Switchable platinum-based tweezers with Pt–Pt bonding and selective luminescence quenching

Abstract

Molecular tweezers incorporating peripheral platinum salphen complexes and a central chelating terpyridine group have been synthesized. The terpyridine can be switched upon metal binding between a free ‘W’ shaped form and a coordinated ‘U’ form. The crystallographic structure of the zinc-closed molecular tweezers was obtained and presented a strong π-stacking between the Pt–salphen units associated with a Pt–Pt bond. The luminescence properties, notably in response to selected guest ions (Zn²⁺, Pb²⁺, Hg²⁺) and the resulting mechanical motion, have been investigated by UV-Vis and emission spectroscopy. While ion coordination to the terpy resulted in no significant changes in the luminescence, a selective intercalation of a second Hg²⁺ associated with a large differential quenching was observed.