溴化钯或乙酰丙酮羰基铑/手性配体催化醛与乙酰胺的不对称酰胺羰化反应研究

采用溴化钯为催化剂前体,与非螯合型双齿膦配体L1(DPPFF)、联吡啶型双齿膦配体L2(P-PHOS)和二茂铁基手性双膦配体L3((S,Rp)-BPPF)制备络合物催化剂,以乙酰丙酮羰基铑为催化剂前体,与手性亚磷酸酯配体L4-L6制备络合物催化剂,将其分别应用于底物环己基甲醛或苯乙醛的不对称酰胺羰化反应中,研究结果表明...     

Investigations into the synthesis and fluorescence properties of Tb(III) complexes of a novel bis-beta-diketone-type ligand and a novel bispyrazole ligand

A novel bis-beta-diketone organic ligand, 1,1'-(2,6-bispyridyl)bis-3-(p-methoxyphenyl)-1,3-propanedione (L1) and its derivatives, a novel bispyrazole ligand, 2,6-bis(5-(4-methoxyphenyl)-1H-pyrazol-3-yl)pyridine (L2) were designed and synthesized and their complexes with Tb(III) ion were successfully prepared. The ligands and the corresponding metal complexes were characterized by elemental analysis, infrared, proton nuclear magnetic resonance spectroscopy and TG-DTA. Analysis of the IR spectra suggested that the lanthanide metal ion Tb(III) coordinated to the ligands via the nitrogen atom of the pyridine ring and the carbonyl oxygen atoms for ligand L1 and the nitrogen atom of the pyrazole ring for ligand L2. The fluorescence properties of the two complexes in solid state were investigated and it was discovered that the Tb(III) ions could be sensitized by both the ligand (L1) and ligand (L2) to some extent. In particular, the complex of ligand (L2) is a better green luminescent material that could be used as a candidate material in organic light-emitting devices (OLEDs) since it could be much better sensitized by the ligand (L2), and the fluorescence intensity of Tb(III) complex of L2 are almost as twice strong as L1's.     

Laser photolysis studies of the photochemical reactions of chromium(III) octaethylporphyrin and tetramesitylporphyrin complexes in toluene solution

A nanosecond laser photolysis study was carried out for the Cr(III) porphyrin complexes of 2,3,7,8,12,13,17,18-octaethylporphyrin, [Cr(OEP)(Cl)(L)], and of 5,10,15,20-tetramesitylporphyrin, [Cr(TMP)(Cl)(L)], in toluene containing water and an excess amount of L (L = axial ligand). The laser photolysis generates the triplet excited state of the parent complex as well as a five-coordinate complex, [Cr(porphyrin)(Cl)], produced by the photodissociation of the axial ligand L. The yields for the formation of the triplet state and the photodissociation of L are found to markedly depend on the nature of both L and porphyrin ligand. The five-coordinate [Cr(porphyrin)(Cl)] readily reacts with both H(2)O and L in the bulk solution to give [Cr(porphyrin)(Cl)(H(2)O)] and [Cr(porphyrin)(Cl)(L)], respectively. The axial H(2)O ligand in [Cr(porphyrin)(Cl)(H(2)O)] is then substituted by the ligand L to regenerate the original complex [Cr(porphyrin)(Cl)(L)]. In principle, the substitution reaction takes place by the dissociative mechanism: the first step is the dissociation of H(2)O from [Cr(porphyrin)(Cl)(H(2)O)], followed by the reaction of the five-coordinate [Cr(porphyrin)(Cl)] with the ligand L to regenerate [Cr(porphyrin)(Cl)(L)]. The rate constants for this ligand substitution reaction are found to exhibit bell-shaped ligand concentration dependence. The detailed kinetic analysis revealed that both ligands L and H(2)O in toluene make a hydrogen bond with the axial H(2)O ligand in [Cr(porphyrin)(Cl)(H(2)O)] to yield dead-end complexes for the substitution reaction. The reaction mechanisms are discussed on the basis of the substituent effects of the porphyrin peripheral groups and the kinetic parameters determined from the temperature dependence of the rate constants.     

新的稀土Eu,Tb(Ⅲ)β-二酮三元配合物的合成与光谱性质

采用Claisen缩合反应合成了一种β-二酮1-(4-氨基苯)-3-苯基丙烷-1,3-二酮(L:C15H13NO2),以元素分析和1H NMR谱确定了其组成,核磁和红外分析结果表明L主要以烯醇式存在。以L为第一配体,分别以邻菲罗啉(phen),2,2’-联吡啶(bipy)为第二配体,合成了新的稀土Eu,Tb(Ⅲ)三元配合物。通过元素分析、红外光谱、紫外光谱、磷光光谱和荧光光谱对合成的配合物进行了表征。荧光光谱表明:稀土铽配合物的发光性能优于稀土铕配合物,进一步研究表明配体L与Tb3+间能级差较匹配,分子内传能效率高;phen对配合物的荧光敏化效果优于bipy,表明第二配体的刚性和共轭性越大,配合物的发光性能越好。     

Effect of the axial ligand on the reactivity of the oxoiron(IV) porphyrin π-cation radical complex: higher stabilization of the product state relative to the reactant state

The proximal heme axial ligand plays an important role in tuning the reactivity of oxoiron(IV) porphyrin π-cation radical species (compound I) in enzymatic and catalytic oxygenation reactions. To reveal the essence of the axial ligand effect on the reactivity, we investigated it from a thermodynamic viewpoint. Compound I model complexes, (TMP(+?))Fe(IV)O(L) (where TMP is 5,10,15,20-tetramesitylporphyrin and TMP(+?) is its π-cation radical), can be provided with altered reactivity by changing the identity of the axial ligand, but the reactivity is not correlated with spectroscopic data (ν(Fe═O), redox potential, and so on) of (TMP(+?))Fe(IV)O(L). Surprisingly, a clear correlation was found between the reactivity of (TMP(+?))Fe(IV)O(L) and the Fe(II)/Fe(III) redox potential of (TMP)Fe(III)L, the final reaction product. This suggests that the thermodynamic stability of (TMP)Fe(III)L is involved in the mechanism of the axial ligand effect. Axial ligand-exchange experiments and theoretical calculations demonstrate a linear free-energy relationship, in which the axial ligand modulates the reaction free energy by changing the thermodynamic stability of (TMP)Fe(III)(L) to a greater extent than (TMP(+?))Fe(IV)O(L). The linear free energy relationship could be found for a wide range of anionic axial ligands and for various types of reactions, such as epoxidation, demethylation, and hydrogen abstraction reactions. The essence of the axial ligand effect is neither the electron donor ability of the axial ligand nor the electron affinity of compound I, but the binding ability of the axial ligand (the stabilization by the axial ligand). An axial ligand that binds more strongly makes (TMP)Fe(III)(L) more stable and (TMP(+?))Fe(IV)O(L) more reactive. All results indicate that the axial ligand controls the reactivity of compound I (the stability of the transition state) by the stability of the ground state of the final reaction product and not by compound I itself.     

5,5'-Diamino-2,2'-bipyridine: a versatile building block for the synthesis of bipyridine/catechol ligands that form homo- and heteronuclear helicates

Herein we present an improved synthesis of 5,5'-diamino-2,2'-bipyridine (1) starting from the pyrrole-protected aminopyridine 4. By standard reactions 1 can easily be transformed into the imine- or amide-bridged dicatechol-bipyridine ligands L1-H4 and L2-H4. Whereas ligand L1 readily forms homodinuclear helicates [(L1)3Ti2]4-, the attempted formation of mono-, tri-, or even oligonuclear coordination compounds from this ligand did not work. However, the amide-connected ligand L2 affords mononuclear ([(L2-H4)PdCl2], [(L2-H4)3Zn]2+), dinuclear ([(L2)3Ti2]4-), and heterotrinuclear coordination compounds ([(L2)3Ti2Zn]2-).     

New fluorenyl-substituted ditopic dioxotetraamine ligands and their copper(II) complexes--synthesis, crystal structure, magnetic properties and solution behavior

A new fluorenyl-substituted dioxotetraamine salicylaldehyde Schiff-base ligand (L1) has been synthesized by the non-template 1 + 2 condensation of ligand 6-(9-fluorenyl)-1,4,8,11-tetraazaundecane-5,7-dione (L) with salicylaldehyde. From reduction of L1 with an excess of NaBH4, a ditopic dioxotetraamine ligand (L2) has been obtained. The copper(II) complex of L1 has been synthesized and its properties were examined by ES-MS and variable-temperature magnetic susceptibility as well as its crystal structure being determined. Detailed studies have been made on solution chemistry of Cu(II) complex of L2 by pH-potentiometric and fluorometric titration.     

The fixation of linear versus loop-type peptidic structures by metal coordination: the coordination chemistry of Val-Val- and Val-Val-Val-bridged dicatechol ligands

The Val-Val-bridged dicatechol ligand L1-H4 forms triplybridged dinuclear complexes with titanium(IV) ions, while the more flexible Val-Val-Val derivative L2-H4 leads to mixtures of complexes containing species with a cyclic arrangement of the ligand; with [cis-MoO2]2+ on the other hand, a well-defined macrocycle [(L2)MoO2]2- is formed which possesses a loop-type structure in the peptidic part of the ligand.     

Isolation and characterisation of transition and main group metal complexes supported by hydrogen-bonded zwitterionic polyphenolic ligands

Reaction of Zr(O(i)Pr)4 or Sn[N(SiMe3)2]2 with the tris-phenol amine ligand H3L(Me/Me) results in the formation of zirconium or tin complexes containing the new C3-symmetric zwitterionic ammonium-trisphenolate ligand HL2-, while increasing the steric bulk of the ligand results in the isolation of a zirconium complex containing the known trianionic ligand L3-.     

Kinetics and mechanism of iron(III) dissociation from the dihydroxamate siderophores alcaligin and rhodotorulic acid

The kinetics and mechanism of siderophore ligand dissociation from their fully chelated Fe(III) complexes is described for the highly preorganized cyclic tetradentate alcaligin and random linear tetradentate rhodotorulic acid in aqueous solution at 25 degrees C (Fe2L3 + 6H+ reversible 2 Fe3+ aq + 3 H2L). At siderophore:Fe(III) ratios where Fe(III) is hexacoordinated, kinetic data for the H(+)-driven ligand dissociation from the Fe2L3 species is consistent with a singly ligand bridged structure for both the alcaligin and rhodotorulic acid complexes. Proton-driven ligand dissociation is found to proceed via parallel reaction paths for rhodotorulic acid, in contrast with the single path previously observed for the linear trihydroxamate siderophore ferrioxamine B. Parallel paths are also available for ligand dissociation from Fe2(alcaligin)3, although the efficiency of one path is greatly diminished and dissociation of the bis coordinated complex Fe(alcaligin)(OH2)2+ is extremely slow (k = 10(-5) M-1 s-1) due to the high degree of preorganization in the alcaligin siderophore. Mechanistic interpretations were further confirmed by investigating the kinetics of ligand dissociation from the ternary complexes Fe(alcaligin)(L) in aqueous acid where L = N-methylacetohydroxamic acid and glycine hydroxamic acid. The existence of multiple ligand dissociation paths is discussed in the context of siderophore mediated microbial iron transport.     

Tuning the Dipolar Second‐Order Nonlinear Optical Properties of Cyclometalated Platinum(II) Complexes with Tridentate N^C^N Binding Ligands

Appropriate functionalization of the cyclometalated ligand, L , and the choice of the ancillary ligand, X, allows the dipolar second‐order nonlinear optical response of luminescent [Pt L X] complexes—in which L is an N^C^N‐coordinated 1,3‐di(2‐pyridyl)benzene ligand and X is a monodentate halide or acetylide ligand—to be controlled. The complementary use of electric‐field‐induced second‐harmonic (EFISH) generation and harmonic light scattering (HLS) measurements demonstrates how the quadratic hyperpolarizability of this appealing family of multifunctional chromophores, characterized by a good transparency throughout much of the visible region, is dominated by an octupolar contribution.     

新型稀土Eu,Tb(Ⅲ)芳香羧酸配合物的合成及发光性能

以2-二苯胺羰基苯甲酸(L)为第一配体,咪唑并[5,6-f]邻菲罗啉(IP)为第二配体,合成出新型稀土铕、铽三元配合物。采用元素分析、红外光谱、紫外-可见光谱对配体和配合物的结构进行了表征。红外光谱分析表明配合物中的稀土离子与第一配体L中的氧原子以及第二配体IP中的氮原子进行了配位。紫外光谱表明配合物主要是由第一配体L吸收能量。通过荧光光谱、荧光量子效率和荧光寿命研究了配合物的荧光性能,结果显示:两种配合物均表现出稀土离子的特征发射,且配合物的荧光量子效率和荧光寿命与发光强度成正比,配合物Tb(L)3IP的各项荧光性能均优于Eu(L)3IP。     

A closed molecular cube and an open book: two different products from assembly of the same metal salt and bridging ligand

Reaction of the bis-bidentate bridging ligand L1 with Co(ClO4)2 or Zn(BF4)2 affords a mixture of complexes [M8(L1)12]X16 and [M6(L1)9]X12 having the same metal : ligand ratio: the former is a molecular cube with a metal ion at each vertex and a bridging ligand spanning each edge, whereas the latter has a metal framework like that of an 'open book' containing cross-linked double helical metal-ligand subunits.     

Dynamic axial ligand-site exchange in facially discriminated ruthenium(II) carbonyl and rhodium(III) halide metalloporphyrins

For a series of six-coordinate RuII(CO)L or RhIII(X-)L porphyrins, which are facially differentiated by having a naphthoquinol- or hydroquinol-containing strap across one face, we show that ligand migration from one face to the other can occur under mild conditions and that ligand-site preference is dependent on the nature of L and X-. For bulky nitrogen-based ligands, the strap can be displaced sideways to accommodate the ligand on the same side as the strap. For the ligand pyrazine, we show 1H NMR evidence for monodentate and bridging binding modes on both faces, dependent on ligand concentration and metalloporphyrin structure, and that interfacial migration is rapid under normal conditions. For monodentate substituted pyridine ligands, there is a site-dependence on structure, and we show clear evidence of dynamic ligand migration through a series of ligand-exchange reactions.     

A new class of mixed ligand complexes bearing bisphenol and 1,10-Phenanthroline for antimicrobial and antioxidant activities: synthesis,spectral and electrochemical studies

Research on Chemical Intermediates - A new class of mixed ligand complexes, [M(L)(phen)2], using a bidentate bischlorophenol ligand H2L (2,2′-methylenebis(4-chlorophenol)) and phenanthroline...     

L-羟基脯氨酸键合手性配体交换色谱固定相的制备及手性拆分

合成出了L—羟基脯氨酸键合手性配体交换固定相，用元素分析和红外光谱对固定相进行了表征。该固定相在反相条件下，以水作流动相，对DL—氨基酸对映异构体有良好的拆分能力。     

Using non-covalent complexes to direct the fragmentation of glycosidic bonds in the gas phase

An investigation of the gas phase chemistry of proton bound oligosaccharide (S)-ligand (L) non-covalent complexes, [S + H + L](+) has been carried out using electrospray ionization (ESI) and tandem mass spectrometry in a quadrupole ion trap. When subjected to collision-induced dissociation (CID), these [S + H + L](+) complexes undergo a range of reactions that can be broadly classified into three main types: (1) Simple dissociation into the individual monomers; (2) cleavage of the oligosaccharide to form B-type sequence ions; (3) cleavage of the ligand species. The second type of reaction is particularly interesting as it can produce a "ladder series" of [B(x) + L](+) ions via ligand induced oligosaccharide bond cleavage. This novel gas phase reaction greatly simplifies the sequencing of oligosaccharides. Both the oligosaccharide and ligand were found to influence the type of reaction pathway observed, with the "ladder series" of [B(x) + L](+) ions being favored for permethylated oligosaccharides and for bifunctional ligands. Cytosine is a particularly good ligand at facilitating the formation of [B(x) + L](+) ions. Analogies with condensed phase chemistry of sugars is made and a potential mechanism for ligand induced oligosaccharide bond cleavage is proposed.     

Synthesis, structural characterization, thermal and electrochemical studies of the N,N'-bis[(3,4-dichlorophenyl)methylidene]cyclohexane-1,4-diamine and its Cu(II), Co(II) and Ni(II) metal complexes

In this study, N,N'-bis[(3,4-dichlorophenyl)methylidene]cyclohexane-1,4-diamine (L) and its Cu(II), Co(II) and Ni(II) complexes were prepared and characterized by the analytical and spectroscopic methods. The analytical data show the composition of the metal complex to be [M(2)L(Cl)(4)(H(2)O)(2)], where L is the Schiff base ligand. The conductance data indicate that all the complexes are non-electrolytes. The compound (L) behaves as a monodentate ligand. But, obtained complexes have binuclear nature. The electrochemical properties of the metal complexes are dependent on reversible, irreversible and quasi-reversible redox waves in the anodic and cathodic regions due to oxidation and reduction of the metal ions. The single crystal of the ligand (L) was obtained from CH(3)CN solution. Space group and crystal system of the ligand are P2(1)/C and monoclinic, respectively.     

Supramolecular Co(II)-[2 x 2] grids: metamagnetic behavior in a single molecule

The magnetic anisotropy of the supramolecular [2 x 2] grid [Co(II)4L4]8+, with a bis(bipyridyl)-pyrimidine-based ligand L, was investigated by single-crystal magnetization measurements at low temperatures. The magnetization curves exhibit metamagnetic-like behavior and are explained by the weak-exchange limit of a minimal spin Hamiltonian including Heisenberg exchange, easy-axis ligand fields, and the Zeeman term. It is also shown that the magnetic coupling strength can be varied by the substituent R1 in the two-position on the central pyrimidine group of the ligand L.