Transition metal systems, electronic structure examination

There are in general three common ways used today to go about examining the electronic structure of transition metal systems. All of these are concerned in one way or another in solving (or getting around) the correlation problem and we will give an overview of all three, underlining their respective strengths and weaknesses "standard" ab initio techniques (the surest and often... 

Several recent studies examined photoinduced ET in dyads featuring transition metal chromophores that are dissimilar to the d6 transition metal polypyridine complexes used in the type 1 and type 2 dyads that have been discussed in the preceding sections. Since the molecular and electronic structure of the excited states involved in these systems is unique from the type 1 and type 2 dyads, results on these systems are discussed separately. 

Transition metal oxides are the systems which make a challenge to any quantum chemical theory. Thus their theoretical investigation constitute an excellent benchmark for Density Functional Theory in both aspects methodological and practical one. Two transition metal oxide molecules are considered here in detail, VO and MoO, with emphasis put on their electronic structure, spectroscopic properties and metal - oxygen bonding features. Applicability of DFT to various electronic states is discussed and the quality of results within various computational schemes is examined. 

From the experimentally determined paramagnetic susceptibility, one can calculate the magnetic moments of the transition metal ions in the system. If the magnetic moment is known, it is simple to calculate the number of unpaired electrons. This throws light on the oxidation number of the metal ion being examined or the central atom of the complex, and also on its low- or high-spin electronic structure. Further, if the number of unpaired electrons in the complex is known, the value of the orbital momentum contribution can be calculated in certain cases this permits conclusions to be drawn about the symmetry of the complex (solvate) (see, e.g., ref. [Bu 73]). 

Metal oxides belong to a class of widely used catalysts. They exhibit acidic or basic properties, which make them appropriate systems to be used as supports for highly dispersed metal catalysts or as precursors of a metal phase or sulfide, chloride, etc. Simple metal oxides range from essentially ionic compounds with the electropositive elements to covalent compounds with the nonmetals. However, taking into account the large variety of metal oxides, the principal objective of this book is to examine only metal oxides that are more attractive from the catalytic point of view, and most specifically transition metal oxides (TMO). In particular, TMO usually exhibit nonstoichiometry as a consequence of the presence of defective structures. The interaction of TMO with surfaces of the appropriate carriers develop monolayer structures of these oxides. The crystal and electronic structure, stoichiometry and composition, redox properties, acid-base character and cation valence sates are major ingredients of the chemistry investigated in the first part of the book. New approaches to the preparation of ordered TMO with extended structure of texturally well defined systems are also included. 

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