Dual Stimuli‐Responsive [2]Rotaxanes with Tunable Vibration‐Induced Emission and Switchable Circularly Polarized Luminescence

Abstract

Aiming at the construction of novel stimuli‐responsive fluorescent system with precisely tunable emissions, the typical 9,14‐diphenyl‐9,14‐dihydrodibenzo[a, c]phenazine (DPAC) luminogen with attractive vibration‐induced emission (VIE) behavior has been introduced into [2]rotaxane as a stopper. Taking advantage of their unique dual stimuli‐responsiveness towards solvent and anion, the resultant [2]rotaxanes reveal both tunable VIE and switchable circularly polarized luminescence (CPL). Attributed to the formation of mechanical bonds, DPAC‐functionalized [2]rotaxanes display interesting VIE behaviors including white‐light emission upon the addition of viscous solvent, as evaluated in detail by femtosecond transient absorption (TA) spectra. In addition, ascribed to the regulation of chirality information transmission through anion‐induced motions of chiral wheel, the resolved chiral [2]rotaxanes reveal unique switchable CPL upon the addition of anion, leading to significant increase in the dissymmetry factors (glum) values with excellent reversibility. Interestingly, upon doping the chiral [2]rotaxanes in stretchable polymer, the blend films reveal remarkable emission change from white light to light blue with significant 6.5‐fold increase in glum values up to ‐0.035 under external tensile stresses. This work provides not only a new design strategy for developing molecular systems with fluorescent tunability but also a novel platform for the construction of smart chiral luminescent materials for practical use.

Curved Nanographenes as Stoppers in a [2]Rotaxane with Two-Photon Excited Emission

“…Since then, an increasingly amount of potentially functional structures such as peptides or proteins, nanoparticles or inorganic clusters, oligonucleotides, subpthalocyanines, drugs, cyclodextrins or calixarenes, ligands, redox or photo-active groups, or radicals have been progressively incorporated as stopper units in rotaxanes. In this sense, we can highlight functional stoppers with luminescence properties . For instance, the anthracene core has been used as fluorescent stopper in rotaxanes, and its emission has been modulated in different stimuli-responsive molecular machines. ,, However, to the best of our knowledge, there are no examples reported of nanographenes only as rotaxane stoppers …”

“…In this sense, we can highlight functional stoppers with luminescence properties. 17 For instance, the anthracene core has been used as fluorescent stopper in rotaxanes, and its emission has been modulated in different stimuli-responsive molecular machines. 17a , 17d , 17e However, to the best of our knowledge, there are no examples reported of nanographenes only as rotaxane stoppers.…”