Coordination assembly and NIR photothermal conversion of Cp*Rh-based supramolecular topologies based on distinct conjugated systems

The controllable construction of intricate metallic supramolecular structures has made noticeable progress in recent years. However, developments in the performance exploration of these complexes are still weak. Herein, three types of supramolecular architectures, Borromean rings, metalla[2]catenanes and metallamacrocycle assemblies, were synthesized based on suitable Cp*Rh (Cp* = eta(5)-pentamethyl-cyclopentadienyl) construction units and two rigid pyridine ligands (L1, L2) with distinct conjugated centers via the self-assembly strategy. Remarkably, the distinct conjugated centers at the two pyridine ligands result in different topologies. The structural study showed that two types of pi-pi stacking interactions stabilized the two topological assemblies Borromean rings and [2]catenanes, while generating active nonradiative pathways and inhibiting the radiative transition process, causing photothermal (PT) conversion in both the solution and solid states. The comparative research studies of the NIR photothermal conversion efficiencies (11.88-23.58%) of molecular Borromean rings or [2]catenanes and metallarectangles demonstrated the function of pi-pi stacking interactions in photothermal conversion. Furthermore, the feasible photothermal conversion of these structures was also observed in the solid state. This research not only provides insights for the development of novel half-sandwich based PT materials, but also paves the way for designing functional materials with appealing applications.