Relevanz und Nutzung von Anionen-pi Wechselwirkungen

In this thesis the relevance and the use of a new intermolecular force between anions and electrondeficient arenes was investigated. In the last ten years the anion-pi interaction has gain a growing interest in the supramolecular community. It should be useful for the design of novel anion receptors. For this purpose the nature of the anion-pi interactions has to be examined. The present studies show the relevance of this interaction in solution and in the solid state. The solid state studies showed a high flexibility in the relative orientation of the anion to the pi-system and that it can easily be influenced by other non-covalent interactions and packing effects. By the use of rigide and highly symmetric receptors the position of the anion is fixed above the center of the pentafluorophenyl group. Whereas in more flexible and less symmetric receptors the anion is pushed into the direction of one rim of the pi-system. Further studies investigated the influence of the anion geometry. While the geometry of the anion seems to play a minor role, the size of the anion controls the molecular packing. Moreover, the stabilization of sensitive anions like the tetraiodide dianion with the help of anion-pi interactions was observed in the solid state. The present studies also confirm a strong dependence of the interactions between the anion and the fluorination degree of the arene. Highly electron deficient phenyl groups interact attractively with the anion, while more electron rich systems lead to an increasing distance between the arene and the anion. An attractive interaction between metallfree, non-charged receptors in the solid state could be shown in the crystal structure of the tetraethylammonium bromide and pentafluorobenzamide cocrystal. The large number of obtained crystal structures proves that an attractive interaction of anions and electron deficient arenes can be observed in the solid state. In many cases the anion is fixed above the pi-center, which indicates that the anion-pi interaction is not only an effect of crystallization. During the solution experiments it was found that the differential binding constants of pentafluorobenzyl ammonium and phosphonium salts give no hint for an attractive interaction between anions and Pentafluorophenyl groups. The weak anion-pi interaction is covered by other competing interactions like CH-anion and coulomb attraction. Further studies revealed a difference in the association constants between benzamide receptors with electron rich and poor phenyl groups. But it could not be clearified if this is an effect of the attractive interaction of anions with pi-systems or just due to the higher acidity of the amide protons. The performed solution experiments could not clear up the role of anion-pi interaction in solution. But it can be suggested, that due to the weakness of this interaction, it can easily be covered by competing interactions or solution effects. But nevertheless, the design of novel anion receptors by using anion-pi interactions can lead to new applications in supramolecular chemistry. For this purpose further investigations of the nature of the intermoleculare force between anion and electron deficient arenes are necesserary.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2011

Author dc:creator

• Giese, Michael Rainer Alexander

Contributors dc:contributor

• Albrecht, Markus

• info:eu-repo/classification/ddc/540
• Supramolekulare Chemie
• Chemie
• Anionenerkennung
• Anionen-pi Wechselwirkung
• anion recognition
• anion-pi interaction
• supramolecular chemistry

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-124434%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:62961