Synthesis and near-infrared photothermal conversion of Cp*Rh-based [2]-catenanes in trapezoidal metallacycles

Abstract

Although the photothermal conversion properties of various self-assembled ensembles based on π–π stacking interactions have been reported, the impact of different stacking modes on their photothermal conversion efficiency has rarely been investigated. In this study, three similar flexible pyridine ligands were assembled with the binuclear Cp*Rh building block B1, leading to the formation of three [2]-catenanes in trapezoidal metallacycles with L-B-B-L, L-L-B-B and B-L-L-B stacks. We demonstrated that the π–π stacking modes of the building blocks can be controlled by adjusting the length and flexibility of the linkers. Comparative research studies of the NIR photothermal conversion efficiencies (57.0–83.7%) of the three [2]-catenanes indicated that the conversion efficiencies of the [2]-catenanes depend on the stacking modes of the building blocks and that the [2]-catenane with the L-B-B-L stack exhibited the best photothermal conversion ability. This research emphasizes the significance of stacking modes and presents a new approach for creating valuable NIR photothermal conversion materials based on half-sandwich metal structures.