Three novel 3D metal–organic frameworks with a 1D ladder, tube or chain as assembly units

Abstract

Three novel metal–organic frameworks, Cu₄(OH)₂(SO₄)(HBTC)₂(bpy)·bpy (1), Cu_1.5(H₂O)(TMBTC)(bpy)·1/2H2O (2) and Cd₂(H₂O)₅(TMBTC)(bpy)₂·NO₃·3H₂O (3), constructed from mixed organic ligands, have been synthesized and characterized. Complex 1 crystallizes in monoclinic space groupC2/c and possesses a 3D three-fold interpenetrating framework. The copper ions were first connected by HBTC and SO₄²⁻ to generate a 1D ladder, which was further linked by a 4,4′-bipyridine ligand to give rise to a 3D interpenetrating framework. Complex 2 crystallizes in monoclinic space groupP2/c and possesses a 3D two-fold interpenetrating framework. Similar to 1, the copper ions were first connected by TMBTC to generate a 1D tubular unit, which can be considered as the assembly block. The 1D tubular unit was further linked by 4,4′-bipyridine ligands to result in the formation of the 3D framework. Complex 3 crystallizes in monoclinic space groupCc and has a three-dimensional structure. Different from 1 and 2, the cadmium ions were first connected by a 4,4′-bipyridine ligand to form a 1D chain as the assembly unit, which was further linked by TMBTC ligand to generate the final 3D framework. The photoluminescence measurement of 3 in the solid state at room temperature showed that complex 3 exhibits luminescence, which can be assigned to an intraligand π → π* transition.