Bis[(dihydrogen pyrophosphato-κ(2)O,O')(2,2':6',2''-terpyridine-κ(3)N,N',N'')copper(II)] 4.5-hydrate

The title copper complex, [Cu(H(2)P(2)O(7))(C(15)H(11)N(3))](2)·4.5H(2)O, consists of two very similar independent Cu(Tpy)H(2)P(2)O(7) monomeric units (Tpy is 2,2':6',2''-terpyridine) plus four and a half water molecules of hydration, some of which are disordered. Tpy units bind through the usual triple bite via their N atoms, and the H(2)P(2)O(7)(2-) anions coordinate through two O atoms from two different phosphate units. Each independent CuN(3)O(2) chromophore can be described as a slightly deformed square pyramid, with one of them having a sixth, semicoordinated, O atom from a centrosymmetrically related CuN(3)O(2) unit in a weakly bound second apical position suggesting an octahedral environment for the cation and weak dimerization of the molecule. The two independent complex molecules are connected via two strong O-H···O interactions between the phosphate groups to form hydrogen-bonded dinuclear units, further linked into [111] columns, resulting in a very complex three-dimensional supramolecular structure through a variety of classical and nonclassical hydrogen bonds, as well as π-π interactions.