulene derivatives using the reaction of vinamidinium salts with thiocarbohydrazide

A new series of marcocyclic ligands, 1,2,4,5,9,10,12,13-octaaza[16]annulene derivatives were synthesized by using the condensation reaction of the correspondingly [2+2] 2-heteroaryl-substituted vinamidinium salts or phenyl vinamidinium salts and derivatives or halo-substituted vinamidinum salt [1A-10A] with thiocarbohydrazide in ethanolic medium under mild condition. Metal complexes were formed by reacting of ethanolic solution of Co, Ni, and Zn with macrocyclic ligand in ethanolic medium under mild condition. Purposed complexes have been characterized with the help of elemental analyses, comparative absorption band of ν(C=N), mass, and NMR. Geometry and complex formulation are out of scope of this work. The biological activities of carohydrazide and thiocarbohydrazide base of the ligands and purposed complexes such as antimicrobial, antitumor, and insecticides have attracted significant attention in bioorganic chemistry.     

Supramolecular assemblies of a bis(terpyridine) ligand and of its [2x2] grid-type Zn(II) and Co(II) complexes on highly ordered pyrolytic graphite

The synthesis and characterisation of bis(terpyridine)-derived ligands which are capable of forming [2x2] grid-like complexes is presented. Additional pyridine substituents on these ligands do not interfere with the complexation process. Adsorbing one of the pure ligands on highly ordered pyrolytic graphite (HOPG) shows a highly ordered structure stabilised by additional weak intermolecular C-H...N hydrogen bonds partially through the extra-pyridines as could be shown by scanning tunneling microscopy (STM) investigations. Similar adsorption experiments with one of the corresponding [2x2] Co(II) grid-type complexes on graphite, led also to a well-organised structure with interdigitation of the extra-pyridine moieties.     

Solid state structure of thorium(IV) complexes with common aminopolycarboxylate ligands

The crystal structures of the complexes formed by reaction of thorium(IV) nitrate with iminodiacetic acid (H(2)IDA), nitrilotriacetic acid (H(3)NTA), and ethylenediaminetetraacetic acid (H(4)EDTA) under hydrothermal conditions are reported. In [Th(HIDA)(2)(C(2)O(4))]·H(2)O (1), the metal atom is chelated by two carboxylate groups from two HIDA(-) anions and by two oxalate ligands formed in situ; two additional oxygen atoms from two more HIDA(-) anions complete the ten-coordinate environment of bicapped square antiprismatic geometry. The uncoordinated nitrogen atom is protonated and involved in hydrogen bonding. Two different ligands are present in [Th(NTA)(H(2)NTA)(H(2)O)]·H(2)O (2), one of them being a O(3),N-chelating trianion which acts also as a bridge toward two neighboring metal ions, and the other being a bis-monodentate bridging species with an uncoordinated carboxylic arm and a central ammonium group. An aqua ligand completes the nine-coordinated, capped square antiprismatic metal environment. The EDTA(4-) anion in [Th(EDTA)(H(2)O)]·2H(2)O (3) is chelating through one oxygen atom from each carboxylate group and the two nitrogen atoms, as in a previously reported molecular complex. Two carboxylate groups are bridging, which, with the addition of an aqua ligand, gives a capped square antiprismatic coordination polyhedron. Aminopolycarboxylate ligands have been much investigated in relation with actinide decorporation and nuclear wastes management studies, and the present results add to the structural information available on their complexes with thorium(IV), which has mainly been obtained up to now by extended X-ray absorption fine structure (EXAFS) spectroscopy. In particular, the bridging (non-chelating) coordination mode of H(2)NTA(-) is a novel feature in this context. All three complexes crystallize as two-dimensional assemblies and are thus novel examples of thorium-organic coordination polymers.     

Synthesis and coordination chemistry of macrocyclic ligands featuring NHC donor groups

Poly-NHC (NHC = N-heterocyclic carbene) ligands emerged almost immediately after the first stable NHCs had been described. Macrocyclic ligands, featuring NHC donor groups and their metal complexes, however, remained rare until recently. This perspective highlights modern developments in the fields of synthesis and coordination chemistry of macrocyclic poly-NHC ligands. These include the synthesis of tetracarbene ligands which were obtained from complexes of β-functionalized isocyanides followed by cyclization of the coordinated iscocyanide ligands to NH,NH-functionalized NHCs and the subsequent metal template controlled bridging alkylation of the NH,NH-NHCs to yield the macrocycle. The template synthesis of ligands featuring a mixed NHC/phosphine donor set like [11]ane-P(2)C(NHC) and [16]ane-P(2)C(NHC)(2) by linkage of NH,NH-NHCs to different phosphines is also presented. Finally, methods for the preparation of cyclic polyazolium salts, their deprotonation and metalation and the different modes of coordination of such macrocyclic poly-NHC ligands are discussed.     

207Pb-1H two-dimensional NMR spectroscopy: a useful new tool for probing lead(II) coordination chemistry

Despite the fact that lead poisoning is the most common disease of environmental origin in the United States, the spectroscopic properties of aqueous Pb(II) coordination compounds have not been extensively investigated. Spectroscopic techniques that can be used to probe the fundamental coordination chemistry of Pb(II) will aid in both the development of water-soluble ligands that bind lead both tightly and selectively and the characterization of potential biological targets. Here, we report the preparation and characterization of a series of Pb(II) complexes of amido- derivatives of EDTA. The 207Pb chemical shift observed in these complexes (2441, 2189, and 1764 ppm for [Pb(EDTA)]2-, Pb(EDTA-N2), and [Pb(EDTA-N4)]2+, respectively) provides an extremely sensitive measure of the local environment and the charge on each complex. These shifts help to map out the lead chemical shift range that can be expected for biologically relevant sites. In addition, we report the first two-dimensional 207Pb-1H heteronuclear multiple-quantum correlation (HMQC) nuclear magnetic resonance spectra and demonstrate that this experiment can provide useful information about the lead coordination environment in aqueous Pb(II) complexes. Because this technique allows 207Pb-1H couplings through three bonds to be identified readily, 207Pb-1H NMR spectroscopy should prove useful for the investigation of Pb(II) in more complex systems (e.g., biological and environmental samples).     

Imidazole-2-ylidenes as Ligands for Palladium Catalyzed Heck Cross Coupling Reaction

N-Heterocyclic carbenes have become universal ligands in coordination chemistry. [1] The design, synthesis, and application of imidazolium salts as precursors of imidazole-2-ylidenes are therefore of substantial interest. [2] The free carbenes with imidazole-2-ylidene structure of A (Scheme 1 ), so called "phosphine mimics", can form metal complexes with high thermal and hydrolytic durability, while N-substituted by different functional groups could produce, in principle, water-soluble; unsymmetrical; and immobilized catalysts. [3]     

Synthesis and structure of novel sugar-substituted bipyridine complexes of rhenium and 99m-technetium

Novel ligands have been obtained from the reaction of 4,4'-dibromomethyl-2,2'-bipyridine with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosylthiol, 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosylthiol or 2,3,4,6-tetra-O-acetyl-alpha-D-thioacetylmannopyranoside in which the sugar residues are thioglycosidically linked to the bipyridine in the 4,4'-position. Cleavage of the acetyl groups affords hydrophilic symmetric ligands with free hydroxyl groups. Reaction of the new glycoconjugated ligands (L) with [Re(CO)(5)Cl] yields fluorescent complexes of general formula [Re(L)(CO)(3)Cl], which were characterised by mass spectrometry, elemental analysis and (1)H and (13)C NMR, IR, UV/Vis and fluorescence spectroscopy. These complexes exhibit excellent solubility and stability in organic solvents or water, depending on the residues of the sugar. One complex, namely tricarbonyl-4,4'-bis[(2,3,4,6-tetra-O-acetyl-beta-D-glycopyranosyl)thiomethyl]-2,2'-bipyridinerheniumtricarbonylo chloride, has been characterised by X-ray crystallography. A non-symmetric structure of the complexes could be assigned. Radiolabelling of the unprotected ligands with [(99m)Tc(H(2)O)(3)(CO)(3)](+) affords the corresponding water-soluble technetium complexes (in quantitative yields), which were characterised by their HPLC radiation traces. The formed complexes are stable for several hours in the presence of histidine but show partial ligand-exchange after one day.     

Complex Formation Equilibria of Unusual Seven-Coordinate Fe(EDTA) Complexes with DNA Constituents and Related Bio-relevant Ligands

Seven-coordinate Fe(EDTA)?CL complexes, where L represents a DNA constituent (uracil, uridine, thymine, thymidine and inosine), methylamine, ammonium chloride or imidazole, were investigated to resolve the solution chemistry of this system. The results show formation of 1:1 complexes with DNA constituents and the other ligands, supporting the hepta-coordination mode of Fe(III) ion. Stability constants of the complexes were measured by potentiometric titration at 25?°C and ionic strength 0.1 mol?L^?1 NaNO₃. The hydrolysis constant of [Fe(EDTA)(H₂O)]^? and the formation constants of the complexes formed in solution were calculated using the non-linear least-squares program MINIQUAD-75. The concentration distributions of the various complex species were evaluated as a function of?pH. The thermodynamic parameters ??H ⁰ and ??S ⁰, calculated from the temperature dependence of the equilibrium constants, were determined for the Fe(EDTA)?Curacil complex. The effect of dioxane as a solvent on the protonation constant of uracil, hydrolysis constants of [Fe(EDTA)(H₂O)]^?, and the formation constants of the Fe(EDTA)?Curacil complex are discussed.