Double stranded chains and interwoven structures: the role of conformational isomerism in coordination polymers

摘要

The 1:3 and 1:1.5 coordination complexes of 1,3-bis(4-pyridyl) propane, 1, [Ni(1)_2(H_2O)_2[NO_3]_2[NO_3]_2·(1)·(H_2O), 2 and [Cd_4(1)_6(NO_3)_8], 3 form a double stranded chain and four-fold interwoven structures, respectively. Complex 2 is an unusual coordination complex where the ligand not only coordinates with the metal salt but also cocrystallizes with the coordination complex. The double stranded linear chains in 2 have 24 membered rings with a Ni…Ni intra-chain distance of 11.53 A and close-pack to form a two dimensional layered structure. The anions, non-coordinating ligands, and the solvated water molecules sandwich between the layers in a bilayer fashion. Complex 3 forms an open network owing to its T-shaped geometry but the conformational flexibility of the ligand blurs the difference between the expected brick wall pattern and the distorted hexagonal network. The internal dimensions between opposite Cd metal centers in the distorted non-planar network are ca 18.3 * 23.2 * 28.5 A. These open networks readily undergo four-fold parallel interpenetration and result in a carpet like structure.