Nickel(ii) metal–organic frameworks with N,N′-di(4-pyridyl)-naphthalenediimide ligands: influence of secondary building unit geometry on dimensionality and framework dimensions

Abstract

When Ni(NO₃)₂·6H₂O and N,N′-di(4-pyridyl)-1,4,5,8-naphthalenetetracarboxydiimide (DPNDI) are reacted, a one-dimensional coordination polymer (1) is formed. However, analogous reactions with either terephthalic acid (2) or 2,6-naphthalenedicarboxylic acid (3) and DPNDI affords two-dimensional, pillared metal–organic frameworks. 2 and 3 contain rectangular voids of different dimensions which are dictated by the carboxylate ligand and the arrangement of the {[M(k²-O₂NO)]₂(μ²-O₂CR)₂} secondary building unit (SBU) that forms the nodes of the framework. The role of SBU geometry, intermolecular face-to-face π–π and lone pair–π interactions involving the DPNDI ligands are discussed.