Open-shell transition-metal complexe

This article is an attempt to review possibilities in a quantum chemical treatment of open-shell systems. In order to cut down the extent of this review, we disregard some problems, especially those concerning macromolecules, polymerization reactions, and open-shell transition-metal complexes. Electron spin resonance is mentioned only briefly, because it has been a topic of many reviews. 

We present three new developments that we compare critically against experimental data - LFDFT [3, 4, 36, 40], SORCI [7] and TDDFT for spin-open-shell transition-metal complexes [14],... 

Chemical Bonding in Open-Shell Transition-Metal Complexes... 

I 8 Chemical Bonding in Open-Shell Transition-Metal Complexes terms of p(rj rj) only,... 

As an example of an open-shell transition-metal complex we discussed some of the pitfalls of present-day DFT and CASSCF calculations in determining accurate spin density distributions in open-shell transition-metal complexes. An accurate description of the spin density and of the electronic structure is mandatory for a subsequent qualitative analysis of the chemical bonding. This could only be accomplished by employing the DMRG algorithm to produce an accurate CASCI-type electronic wave function. 

It can thus be anticipated that theoretical research into the description of open-shell molecules, and especially into open-shell Transition-metal complexes and clusters, will continue to be important and successful in the future. 

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