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In view of a renewed interest in the structural chemistry of organic derivatives of antimony(V) during the last decade, a brief account of the same is presented highlighting points of special importance and future growth. Attention is focussed on the structural and bonding aspects. Details about their synthesis are only included when they are applicable in general. [ABSTRACT FROM AUTHOR]

The available models and experimental results used in the description of magnetic order phenomena have been recently summarized in several papers. Among the materials showing low-dimensional magnetism, fluorides are of great interest as they provide examples for most of the different theoretical models. This article emphasizes the relationships between crystallographic features and dimensionality of the magnetic interactions in fluorides. The involved compounds are characterized by rings, chains, layers and three-dimensional arrangements of fluorinated MF6 octahedra. Spin-flop and zero-point spin-reduction phenomena are also considered, as many fluorides exhibit these behaviors. [ABSTRACT FROM AUTHOR]

The spectral and magnetic properties of simple high spin cobalt(II) complexes are reviewed with the aim of showing how it is possible to relate the experimental data to the electronic structure and the coordination geometry of the complexes. It is hoped that this may be of help to all researchers who need to characterize cobalt(II) complexes or use cobalt(II) as a spectroscopic probe. The data relative to electronic, EPR, MCD, NMR spectra as well as to magnetic susceptibility measurements are interpreted within an Angular Overlap approach. Energy level diagrams are employed to calculate the electronic spectra and then, applying the relevant perturbation μ, g, A values are calculated for different chromophores in different coordination environments. The underlying theory is sketched paying in every case much attention to show the possibility of calculating the electronic properties in low symmetry environments. An extensive compilation of available experimental data is presented. The chromophores are classified according to the coordination number and according to the donor atom set. [ABSTRACT FROM AUTHOR]

An account of the quantum theory of the molecular hypothesis for chemical substances is presented, and is used as a basis for a critical discussion of the theory of natural optical activity. Atoms and molecules are characterized as composite elementary excitations (or quasi-particles) of the macroscopic quantum-mechanical system we call matter, and the spontaneously broken space inversion symmetry revealed by the existence of optical isomerism is studied in this context. Special attention is paid to the representation of the space-inversion operator {ie1-1}. Finally a variety of microscopic quantum theories of natural optical activity are critically reviewed. [ABSTRACT FROM AUTHOR]

The present article reviews the photochemical deactivation modes and properties of electronically excited metallotetrapyrroles. Of the wide variety of complexes possessing a tetrapyrrole ligand and their highly structured systems, the subject of this survey is mainly synthetic complexes of porphyrins, chlorins, corrins, phthalocyanines, and naphthalocyanines. All known types of photochemical reactions of excited metallotetrapyrroles are classified. As criteria for the classification, both the nature of the primary photochemical step and the net overall chemical change, are taken. Each of the classes is exemplified by several recent results, and discussed. The data on exciplex and excimer formation processes involving excited metallotetrapyrroles are included. Various branches of practical utilization of the photochemical and photophysical properties of tetrapyrrole complexes are shown. Motives for further development and perspectives in photochemistry of metallotetrapyrroles are evaluated. [ABSTRACT FROM AUTHOR]

Several tetrapyrroles are employed by Nature to carry out fundamental biological functions and synthetic models compounds have been extensively used in order to understand the mechanisms of action of natural systems. One of the structures present in many enzymes is the corrinoid structure. It consists of a tetrapyrrolic macrocycle, where a direct link between two pyrrole rings exists. Such a direct link and the different degrees of unsaturation that can be introduced into the macrocycle modulate its chelating properties towards metal ions and its reactivity. A most interesting example of the corrinoid structure is corrole, a macrocycle where an 18 electron aromatic π system analogous to that of a porphyrin is maintained. Corrole has been shown to be a versatile ligand capable of coordinating transition and main group metals without significant distortion of the macrocycle plane. The present article reviews the developments of the chemistry of corrole and its metal complexes considering the synthetic procedures that can be followed in order to prepare such compounds, their spectroscopic characterization and redox reactivity and demonstrates the peculiar ligand field effect of this macrocycle. The chemistry of other synthetic corrinoids is also reviewed with special attention to their preparation procedures and axial ligand binding reactions. [ABSTRACT FROM AUTHOR]

The noble metals ruthenium, osmium, rhodium, iridium, palladium, platinum, silver, and gold form a variety of complexes M(P) LL′ with tetrapyrrole ligands which are studied in many laboratories because their coordination chemistry and catalytic power is similar to that of the corresponding iron and cobalt tetrapyrroles forming the prosthetic groups in heme proteins and vitamin B12. Apart from the corrins and corroles which are treated in the second article of this volume, the main interest is devoted to noble metal complexes of porphyrins, but complexes of hydroporphyrins, porphyrin analogs, homologs, porphyrinoids, and phthalocyanines are also mentioned where appropriate. The treatise is organized into four main topics: metal insertion ("equatorial coordination chemistry", Sect. 2, formation of the M(P) entity), substitution and redox reactions ("axial coordination chemistry", Sect. 3, exchange of axial ligands L and L′), organometallic chemistry (a special case of axial coordination chemistry, Sect. 4), and notes on current special chemical topics like electrochemistry, catalysis, supramolecular chemistry, and biological applications. Where possible, the material is compressed in schemes and tables giving a synopsis of consecutive reactions of Ru/Os and Rh/Ir dyads. The two other dyads, Pd/Pt and Ag/Au, are so strongly governed by the square planar d8 configuration that they are practically devoid of axial coordination chemistry. The redox reactions of the Ru/Os dyad live on the switches between d6-d5 and d6-d4-d2 configurations mostly with octahedral geometry about the metal, those of the Rh/Ir dyad on the switches between the d6-d7-d8 configurations, giving rise to octahedral, square-pyramidal, and square planar geometries. The occurrence of the dinuclear or mononuclear Rh d7 systems give a special touch of radical chemistry to the organometallic chemistry of rhodium porphyrins which is expected to be fruitful to organometallic chemistry as a whole. Although a broad overview was intended, many entries are just given in keywords or tables in order to give the reader a chance to get more information. Nevertheless, out of nearly 500 papers scrutinized, only nearly 400 references appear in order to keep the volume and the writing time within certain limits, and any research group missing a paper in this review is asked for patience with the authors. [ABSTRACT FROM AUTHOR]