Self-Recognition of 3D Porous Frameworks: Fourfold Diamondoid or Threefold Cuboidal Interpenetrating Nets Formed by Varying Pillar Motifs

Abstract

Compound [Ni(2,6-ndc)(bpe)(H2O)] n (1) was prepared by the hydrothermal reaction of 2,6-naphthalenedicarboxylic acid (2,6-H2ndc) and trans-1,2-bis(4-pyridyl)ethylene (bpe) with Ni(NO3)2·6H2O under alkaline (NaOH) conditions. Treatment of 2,6-H2ndc, 4,4′-bipyridine (4,4′-bpy) with M(NO3)2·6H2O (M = Ni or Co) under similar conditions afforded compounds [Ni2(2,6-ndc)2(4,4′-bpy)] n (2) and [Co2(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···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.