Polymorphism and pseudopolymorphism in calixarenes:: acetonitrile clathrates of p-But-calix[n]arenes (n = 6 and 8)

Here we present four new structural determinations of p-Bu-t-calixarene acetonitrile clathrates, namely p-Bu-t-calix[6]arene.1.5MeCN (1), p- Bu-t-calix[6]arene.2MeCN (2), p-Bu-t-calix[8]arene.4MeCN (3) and p-Bu-t-calix[8]arene.2MeCN (4), and utilise the Cambridge Structural Database to highlight the extent of polymorphism and pseudopolymorphism within the solvent clathrate structures of these key compounds. Compounds 1 and 2 are the first examples of polymorphism and pseudopolymorphism in p-Bu-t-calix[6]arene solvent clathrates, the former phenomenon having been previously seen in p-Bu-t-calix[4] arene toluene clathrates and the latter in p-Bu-t-calix[8] arene pyridine clathrates, while compounds 3 and 4 themselves exhibit pseudopolymorphism.