Crystal structures of calixarenes

We carried out a search of the files from the Cambridge Crystallographic Data Centre [57] for structures of calix[4]arenes and calix[5]arenes. In this first section, we concentrate on cone-shaped calix[4]arenes which contain guest molecules and these are listed in Table 1. There are also three structures of calix[5]arenes all with the cone structure and details are also given in Table 1. 

Even so for the symmetric structures, CUPWAL, DACLUO and DUTBUP, variations in torsion angles of ca 10° are found. The 0...0 distances around the cone average at 2.67A for molecules with = H. Only one structure for calix[5]arene is available in the database [58], BIMXIE, calix[5]arene bis(acetone)clathrate though recently two other structures (called XXXXXX,YYYYYY in Table 1) have been determined viz tetramethylbutylcalix[5]arene and tetramethylbutylcalix[5]arene toluene clathrate [68]. As is apparent from the torsion angles in Table 1, these three structures have relatively similar conformations. The 0...0 distances around the cone average at 2.84A. 

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