The crystal structures of 6-methylene-2,2,3,9,9,10,10-octamethyl-14-crown-4 (1), 2,2,3,3,6,9,9,10,10-nonamethyl-14-crown-4 (2) and its LiSCN complex (2·LiSCN), 6-methylenedibenzo-14-crown-4 (3), 6-methyldibenzo-14-crown-4 (4), and dibenzo-14-crown-4 (5), have been determined by X-ray diffraction. These results, in addition to published literature data, are used to compare the conformational changes of flexible vs. rigid 14-crown-4 molecules when each is complexed with LiSCN. In dibenzo-14-crown-4 the oxygen atoms are suitably arranged prior to complexation to form the base of a square pyramidal complex upon complexation with LiSCN, while 2,2,3,3,6,9,9,10,10-nonamethyl-14-crown-4 and other flexible ligands must undergo significant rearrangement of the ring system in order to achieve this configuration.