Multinuclear Ag Clusters Sandwiched by Pt Complex Units: Fluxional Behavior and Chiral-at-Cluster Photoluminescence

Angew Chem Int Ed Engl. 2021 May 3;60(19):10654-10660. doi: 10.1002/anie.202101460. Epub 2021 Mar 23.

Abstract

Multinuclear Ag clusters sandwiched by Pt complex units were synthesized and characterized by single crystal X-ray diffraction and NMR studies. The sandwich-shaped multinuclear Ag complexes showed two different types of fluxional behavior in solution: rapid slippage of Pt complex units on the Ag3 core and a reversible demetalation-metalation reaction by the treatment with Cl anion and Ag ion, respectively. The Ag2 complex obtained by demetalation reaction from the Ag3 complex displayed U to Z isomerization. These multinuclear Ag complexes showed strong photoluminescence whose properties depended on the existence of Pt→Ag dative bonds. The Ag3 complex, identified to be "chiral-at-cluster", was optically resolved by the formation of a diastereomeric salt with a chiral anion. The enantiomers show circular dichroism (CD) and circularly polarized luminescence (CPL) properties which is unprecedented for compounds based on a chiral sandwich structure. Theoretical calculations allow to understand their structural features and photophysical properties.

Keywords: Ag cluster; Pt complex; fluxional behavior; photoluminescence; sandwich complex.