Crowned tetrameric spirocyclic water chain: An unusual building block of a supramolecular metal-organic host

A 3D supramolecular metal-organic host could be realized in solid in which the water assembly as a whole acted as a building block of the 3D framework with rectangular channels where guest molecules reside, adding a new dimension to water cluster research where the role of water has been shifted from its usual behavior of guest to that of a host. The crystal structure of the compound, {[Cu(mal)(2)](picH)(2)center dot 5H(2)O}(n), 1 [mal = malonate dianion, picH = protonated 2-amino-4-picoline], synthesized from purely aqueous media, shows that the Cu(II)-malonate 2D coordination polymeric sheets are locked together by the water assembly that lines up perpendicular to the Cu(II)-malonate sheets constituting a 3D infinite supramolecular host where within the channels protonated 2-amino-4-picoline auxiliary ligands are accommodated. A spirocyclic tetrameric water chain having a dimeric crown on it describes the composition of the water assembly that runs down the c-axis.