1,1′‐Binaphthyl Consisting of Two Donor–π–Acceptor Subunits: A General Skeleton for Temperature‐Dependent Dual Fluorescence

Abstract

Temperature‐dependent dual fluorescence with the anti‐Kasha's rule is of great interest, but is a very challenging property to achieve in small organic molecules. The highly sensitive temperature‐dependent dual fluorescence of 2,2′‐bis(dimethylamino)‐6,6′‐bis(dimesitylboryl)‐1,1′‐binaphthyl (BNMe2‐BNaph), which essentially consists of two donor–π–acceptor (D‐π‐A) subunits, inspired the exploration of the importance of its structural features and the general utility of this molecular design. The reference compound MBNMe2‐BNaph, which lacks one electron‐accepting Mes2B, is found to show less sensitive temperature‐dependent dual fluorescence, suggesting that the structure of BNMe2‐Bnaph, consisting of two symmetrical D‐π‐A subunits, is very important for achieving highly sensitive temperature‐dependent dual fluorescence. In addition, it is found that another two 1,1′‐binaphthyls, CHONMe2‐BNaph and CNNMe2‐BNaph, which also consist of two D‐π‐A subunits with Mes2B groups replaced by CHO and CN, respectively, also show temperature‐dependent dual fluorescence, with the fluorescence changing in a similar manner to BNMe2‐BNaph, indicating the general utility of the current molecular design for temperature‐dependent dual fluorescence. Furthermore, the temperature‐dependent dual fluorescence behaviors, such as the relative intensities of the two emission bands, the separation of the two emissions bands, and the sensitivity of the fluorescence intensity ratio to temperature, are greatly influence by the electron acceptors.

Perylene Bisimide and Naphthyl‐Based Molecular Dyads: Hydrogen Bonds Driving Co‐planarization and Anomalous Temperature‐Response Fluorescence

“…We further assume that the ICT state of PBI‐2NM virtually has very weak or negligible emission, while the emission is mainly from the LE state. The quench of the ICT emission is not uncommon . As for the ICT state incorporating the electron donor–acceptor moiety linked by the C−C triple bond, its drastic emission quenching has been reported in a number of cases .…”

Perylene Bisimide and Naphthyl‐Based Molecular Dyads: Hydrogen Bonds Driving Co‐planarization and Anomalous Temperature‐Response Fluorescence

“…Thec oplanar PBI-2NM possesses ICT as the lowest lying singlet state (S 1 )w hile the twisted configuration mainly has the LE character.Wefurther assume that the ICT state of PBI-2NM virtually has very weak or negligible emission, while the emission is mainly from the LE state.T he quench of the ICT emission is not uncommon. [11,12] As for the ICT state incorporating the electron donor-acceptor moiety linked by the CÀCt riple bond, its drastic emission quenching has been reported in anumber of cases. [52] This may be rationalized, in aqualitative manner, by its spatial separation in charge,and hence the small radiative recombination rate,which is then subject to any non-radiative deactivation processes.Aconvincing one may be ascribed to the non-radiative charge recombination coupled with the ground state.…”

“…With the design, various fluorescence probes such as temperature, viscosity, pH, polarity, pressure, and even chemicals have been developed . Fluorophores with both local excited (LE) state emission and intramolecular charge transfer (ICT) emission are good candidates for the design of the probes . These fluorophores are generally composed of a donor (D) and an acceptor (A) moieties bridged by a conjugated moiety.…”

“…[1][2][3][4][5][6][7][8][9] Fluorophores with both local excited (LE) state emission and intramolecular charge transfer (ICT) emission are good candidates for the design of the probes. [10][11][12][13][14] These fluorophores are generally composed of ad onor (D) and an acceptor (A) moieties bridged by ac onjugated moiety.H owever,m ost of the ICT related research was performed with variations among the donor, the acceptor,a nd the bridging units.T oe nhance the stimuli-responsiveness and to broaden the functionality of ICT related fluorescent systems,proton transfer, [15][16][17][18][19][20][21] cyclization, [22][23][24] and other intramolecular interactions [25][26][27][28] have been employed to regulate the degree of conjugation of the structure between the donor and the acceptor.One possibility for the design is to introduce an alkynyl group into the bridge connecting the donor and the acceptor as ap art of the conjugated structure.W ith the design, the donor and the acceptor can freely rotate around the linker,e nabling reversible transformation between ac onjugated state and adis-conjugated state.Unfortunately,the rotation is generally too fast to allow absorption and emission at as pecific conformation, which impedes their design toward smart molecular systems.Astrategy to solve the problem, to our viewpoint, is to introduce weak but sufficient interactions to improve the stability of the conjugated structures via hindering the rotation. To realize such adesign, H-bonding seems to be ac ase in point, which has been used in the fixation of certain conformations of molecular systems.…”

Perylene diimide-based supramolecular polymer with temperature-sensitive ratiometric fluorescence responsiveness in solution and gels

“…Temperature-sensitive fluorescent materials are attracting increasing attention due to their application potential in fields from biosensing to information encryption. [1][2][3][4] In these applications, ratiometric fluorescence is preferred because it provides high resolution and allows accurate and quantitative readout in combination with a simple fluorescence change. [5][6][7][8][9][10][11][12][13][14][15] Different material systems have been developed to get thermo-sensitive ratiometric fluorescence, including hybrid nanoparticles, carbon dots, polymer systems, rare-earth complexes, etc.…”