氧和碳酸根桥联的双核铁(Ⅲ)配合物的合成、结构和光谱研究

氧桥联的双核铁配合物一直是无机化学工作者十分感兴趣的研究课题 .近年来 ,由于在生物体内发现多种金属蛋白和金属酶的活性中心存在氧和羧酸根桥联的双核铁结构单元 ,如蚯蚓血红蛋白 [1]、甲烷单加氧酶 [2 ]、核糖核酸还原酶 [3]、饱和脂肪酸还原酶 [4 ]和紫色酸性磷酸酶 [5]等 ,使得对氧桥联的双核铁配合物的研究成为当前生物无机化学研究中的热点之一[6] .为进一步了解氧桥联的双核铁配合物的物理化学性质 ,我们在系统研究的基础上 ,合成了一个新的氧和碳酸根桥联的双核铁配合物 ,测定了其晶体结构 ,研究了其电子吸收光谱 .1　实验部分1 …     

草酰胺桥联异三核配合物的电化学及磁学性质

异三核草酰胺桥联配合物;循环伏安法;反铁磁作用;草酰胺桥联异三核配合物的电化学及磁学性质     

中心氧三核过渡金属羰基簇合物的穆斯堡尔谱研究

中心氧三核过渡金属羰基簇合物的穆斯堡尔谱研究王友桐（中国科学院福建物质结构研究所，福州，３５０００２）关键词：三核簇合物，穆斯堡尔谱学引言由于三重桥氧三核铁、铬羰基簇合物具有特殊的结构特征、磁性、催化性能和电子特性，已引起了许多学者的兴趣￣［１－３］...     

咪唑桥联Cu-Co交替异多核和长链配合物的合成、表征和ESR研究

三种咪唑桥Cu-Co交替异三核、二种Cu-Co交替长链配合物已经合成,反射光谱研究确证配合物中咪唑桥的存在。ESR研究阐明了配合物中Cu~(2+)与配体间的成键性质。     

修饰剂结构对桥氧双核锰2，2＇－联吡啶配合物电化学的影响

修饰剂结构对桥氧双核锰２，２＇－联吡啶配合物电化学的影响吴丛笑，郑军伟，陆天虹（中国科学院长春应用化学研究所电分析化学开放实验室，长春，１３００２２）关键词桥氧双核锰２，２＇－联吡啶配合物，烟酸，异烟酸，２－羧酸吡啶锰酶在生物体系中作为一类重要的氧化...     

两种双核配合物催化PNPP水解反应的机理研究

Cu-Cu(Ⅱ)和Cu-Zn(Ⅱ)草酰胺桥联双核配合物被合成和表征．研究了该同核和异核配合物催化PNPP水解的动力学和机理,建立了一种双核配合物催化PNPP水解的动力学数学模型．结果表明：在缓冲溶液中随着溶液pH的增大,草酰胺桥联双核配合物催化PNPP水解速率提高;配合物中的两个金属离子在催化PNPP水解过程中具有协同效应;这两种草酰胺桥联双核配合物在催化PNPP水解中表现出较好的催化活性．     

咪唑桥联Cu-Co交替异多核和长链配合物的合成、表征和ESR研究

三种咪唑桥Cu-Co交替异三核、二种Cu-Co交替长链配合物已经合成,反射光谱研究确证配合物中咪唑桥的存在。ESR研究阐明了配合物中Cu²⁺与配体间的成键性质。     

三乙四胺钴配合物氧合结构和老化机理

以固相法合成的三乙四胺钴配合物为研究体系,采用正离子电喷雾串联质谱、紫外-可见吸收光谱、拉曼共振光谱和红外光谱等表征手段,研究了配合物与氧分子的相互作用过程及配合物在吸氧过程中的结构变化。结果表明,三乙四胺钴配合物的吸氧过程是一个动态的变化过程,氧合产物由双氧双桥联的氧合配合物CoⅢL-(O2)2-CoⅢL形式向双羟基桥联的老化配合物CoⅢL-(OH)2-CoⅢL形式转变;18O2同位素标记实验验证了Co-O-O-Co的存在。酸解实验说明OH桥联配合物的形成是造成可逆性差的根本原因。这些结果为探知多胺钴配合物的氧合结构和老化机理提供了新的研究方法和实验依据。     

氧桥联双核钛、镍配合物的合成及催化制备双峰聚乙烯

从2种氧原子桥联双膦化合物双(2-二苯基膦苯基)醚(1a)和4,5-双(二苯基膦)-9,9-二甲基氧杂蒽(1b)出发,合成氧原子桥联双膦亚胺钛、镍配合物.在甲苯中回流条件下首先将化合物1a和1b与叠氮三甲基硅烷发生Staudinger反应,分别生成单和双膦亚胺前驱体2a和2b.然后再与环戊二烯基三氯化钛反应,脱去三甲基氯硅烷后得到相应膦亚胺过渡金属钛配合物3a和3b.单钛中心配合物3b进一步与乙二醇二甲醚溴化镍反应生成钛-镍异核双中心配合物4b.通过1H NMR,13C NMR,31P NMR,FTIR及元素分析对产物进行了表征,并利用X射线单晶衍射分析确定了配合物3a和3b的分子结构.在助催化剂甲基铝氧烷(MAO)作用下,配合物3a和4b对乙烯聚合均表现出较高的催化活性,其中双钛中心配合物3a催化得到较宽分子量的聚乙烯产物,而异核双中心配合物4b催化得到呈双峰分布的聚乙烯产物.     

Schiff碱配合物的研究II: 一些Fe(III)配合物的磁性质与电化学行为

Fe(III)schiff碱配合物的磁性质和电化学还原性是该类配合物的基本特性, 本文研究三种配合物, 单核高自旋配合物, 单核低自旋配合物以及氧桥双核配合物的核磁共振性质电化学还原性。     

An internal doping method for the preparation of transparent hybrid xerogels containing nano-sized iron particles

Sol-gel copolymerization of iron tricarbonyl-2-(triisopropoxysilyl)-1,3-butadiene with 1,6-bistriethoxysilylhexane and 1,4-bistriethoxysilylbenzene followed by drying produced bridged polysilsesquioxane xerogels. These porous, transparent hybrid materials containing the iron metal precursor were irradiated (UV) and heated under vacuum resulting in the deposition of nano-sized iron particles doped in the xerogels. EDAX and electron diffraction techniques were used to characterize the iron phases. The TEM images of these doped xerogels provided additional information regarding the domain size of the iron phase.Using a combination of external doping of Cd²⁺ and S^2– ions and internal doping of Fe°, mixed Fe/CdS phases were prepared within the porous bridged polysilsesquioxane xerogels. The resulting doped xerogels were found to have retained their porous morphology.     

Characterization of [2Fe–2S]‐Cluster‐Bridged Protein Complexes and Reaction Intermediates by use of Native Mass Spectrometric Methods

Many iron–sulfur proteins involved in cluster trafficking form [2Fe–2S]‐cluster‐bridged complexes that are often challenging to characterize because of the inherent instability of the cluster at the interface. Herein, we illustrate the use of fast, online buffer exchange coupled to a native mass spectrometry (OBE nMS) method to characterize [2Fe–2S]‐cluster‐bridged proteins and their transient cluster‐transfer intermediates. The use of this mechanistic and protein‐characterization tool is demonstrated with holo glutaredoxin 5 (GLRX5) homodimer and holo GLRX5:BolA‐like protein 3 (BOLA3) heterodimer. Using the OBE nMS method, cluster‐transfer reactions between the holo‐dimers and apo‐ferredoxin (FDX2) are monitored, and intermediate [2Fe–2S] species, such as (FDX2:GLRX5:[2Fe–2S]:GSH) and (FDX2:BOLA3:GLRX5:[2Fe–2S]:GSH) are detected. The OBE nMS method is a robust technique for characterizing iron–sulfur‐cluster‐bridged protein complexes and transient iron–sulfur‐cluster transfer intermediates.     

Effect of Inter‐Porphyrin Distance on Spin‐State in Diiron(III) μ‐Hydroxo Bisporphyrins

The synthesis, structure, and properties of bischloro, μ‐oxo, and a family of μ‐hydroxo complexes (with BF₄^?, SbF₆^?, and PF₆^? counteranions) of diethylpyrrole‐bridged diiron(III) bisporphyrins are reported. Spectroscopic characterization has revealed that the iron centers of the bischloro and μ‐oxo complexes are in the high‐spin state (S=⁵/₂). However, the two iron centers in the diiron(III) μ‐hydroxo complexes are equivalent with high spin (S=⁵/₂) in the solid state and an intermediate‐spin state (S=³/₂) in solution. The molecules have been compared with previously known diiron(III) μ‐hydroxo complexes of ethane‐bridged bisporphyrin, in which two different spin states of iron were stabilized under the influence of counteranions. The dimanganese(III) analogues were also synthesized and spectroscopically characterized. A comparison of the X‐ray structural parameters between diethylpyrrole and ethane‐bridged μ‐hydroxo bisporphyrins suggest an increased separation, and hence, less interactions between the two heme units of the former. As a result, unlike the ethane‐bridged μ‐hydroxo complex, both iron centers become equivalent in the diethylpyrrole‐bridged complex and their spin state remains unresponsive to the change in counteranion. The iron(III) centers of the diethylpyrrole‐bridged diiron(III) μ‐oxo bisporphyrin undergo very strong antiferromagnetic interactions (J=?137.7 cm^?1), although the coupling constant is reduced to only a weak value in the μ‐hydroxo complexes (J=?42.2, ?44.1, and ?42.4 cm^?1 for the BF₄, SbF₆, and PF₆ complexes, respectively).     

A sulfido-bridged diiron(II) compound and its reactions with nitrogenase-relevant substrates

The active site iron-molybdenum cofactor of nitrogenase has sulfide-bridged pairs of redox-active, trigonal pyramidal iron atoms that are postulated to be the site of N2 transformation. A synthetic compound is described in which two three-coordinate iron(II) ions are bridged similarly by sulfide. The compound binds nitrogen donors to become trigonal pyramidal and cleaves the N-N bond of phenylhydrazine with oxidation of iron(II) to iron(III).     

Synthesis of ferrocenoporphyrinophanes stacked with metals and aromatic rings

Double and triple layered porphyrinophanes bridged with 1,1′- or 1,3-disubstituted ferrocene moieties and their iron complexes have been synthesized.     

Dimeric iron n-confused porphyrin complexes

A dimeric iron N-confused porphyrin, [Fe(NCTPP)]2 was obtained from the anaerobic reaction of Fe(NCTPP)Br with NaSePh while under aerobic conditions a hydroxo bridged iron dimer with Na bridging the outer-N atoms was obtained and oxygenation occurred on the inner core pyrrolic carbon to form a novel ONCTPP porphyrinic ring.     

Computational study of iron(II) and -(III) complexes with a simple model human H ferritin ferroxidase center

Interaction of iron ions with a six-amino acid model of the ferroxidase center of human H chain ferritin has been examined in density functional theory calculations. The model, based on experimental studies of oxidation of Fe2+ at the center, consists of Glu27, Glu62, His65, Glu107, Gln141, and Ala144. Reasonable structures are obtained in a survey of types of iron complexes inferred to occur in the ferroxidase reaction. Structures of complexes of the model center with one and two Fe2+ ions, with diiron(III) bridged by peroxide and bridged by oxide-peroxide combinations, have been optimized. Calculations on diiron(III) complexes confirm that stable peroxide-bridged complexes can form and that the Fe-Fe distance in at least one is consistent with the experimental Fe-Fe distance observed in the blue peroxodiferric complex of ferritin.     

A Series of Low-Coordinate Iron Selenido Complexes: Reactivity of a Linear Iron(I) Silylamide towards Selenium

A variety of different low-coordinate iron selenide complexes is reported. These are obtained by reaction of the linear iron(I) silylamide K{18c6}[Fe(N(Dipp)SiMe₃)₂] (Dipp=2,6-diisopropylphenyl) with red selenium. Careful adjustment of the reaction conditions results in the formation of unique low-coordinate selenido iron complexes, namely a monoselenide bridged [2Fe−1Se]²⁺ complex, as well as mononuclear iron per- and triselenides. Further, C−H bond activation of one of the silylamide ligands by a putative terminal iron monoselenide is observed.     

C−H and C−N Activation at Redox‐Active Pyridine Complexes of Iron

Pyridine activation by inexpensive iron catalysts has great utility, but the steps through which iron species can break the strong (105–111 kcal mol⁻¹) C−H bonds of pyridine substrates are unknown. In this work, we report the rapid room‐temperature cleavage of C−H bonds in pyridine, 4‐tert‐butylpyridine, and 2‐phenylpyridine by an iron(I) species, to give well‐characterized iron(II) products. In addition, 4‐dimethylaminopyridine (DMAP) undergoes room‐temperature C−N bond cleavage, which forms a dimethylamidoiron(II) complex and a pyridyl‐bridged tetrairon(II) square. These facile bond‐cleaving reactions are proposed to occur through intermediates having a two‐electron reduced pyridine that bridges two iron centers. Thus, the redox non‐innocence of the pyridine can play a key role in enabling high regioselectivity for difficult reactions.     

Electronic structure of dinuclear iron nitrosyl complexes with different ligands at two iron centers

The electronic structures of three dinuclear iron complexes were determined with the DFT method. The complexes contain a {Fe(NO)₂}⁹ unit and thiolate, nitrosyl, carbonyl and amine ligands at the second iron atom. The two iron atoms are bridged by thiolate ligands. In the lowest energy states of these complexes, the iron atoms possess spin S = 1, 3/2 or 5/2, depending on the coordinated ligands and their mutual arrangement. Nitrosyl is coordinated as NO⁻ antiferromagnetically coupled to iron, and the two iron units are antiferromagnetically coupled to each other.