Controlling Noncovalent π–π Interactions in Dimers Toward Thermally Reversible Switching Between Monomer and Excimer Fluorescence

Thermochromic fluorescent materials (TFMs) have garnered great attention due to their unique fluorescence transition responsive to temperature. However, the application of TFMs is limited due to defects such as low thermosensitivity and a high temperature-responsive threshold value. In this case, this work explores a feasible strategy for designing TFMs. On the one hand, a sterically hindered unilateral tetraphenylethylene (TPE) substituent is introduced into pyrene chromophore in a meta-linkage mode. This type of molecular architecture is aimed at the integration of both aggregation-induced emission (AIE) character and isolated π–π pyrene dimer stacking, facilitating the achievement of the high contrast of emission intensity (i.e., strongly emissive aggregation state versus weakly emissive dispersion state) and color (i.e, excimer versus monomer). On the other hand, an effective matrix platform featured with alky chain length-dependent temperature-induced phase transition is constructed to assist the fabrication of desired patterns through temperature-controlled reversible phase transition between crystalline non-dispersion and liquated dispersion states. The findings demonstrate that these studied TFMs can be potentially applied to temperature indicators and switchable dynamic interior decoration, which provides a new avenue for the design of TFMs.