Yuancheng Wang

Tuning the Solid State Emission of the Carbazole and Cyano‐Substituted Tetraphenylethylene by Co‐Crystallization with Solvents

Solid state emissive materials with high quantum yields and tunable emissions are desirable for various applications. A new TPE derivative (1) with two carbazole moieties and two cyano groups is reported, which shows typical aggregation induced emission behavior. Four crystals 1a, 1b, 1c, and 1d are obtained after crystallization from N,N-dimethylformamid (DMF), trichloromethane (CHCl3 ), tetrahydrofuran (THF), and dichloromethane (CH2 Cl2 ), respectively. Crystal structural analyses reveal that (i) molecules of 1 co-crystallize with DMF, CHCl3 , THF, and CH2 Cl2 in 1a, 1b, 1c, and 1d, respectively, and (ii) conformations of 1 are different within 1a, 1b, 1c, and 1d, and compound 1 within crystal 1a adopts the most twisting conformation. Crystalline solids 1a, 1b, 1c, and 1d exhibit high emission quantum yields up to 0.65, but their emission colors are varied from blue to green. In comparison, the amorphous solid of 1 is yellow-emissive with emission maximum at 542 nm. Moreover, the blue- or green-emissive crystalline solids and the yellow-emissive amorphous solid can be inter-converted by the grinding of crystalline solids and exposure of the amorphous solid to vapors of appropriate solvents. It is also demonstrated that microrods of 1a, 1b, and 1d show typical optical waveguiding behavior.

Intramolecular Singlet Fission in an Antiaromatic Polycyclic Hydrocarbon

Singlet fission (SF), in which one singlet exciton (S1 ) splits into two triplets (T1 ) on adjacent molecules through a correlated triplet-pair 1 (TT) state, requires precise but difficult tuning of exciton energetics and intermolecular electronic couplings in the solid state. Antiaromatic 4nπ dibenzopentalenes (DPs) are demonstrated as a new class of single-chromophore-based intramolecular SF materials that exhibit an optically allowed S2 state with E(S2 )>2×E(T1 ) and an optically forbidden S1 state. Ultrafast population transfer from a high-lying S2 state to a 1 (TT) state was observed in monomeric solution of styryl-substituted DP (SDP) on a sub-picosecond timescale. There is evidence of exciton diffusion (ED) of the 1 (TT) state to yield two individual long-lived triplets in SDP thin film. The overall triplet yield via intramolecular SF and subsequent triplet-pair diffusion can be as high as 142±10 % in thin film.

Pyridinium-Substituted TetraphenylethyleneEntailing Alkyne Moiety: Enhancement of Photosensitizing Efficiency and Antimicrobial Activity

Apart from sensing and imaging, luminogens with aggregation-induced emission (AIE) are also interesting for photosensitizing. The photosensitizing behavior and bacteria-killing performance of a pyridinium-substituted tetraphenylethylene with an alkyne group (TPE-A-Py+ ) is reported herein. Interestingly, TPE-A-Py+ exhibits higher photosensitizing efficiency than TPE-Py+ (without alkyne group) when I- was used as a counteranion. This is well explained by the fact that the ΔΕST between the excited singlet state (S1 ) and triplet state (T1 ) was lower for TPE-A-Py+ than for TPE-Py+ , according to theoretical calculations. Moreover, replacement of I- with other anions (PF6- , N(SO2 CF3 )2- and BPh4- ) led to a decrease of photosensitizing efficiency for TPE-A-Py+ . Notably, TPE-A-Py+ could be used as an efficient photosensitizer to photo-inactivate ampicillin-resistant (ampr ) E. coli at low concentration under white-light irradiation very quickly.