N(1)取代5-氟尿嘧啶乙酸、5-氟尿嘧啶丙酸与Cu(Ⅱ)、Co(Ⅱ)、Ni(Ⅱ)、Zn(Ⅱ)、Mn(Ⅱ)的配合物的合成及表征

合成了N(1)取代5-氟尿嘧啶乙酸、5-氟尿嘧啶丙酸与铜(Ⅱ)、钴(Ⅱ)、镍(Ⅱ)和锰(Ⅱ)的十种金属配合物。通过元素分析、差热-热重分析确定了它们的化学组成,并对这些化合物进行了红外光谱、氢核磁共振谱,电子光谱的表征。讨论了各配合物中金属离子与配体的配位状态。在Cu(Ⅱ)配合物中,Cu(Ⅱ)是与配体的N³原子和C⁴上的羰基氧原子配位,其他金属配合物中,金属离子是与配体的C²的羰基氧原子和羧基配位。     

D-葡萄糖D-果糖与硼的有机物形成配合物的稳定性研究

葡萄糖异构酶加速葡萄糖与果糖的平衡,平衡时果糖含量为42％左右,体系中加入一些硼酸盐,果糖的含量提高到80％左右,究其原因可能是由于葡萄糖和果糖与硼酸盐形成不同稳定性的配合物。虽然Roy,Conner,Daris,Belcher,Lorand等都已报导了这些配合物的稳定常数,概括结果分歧较大。Belcher曾首次报导了硼酸与D-果糖的配位数为     

2-丙基-1H-4，5-咪唑二酸构筑的镉(Ⅱ)配位聚合物的合成、晶体结构、形貌及荧光性质

通过水热方法 ,采用H3pimda(2-propyl-1H-imidazole-4,5-dicarboxylic acid)与CdSO4.8/3H2O和Nd2O3反应,合成了1个具有一维孔道的配位聚合物[Cd(H2pimda)2]n(1),并对其结构和荧光性质进行了研究。结构分析结果表明该聚合物的晶体属于单斜晶系,P21/n空间群。4个H2pimda-配体桥联4个镉(Ⅱ)离子形成了1个方环,这些环通过镉(Ⅱ)离子与H2pimda-配体的配位作用形成了1个具有一维孔道的三维框架结构。值得关注的是配合物1的晶体呈现一种微米管的外型。研究表明,该聚合物中在室温下能发出很强的兰色荧光。     

Synthesis,thermal stability and structural characterisation of iron(II) phthalocyanine complex with 4-cyanopyridine

A new complex of bis-axially coordinated iron(II) phthalocyanine by 4-cyanopyridine (4-CNpy) has been obtained in crystalline form as an adduct with two 4-CNpy molecules. The [FePc(4-CNpy)₂] · 2(4-CNpy) crystallises in the monoclinic system, space group P2₁/c with two molecules in the unit cell. The iron(II) coordinates four isoindole nitrogen atoms of the almost planar phthalocyaninato(2−) macroring and axially two nitrogen atoms of 4-CNpy molecules. The coordination polyhedron around the Fe(II) atom approximates to a tetragonal by-pyramid. Four equatorial Fe–N bonds are shorter (1.936(2) Å) than two axial Fe–N bonds (2.027(2) Å). The centrosymmetric FePc(4-CNpy)₂ molecules form alternating sheets parallel to the bc crystallographic plane and solvated 4-CNpy molecules that are anti-parallel oriented by their polar cyano groups are located between the sheets of FePc(4-CNpy)₂ molecules. Ligation of the intermediate-spin iron(II) phthalocyanine by 4-CNpy molecules leads to the low spin Fe(II) complex. The importance of the d(π) → π^∗(Pc) back donation is manifested in the difference between the values of C–N isoindole and C–N azamethine bond lengths of the Pc macrocycle. The thermal analysis of the crystals of [FePc(4-CN)₂] · 2(4-CNpy) shows two steps responsible for a loss of solvated (∼170 °C) and coordinated (∼235 °C) 4-CNpy molecules.     

One‐Dimensional,Cofacial Porphyrin Polymers Formed by Self‐Assembly of meso‐Tetrakis(ERE Donor) Zinc(II) Porphyrins

A series of meso‐tetrakis‐(ERE donor) zinc(II) porphyrins n Zn (ERE donor=4‐R‐3,5‐bis[(E)‐methyl]phenyl; 1 Zn: E=NMe₂, R=Br; 2 Zn: E=NMe₂, R=H; 3 Zn: E=OMe, R=Br; 4 Zn: E=OMe, R=H) have been synthesized in excellent yields. As a result of the combination of a Lewis acidic site and eight Lewis basic sites within one molecule, monomeric molecules of n Zn self‐assemble to form one‐dimensional porphyrin polymers [ n Zn]_∞ in the solid state, as confirmed for 1 Zn and 3 Zn by X‐ray crystallography. The coordination environment around the zinc(II) ions in these polymers is octahedral. They are ligated by four equatorial nitrogen atoms of the porphyrin and two apical E atoms (E=N, O) provided by the EBrE donor groups of adjacent n Zn molecules. Complexes 2 Zn and 4 Zn did not form single crystals, but solid‐state UV/Vis analysis points to the formation of similar structures. Solution UV/Vis and ¹H NMR spectroscopy indicated that interactions between 1 Zn and 2 Zn monomers in the polymers are stronger than between 3 Zn and 4 Zn monomers. Interestingly, they also revealed that the presence of a neighboring bromine atom in the EBrE donor groups has a considerable influence on the coordination properties of the benzylic N or O atoms. The zinc(II) ions of the porphyrins most likely adopt only hexacoordination in the solid state, owing to the unique predisposition of Lewis acidic and basic sites in the n Zn molecules. Several parameters of the aggregates, for example, the interplanar separation between porphyrins and the zinc–zinc distances, change as a function of the coordinating E groups. The high degree of modularity in their synthesis makes these zinc(II) porphyrins an interesting new entry in noncovalent multiporphyrin assemblies.     

Elucidating the Coordination Chemistry and Mechanism of Biological Nitrogen Fixation

How does the enzyme nitrogenase reduce the inert molecule N₂ to NH₃ under ambient conditions that are so different from the energy‐expensive conditions of the best industrial practices? This review focuses on recent theoretical investigations of the catalytic site, the iron–molybdenum cofactor FeMo‐co, and the way in which it is hydrogenated by protons and electrons and then binds N₂. Density functional calculations provide reaction profiles and activation energies for possible mechanistic steps. This establishes a conceptual framework and the principles for the coordination chemistry of FeMo‐co that are essential to the chemical mechanism of catalysis. The model advanced herein explains relevant experimental data.     

Characterization and properties of the copper(II/I) complexes of macrocyclic hexathiaether ligand [21]aneS6

The copper(II/I) complexes of hexathiaether macrocyclic ligand, 1,4,8,11,15,18-hexathiacyclohenicosane ([21]aneS₆), were synthesized, and characterized by electrochemical and spectroscopic techniques. Cyclic voltammetric studies indicate that Cu([21]aneS₆)^2+/+ forms a reversible one-electron redox couple. The electrochemical potential obtained for Cu([21]aneS₆)^2+/+ (E^f = 0.89 V, against SHE) was found to be the highest potential reported to date for a Cu^2+/+ macrocyclic system in aqueous solution. By employing the Nernst equation, we can infer that the practical upper limit for formal potential of Cu(II/I)L systems maybe close to this high value. Stability constant data obtained for these complexes indicate that Cu([21]aneS₆)⁺is 12 orders of magnitude greater in stability than that of Cu([21]aneS₆)²⁺ indicating the favorable nature of this large macrocyclic ligand towards formation of Cu(I) complexes over Cu(II) complexes. Crystal structure of Cu([21]aneS₆)⁺ ( Fig. 2) shows that four sulfurs adjacent to one another are coordinated to Cu⁺ ion in this complex. Bond angles and distances calculated for the crystal indicate that it is a distorted tetrahedron, a geometry commonly encountered by Cu(I) complexes. This is the first report of synthesis and characterization of a metal coordinated [21]aneS₆ complex.     

CaII Binding Regulates and Dominates the Reactivity of a Transition‐Metal‐Ion‐Dependent Diesterase from Mycobacterium tuberculosis

The diesterase Rv0805 from Mycobacterium tuberculosis is a dinuclear metallohydrolase that plays an important role in signal transduction by controlling the intracellular levels of cyclic nucleotides. As Rv0805 is essential for mycobacterial growth it is a promising new target for the development of chemotherapeutics to treat tuberculosis. The in vivo metal‐ion composition of Rv0805 is subject to debate. Here, we demonstrate that the active site accommodates two divalent transition metal ions with binding affinities ranging from approximately 50 nm for Mn^II to about 600 nm for Zn^II. In contrast, the enzyme GpdQ from Enterobacter aerogenes, despite having a coordination sphere identical to that of Rv0805, binds only one metal ion in the absence of substrate, thus demonstrating the significance of the outer sphere to modulate metal‐ion binding and enzymatic reactivity. Ca^II also binds tightly to Rv0805 (K_d≈40 nm ), but kinetic, calorimetric, and spectroscopic data indicate that two Ca^II ions bind at a site different from the dinuclear transition‐metal‐ion binding site. Ca^II acts as an activator of the enzymatic activity but is able to promote the hydrolysis of substrates even in the absence of transition‐metal ions, thus providing an effective strategy for the regulation of the enzymatic activity.     

Synthesis,Electrochemistry, and Photophysical Studies of Ruthenium(II) Polypyridine Complexes with D–π–A–π–D Type Ligands and Their Application Studies as Organic Memories

A new class of ruthenium(II) polypyridine complexes with a series of D–π–A–π–D type (D=donor, A=acceptor) ligands was synthesized and characterized by ¹H NMR spectroscopy, mass spectrometry, and elemental analysis. The photophysical and electrochemical properties of the complexes were also investigated. The newly synthesized ruthenium(II) polypyridine complexes were found to exhibit two intense absorption bands at both high‐energy (λ=333–369 nm) and low‐energy (λ=520–535 nm) regions. They are assigned as intraligand (IL) π→π* transitions of the bipyridine (bpy) and π‐conjugated bpy ligands, and IL charge‐transfer (CT) transitions from the donor to the acceptor moiety with mixing of dπ(Ru^II)→π*(bpy) and dπ(Ru^II)→π*(L) MLCT characters, respectively. In addition, all complexes were demonstrated to exhibit intense red emissions at approximately λ=727–744 nm in degassed dichloromethane at 298 K or in n‐butyronitrile glass at 77 K. Nanosecond transient absorption (TA) spectroscopy has also been carried out, establishing the presence of the charge‐separated state. In order to understand the electrochemical properties of the complexes, cyclic voltammetry has also been performed. Two quasi‐reversible oxidation couples and three quasi‐reversible reduction couples were observed. One of the ruthenium(II) complexes has been utilized in the fabrication of memory devices, in which an ON/OFF current ratio of over 10⁴ was obtained.     

Nanoscale MnII‐Coordination Polymers for Cell Imaging and Heterogeneous Catalysis

A mixed ligand approach was exploited to synthesize a new series of Mn^II‐based coordination polymers (CPs), namely, CP1 {[Mn(μ‐dpa)(μ‐4,4′‐bp)]?MeOH}_∞, CP2 {[Mn₃(μ‐dpa)₃(2,2′‐bp)₂]}_∞, CP3 {[Mn₃(μ‐dpa)₃(1,10‐phen)₂]?2 H₂O}_∞, CP4 {[Mn(μ‐dpa)(μ‐4,4′‐bpe)_1.5]?H₂O}_∞, CP5 {[Mn₂(μ‐dpa)₂(μ‐4,4′‐bpe)₂]? DEF}_∞, and CP6 {[Mn(μ‐dpa)(μ‐4,4′‐bpe)_1.5]? DMA}_∞ (dpa=3,5‐dicarboxyphenyl azide, 2,2′‐bp=2,2′‐bipyridine, 1,10‐phen=1,10‐phenanthroline, 4,4′‐bpe=1,2‐bis(4‐pyridyl)ethylene, 4,4′‐bp=4,4′‐bipyridine, DEF=N,N‐diethylformamide, DMA=N,N‐dimethylacetamide), to develop multifunctional CPs. Various techniques, such as single‐crystal X‐ray diffraction (SXRD), FTIR spectroscopy, elemental analysis, and thermogravimetric analysis, were employed to fully characterize these CPs. The majority of the CPs displayed a four‐connected sql topology, whereas CP4 and CP6 exhibited a two‐dimensional SnS network architecture, which was further entangled in a polycatenation mode. Compound CP1 displayed an open framework structure. The CPs were scaled down to the nanoregime in a ball mill for cell imaging studies. Whereas CP2 and CP4 were employed for cell imaging with RAW264.7 cells, CP1 was exploited for both cell imaging and heterogeneous catalysis in a cyanosilylation reaction.