Azolium-Linked Cyclophanes: Effects of Structure, Solvent, and Counteranions on Solution Conformation Behavior

Murray Baker, David Brown, Charles Heath, Brian Skelton, Allan White, C.C. Williams

Research output: Contribution to journalArticlepeer-review

33 Citations (Scopus)

Abstract

This paper describes the synthesis, structural characterization, and solution behavior of some xylyl-linked imidazolium and benzimidazolium cyclophanes decorated with alkyl or alkoxy groups. The addition of alkyl/alkoxy chains to the cyclophanes allows for studies in chlorinated solvents, whereas previous solution studies of azolium cyclophanes have generally required highly polar solvents. The azolium cyclophanes may exist in a syn/syn conformation (azolium rings mutually syn, arene rings mutually syn) or a syn/anti conformation (azolium rings mutually syn, arene rings mutually anti). The preferred conformation is significantly affected by (i) binding of bromide (ion pairing) to the protons on the imidazolium or benzimidazolium rings, which occurs in solutions of bromide salts of the cyclophanes in chlorinated solvents, and (ii) the addition of alkoxy groups to the benzimidazolium cyclophanes. These structural modifications have also led to cyclophanes that adopt conformations not previously identified for similar azolium cyclophane analogues. Detailed 1H NMR studies for one cyclophane identified binding of bromide at two independent sites within the cyclophane.
Original languageEnglish
Pages (from-to)9430-9452
JournalThe Journal of Organic Chemistry
Volume73
Issue number23
DOIs
Publication statusPublished - 2008

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