Intermolecular conformational analysis

The highly selective processes of molecular recognition are, of course, of stereochemical nature. Thus may be defined a supramolecular stereochemistry that extends from supermolecules to polymolecular assemblies. Different spatial dispositions of the components of a supermolecule with respect to each other lead to supramolecular stereoisomers. Their eventual interconversion will depend on the properties of the interactions that hold them together, i.e. on the variation of the intermolecular interaction energy with distances and angles. There is thus an intermolecular conformational analysis like there is an intramolecular one. 

Waluk J (2000) Conformational aspects of intra and intermolecular excited state proton transfer. In Waluk J (ed) Conformational analysis of molecules in excited State. Willey-VCH, Weinheim, pp 57-112... 

Earlier work in this area of shape analysis focused on QSAR studies accounting for conformational features of molecules, such as interatomic distances [89], explicit atomic coordinate sets [90], computed intermolecular distances [91], and simpler shape descriptors such as molecular volume [92]. Each of these descriptor types formally requires conformational analysis, and therefore produces, accordingly, a family of solutions for most structures. 

The crystal structure of PHB is a orthorhombic form with unit cell parameters fl = 0.576 nm, = 1.320 nm, and c(fiber axis)=0.596 nm, and space group P2,2,2, (Alper et al. 1963 Okamura and Marchessault 1967). The conformational analysis by intermolecular energy calculation has indicated that the PHB molecule has a left-handed 2j helix conformation (Comibert and Marchessault 1972 Yokouchi et al. 1973 Bruckner et al. 1988). The crystal structure of random copolymers of 3HB and 3HV has been investigated extensively (Bloembergen et al. 1986 Kamiya et al. 1991 VanderHart et al. 1995). A structural characteristic of poly(3HB-co-3HV) is isodimorphism, i.e., cocrystallization, of the two monomer units. In contrast, the cocrystallization of 3HB with 3HH or (7 )-6-hydroxyhexanoate (6HH) does not occur. 

From the i.r. spectrum of a single crystal of methyl -D-glucopyranoside 2,3,4,6-tetranitrate the intermolecular interactions of the nitrate groups have been calculated,and i.r. data from the 400-800 cm range have been used in the conformational analysis of, for example, methyl -D-glucopyranose 2,3,6-trinitrate."" The i.r. spectra of several mono- and dinitrates of methyl a- and )S-D-glucopyranosides are referred to in Chapter 22. 

---