Layered and pillar-layered metal-organic frameworks based on pinwheel trinuclear zinc-carboxylate clusters

Three new Zn(ii) metal-organic coordination polymers, [Zn ₃(STDC)₃(py)₂] (1), [Zn₃(STDC) ₃(4,4′-bpy)] (2), [Zn₃(STDC)₃(bpea)] · 3H₂O (3), where H₂STDC = trans-stilbene-4, 4′-dicarboxylic acid, py = pyridine, 4,4′-bipy = 4,4′-bipyridine, bpea = 1,2-bis(4-pyridyl)ethane, were prepared by solvothermal reactions of Zn(ii) acetate with H₂STDC in the presence of py or linear bis(pyridyl) molecules. Compound 1 is a 2D triangle-tessellated layered network based on a pinwheel trinuclear zinc-carboxylate clusters as secondary building unit with py as the terminal ligand. Compounds 2 and 3 contain similar layers, which are linked into layer-pillared 3D frameworks by the ditopic bipy or bpea ligand in place of py. Comparing the structures of 2 and 3, the increase in pillar length does not lead to increased multiplicity in interpenetration, due to the limitation of the intralayer space dimensions, but it induces expanded and unequal interlayer separations.