Two metal-organic frameworks (MOFs) based on binuclear and tetranuclear units: Structures, magnetism and photoluminescence

Two new MOFs, [Mn(HBTC)(2-PyBim)(H2O)] (1) and [Zn-2(BTC)(OH)(2-PyBim)] (2) (H3BTC = 1,3,5-benzenetricarboxylic acid, 2-PyBim = 2-(2-pyridyl) benzimidazole), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction (XRD), infrared spectroscopy (IR), elemental analysis (EA). In 1, adjacent two Mn(II) ions are connected into binuclear Mn-2 units which are bridged by HBTC2- anions to generate a two-dimensional (2D) (4,4) network. In 2, the Zn(II) ions are connected into tetranuclear Zn-4 units which are bridged by the BTC3- anions to generate a 2D (3,6)-connected non-interpenetrating CdI2-type network with (4(3))(2)(4(6).6(6).8(3)) topology symbol. Both 1 and 2 are extended into 3D supramolecular structure by hydrogen bonds and pi center dot center dot center dot pi interactions. Magnetic studies of 1 indicate that it exhibits ferromagnetic coupling between the binuclear Mn(II) ions, polymer 2 was found to exhibit photoluminescence at about 437 nm (lambda(ex) = 365 nm). (C) 2011 Elsevier B. V. All rights reserved.