Metal–Organic Frameworks Based on Flexible\nV-Shaped Polycarboxylate Acids: Hydrogen Bondings, Non-Interpenetrated\nand Polycatenated

Abstract

Solvothermal reactions of 4,4′-dicarboxydiphenylamine\n(H₂L) with 4,4′-bis­(imidazol-1-yl)­phenyl (BIP) and\n4,4′-bis­(imidazol-1-yl)­diphenyl\n(BIBP) in the presence of cobalt­(II), cadmium­(II), zinc­(II) salts\nin H₂O/CH₃CN or H₂O/DMF produced\nfive new complexes, namely, [Co₂(L)₂(BIP)₂·3H₂O]_<i>n</i> (<b>1</b>), [Co­(L)­(BIP)·2CH₃CN]_<i>n</i> (<b>2</b>), [Co­(L)­(BIBP)·H₂O]_<i>n</i> (<b>3</b>), [Cd­(L)­(BIBP)]_<i>n</i> (<b>4</b>), [Zn­(L)­(BIBP)]_<i>n</i> (<b>5</b>). Compound <b>1</b> has binuclear Co­(II) clusters,\nwhich are linked by L^2– and BIP to generate a rare\nthree-dimensional (3D) non-interpenetrated <b>cds</b>-type framework,\nand displays ferromagnetic character. Compound <b>2</b> possesses\nunusual 3-fold 2D → 2D polycatenation of (4, 4) nets. Compound <b>3</b> reveals a (4, 4) grid topology with very strong hydrogen\nbondings due to the abundant uncoordinated carboxyl groups, which\nload in the structure like a freely dangling arm. Compound <b>3</b> also displays weak ferromagnetic character. Compounds <b>4</b> and <b>5</b> are isomorphic. H₂L and BIBP ligands\nin <b>4</b> and <b>5</b> interact with a metal center\nto form wave-like 2D sheets. In addition, the thermal stabilities\nand photochemical properties of compounds have been studied.