ISSN:
1573-8779
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Summary On the basis of the foregoing, we can reach the following conclusions. 1. In molecular AC with charge transfer, as in binary CTC, with the exception of AC with a 4-membered bridge, intermolecular plane-parallel (or almost plane-parallel) pairing of the planes of the donor and acceptor molecular fragments takes place, leading to intermolecular π~π* charge transfer. 2. The type of orientation of the resulting donor-acceptor pairs in the case of the AC crystal depends to a significant extent on the length of the isolating bridge. It is possible to observe either isolated DA pairs or DA subunits which are “cross-linked” by intramolecular nonvalence interaction, or the formation of mixed stacks of planes, similar to those of binary CTC. In AC crystals these stacks may be oriented in one or two directions. 3. At the same time, organization of the subunits of the binary CTC in columns is almost always observed. 4. An appreciable change in the donor or acceptor parts with preservation of the length of the isolating bridge in the molecules alters their configuration as a whole, the packing motif in the crystal, and hence the nature of the donor-acceptor interactions of the molecules. 5. In AC molecules, in addition to the intermolecular π~π* charge transfer characteristic of all CTC. it is possible in a number of cases to observe crystallographic features leading to intramolecular n~π* interaction, that is, to observe “double complex formation.” Both types of DA interaction have been proved by spectroscopy. 6. For all CTC, the presence of bulky substituents on the donor or acceptor fragments leads to loosening of the DA pairs or even to the disappearance of the stacks. 7. Increase in the length of the isolating bridge in AC leads to a decrease in the probability of intermolecular overlap. At the same time there may be an increase in the tendency of the DA fragments to show intramolecular “saturation.”
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00746241
