Hydrocondensation of CO2

New bis(diphenylphosphino) methane, (dpm) complexes of palladium have been prepared from PdCl₂dpm, either by borohydride reduction or halide abstraction in the presence of added ligand. The catalytic activities of these and other polynuclear palladium and copper complexes in the CO₂/H₂ reaction have been tested. The result confirm the catalytic formation of alkyl formate and dialkyl formamide, but the juxtaposition of two or more metal centres does not appear to promote the catalytic formation of C₂-compounds (oxalate)     

Extended Fe₄ butterfly complexes: theoretical analysis of magnetic properties and magnetostructural maps

The inclusion of additional metal atoms in Fe? butterfly complexes drastically modifies their magnetic properties. Exchange interactions of a Fe?Y? complex have been calculated using theoretical methods based on density functional theory. The calculated values are in good agreement with experimental data showing that the change in the nature of bridging ligands induces a dramatic decrease of the antiferromagnetic wing-body interaction while the body-body interaction between the two central iron atoms is ferromagnetic. Finally, we propose a new tool to facilitate the understanding of the magnetic properties in polynuclear iron complexes. Magnetostructural maps allow us to correlate the calculated exchange coupling constants with metal-metal distances for the dinuclear or polynuclear iron complexes that we have studied.     

Direct metal-metal interaction contributions to quadratic hyperpolarizability: a study on dirhenium complexes

We present a comparative study of the metal-metal interaction effect on the static quadratic hyperpolarizabilities of two typical dinuclear rhenium clusters. The electronic structures, excitation spectra, dipolar moments, static polarizabilities, and quadratic hyperpolarizabilities of the two complexes with direct metal-metal interactions have been computed and analyzed with the use of high-level DFT/TDDFT methods. The geometries and the first intense excitations agree with the relevant reported measurements. The orbital decomposition scheme ( J. Phys. Chem. A 2006, 110, 1014-1021) has been applied to analyze the relationship between the electronic structures and nonlinear optical (NLO) properties of these two complexes. We propose an unprecedented NLO response mechanism featuring the contribution of the direct metal-metal interaction transition process in these dinuclear rhenium complexes. This contribution positively enhances the quadratic hyperpolarizability and relates to the intensity of the metal-metal interactions of the complexes. The results are helpful to the development of NLO chromophores in polynuclear metal clusters through the molecular design technique.     

Molecular Design of Luminescent Metal-Based Materials

Polynuclear transition metal complexes have been shown to exhibit rich luminescence behavior. The recent reports on the potential applications of alkynyl metal complexes as nonlinear optical materials, molecular wires and rigid-rod materials, and the wide variety of possible bonding modes of the alkynyl moiety have aroused our interest in investigating their potential in the design and synthesis of di- and polynuclear metal complexes. In this presentation, the design and successful isolation of a series of soluble di- and polynuclear transition metal acetylides with rich luminescence behavior will be described11,21.     

Triazoles and tetrazoles: Prime ligands to generate remarkable coordination materials

The current great interest in preparing functional metal-organic materials is inevitably associated with tremendous research efforts dedicated to the design and synthesis of new families of sophisticated multi-nucleating ligands. In this context, the N-donor triazole and tetrazole rings represent two categories of ligands that are increasingly used, most likely as the result of the recent dramatic development of “click chemistry” and Zeolitic Imidazolate Frameworks (ZIFs). Thus, azole-based complexes have found numerous applications in coordination chemistry.In the present review, we focus on the utilization of 1,2,3-triazole, 1,2,4-triazole and tetrazole ligands to create coordination polymers, metal complexes and spin-crossover compounds, reported to the end of 2009. In the first instance, we present a compendium of all the relevant ligands that have been employed to generate coordination polymers and Metal-Organic Frameworks (MOFs). Due to the huge amount of reported MOFs and coordination polymers bearing these azole rings, three representative examples for each category (therefore nine in total) are described in detail. The second section is devoted to the use of the bridging abilities of these azole ligands to prepare metal complexes (containing at least two metal centers). Given the large number and the great structural diversity of the polynuclear compounds found in the literature, these have been grouped according to their nuclearity. Finally, in the last section, the triazole- and tetrazole-containing coordination compounds exhibiting spin-crossover properties are presented.     

The Active Sites in Manganese-Containing Metalloproteins and Inorganic Model Complexes

Manganese is an essential trace element, forming the active sites of a number of metalloproteins. Several metalloproteins contain two or more manganese ions per subunit. The structural properties of these enzymes and the experimental evidence for their proposed structures are described. Parallel to the efforts of biochemists, who are seeking to understand the function of these enzymes on a molecular level, inorganic chemists have been investigating the coordination chemistry of bi- and polynuclear complexes of manganese which contain O, N donor atoms and a variety of bridging O, N ligands. A large number of such complexes have been synthesized, their X-ray structures determined and their magnetic and spectroscopic properties studied in detail. In some instances the electronic and spectroscopic properties of these model compounds are amazingly similar to those of the biomolecules. This has led to a deeper understanding of the structure and sometimes of the function of the metalloproteins. Research on manganese metalloproteins with polynuclear active sites represents a fascinating example of interdisciplinary cooperation between physicists, biochemists and inorganic chemists.     

p‐tert‐Butylcalix[8]arene: An Extremely Versatile Platform for Cluster Formation

p‐tert‐Butylcalix[4]arene is a bowl‐shaped molecule capable of forming a range of polynuclear metal clusters under different experimental conditions. p‐tert‐Butylcalix[8]arene (TBC[8]) is a significantly more flexible analogue that has previously been shown to form mono‐ and binuclear lanthanide (Ln) metal complexes. The latter (cluster) motif is commonly observed and involves the calixarene adopting a near double‐cone conformation, features of which suggested that it may be exploited as a type of assembly node in the formation of larger polynuclear lanthanide clusters. Variation in the experimental conditions employed for this system provides access to Ln₁, Ln₂, Ln₄, Ln₅, Ln₆, Ln₇ and Ln₈ complexes, with all polymetallic clusters containing the common binuclear lanthanide fragment. Closer inspection of the structures of the polymetallic clusters reveals that all but one (Ln₈) are in fact based on metal octahedra or the building blocks of octahedra, with the identity and size of the final product dependent upon the basicity of the solution and the deprotonation level of the TBC[8] ligand. This demonstrates both the versatility of the ligand towards incorporation of additional metal centres, and the associated implications for tailoring the magnetic properties of the resulting assemblies in which lanthanide centres may be interchanged.     

Metal ion selectivity of oligopeptides

Metal binding affinity and selectivity of peptides are reviewed with a special emphasis on the high structural variety of peptide complexes. The most common structural type of these complexes is built up by the deprotonation and metal ion coordination of subsequent amide groups in the form of fused five-membered chelate rings. The metal ion selectivity of this process and the role of various anchoring groups are discussed in detail. The highest metal binding affinity of peptides is connected to the presence of two anchoring groups in appropriate location (the "double anchor"): e.g. the NH2-Xaa-Xaa-His/Cys/Asp/Met-Xaa sequence. Among the side chain donor functions, the imidazole of histidyl and thiolate of cysteinyl residues are the most effective ligating groups and their involvement in metal binding results in a great variety of different macrochelate or loop structures and/or formation of various polynuclear complexes. Examples of these structural motifs and their possible applications have been thoroughly discussed.     

Methods for the Synthesis of μ-Hydrocarbon Transition Metal Complexes without Metal–Metal Bonds

Transition metal complexes in which hydrocarbons serve as σ,σ-, σ,π- or π,π-bound bridging ligands are currently of great interest. This review presents efficient and directed syntheses for such compounds, which often have very aesthetic structures. These reactions are among the most important reaction types in modern organometallic chemistry. They can be a useful aid for the synthesis of tailor-made compounds, for example, for models of catalytic processes and, specifically, for the construction of heterometallic compounds. We will discuss reactions of electrophilic complexes with nucleophilic ones, numerous transformations of (functionalized) hydrocarbons with metal complexes, the currently very topical complexes with bridging acetylide and carbide ligands, and organometallic polymers, which can be expected to have interesting and novel materials properties. Chisholm

1 M. H. Chisholm, Polyhedron 1988 , 7, 757–1077.

has described the importance of these complexes as follows: “Central to the development of polynuclear and cluster chemistry are bridging ligands and central to organometallic chemistry are metal–carbon bonds. Thus bridging ligands hold a pivotal role ins the development of Binuclear and polynuclear organometallic chemistry”.     

Trapping and manipulating excited spin states of transition metal compounds

This tutorial review describes how complexes of iron(II) (and, rarely, other metal ions) can be switched between their high- and low-spin states by different physical stimuli. At low temperatures, it is possible to trap a compound in a metastable excited spin-state which, in favourable cases, may be stable to thermal relaxation below temperatures as high as 130 K. The selective switching and trapping of individual spin centres in polynuclear compounds, and the interplay between spin centres as they relax back to their ground states, are also discussed. Similar phenomena, in which spin transitions are coupled to charge transfer phenomena, can also occur in inorganic and metal-organic cyanometallate compounds and in cobalt-semiquinonate complexes.     

Metal-directed assembly of coordination oligomers

Bridging ligands containing two spatially separated 2,2′:6′,2′-terpyridinyl metal-binding domains have been prepared and used for the controlled assembly of coordination oligomers incorporating ruthenium(II) and other metal ions. Two such bridging ligands have been structurally characterised. The systematic synthesis of a range of homo- and heterometallic polynuclear complexes incorporating these bridging ligands and a variety of terminator 2,2′:6′,2′- terpyridines is described.     

Electronic energy transfer and collection in luminescent molecular rods containing ruthenium(II) and osmium(II) 2,2':6',2"-terpyridine complexes linked by thiophene-2,5-diyl spacers

The electronic absorption spectra, luminescence spectra and lifetimes (in MeCN at room temperature and in frozen n-C3H7CN at 77 K), and electrochemical potentials (in MeCN) of the novel dinuclear [(tpy)Ru(3)Os(tpy)]4+ and trinuclear [(tpy)Ru(3)Os(3)Ru(tpy)]6- complexes (3 = 2,5-bis(2,2':6',2'-terpyridin-4-yl)thiophene) have been obtained and are compared with those of model mononuclear complexes and homometallic [(tpy)Ru(3)Ru(tpy)]4+, [(tpy)Os(3)Os(tpy)]4+ and [(tpy)Ru(3)Ru(3)Ru(tpy)]6+ Complexes. The bridging ligand 3 is nearly planar in the complexes, as seen from a preliminary X-ray determination of [(tpy)Ru(3)Ru(tpy)][PF6]4, and confers a high degree of rigidity upon the polynuclear species. The trinuclear species are rod-shaped with a distance of about 3 nm between the terminal metal centres. For the polynuclear complexes, the spectroscopic and electrochemical data are in accord with a significant intermetal interaction. All of the complexes are luminescent (phi in the range 10(-4)-10(-2) and tau in the range 6-340 ns, at room temperature), and ruthenium- or osmium-based luminescence properties can be identified. Due to the excited state properties of the various components and to the geometric and electronic properties of the bridge, Ru --> Os directional transfer of excitation energy takes place in the complexes [(tpy)Ru(3)Os(tpy)]4+ (end-to-end) and [(tpy)Ru(3)Os(3)Ru(tpy)]6+ (periphery-to-centre). With respect to the homometallic case, for [(tpy)Ru(3)Os(3)Ru(tpy)]6+ excitation trapping at the central position is accompanied by a fivefold enhancement of luminescence intensity.     

The synthesis of diene and of vinyl copolymers containing predetermined quantities of polynuclear hydrocarbon or heterocyclic adducts—I. The formation and stability toward tetrahydrofuran of alkali metal salts of polynuclear hydrocarbons

The formation and stabilities of complexes formed in THF between various polynuclear hydrocarbons and excess sodium and lithium metal have been studied. Anthracene and acenaphthylene, which possess high electron affinities, form dianions with either metal whilst phenanthrene forms the dianion only with lithium. Both phenanthrene and naphthalene give solely radical ions on reaction with sodium; it is found that the formation of the naphthalene dianion with lithium is inversely dependent on the naphthalene concentration.The radical anions of all four polynuclear hydrocarbons are relatively stable to the THF solvent whereas the dianions react appreciably in a matter of days to form a variety of adducts and derivatives which have been isolated and identified by NMR spectroscopy.     

含5-氯水杨醛Schiff碱配体的镍和铜配合物的合成及晶体结构

合成了2个含三齿Schiff碱配体和单齿N-杂环分子的多核过渡金属配合物:1个含5-氯水杨醛缩对硝基苯甲酰腙(H2L1)和吗啡啉(Mf)的镍髤配合物[Ni(L1)(Mf)](1),1个含5-氯水杨醛缩水杨酰腙(H2L2)和吡啶(Py)的铜髤配合物[Cu2(L2)2(Py)2](2),并通过元素分析、红外光谱、紫外光谱以及单晶衍射等手段进行表征。在配合物1中,中心Ni髤与酰腙配体(L12-)的酚氧、亚胺氮、去质子酰胺氧原子以及中性吗啡啉氮原子配位形成平面四方形的N2O2配位构型,相邻配合物通过分子间氢键作用构筑成一维超分子链状结构。配合物2中含有2个晶体学上独立的双核铜髤配合物,相邻配合物分子的酚氧原子分别桥联2个[Cu(L2)(Py)]基本单元,形成2个含有Cu2(μ-O)2核心的配合物。每个Cu髤原子具有五配位的NONO(O)四角锥配位构型。     

大环多胺及其金属配合物的研究新进展

论述了大环多胺及其金属配合物的合成应用研究进展,阐述了单核,双核及多核大环多胺的类型及其与金属的配合情况,全面地论述了该类化合物的超分子识别及其对核酸的切割作用,并讨论了其在金属配合物的荧光及其发光性能.     

Tetrazoles as ligands,part I. Transition metal(II) salts and complexes of 5-cyanotetrazole

Summary Transition metal(II) ions and 5-cyanotetrazole (CNHT) form two types of compounds; type I with two 5-cyanotetrazolate (CNT) ions and an additional CNHT molecule and type II with only the two [CNT]^– ions. Water molecules are invariable included in all compounds and are considered to be essential for the existence of the crystal structure. The complexes were identified and characterized by chemical analyses, i.r. and ligand field spectra. Some structural features have been predicted from these spectra and a polynuclear complex formation is apparent.     

CD spectra of polynuclear complexes of diimine ligands: theoretical and experimental evidence for the importance of internuclear exciton coupling

We have recently reported on dinuclear complexes Lambda,Lambda-[Co(2)L(2)Cl(2)]CoCl(4) of two novel chiral ligands (1a and 1b) which contain pyridyl-imine chelate groups (Telfer, S. G.; Sato, T.; Kuroda, R. Chem. Commun. 2003, 1064-1065). The absolute configuration of the cobalt(II) centers was unambiguously assigned by X-ray crystallography. However, the sign of the exciton couplets in their CD spectra was opposite to that expected on the basis of the stereochemistry of the metal centers. We present a rationalization of these anomalous spectra in terms of an "internuclear" exciton coupling model which takes into account the coupling of chromophores located on different metal centers. We have performed a series of semiempirical (ZINDO) calculations which provide quantitative support to this model. These findings show that the absolute configuration of the metal centers in a polynuclear complex may be incorrectly assigned on the basis of CD data if internuclear coupling effects are not taken into consideration. We summarize the CD spectral data of number of other chiral polynuclear complexes from the literature, including dinuclear complexes bridged by the 2,2'-bipyrimidine ligand, complexes of the HAT ligand, and dinuclear triple-stranded helicates. The amplitude of the CD spectra of many of these complexes is not additive with the number of chromophores. These anomalous spectra can be accounted for by taking internuclear coupling effects into consideration.     

Phenoxide bridged tetranuclear Co(II), Ni(II), Cu(II) and Zn(II) complexes: electrochemical, magnetic and antimicrobial studies

Phenoxide bridged later first row transition metal(II) complexes have been prepared by the interaction of later 3d transition metal(II) chlorides with tetranucleating compartmental Schiff base ligand system derived from 2,6-diformyl-4-methylphenol, p-phenylenediamine and 2-hydrazinobenzothiazole. Ligand and complexes were characterized by analytical, spectral (IR, UV-visible, ESR, FAB-mass and fluorescence), magnetic and thermal studies. All complexes are found to have octahedral geometry. The mutual influence of metal centres in terms of cooperative effect on the electronic, magnetic, electrochemical and structural properties was investigated. The Schiff base and its complexes have been screened for their antibacterial (against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa) and antifungal activities (against Aspergillus niger, and Candida albicans).     

Designing tridentate ligands for ruthenium(II) complexes with prolonged room temperature luminescence lifetimes

Coordination complexes have been used extensively as the photoactive component of artificial photosynthetic devices. While polynuclear arrays increase the probability of light absorption, the incorporation of the stereogenic Ru(2,2'-bipyridine)(3)(2+) motif gives rise to diastereomeric mixtures whereas the achiral Ru(2,2':6',2"-terpyridine)(2)(2+) motif creates stereopure polynuclear complexes. Thus, polynuclear arrays composed of ruthenium(II) complexes of tridentate ligands are the targets of choice for light-harvesting devices. As Ru(II) complexes of tridentate ligands have short excited state lifetimes at room temperature (r. t.), considerable effort has been focused on trying to increase their r. t. luminescence lifetime for practical applications. This tutorial review will report on the sophisticated synthetic strategies currently in use to enhance the room temperature photophysical properties of Ru(II) complexes of tridentate ligands.