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)](H(2)O)(0.5)}(n) (2), {Ni(0.5)(bpydbH)(H(2)O)](DMF)(2)}(n) (3), {Cu(2)(bpydb)(2)](H(2)O)(0.5)}(n) (4), {Zn(bpyHdb)(2)}(n) (5) and {Cd(0.5)(bpydb)(0.5)(DMF)](H(2)O)}(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-HO interactions. Compound 5 manifests a novel 4-connected interpenetrating framework, constructed by 2D (4,4) layers and interbedded N-HO 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.