First Pseudorotaxane-Like [3]Complexes Based on Cryptands and Paraquat:  Self-Assembly and Crystal Structures

• Published in: Journal of the American Chemical Society 2003-08, Vol.125 (31), p.9367-9371
• Main Authors: Huang, Feihe, Gibson, Harry W, Bryant, William S, Nagvekar, Devdatt S, Fronczek, Frank R
• Format: Article
• Language: English
• Subjects: Chemistry; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; General and physical chemistry; Heterocyclic compounds; Organic compounds; Physics; Solution properties; Solutions; Structure of solids and liquids; crystallography; Structure of specific crystalline solids
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja034968h

A new cryptand, bis(1,3,5-phenylene)tri(1,4,7,10-tetraoxadecyl) (3a), has been synthesized in good yield from bis(5-hydroxy-1,3-phenylene)-26-crown-8 (2a) and tri(ethylene glycol) ditosylate using pseudo-high dilution conditions. 3a forms a strong 1:1 complex with paraquat (1) in acetone solution with a high apparent association constant, 1.4 × 104 M-1. A stoichiometry of 1:1 was also observed by mass spectrometry in the gaseous state. However, in the solid state, as determined by X-ray crystallography, the two complexes of 3a and the previously reported homologous cryptand, bis(1,3,5-phenylene)tri(1,4,7,10,13-pentaoxatridecyl) (3b), with paraquat (1) have 2:1 stoichiometry. A unique feature of these trimolecular pseudorotaxane-like complexes is that the guest occupies parts of the cavities of two cryptand molecules. For the first time it was found that in cryptand-based complexes, different stoichiometries are possible for the same host−guest pair.