Chain-Length-Selective Intermolecular Charge-Transfer Regulation via Competitive and Cooperative Pathways in Solid-State Macrocyclic Host-Guest Systems.

Abstract

Dynamic regulation of intermolecular charge-transfer (CT) interactions in the solid state remains a key challenge in developing responsive functional materials. Herein, a dual-mode supramolecular strategy-is reported based on competitive and cooperative host-guest interactions-for constructing dynamic macrocycle-based CT complexes with tunable optical and photothermal properties in response to aliphatic aldehyde vapors. Two pillararene-derived macrocyclic hosts, EtLP6 and EtFLP6, form disordered CT assemblies with F4TCNQ via solvent-free grinding. These CT complexes exhibit chain-length-dependent vapochromic behavior governed by distinct mechanisms: guest-triggered disassembly or reassembly of D-A structures in EtLP6-F4TCNQα (competitive regulation), and aldehyde-assisted ternary CT assembly in EtFLP6-F4TCNQα (cooperative regulation). Single-crystal structures incorporating X-ray powder diffraction and spectral analyses reveal vapor-induced structural transformations that correlate directly with near-infrared (NIR) absorption changes. Notably, such CT-state modulation enables the first vapor-regulated organic photothermal cocrystal system, with conversion efficiency tunable from non-detectable levels to over 11% under 808 nm irradiation. This work establishes a versatile framework for designing solid-state supramolecular materials with multi-responsive optical and thermal functions via macrocyclic host-guest chemistry.