Metal complexes polynuclear

Magnetic exchange in polynuclear metal complexes. E. Svrin, Coord. Chem. Rev., 1970, 5, 313-347 (230). 

The goal of precise synthesis of supported mononuclear and polynuclear metal complexes can be traced to the early work of Yermakov [1], Ballard [2], and others. Their work stimulated the hvely field referred to as surface organometalhc chemistry [3-6]. The success and importance of precise synthesis of supported molecular catalysts are illustrated by the apphcation of supported metallocene catalysts for industrial alkene polymerization [7j. 

Byers, P.K, Carr, N. and Stone, F.G.A. (1990) Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 106. Synthesis and reactions of the alkylidyne complexes [M ( CR)(CO)2 (C6F5)AuC(pz)3 j (M = W or Mo, R — alkyl or aryl, pz — pyrazol-l-yl) crystal structure of pjC PtAu(C6F5)( l3-CMe)(CO)2(PMe2Ph)2 (C6F5)AuC(pz)3 ]. Journal of the Chemical Society, Dalton Transactions, (12), 3701—3708. 

It has been our goal for some time to run photochemical energy storage reactions without relay molecules or separate catalysts. We have concentrated on the photochemistry of polynuclear metal complexes in homogeneous solutions, because we believe it should be possible to facilitate multielectron transfer processes at the available coordination sites of such cluster species. 

Balzani V., Campagna S., Denti G. and Serroni S. (1992) Supramolecular Photochemistry Antenna Effect in Polynuclear Metal Complexes, in Kochanski E. (Ed.), Photoprocesses in Transition Metal Complexes, Biosystems and Other Molecules. Experiment and Theory, Kluwer Academic Publishers, Dordrecht, p. 233. 

There are many examples today of polynuclear metal complexes yielding a parent ion in the mass spectra, but initially their observation for high molecular weight compounds, such as di[bis(pentafluorophenyl)-phosphidoirontricarbonyl] (I), having a molecular ion of mje 1010 (90) was considered unusual, as were the binuclear chromium complexes (II)... 

The typical approach used to prepare polynuclear metal complexes is the so-called complexes as metals and complexes as ligands strategy, briefly illustrated... 

Figure 7. Divergent synthetic strategy to obtain polynuclear metal complexes of dendrimer shape. - ° Each deprotected compound of the dive ent synthetic approach can be used as a core in convergent synthetic processes. Some of these routes starting from a tetranuclear core are illustrated in Figure 8.

The interest in highly branched polynuclear metal complexes, and more generally in dendritic species, is related not so much to their size, but rather to the presence of different components. An ordered array of different components can in fact generate valuable properties, such as the presence of cavities having different size, surfaces with specific functions, gradients for photoinduced directional energy and electron transfer, and sites for multielectron transfer catalysis. Studies along these directions are underway in our laboratories. 

Synthetic polymers stabilize metal colloids as important catalysts for multi-electron reactions. Polynuclear metal complexes are also efficient catalysts for multielectron processes allowing water photolysis. 

A colloidal polynuclear metal complex was proved to be an effective catalyst for water photolysis in combination with Ru(bpy)3 probably because its capability of multi-electron process. The details are described in the next chapter. 

Polymers play important roles in water photolysis. For multi-electron processes, polymer supported metal colloids or colloidal polynuclear metal complexes are very useful as catalysts. Unstable semiconductors with a small bandgap which photolyse... 

Polymers are attracting much attention as functional materials to construct photochemical solar energy conversion systems. Polymers and molecular assemblies are of great value for a conversion system to realize the necessary one-directional electron flow. Colloids of polymer supported metal and polynuclear metal complex are especially effective as catalysts for water photolysis. Fixation and reduction of N2 or C02 are also attractive in solar energy utilization, although they were not described in this article. If the reduction products such as alcohols, hydrocarbons, and ammonia are to be used as fuels, water should be the electron source for the economical reduction. This is why water photolysis has to be studied first. 

Table 5 Polynuclear Metal Complexes in Photochemical Hydrogen Production from Water...

Luminescence Behavior of Polynuclear Metal Complexes of Copper (I), Silver (I), and Gold (I)... 

Much attention is currently devoted to the synthesis and properties of shape-persistent macrocycles[l]. Such compounds are interesting for a variety of reasons including formation of columnar stacks potentially capable of performing as nanopores for incorporation into membranes or for the generation of nanowires[2]. Furthermore, in shape-persistent macrocycles incorporating coordination units, enc/o-cyclic metal-ion coordination may be exploited to generate nanowires[3], whereas e.ro-cyclic coordination can be used to construct large arrays of polynuclear metal complexes[4]. Shape-persistent macrocycles with reactive substituents may also be linked to other units to yield multicomponent, hierarchical structures. 

Dendritic Polynuclear Metal Complexes with Made-to-Order Luminescent and Redox Properties [G. Denti, S. Campagna, V. Balzani, Chapt. 3, pp. 69-106]. 

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