Coordination chemistry, computer representation

To conclude this section, it could be helpful to make a connection between the pictorial discussion we have just given and the type of computation that one can carry out in quantum chemistry. The double cone topology shown in Figure 9.3 can be represented mathematically by Eqs 9.3a and 9.3b. Qx, Qx, are the branching space coordinates. This equation is valid close to the apex of the cone. (A full discussion of the analytical representation of conical intersections can be found in references 9 and 10.)... 

The first task of chemoinformatics is to transform chemical knowledge, such as molecular structures and chemical reactions, into computer-legible digital information. The digital representations of chemical information are the foundation for all chemoin-formatic manipulations in computer. There are many file formats for molecular information to be imported into and exported from computer. Some formats contain more information than others. Usually, intended applications will dictate which format is more suitable. For example, in a quantum chemistry calculation the molecular input file usually includes atomic symbols with three-dimensional (3D) atomic coordinates as the atomic positions, while a molecular dynamics simulation needs, in addition, atom types, bond status, and other relevant information for defining a force field. 

Meanwhile, cation - crown complexes were fully optimized by ab initio QM techniques in the gas phase, allowing to investigate the effect of electronic reorganization (mainly charge transfer + polarization effects) on the recognition properties/15,161 QM/MM hybrid methods which combine a QM representation of the ion coordination sphere with a MM representation of the more remote species, have been tested on 18C6/ cation complexes/17, 18] Typical applications of "computational approaches in supramolecular chemistry" up to 1994 can be found in ref. [191 There are also reviews on more specialized fields like calixarenes/20,21]... 

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