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.