Construction of extremely low-symmetry double-stranded helicates based on terpyridine ligands with consecutive unsymmetrical modification
摘要
The development of artificial supramolecular double-stranded helical structures has received widespread attention; however, the reports focusing on the construction and resolution of double-stranded helical assemblies based on terpyridine are relatively scarce. Herein, we report a series of extremely low-symmetry double-stranded helicates (S3, S4, and SR/S) based on the head-to-tail coordination mode of ladder-style ligands (L3, L4, and LR/S), which are apparently different from the conventional helicates with symmetrical axis. The ladder-style tridentate ligand L3 was first designed and synthesized by characteristic consecutive unsymmetrical modification of terpyridine. The chiral group 2,6-bis(oxazolinyl)pyridine (PyBox) was designed at the tail of tridentate ligand L3 and achieved the chiral resolution of the assembly. Moreover, the self-assembly of mixed three ladder-style ligands (didentate L2, tridentate L3, and tetradentate L4) and single terpyridine ligand (L1) with Zn(II) also exhibited excellent narcissistic self-sorting behavior, without any statistical mixture.