Precise synthesis of π-conjugated [3]catenanes and Solomon link for photothermal responses via a dual-tuning strategy

Mechanically interlocked supramolecular compounds have garnered widespread attention but it remains challenging to investigate topological adjustments in such complicated structures. Here, the authors use a bidentate pyridyl ligand featuring an extended π-conjugated plane for coordination-directed self-assembly to engineer three different kinds of sophisticated complexes, including three Linear [3]catenanes 1(OTf)₁₂, 2(OTf)₁₂ and 3(OTf)₁₂, two Borromean rings 4(OTf)₁₂ and 5(OTf)₁₂, and one heterometallic Solomon link 6(OTf)₈ by modulating the Ru···Ru distances and conjugation planes of the building units or incorporating bridging silver ions. Subtle alterations in the building units can yield a diversity of topological architectures. Differences in the photothermal conversion properties of 1(OTf)₁₂ - 6(OTf)₈ are investigated. Various photothermal conversion efficiencies (23% - 81%) are obtained because of the synergistic effect of π···π stacking interactions and the free radical effect of building units. This finding enables the precise regulation of topology, thereby leading to a remarkable enhancement in photothermal conversion efficiency.