Amalgamating 4′-substituted 4,2′:6′,4′′-terpyridine ligands with double-helical chains or ladder-like networks

Abstract

The reaction of five 4,2′:6′,4′′-terpyridine ligands containing diverse 4′-substituents with Hg(NCS)₂ by layering methods afforded crystals of five novel Hg^II-based coordination polymers (1–5) that have been structurally characterized by both powder and single-crystal X-ray diffraction analysis. Similar one-dimensional (ID) polymeric chains were observed in the structures of polymers 1–3 where Hg^II serves as a mononuclear node to link ligands in a linear mode. All 1D chains in these complexes form double-helical structures through significant inter-chain π-stacking interactions, whereas the packing modes were slightly different in the three compounds, resulting from the influence of 4′-substituents. It was interesting to note that the structures of isomorphic 4 and 5 are completely different from those in 1–3. In the former cases, 1D ladder-like architectures that are assembled through the bridging thiocyanate groups were revealed, while remaining the extra 4′-pyridyl units non-coordinated.