An investigation of the positional isomeric effect of terpyridine derivatives: Self-assembly of novel cadmium coordination architectures driven by N-donor covalence and π⋯π non-covalent interactions

Four cadmium compounds based on two pyridyl substituted terpyridine isomers, namely {[Cd3(L1)2(SCN)6](THF)2}n (1), [Cd2(L1)(CH3OH)Cl4]n (2), [Cd2(L2)2(N3)4] (3) and [Cd2(L2)2(SCN)4] (4) (L1 = 4′-(3-pyridyl)-2,2′:6′,2″-terpyridine, L2 = 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine) have been synthesized and characterized by IR, elemental analyses, and luminescent spectroscopy with the purpose of investigating the influence of isomeric effect on network assembly. In compounds 1 and 2, L1 as a mono-tridentate bridging ligand links CdII atoms into 1D grid-like and 2D wave-like polymers. In contrast, in compounds 3 and 4, L2 as a chelating ligand forms CdII dimeric structures. The different coordination behaviors and the positional isomer effect were discussed under the same reaction conditions. In addition, three kind of π⋯π interactions in the four compounds were summarized, two of which could not be observed on tpy-based complexes.

Graphical abstractThe reaction of two pyridyl substituted terpyridine isomers L1 and L2 with CdII atoms resulted in different dimensional architectures. L1 as a mono-tridentate bridging ligand links Cd3 and Cd4 clusters into 1D grid-like and 2D wave-like polymers, respectively. However, L2 as a chelating ligand forms binuclear structures.Figure optionsDownload full-size imageDownload as PowerPoint slide