Inhibitory activity of bivalent transition-metal complexes with diamines toward a diamine oxidase

Various complexes of bivalent transition metals with diamines have been synthesized and studied “in vitro” with a diamine oxidase. The inhibition type and K_i value of these compounds have been determined. For the linear-chain diamine complexes the inhibition was competitive and the highest inhibition was for the 1,3-diaminopropane-copper complexes.     

Catalytic applications of transition-metal complexes bearing diphosphinidenecyclobutenes (DPCB)

The preparation and characterization of sterically protected diphosphinidenecyclobutenes bearing two two-coordinate phosphorus atoms are described from the viewpoint of the development of a novel type of bidentate ligand for transition-metal complexes. They form complexes with group 6 metals such as chromium, molybdenum and tungsten, group 8 metals such as ruthenium, group 10 metals such as palladium and platinum, and group 11 metals such as copper and gold. Some of them can be used as catalysts for synthetic reactions such as cross-coupling of the Sonogashira type, Suzuki-Miyaura coupling, Ullmann coupling, Kosugi-Migita-Stille coupling, cyanation, polymerization of ethylene, dehydrogenative hydrosilylation of ketones, hydroamination of 1,3-butadienes, and direct alkylation or amination of allylic alcohols of Tsuji-Trost reactions.     

The electronic structure of transition-metal carbonyl complexes of norbornadiene and mesitylene

The photoelectron spectra of several transition-metal carbonyl complexes of norbornadiene and mesitylene have been measured. The data for the norbordiene complexes have been compared with those reported previously for norbornadieneiron tricarbonyl. The shifts in energies of the π orbitals of the ligands introduced by the metal carbonyl moieties are remarkably insensitive to the choice o0f transition metal or geometry of the complex. However, the characters of the metal d-orbital ionization bands are markedly affected by the choice of ligand.     

Bias effects on the electronic spectrum of a molecular bridge

In this paper the effect of bias and geometric symmetry breaking on the electronic spectrum of a model molecular system is studied. Geometric symmetry breaking can either enhance the dissipative effect of the bias, where spectral peaks are disabled, or enable new excitations that are absent under zero bias conditions. The spectral analysis is performed on a simple model system by solving for the electronic response to an instantaneously impulsive perturbation in the dipole approximation. The dynamical response is extracted from the electronic equations of motion as expressed by the Keldysh formalism. This expression provides for the accurate treatment of the electronic structure of a bulk-coupled system at the chosen model Hamiltonian electronic structure level.     

Dinuclear cyano-bridged CoIII-FeII complexes as precursors for molecular mixed-valence complexes of higher nuclearity

The preparation and characterization of a series of trinuclear mixed-valence cyano-bridged Co(III)-Fe(II)-Co(III) compounds derived from known dinuclear [[L(n)Co(III)(mu-NC)]Fe(II)(CN)(5)](-) complexes (L(n)() = N(5) or N(3)S(2) n-membered pendant amine macrocycle) are presented. All of the new trinuclear complexes were fully characterized spectroscopically (UV-vis, IR, and (13)C NMR). Complexes exhibiting a trans and cis arrangement of the Co-Fe-Co units around the [Fe(CN)(6)](4-) center are described (i.e., cis/trans-[{L(n)Co(III)(mu-NC)](2)Fe(II)(CN)(4)](2+)), and some of their structures are determined by X-ray crystallography. Electrochemical experiments revealed an expected anodic shift of the Fe(III/II) redox potential upon addition of a tripositively charged [Co(III)L(n)] moiety. The Co(III/II) redox potentials do not change greatly from the di- to the trinuclear complex, but rather behave in a fully independent and noncooperative way. In this respect, the energies and extinction coefficients of the MMCT bands agree with the formal existence of two mixed-valence Fe(II)-CN-Co(III) units per molecule. Solvatochromic experiments also indicated that the MMCT band of these compounds behaves as expected for a class II mixed-valence complex. Nevertheless, its extinction coefficient is dramatically increased upon increasing the solvent donor number.     

单核第一过渡周期金属水氧化催化剂（英文）

由于传统化石能源的不可再生性,其储量日益减少.同时,传统化石能源的使用对环境产生了巨大影响,给人类社会带来了一系列问题,包括温室效应、酸雨等.因此,进入二十一世纪以后,人类面临着日益严峻的能源危机和环境问题,寻找清洁、高效的替代能源已经迫在眉睫.太阳能被认为是一种洁净的可再生能源.自然界通过光合作用将太阳能转化为化学能,在这一过程中,水被氧化产生氧气,同时释放出的电子和质子通过和二氧化碳作用生成碳水化合物.为了模拟这一过程,人工光合作用可以直接将电子和质子结合形成氢气.由此生成的氢气也被认为是洁净的可再生能源,因为在其燃烧过程中只产生水.因此,通过光致水分解析氢析氧的人工光合作用受到了越来越广泛的重视.水分解可以分为两个独立的半反应,即水的氧化析氧和水的还原析氢.水的氧化无论在热力学还是动力学方面,都存在着非常大的阻碍.在热力学上,两分子的水氧化生成一分子氧气需要提供很多能量(ΔE=1.23 V vs NHE).在动力学上,由于涉及到四个氢原子和两个氧原子的重组,并且涉及到氧氧键形成并释放出一分子氧气,因此水氧化是一个非常缓慢的过程.在自然界,水的氧化主要发生在光合作用中,在绿色植物的叶绿体中完成.通过对光合作用的研究,科学家们发现氧气的产生由光系统Ⅱ(PSII)中的释氧中心来完成.释氧中心是一个钙锰簇合物,由四个锰和一个钙组成(Mn_4CaO_x).自然界水分解产生氧气的过程给了我们很大启示,对设计和研究高效稳定的水氧化催化剂具有一定的指导意义.目前水氧化催化剂主要有两大类.第一类是基于材料的水氧化催化剂.该类催化剂的催化效率高,过电势小,但是对水氧化催化过程的机理缺乏深入研究.第二类是基于金属配合物的分子催化剂.相比基于材料的催化剂,分子催化剂具有以下特点:(1)分子催化剂的结构可以通过实验手段表征清楚;(2)可以结合光谱对水氧化的机理进行深入研究,可以对催化过程中间体进行表征;(3)催化剂的结构可以从分子水平上进行修饰,因此可以更好地研究催化效率与结构之间的关系,为设计高效、稳定的催化剂提供必要信息;(4)比较容易组装成分子器件从而应用到实际的水氧化装置中;(5)通过实验与理论的结合,对氧氧成键提出新的认识与理解.近几年来,一些单核的金属配合物逐渐被发现可以高效、稳定地催化水氧化.研究表明,一些基于钌和铱的催化剂具有良好的催化活性,但由于金属钌和铱储量少、价格昂贵等因素,限制了该类催化剂的大量使用.由于第一过渡系金属元素具有储量丰富、安全无毒、廉价易得等优势,第一过渡周期金属化合物逐渐成为科学家们研究的热点.近几年来,基于第一过渡系金属的水氧化催化剂已经有大量报道.本文主要总结了近几年来基于第一过渡系金属的单核水氧化分子催化剂.通过对催化机理进行深入的讨论,特别是对氧氧成键的总结,本文将对设计合成结构新颖、具有高催化效率和良好稳定性的水氧化分子催化剂提供理论依据.     

Bond multiplicity in transition-metal complexes: applications of two-electron valence indices

In the present study the applicability of the bond multiplicities from the Nalewajski and Mrozek valence indices was demonstrated for a variety of transition metal-based systems. The Nalewajski-Mrozek valence indices and bond multiplicity indices have been implemented in the Amsterdam Density Functional program. Selected examples comprise the carbonyl complexes (selected tetra- and hexacarbonyls, binary monocarbonyls of the first-row transition metals), phosphines, the ligands' trans-influence, as well as multiple metal-ligand and metal-metal bonds. The results show that the calculated bond multiplicity indices correspond well to experimental predictions based on bond lengths and vibrational frequencies for all discussed classes of complexes. Almost perfect linear correlation between the bond indices and vibrational frequencies was observed for carbonyls and the oxo complexes; the calculated bond multiplicity reproduces the accepted order for the trans-influence of different ligands, rationalizes unusually low vibrational freqencies in the [OsO 3N] (-)complex compared to other nitrido complexes, explains the geometrical asymmetry in the MoO 3 solid, and confirms the multiple character of the metal-metal bond in the [Re 2Cl 8] (2-) complex. Thus, the Nalewajski and Mrozek method can be successfully used as a supplementary analysis tool for electronic structure for studies involving transition metal complexes.     

Dinuclear palladium-azido complexes containing thiophene derivatives: reactivity toward organic isocyanides and isothiocyanates

Cyclopalladated tetranuclear Pd(II) complexes, [Pd2(micro-Cl)2(Y)]2 (Y = L1 or L2; H2L1 = di(2-pyridyl)-2,2'-bithiophene; H2L2 = 5,5'-di(2-pyridyl)-2,2':5',2'-terthiophene), containing two pyridyl-alpha, alpha'-disubstituted derivatives of thiophene were prepared. Treating these products with PR3 and subsequently with NaN3 produced the dinuclear Pd-azido complexes [(PR3)2(N3)Pd-Y-Pd(N3)(PR3)2] (Y = L1 or L2) or a cyclometallated complex [(PR3)(N3)Pd-Y'-Pd(N3)(PR3)] (Y' = C,N-L2). Reactions of these Pd-azido complexes with CN-Ar (Ar = 2,6-Me(2)C(6)H(3), 2,6-i-Pr(2)C(6)H(3)) or R-NCS (R = i-Pr, Et, allyl) led to the complexes containing end-on carbodiimido groups [(PMe3)2(N[double bond]C[double bond]N-Ar)Pd-Y-Pd(N[double bond]C[double bond]N-Ar)(PMe3)2] or S-coordinated tetrazole-thiolato groups {(PMe3)2[CN4(R)]S-Pd-Y-Pd-S[CN4)(R)](PMe3)2}. Interestingly, when treated with elemental sulfur, the carbodiimido complexes transformed into the cyclometallated derivatives, [(PMe3)(N[double bond]C[double bond]N-Ar)Pd-Y'-Pd(N[double bond]C[double bond]N-Ar)(PMe3)] (Y' = C,N-L1, C,N-L2). We also report the preparation of linear, thienylene-bridged dinuclear Pd complexes [L2(N3)Pd-X(or X')-Pd(N3)L2] (L = PMe3 or PMe2Ph; H2X = 2,2'-bithiophene or H2X' = 2,2':5',2'-terthiophene) and their reactivity toward organic isocyanide and isothiocyanates.     

Direct comparison of the magnetic and electronic properties of samarocene and ytterbocene terpyridine complexes

A new complex, Cp* 2Sm(tpy) ( 1, where Cp* = C 5Me 5, tpy = 2,2':6',2'-terpyridine) and its one-electron oxidized congener [Cp* 2Sm(tpy)]PF 6 ([ 1] (+)) have been synthesized and characterized with the aim of comparing their electronic and magnetic behavior to the known ytterbium analogues: Cp* 2Yb(tpy) ( 2) and [Cp* 2Yb(tpy)]OTf ([ 2] ( + )). These new samarium complexes have been characterized using single-crystal X-ray diffraction, (1)H NMR spectroscopy, cyclic voltammetry, optical spectroscopy, and bulk magnetic susceptibility measurements. All data for 1 indicate a Sm(III)-tpy* (-)[(4f) (5)-(pi*) (1)] ground-state electronic configuration similar to that found previously for 2 [(4f) (13)-(pi*) (1)]. Structural comparisons reveal that there are no significant changes in the overall geometries associated with the neutral and cationic samarium and ytterbium congeners aside from those anticipated based upon the lanthanide contraction. The redox potentials for the divalent Cp* 2Ln(THF) n precursors ( E 1/2(Sm (2+)) = -2.12 V, E 1/2(Yb (2+)) = -1.48 V) are consistent with established trends, the redox potentials (metal-based reduction and ligand-based oxidation) for 1 are nearly identical to those for 2. The correlation in the optical spectra of 1 and 2 is excellent, as expected for this ligand-radical based electronic structural assignment, but there does appear to be a red-shift ( approximately 400 cm (-1)) in all of the bands of 1 relative to those of 2 that suggests a slightly greater stabilization of the pi* level(s) in the samarium(III) complex compared to that in the ytterbium(III) complex. Similar spectroscopic overlap is observed for the monocationic complexes [ 1] (+) and [ 2] (+). Bulk magnetic susceptibility measurements for 1 reveal significantly different behavior than that of 2 due to differences in the electronic-state structure of the two metal ions. The implications of these differences in magnetic behavior are discussed.     

Low-coordinate transition-metal complexes of a carbon-substituted hemiporphyrazine

The metallation of the core-modified phthalocyanine analogue dicarbahemiporphyrazine with manganese, iron, and cobalt results in the formation of low-coordinate metal(II) complexes. All three compounds are produced by the reaction of metal carbonyls with the free base macrocycle. As in many other carbaporphyrinoids, the internal C-H bonds remain intact upon metallation, resulting in the formation of two long-range agostic-type interactions. Each metal can thus be considered as a three-coordinate ion, where two inner isoindolene nitrogens and a single axial pyridine are bound to the metal. The manganese and cobalt complexes, Mn(dchp)py and Co(dchp)py, are nearly isostructural, but the iron complex, Fe(dchpH2)py, exhibits a reduction at an iminic double bond upon metallation.     

Synthesis of conjugated polymers with pendant ruthenium terpyridine trithiocyanato complexes and their applications in heterojunction photovoltaic cells

Two conjugated polymers based on poly(phenylenethiophene) and poly (fluorenethiophene) main chain functionalized with pendant trithiocyanato ruthenium terpyridine complexes were synthesized by the Suzuki coupling reaction. The ruthenium complexes can extend the absorption band to longer wavelength and enhance the photosensitivity in this region. The polymers exhibit very broad absorption band spanning from 400 to 750 nm due to the presence of π‐conjugated system and the ruthenium complexes. Such enhancement in optical absorption enables the utilization of solar light in the near IR region. By space charge limited current modeling, the hole carrier mobilities of the polymers were calculated to be in the order of 10^?4 cm² V^?1 s^?1, which greatly facilitate the transport of charges after the separation of excitons. Heterojunction photovoltaic cells with simple structure ITO/polymer/C₆₀/Al were fabricated. Under simulated AM1.5 solar light illumination, the short circuit currents, open circuit voltages, and power conversion efficiencies of the photovoltaic cells were measured to be 1.53–2.58 mA cm^?2, 0.12–0.24 V, and 0.084–0.12%, respectively. Deposition of PEDOT:PSS on ITO surface did not show significant difference in device performance. Plot of incident photon to charge efficiency as the function of wavelength suggests that absorption by both conjugated main chain and ruthenium complex are essential to the photocurrent generation. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1305–1317, 2008     

Dinuclear titanium complexes with methylphenylsilylene bridge between cyclopentadienyl rings. Synthesis, characterization and reactivity towards ethylene

The new ansa-titanocene dichloride [{(SiMePh)(η⁵-C₅H₄)₂}TiCl₂] (1) was prepared by one pot reaction, whereas synthesis of its methylated analogue [{(SiMePh)(η⁵-C₅Me₄)₂}TiCl₂] (3) was performed in two steps with isolation of corresponding silane intermediate SiMePh(HC₅Me₄)₂ (2). The reaction of 1 and 3 with TiCl₄ afforded the dinuclear complexes [(SiMePh){(η⁵-C₅R₄)TiCl₃}₂] (R = H (4) and R = Me (5)). The catalysts formed from 4 and 5 after their activation with excess MAO exhibited a modest activity in ethylene polymerization. The polymer products consisted of high molar mass linear polyethylenes with a broad molar mass distribution. The presence of three paramagnetic titanium species in the mixture 4/MAO was revealed by EPR spectroscopy. All new prepared compounds 1-5 were characterized by multinuclear NMR, EI-MS, IR, and solid-state structures of 1, 3 and 5 were determined by X-ray single crystal diffraction.     

Heterodinuclear transition-metal complexes with multiple metal-metal bonds

Interactions between a pair of transition-metals can range from weak antiferromagnetic coupling to bonds of the highest multiplicity known in chemistry, for example, quadruple in isolatable compounds. Tremendous effort has been invested in studying homodinuclear transition-metal-metal bonds. In contrast, relatively little attention has been devoted to heterodinuclear analogues, as it is substantially more challenging to prepare and handle such entities. Yet, in this largely unexplored area of transition-metal chemistry, novel chemical interactions with unprecedented reactivities are likely to be found. Heterodinuclear analogues of diatomic transition-metal dimers being yet inaccessible, dinuclear complexes with Werner-type ligands provide examples of high-multiplicity bonds between different d elements in their least-perturbed form. Such compounds provide an opportunity to probe fundamental issues of chemical bonding between transition-metals, by revealing how and to what extent such bonds are affected by differences in the two metals. Complexes wherein electronically unsaturated heterodinuclear cores are stabilized by pi-acidic ligands (such as CO) hold the potential of new chemical reactions (including catalytic) that capitalize on the synergetic effect of two transition-metal centers.     

Oligothiophene isocyanides for platinum-based molecular electronic applications

Understanding molecular orientation on a metal surface is key to designing molecular electronic device junctions. Though platinum device electrodes are of particular interest as a more stable alternative to the often used gold electrodes, the chemisorption of conducting molecules onto platinum surfaces has not been thoroughly studied. We present herein the first detailed study of the ability and manner in which soluble oligothiophene isocyanides, of lengths ranging from 2 to 7 nm, chemisorb onto platinum surfaces and nanoparticles. It was found that these oligothiophene isocyanides stand at a 41 degrees angle from the platinum surface normal, suggesting their applicability in molecule-bridged platinum electrode devices.     

Studies directed toward the synthesis of chiral tungsten and molybdenum carbonyl complexes

A major challenge that must be met for an asymmetric intermolecular Pauson-Khand reaction is to be able to limit the possible positions on the metal complex for the organic partners. Toward this end, the synthesis of monometallic systems derived from M(CO)₆ and two bidentate ligands, in which the number of possible coordination sites is reduced to two, has been investigated.