摘要:

The compounds which form in aqueous solutions containing iron(III) and chelating ligands are considered and the control of iron(III) hydrolysis as a synthetic strategy for the preparation of iron(III) species of different nuclearities is explained. The relevance of such complexes to naturally occurring iron species is discussed. Hydroxide, oxide, carboxylate and alkoxide bridged iron(III) aggregates are compared to iron(III) clusters in Nature with particular attention paid to the way in which their formation can aid in understanding the biomineralization of iron. The structures of trapped mineralized iron(III) oxyhydroxide clusters are proposed as good models for the iron storage protein ferritin, which itself is best regarded as a cluster species. Synthetic strategies for producing clusters of different shapes and sizes are suggested.

ISSN:0260-3594    

DOI:10.1080/02603599408035845

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Heterogeneous photocatalysis occurs over semiconductor particulates irradiated with light of proper wavelengths, which generates charge carriers (electrons and holes). These e /h+pairs are ultimately positioned at the particle surface to undergo a variety of events (recombination, trapping) in competition with other processes (redox chemistry). These charge carriers may be implicated in photocatalytic transformations of inorganic anions (cyanides, sulfides) and reduction of precious and/or toxic metals. When organic compounds are present in aerated suspensions, the photocatalytic oxidation leads to total mineralization to carbon dioxide and inorganic anions (for example, chloride from chlorinated organics). The present Comment focuses on the fundamental and primary events occurring in the heterogeneous photocatalysis on semiconductor metal oxides, with particular reference to TiO2and reports on the mechanism of some redox transformations concerning inorganic and organic species. Actual research on photocatalytic materials and on solar detoxification is outlined.

ISSN:0260-3594    

DOI:10.1080/02603599408035846

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Rapid growth in the range of polydentate ligands prepared in recent decades has produced firstly macromonocyclic systems and subsequently macropolycyclic encapsulating ligands. Intermediate between these can be identified a set of topologically distinctive ligands whose collective grouping is based on their capacity to satisfy fully the coordination demands of metals ions and bind sets of three adjacent donors to polyhedral faces. This family of ligands offer pseudo-encapsulation of metal ions; whereas a macrobicycle may act as a “cage” or “prison” for a metal ion by trapping it in the cavity, the ligands described here present themselves as “open prisons” because of their less complete framework. The concept and types of pseudo-encapsulating ligands extant is examined here for saturated hexaamines which act as sexidentate ligands and commonly form octahedral complexes. Examples of the various topologies assigned as pseudo-encapsulating hexaamine ligands are described. In particular, the differing shape-directed coordination chemistry ofsyn− andanti−diammac (6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6,13-diamine) is examined in some detail. The latter isomer is a sterically efficient ligand which forms complexes with “compressed” coordination spheres and extreme physical properties, whereas the former isomer displays no such effects.

ISSN:0260-3594    

DOI:10.1080/02603599408035847

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Cyclopentadienylcobalt fragments [CpCo] are used as the building blocks of oligonuclear complexes with hydrocarbons as bridging ligands. The main reaction routes are addition of several [CpCo] to an unsaturated hydrocarbon ligand, often resulting in an unusual coordination mode of the latter, and CH-activation. The range of addition products includes dinuclear complexes of hexatriene, cycloheptatriene and alkenylbenzenes as well as cluster complexes with face capping arene ligands. The more important products from CH-activation are CpCo-complexes of cobaltafulvenes, dinuclear cycloheptatrienyl bridged heterobimetallic hydrido complexes and cluster complexes with face capping alkylidyne or alkyne ligands.

ISSN:0260-3594    

DOI:10.1080/02603599408035848

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0260-3594    

DOI:10.1080/02603599408035844

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor