Multistimuli-Responsive Copper(I) Complexes Exhibiting Thermally Activated Delayed Fluorescence

Multistimuli-responsive luminescence has attracted increasing attention due to its promising applications. This study presents two new Cu(I) heteroleptic complexes 1 and 2, each featuring distinct N-heterocyclic fragments (pyrazinyl and pyridyl). Both complexes display reversible multistimuli-responsive luminescence and thermally activated delayed fluorescence. It is demonstrated that the reversible multistimuli-responsive luminescence is mainly associated with the breaking and restoring of NH···O hydrogen bonds, induced by grinding, heating, and exposure to CH₂Cl₂ vapor, as supported by single-crystal and powder X-ray diffraction and FT-IR analyses. Importantly, the type of stimuli, luminescent color, and contrast between two interconvertible luminescent colors can be modulated by modifying the structure of the pyridyl ring skeleton, such as by introducing an N atom. The results provide new insights into the design and synthesis of low-cost multistimuli-responsive luminescent materials with adjustable luminescent color and color contrast by rational modification of the diimine heterocyclic skeleton.