Oxoanion and cation effects on the structural morphology of coordination polymers incorporating a kinked organodiimine tethering ligand

Abstract

Combination of divalent cobalt salts with the kinked and hydrogen-bonding capable organodiimine 4,4′-dipyridylamine (dpa) has afforded a family of coordination polymers where the anion plays a determining structure directing role. Use of the perchlorate salt results in the coordination polymer {[Co(H₂O)₂(dpa)₂](ClO₄)₂·2 dpa·2 H₂O} (1), which possesses cationic [M(H₂O)₂(dpa)₂]_n²ⁿ⁺ grid-like layer motifs. Unligated perchlorate anions, dpa molecules, and water molecules of crystallization are situated within the incipient rhomboid voids. Employing cobalt sulfate or nitrate as the metal source afforded {[Co(dpa)₂(H₂O)(SO₄)]·2 H₂O} (2) and {[Co(dpa)₂(H₂O)(NO₃)](NO₃)} (3), which display related 3-D quadruply interpenetrated [Co(dpa)₂]_n²ⁿ⁺ adamantoid frameworks. The cadmium perchlorate derivative {[Cd(H₂O)₂(dpa)₂](ClO₄)₂·2 dpa·2 H₂O} (4) displays a 2-D polymeric structure similar to that of 1. However 4 manifests a different layer stacking pattern from that in 1, revealing a subtle cation-based structure-directing effect. All materials were characterized via single crystal X-ray diffraction, infrared spectroscopy, and thermogravimetric analysis.