Self-recognition of 3D porous frameworks: Fourfold diamondoid or threefold cuboidal interpenetrating nets formed by varying pillar motifs

Compound [Ni(2,6-ndc)(bpe)(H2O)] (n) (1) was prepared by the hydrothermal reaction of 2,6-naphthalenedicarboxylic acid (2,6-H(2)ndc) and trans-1,2-bis(4-pyridyl)ethylene (bpe) with Ni(NO3)(2)center dot 6H(2)O under alkaline (NaOH) conditions. Treatment of 2,6-H(2)ndc, 4,4'-bipyridine (4,4'-bpy) with M(NO3)(2)center dot 6H(2)O (M = Ni or Co) under similar conditions afforded compounds [Ni-2(2,6-ndc)(2)(4,4'-bpy)] (n) (2) and [Co-2(2,6-ndc)(2)(4,4'-bpy)] (n) (3), respectively. A single-crystal X-ray diffraction study revealed that compound 1 adopts a 3D fourfold interpenetrating diamondoid network stabilized by inter-net OH center dot center dot center dot O hydrogen bonds. The anionic 2,6-ndc ligand presents two different bonding characteristics, bis(monodentate) and bis(chelating bidentate) modes. A solid-state structural analysis revealed that compounds 2 and 3 are isomorphous and isostructural. Both present a 3D threefold interpenetrating cuboidal framework, consisting of a 2D (4,4)-net of interconnected [M (2)(O2C)(4)] (M = Ni, Co) paddle-wheel dinuclear units, and pillared by 4,4'-bpy ligands. The degree of interpenetration of these compounds could be adjusted successfully by varying only the organic pillar motifs.