Hui Zhao

Phosphorescence has rarely been observed in pure organic chromophore systems at room temperature. We herein report efficient phosphorescence from the crystals of benzophenone and its derivatives with a general formula of (X-C6H4)2C═O (X = F, Cl, Br) as well as methyl 4-bromobenzoate and 4,4′-dibromobiphenyl under ambient conditions. These luminogens are all nonemissive when they are dissolved in good solvents, adsorbed on TLC plates, and doped into polymer films, because active intramolecular motions such as rotations and vibrations under these conditions effectively annihilate their triplet excitons via nonradiative relaxation channels. In the crystalline state, the intramolecular motions are restricted by the crystal lattices and intermolecular interactions, particularly C−H···O, N−H···O, C−H···X (X = F, Cl, Br), C−Br···Br−C, and C−H···π hydrogen bonding. The physical constraints and multiple intermolecular interactions collectively lock the conformations of the luminogen molecules. This structural rigidification effect makes the luminogens highly phosphorescent in the crystalline state at room temperature.

Polymers featuring photolabile groups are the subject of intense research because they allow the alteration of polymer properties simply by irradiation. In particular, the o-nitrobenzyl group (o-NB) is utilized frequently in polymer and materials science. This Perspective pays particular attention to the increasing utilization of this chemical group in polymer chemistry. It covers the use of (i) o-NB-based cross-linkers for photodegradable hydrogels, (ii) o-NB side chain functionalization in (block) copolymers, (iii) o-NB side chain functionalization for thin film patterning, (iv) o-NB for self-assembled monolayers, (v) photocleavable block copolymers, and (vi) photocleavable bioconjugates. We conclude with an outlook on new research directions in this rapidly expanding area.

Tetraphenylethene (TPE)-containing polytriazoles (P3) with high molecular weights in high yields was synthesized by the Cu(I)-catalyzed click polymerization of diyne with diazides. The diyne and diazide monomers, namely 1,4-bis(propargyloxy) benzene (1), 1,2-bis[4-(azidohexyloxy)phenyl]-1,2- diphenylethene (2a), and 1,2-bis[(4-azidomethyl)phenyl]-1,2-diphenylethene (2b), were synthesized. The monomer structures were confirmed by spectroscopic analyses. The click polymerization in organic media using an organosoluble catalyst of Cu(PPh₃)₃Br. Utilizing the novel AIE effect, the polytriazoles are used as chemosensors for the detection of explosives in the aggregate and solid states. The emission quenching is observed at a concentration as low as 0.1 μg/mL or 0.1 ppm. The changes in the φ_F values of P3 in the aqueous mixtures with different water fractions further confirm the AIE characteristics of the polymers.