Zhuoran Kuang

Solvent polarity dependence on excited charge-transfer state properties in donor-acceptor-donor thermally activated delayed-fluorescence molecule

The photophysical properties of a donor-acceptor-donor (D-A-D) molecule based on oxadiazole, 2,5-bis(4-(10 H -phenoxazin-10-yl)phenyl-1,3,4-oxadiazole (2PXZ-OXD), have been systematically investigated by means of steady state and transient spectroscopy. A significant increase of Stokes shift with increasing solvent polarity indicates that a dipolar charge-transfer state is produced upon excitation. Further quantum chemical calculations show that the dipole moment of singlet excited state is much larger than that of triplet excited state, where singlet excited state is much more dependent on the polarity of solvents. The symmetry-breaking charge transfer states of quadrupole molecule induced by solvent polarity, exhibit large energy loss of singlet state with increasing of polarity. The energy gap is controlled by solvent polarity because of solvation. Furthermore, the emissive oscillator strength is dependent on the polarity, and the non-emissive relaxation resulted from the strong solvation reduces the luminescence properties of emitter.

Probing Laser‐Induced Heterogeneous Microenvironment Changes in Room‐Temperature Ionic Liquids

Modulating the heterogeneous microenvironment in room-temperature ionic liquids (RTILs) by external stimuli is an important approach for understanding and designing external field-induced chemical reactions in natural and applied systems. Here, we report for the first time the redistribution of oxygen molecules related to microstructure changes in RTILs induced by an external laser field, which is probed simultaneously by the triplet-state dynamics of porphyrin. A remarkably long-lived triplet state of porphyrin is observed with changes of microstructures after irradiation, suggesting that charge-shifted O2 molecules are induced by the external field and/or rearranged intrinsic ions move from nonpolar domains into the polar domains of RTILs through electrostatic interactions. The results suggest that heterogeneous systems like ionic liquids in the presence of external stimuli can be designed for reaction systems associated with not only O2 but also for CO2 , CS2 , etc. and many other similar solvent molecules for many promising applications.