Diverse Entangled Metal−Organic Framework Materials Incorporating Kinked Organodiimine and Flexible Aliphatic Dicarboxylate Ligands: Synthesis, Structure, Physical Properties, and Reversible Structural Reorganization

Abstract

Hydrothermal synthesis has afforded a family of divalent metal adipate (adp) coordination polymers incorporating the kinked dipodal organodiimine 4,4'-dipyridylamine (dpa). As revealed by single-crystal X-ray diffraction, the structures of these materials are critically dependent on the metal coordination geometry, the carboxylate binding modes, and the conformations of the flexible adipate moieties. In all cases, hydrogen-bonding interactions imparted by the dpa tethers also play a structure-directing role. All materials were further characterized via infrared spectroscopy and elemental and thermogravimetric analysis. [Co(adp)(dpa)] (1) displays doubly interpenetrated three-dimensional (3-D) networks with a decorated alpha-Po-type (pcu) topology. In contrast, [Ni(adp)(dpa)(H2O)] (2) possesses a triply interpenetrated binodal cooperite-type (pts) framework, the highest level of interpenetration yet reported for this structure type. [Zn(adp)(dpa)].H2O (3) presents mutually inclined polycatenated 2-D graphitic layers consisting of neutral dimeric [Zn2(mu2-adp)2] kernels conjoined by dipodal dpa ligands. Compound 1 exhibited weak antiferromagnetic coupling between its carboxylate-bridged Co atoms, following Curie-Weiss behavior with Theta=-3.3 K. Compound 3 manifested blue light emission under ultraviolet excitation, as well as a reversible structural reorganization upon dehydration/rehydration.