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) x 2 H(2)O and Ni(Im)(6)(1,5nds) x 2 H(2)O, exhibit only charge-assisted hydrogen bonds between the octahedral M(Im)(6)(2+) cations and the disulfonate anions.