The synthesis and crystal structures of 48 new rare-earth (RE?=?La3+—Y3+)-3,5-dihalogenated benzoic acid (3,5-dibromobenzoic acid [3,5-dBrBA] and 3-bromo-5-iodobenzoic acid [3,5-BrIBA])-terpyridine [TPY] complexes are reported. Ligand based supramolecular assembly drives the formation of five distinct structure types across the lanthanide series. Featured in these structures are multiple significant halogen bonding interactions occurring at the terminal halide substituents in the form of halogen–halogen, halogen–oxygen, and halogen–π interactions. This series complements previous efforts to synthesize and evaluate a catalogue of Ln-halobenzoic acid-TPY materials. With these data, a comparison of the influence of halogen interactions on supramolecular assembly is provided. As one might expect, the frequency with which halogen bonding occurs and the displacement of other assembly mechanisms, depends on the number and polarizability of the halogen species. Structures across these series fall into multiple distinct structure types, as defined by tecton geometry. Since these tectons are isostructural across each respective series, trends in halogen bond propensity can be derived. In this comparison, the likelihood of halogen bonding and disruption of π–π stacking is shown to increase as halogen size increases.
Graphic AbstractTwo new series of rare-earth (RE = La3+–Y3+)-3,5-dihalogenated benzoic acid (3,5-dibromobenzoic acid and 3-bromo-5-iodobenzoic acid)-terpyridine complexes are synthesized and compared, with respect to supramolecular assembly, to each other and previously reported RE-halogenated benzoic acid-terpyridine series in order to study the role of halogen bonding in this system.