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), {[Cd2(3,4′-bpdc)2(bib)1.5(H2O)]n·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.