The HETTAP approach: self-assembly and metal ion sensing of dumbbell-shaped molecules and clip molecules

The pentacoordinated terpyridine-phenanthroline zinc(II) complex motif, conceived along the HETTAP concept, allows the preparation of a set of multicomponent supramolecular dumbbell and clip assemblies from various bisterpyridines. All assemblies show a notable luminescence at 350-400 nm. The formation of dumbbell Zn2(1b)2(2b)]4+ is convincingly demonstrated from the X-ray crystal structure analysis. Both dumbbell Zn2(1b)2(2b)]4+ and clip Zn2(1d)(2b)]4+ allow the monitoring of Hg2+ ions due to highly selective quenching of the emission that is driven by a Zn2+ --> Hg2+ exchange process, while the more-strained clip Zn2(1d)(2c)]4+ does not undergo such metal exchange and does not show quenching of the luminescence. Consequently, these assemblies exhibit a highly selective response due solely to supramolecular effects.