Mechanical Grinding-Induced Intermolecular Charge Transfer for Near-Infrared Photothermal Conversion

In this study, charge-transfer-type compounds comprising synthesized naphthalenediimide derivative (HNDISA) or its Pb-based coordination polymer (Pb-NDISA) and suitable primary or secondary amine organic molecules were prepared by the solvent-free mechanical grinding method. The coloration phenomenon arising from charge transfer during grinding serves as a discriminative tool for distinguishing various organic guest molecules. The porous structure of Pb-NDISA crystals facilitates the infiltration of guest molecules and contributes to the preservation of the intermolecular charge transfer state. Moreover, the intermolecular charge transfer induced by grinding exhibits remarkable stability in an ambient atmosphere, underscoring the pivotal role of well-ordered molecules in the mechanical grinding procedure. This mechanochromic phenomenon holds promise for the detection and sensing of organic molecules, while the exceptional charge-transfer absorption characteristics offer the potential for efficient near-infrared photothermal conversion.