Tuning Structural Topologies of Three Photoluminescent Metal-Organic Frameworks via Isomeric Biphenyldicarboxylates

Three new cadmium compounds, [Cd(2,4'-bpdc)(bib)(0.5)] (1; 2,4'-bpdc = biphenyl-2,4'-dicarboxylate and bib = 1,4-bis(2-methyl-imidazol-1-yl)butane), {[Cd-2(3,4'-bpdc)(2)(bib)(1.5)(H2O)](n)center dot H2O](n) (2; 3,4'-bpdc = biphenyl-3,4'-dicarboxylate), and [Cd (4,4'-bpdc)(bib)] (3; 4,4'-bpdc = biphenyl-4,4'-dicarboxylate), have been successfully synthesized by the assembly of Cd2+ ions, bib ligands, and isomeric bpdc ligands, respectively. This paper presents a comparative study on the tuning of structural topologies using three isomers of biphenyldicarboxylates as bridging ligands. Compound 1 based on 2,4'-bpdc features a three-dimensional (3D) framework with 6-connected mab topology. Compound 2 based on 3,4'-bpdc is another 3D framework, but it possesses a rare 3-fold interpenetrating 4,6-connected fsh net, while compound 3 based on linear 4,4'-bpdc shows unusual 2D -> 3D parallel polycatenation of (4,4) layers. Furthermore, the luminescent properties of three compounds are investigated in the solid state.