New Host Family Based on Small-Ring Compounds

Article abstract of DOI:10.1021/ja00202a030

Three- and four-membered ring compounds with functional groups and bulky substituents have proved to be a rewarding new source of inclusion hosts.These hosts form clathrates with a variety of uncharged organic molecules ranging from protic dipolar to apolar compounds (168 different inclusion species).Formation and selectivity depend in a systematic manner on structural parameters of the host, such as the nature, number, and position of functional groups, the substituents, and ring size.X-ray structure analyses of two inclusion compounds <1*t-BuOH (1:1):P2₁2₁2₁; = 9.782 (1), b = 11.376 (1), c = 17.603 (1) Angstroem; Z = 4. 17*MeCN (1:1): Pbcn; a = 12.314 (1), b = 16.074 (1), c = 12.938 (1) Angstroem; Z = 4> and of a free host molecule <1: P2₁; a = 7.339 (2), b = 11.657 (4), c = 9.149 (3) Angstroem; β = 110.07⁰; Z = 2> are reported, revealing the building principles of the new clathrate family.The structures exhibit linear chains of inter-/intramolecular H bridges between carboxylic groups in the free host 1 and H-bridge aggregation of host and guest molecules in infinite helical chains for the 1*t-BuOH (1:1) inclusion.In 17*MeCN (1:1), the guest molecules are tightly enclosed by the host framework without further specific interactions.