The X-ray crystal structure of the p-sulfonatocalix[5]arene(5-) anion (1b) in the form of the dimeric hydrate Na-10-[p-sulfonatocalix[5]arene](2) . 33.5H(2)O (2) is reported. The reactions of 1b with a number of transition metal salts to form transition metal bridged bis(calixarene) inclusion complexes have also been investigated. The X-ray crystal structure of the "Co(H2O)(4)(2+)" bridged species Na-8[Co(H2O)(4)(p-sulfonatocalix[5]arene)(2)]. 2CH(3)C(O)N(CH3)(2) . 37H(2)O (3) which incorporates a "supercavity" large enough to encompass 2 N,N-dimethylacetamide (dma) guest molecules as well as ca. 15 water molecules and Na+ ions is reported. Crystal data are as follows : for 2, monoclinic space group P2(1)/c, Z = 4, a = 22.0644(4), b = 19.1180(3), c = 27.7834(4) Angstrom, beta = 91.780(1), V = 11714.1(5) Angstrom(3); complex 3, orthorhombic space group Pruna, Z = 4, a = 22.2271(5), b = 30.1693(6), c = 18.8503(4) Angstrom, V = 12640.6(5) Angstrom(3).