Syntheses, structures and physical properties of transition metal-organic frameworks assembled from trigonal heterofunctional ligands

Six novel metal-organic frameworks (MOFs), {Mn(bpydb)(bpyHdbH)}(n) (1) {[Co-2(bpydb)(2)](H2O)(0.5)}(n) (2), {[Ni-0.5(bpydbH)(H2O)](DMF)(2)}(n) (3), {[Cu-2(bpydb)(2)](H2O)(0.5)}(n) (4), {Zn(bpyHdb)(2)}(n) (5) and {[Cd-0.5(bpydb)(0.5)(DMF)](H2O)}(n) (6), were successfully synthesized by assembling transition metal salts with trigonal heterofunctional ligand 4,4'-(4,4'-bipyridine-2,6-diyl) dibenzoic acid (bpydbH(2)) under hydrothermal and/or solvothermal conditions. Compound 1 features a rare 4-fold interpenetrating (3,5)-connected framework with hms-type topology. Isostructural compounds 2 and 4, constructed by M-2(COO)(4) secondary building units, exhibit a robust 3D framework with alb topological type in 2-fold interpenetrating mode. Compound 3 consists of 2D (4,4) networks, which are further assembled into the new topological framework with the symbol (5(3).6(2).8)(5(3).6(3))(2) through O-H center dot center dot center dot O interactions. Compound 5 manifests a novel 4-connected interpenetrating framework, constructed by 2D (4,4) layers and interbedded N-H center dot center dot center dot O interactions. Non-interpenetrating honeycomb networks are observed in compound 6, and further packed into a 3D framework featuring 1D channels. The magnetic susceptibility of compound 2 indicates antiferromagnetic interactions between cobalt ions. The photoluminescent properties of 5 and 6 were investigated in the solid state at room temperature.