Entatic state theory

According to the induced rack and the entatic state theories, the Cu(II) coordination sphere in the blue copper proteins is strained into a Cu(I)-like structure. Such hypotheses are hard to test experimentally, but with theoretical methods it is quite straightforward. The actual coordination preferences of the copper ion can be determined by optimizing the geometry of the ion and its ligands in vacuum if the optimized structure is almost the same as in the proteins, strain is most probably of minor importance for the geometry. 

R 22 J. Autschbach and T. Ziegler, Double Perturbation Theory A Powerful Tool in Computational Coordination Chemistry , p. 83 R 23 I.P. Georgakaki, L.M. Thomson, EJ. Lyon, M.B. Hall and M.Y. Darens-bourg, Fundamental Properties of Small Molecule Models of Fe-Only Hydrogenase Computations Relative to the Definition of an Entatic State in the Active Site , p. 238 Vol. 243, 2003... 

Much of the work on solvation effects has concentrated on modeling the shift of the centre of an electronic absorption or emission band that occurs on solvation, i.e.. the solvatochromic shift. According to the Franck-Condon principle the centre of such a band corresponds to the vertical excitation energy (from an initial to final electronic state) at a fixed nuclear geometry. Solvation of a chromophore thus implies that while the system in its initial electronic state is in equilibrium with its environment, it is not so in its vertically excited state. On excitation of the solute the electronic polarization of the solvent is assumed to relax instantaneously while the ori-entational/distortional polarization is thought of as remaining frozen, a view which may be somewhat simplistic. Within the reaction-field model application of the above theory to a solvated dipole results in a solvent shift of... 

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