Two unusual (4,6)- and 8-connected metal–organic frameworks constructed from flexible 1,4-benzenebis(thioacetic acid) and pyridine-based ligands

Abstract

Two unusual metal–organic frameworks (MOFs) [CoL(4,4′-bipy)]_n (1) and [Ni₂L₂(bpp)₂(H₂O)]_n (2) (H₂L = 1,4-benzenebis(thioacetic acid), bipy = 4,4′-bipy, bpp = 1,3-di(4-pyridyl)propane), have been synthesized and characterized by single-crystal X-ray diffraction. MOF 1 can be considered as constructed by 2D layers, which consist of left- and right-handed helical chains and is further linked by L²⁻ ligands into a 3D (4,6)-connected network with a Schläfli symbol of (4²·5²·6²)(4²·5⁶·6⁴·7³). MOF 2 is an unique 3D 8-connected self-penetrating network with a Schläfli symbol of (4²⁴·6⁴), in which the dinuclear {Ni₂} subunits are linked by L²⁻ ligands to form 2D layers along the ac plane and further expanded to a 3D network by bpp ligands. The experimental magnetic susceptibility of MOFs are interpreted with the uniform 1D chain character for 1 and the dimeric nickel law for 2, yielding the exchange integral (J) values of −1.32(2) cm⁻¹ and 1.32(2) cm⁻¹, respectively. The exchange integrals indicate weak antiferromagnetic interactions in 1, and weak ferromagnetic interactions in 2.