From diamondoid network to (4,4) net: effect of ligand topology on the supramolecular structural diversity.

While N,N'-bis(4-pyridyl)urea affords a 5-fold interpenetrated diamondoid network, its positional isomer N,N'-bis(3-pyridyl)urea gave a net-to-net hydrogen-bonded (4,4) net (square grid network) displaying temperature-dependent anion-induced reversible single-crystal-to-single-crystal disorder-order phase transition, when the ligands are reacted with zinc perchlorate.