Covalent interactions, semi-empirical

TOWARDS AN ACCURATE SEMI-EMPIRICAL MOLECULAR ORBITAL TREATMENT OF COVALENT AND NON-COVALENT BIOLOGICAL INTERACTIONS... 

There has been considerable recent activity developing appropriate parameters to allow semi-empirical methods to describe a variety of biologically important systems, and their related properties, such as (i) enzyme reactivity, including both over- and through-barrier processes, (ii) conformations of flexible molecules such as carbohydrates, (iii) reactivity of metalloenzymes and (iv) the prediction of non-covalent interactions by addition of an empirical dispersive correction. In this review, we first outline our developing parameterisation strategy and then discuss progress that has been made in the areas outlined above. 

Of greater interest and complexity are the spectra of the more covalent" acetylacetonate complexes. Especially interesting are the complexes of transition metal ions having partially filled d orbitals which can interact with appropriate ligand orbitals as well as give rise to various charge-transfer transitions. Several semi-empirical theoretical analyses coupled with experimental observations have provided a reasonable framework within which to understand the spectral properties of metal acetylacetonates. 

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