Amine guest size and hydrogen-bonding influence the structures of p-tert-butylcalix[4]arene inclusionsIssued as NRCC No. 43850. E. B. B. and J. A. R. thank NSERC for partial support of this work.
Abstract
A novel structure involving a 2(p-tert-butylcalix[4]arene)·3.5(1,4-butanediamine) inclusion compound shows amine sites both exo and endo to the cavity, with the amine hydrogen-bonding to itself as well as to the host hydroxyl groups; for bulky amines with large pKa values, steric factors are more important than basicity, and the formation of a 1∶1, high-symmetry host–guest structure is preferred over a low-symmetry hydrogen-bonded structure.