Metal-Organic Frameworks with Direct Transition Metal-Sulfonate Interactions and Charge-Assisted Hydrogen Bonds

Seven compounds with framework structures made of divalent metal-imidazole (Im) complexes (M(II) = Co, Ni, and Mn) linked by 1,5-napthalenedisulfonate (1,5nds) were synthesized and structurally characterized. Five of these compounds, Mn(Im)4(1,5nds) (two forms), Co(Im)4(1,5nds) (two forms), and Ni(Im)4(1,5nds), contain direct sulfonate-metal coordination and represent the first such compounds with open d-shell transition metals without Jahn−Teller distortion. The two disulfonate ligands in these octahedrally coordinated metal centers are found in both trans- and cis-geometries and link the centers into chains. The chains are held together by charge-assisted hydrogen bonds between sulfonate and imidazole ligands from different chains. The remaining two compounds, Co(Im)6(1,5nds)·2H2O and Ni(Im)6(1,5nds)·2H2O, exhibit only charge-assisted hydrogen bonds between the octahedral M(Im)62+ cations and the disulfonate anions.