A fivefold interpenetrating diamondoid framework constructed by flexible dipyridyl and dicarboxylate ligands.

A novel three-dimensional Cd(II) complex, poly[aqua{μ2-1,4-bis[2-(pyridin-4-yl)ethenyl]benzene-κ(2)N:N'}[μ4-2,2'-(1,4-phenylene)diacetato-κ(4)O,O':O'',O''']cadmium(II)], [Cd(C10H8O4)(C20H16N2)(H2O)]n, has been prepared by hydrothermal assembly of Cd(NO3)2·4H2O, 1,4-bis[2-(pyridin-4-yl)ethenyl]benzene (1,4-bpeb) and 2,2'-(1,4-phenylene)diacetic acid (1,4-H2pda). Each Cd(II) centre is located on a twofold axis in a distorted pentagonal bipyramidal coordination environment formed by one O atom from a water molecule, which lies on the same twofold axis, four O atoms from two different 1,4-pda ligands and two N atoms from two different 1,4-bpeb ligands. The Cd(II) centres are bridged by the 1,4-bpeb and 1,4-pda ligands, which lie across centres of inversion. The three-dimensional net can be regarded as a diamondoid network by treating the Cd(II) atoms as nodes and the 1,4-bpeb and 1,4-pda ligands as linkers. The single net leaves voids that are filled by mutual interpenetration of four independent equivalent frameworks in a fivefold interpenetrating architecture.