Tiegang Ren

Influence of different ancillary ligand on the phosphorescent properties of platinum(II) complexes

In past two decades, lots of bidentate Pt(II) complexes are developed as potential organic light emitting diodes due to their simple synthetic process. The relative low quantum efficiency is one of the major blocks for their applications. Two new heteroleptic Pt(II) complexes bearing an n-hexyloxy substituted phenyllepidine-based ligand and either a picolinate (pic) (1) or acetylacetonate (acac) (2) ancillary ligand are synthesized as orange-red-emitter by Wawrzinek and coauthors. The quantum efficiency of 2 is much larger than that of 1 indicating that the variation of ancillary ligand has a great effect on the performance. Inspired by it, other two new bidentate Pt(II) complexes are theoretically designed with the same primary ligand along with pyrazolone (pzl) (3) or N-substituted carbazole (NCaz) (4) ancillary ligand. The phosphorescent properties are explored by density functional theory (DFT) and time dependent DFT (TDDFT) methods with the ultimate goal to explore the influence of ancillary ligand. Moreover, the emission rule is confirmed. Finally, the quantum yield is estimated according to the radiative rate constant (kr) and nonradiative rate constant (knr). The smaller knr is the vital item to determine the high quantum yield.

Protic pyrazolium ionic liquids for efficient chemical fixation of CO2: design, synthesis, and catalysis

The conversion of carbon dioxide into organic products under benign conditions is still challenging. Ionic liquids are regarded as efficient and “green” catalysts from a sustainability view point. However, little attention has been focused on pyrazolium ILs although they are structural isomers of imidazolium ILs. Even fewer studies have been performed on protic pyrazolium ILs. In this work, three new protic pyrazolium ILs, HTMPzBr, HMM3PzBr, and HMM5PzBr, have been synthesized to explore their catalytic activity for the coupling reaction of carbon dioxide and propylene oxide. Both theoretical calculations and experimental characterization have verified that HTMPzBr and HMM5PzBr have similar catalytic activity, which is higher than that of HMM3PzBr. The role of various weak interactions, especially hydrogen bonds, in the reaction is elucidated by detailed theoretical analysis. The sequence of catalytic activity predicted by the Double-IL theoretical model is totally consistent with the experimental result. It is reasonable to design ionic liquids from a molecular level if a suitable theoretical model is applied, and this would provide some guidance for further experimental study.