Three unique MOFs constructed by 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene and dicarboxylates: From rhombic tetrameric zinc(II) 2D layer to 2D + 2D → 3D polycatenated frameworks

Abstract

Three metal–organic networks, namely, [Zn2(Hnip)(4-bpdb)(nip)2(μ3-OH)] (1), {[Zn(tbip)(4-bpdb)1.5]·CH3OH}n (2), and {[Ni(1,3-bdc)(4-bpdb)]·2H2O}n (3) (4-bpdb=1.4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, H2nip=5-nitroisophthalic acid, H2tbip=5-tert-butylisophthalic acid, and 1,3-H2bdc=1,3-benzenedicarboxylic acid) are synthesized under hydrothermal conditions. The structure of 1 is built around uncommon rhombic {Zn4} clusters with double Td and double Oh Zn(II) geometries, which extend into a 2D network by the rigid deprotonated H2nip and 4-bpdb bridges. Meanwhile, 2 presents a novel 2D→3D parallel polycatenated framework assembled from 2D bilayers with cuboids as the fundamental building units. Compound 3 features an interesting 2D→3D inclined polycatenated network based on 44-sql subunits. Moreover, the thermal stabilities, photoluminescence, and magnetic properties of the compounds are also discussed.