Inclusion complexation molecular basis

Enantiomeric resolution of solutes that fit within the molecular cavity, which is chiral, results in the formation of an inclusion complex (Ref. 169 and Fig. 4). In general, the enantiomers are separated on the basis of formation constants of the host-guest complexes. The enantiomer that forms the more stable complex has a greater migration time because of this effect. The chiral recognition mechanism for cyclodextrin enantioseparation has been discussed in several works (163-168). 

The inclusion of relativistic effects is essential in quantum chemical studies of molecules containing heavy elements. A full relativistic calculation, i.e. based upon Quantum Electro Dynamics, is only feasible for the smallest systems. In the SCF approximation it involves the solution of the Dirac Fock equation. Due to the four component complex wave functions and the large number of basis functions needed to describe the small component Dirac spinors, these computations are much more demanding than the corresponding non-relativistic ones. This limits Dirac Fock calculations, which can be performed using e.g. the MOLFDIR package [1], to small molecular systems, UFe being a typical example, see e.g. [2]. 

It should be noted that the different structures of amylose and amylopectin confer distinctive properties to these polysaccharides (Table II). The linear nature of amylose is responsible for its ability to form complexes with fatty acids, low-molecular-weight alcohols, and iodine these complexes are called clathrates or helical inclusion compounds. This property is the basis for the separation of amylose from amylopectin when starch is solubilized with alkali or with dimethylsulfoxide, amylose can be precipitated by adding 1-butanol and amylopectin remains in solution. 

These considerations lead to what we call focused models (FM). In these models of complex material systems, the attention is focused on a small part, treated at higher level of accuracy than the remainder. The part treated at a higher level, that we call the main part M, should include all the molecular units of the whole systems we consider necessary to get an accurate description of the desired molecular property or process. The remainder of the system, called S, should have a supporting function in the determination of the property. Actually, in focused model, the definition of M is not univocal but must be checked on the basis of the results. To give an example, systems composed by a chromophore which exhibits strong specific interactions between with some molecular units of the host, require the inclusion into M of molecular entities of the hosting. 

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