Tris(1,10-phenanthroline-kappa2N,N')cadmium(II) bis(perchlorate) 3.5-hydrate: a water chain stabilized by perchlorate anions.

The title compound, [Cd(C(12)H(8)N(2))(3)](ClO(4))(2).3.5H(2)O, contains a cross-shaped one-dimensional channel along the c axis which encapsulates an ordered water chain. This water chain features a centrosymmetric cyclic water hexamer unit with a chair-like conformation. Neighbouring hexamers are linked by bridging water molecules. The host perchlorate anions recognize and stabilize the guest water chain via three kinds of hydrogen-bond patterns, leading to the formation of a complex one-dimensional {[(H(2)O)(7)(ClO(4))(4)](4-)}(n) anionic chain. One perchlorate acts as a single hydrogen-bond acceptor dangling on the chain, the second perchlorate on the chain serves as a double hydrogen-bond acceptor for only one water molecule to form an R(2)(2)(6) ring, where both entities lie on a twofold axis, while the third perchlorate, which also lies on a twofold axis, accepts two hydrogen bonds from two equivalent water molecules and is involved in the construction of an R(6)(5)(14) ring.