IntroductionC­Methylcalix[4]resorcinarene1is a resorcinol­based macrocycle which commonly assumes a bowl­shaped conformation in organic media.1The curved architecture of such calix[4]resorcinarenes, and the phenolic groups on the upper rim, render them ideal for both the inclusion of appropriately sized and shaped species2,3as well as interaction with metal ions4or hydrogen­bonding species at the periphery.5A range of assemblies with defined interiors and interesting extended structures have been obtained usingC­methylcalix[4]resorcinarene. For example, in the presence of 4,4′­bipyridyl, capsules based on two calix[4]resorcinarene molecules result,6as is the case in the presence of propan­2­ol.7These structures are both assembled through hydrogen bonding. Similarly, hydrogen­bonding interactions with water molecules are instrumental in the assembly ofC­methylcalix[4]resorcinarene into a spherical hexamer.8However, its assembly in the presence of curved molecules for which there is complementary size and shape with the cavity has not been explored. Suitable guests include 18­crown­62and [2.2.2]cryptand (shown as its Na+complex3), and in this context we note that the similarly bowl­shapedp­sulfonatocalix[4]arene, and a resorcinarene­based cavitand, are capable of forming host–guest complexes with 18­crown­69–13and [2.2.2]cryptand14respectively. In the case of 18­crown­6 withp­sulfonatocalix[4]arene a range of structural types have been observed, including dimeric capsules,9,10,11clay­like bilayers12and helices.13Herein we establish that a 1∶2.5 assembly can be obtained from a mixture of the calix[4]resorcinarene and crown ether, and that a 1∶1 assembly forms from the mono­deprotonated calix[4]resorcinarene and the cryptand as its sodium complex.