ESR and NMR Studies of a Novel Conjugated Donor−Acceptor Polymer Containing Magnetic Spins: Poly[bicarbazolylene-alt-phenylene-bis(cyanovinylene)]

Elemental-Doping-Induced Orbital Redistribution in Conjugated Polymer Boosts Charge-Transfer-Mediated Singlet Oxygen Production

Beyond the traditional exciton-based energy transfer, carrier-involved charge transfer provides an alternative pathway to overcoming spin restriction in photocatalytic singlet oxygen (1O2) generation. However, the charge-transfer-mediated method usually suffers from insufficient charge-carrier concentration and distribution, which are related to the electronic band structure. Herein, exemplified by polymeric carbon nitride (PCN), we propose an orbital-redistribution strategy for facilitating charge-transfer-mediated 1O2 generation. On the basis of theoretical simulation and spectroscopic characterizations, we demonstrated that the incorporation of bromine could dramatically facilitate the redistribution of the HOMO and LUMO in PCN, resulting in promoted exciton dissociation and adjacent electron/hole distribution. Benefiting from those, bromine-doped polymeric carbon nitride (Br-PCN) exhibited an obvious enhancement in the production of 1O2 via a two-step charge-transfer process. This work not only uncovers a promising method for regulating photoexcitation in polymeric photocatalysts but also sheds new light on photocatalytic 1O2 generation.

Ambient Cross-linking System Based on the Knoevenagel Condensation Reaction between Acetoacetylated Sucrose and Aromatic Dicarboxaldehydes

An ambient cross-linking system based on the Knoevenagel condensation reaction between acetoacetylated sucrose and aromatic dicarboxaldehydes was demonstrated. In this study, we use a rheological instrument to measure the gel time to predict and elucidate the likely reaction mechanism of the system, and we prepare films based on the mechanistic results. Acetoacetylated sucrose and 4,4'-biphenyldicarboxaldehyde were used as raw materials, piperidine was used as the catalyst, and nonvolatile dimethyl sulfoxide (DMSO) was used as the solvent. After mixing 4,4'-biphenyldicarboxaldehyde and piperidine for 30 min, the acetoacetylated sucrose was added, thus producing the shortest gel time. Then, the gel was characterized by Fourier transform infrared spectroscopy. In addition, three films were prepared by this approach with different aromatic dicarboxaldehydes, and the properties of the coatings were characterized by differential scanning calorimeter, dynamic mechanical analysis thermogravimetric analysis, and swelling ratio. It was found that these films have high Young's modulus, high glass transition temperatures, high pencil hardnesses, and low swelling ratios.

Convenient Synthesis of Heterocyclic Azo Dyes in the Class of Pyranopyrazoles and Chromenes

A series of novel azo group fused 2 H-chromenes and 4 H-chromenes were synthesised as well as pyranopyrazole derivatives via the Knoevenagel condensation reaction of C–H acid compounds with 5-(arylazo)salicylaldehydes by a nucleophilic addition to the carbonyl group followed cyclisation.