Substituent-Directed Conformational Preorganization Enabling Self-assembly of [2]Catenanes with Photothermal Conversion Properties

Abstract

Mechanically interlocked structures exhibit remarkable adaptability and versatility due to their unique topologies, offering promising applications in molecular machines, smart materials, and energy conversion. In this work, a strategy for directing different topological configuration between metallarectangle and [2]catenane is demonstrated through the incorporation of -Br and -OCH₃ groups with distinct steric effects. Their differing size and spatial constraints promote ligand preorganization, facilitating controlled self-assembly and interlocking. Two metallarectangles (2a, 1b) and four [2]catenanes (2b, 3b, 4b, 5b) were synthesized via coordination-driven self-assembly and characterized by single-crystal X-ray diffraction, NMR spectroscopy, and ESI-TOF-MS. The photothermal properties were evaluated, revealing that 2b exhibits the highest performance, achieving a temperature change of 28 °C under 1.5 W irradiation. And the conversion efficiency ranges from 37.74% to 30.13% with varying power, attributing to the strong absorption at 730 nm and enhanced π-stacking interactions within the interlocked architecture. This study provides new insights into the rational design of functional topological complexes and highlights their potential in photothermal energy conversion.

Keywords

Half-sandwich unit / [2]catenane / Photothermal conversion / Structural regulation / Stacking interactions / Self-assembly / Coordination structures

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2025 SIOC, CAS, Shanghai, & WILEY-VCH GmbH