Theoretical Study On The Electronic Structures And Optical Properties Of Oxadisilole-Substituted Acenes And 5-(2-Pyridyl) Pyrazolate Boron Complexes

In recent years, there has been considerable research interest in organic light-emitting diodes (OLEDs) since the first discovery of an organic electroluminescent device by Tang and Van Slyke. Enormous progress has been made in the improvements of quantum efficiencies, thermal stability, color range and purity. However, charge transport efficiency and balance in organic materials plays the key role for the performance of OLEDs. The ground states calculations on the studied compounds were performed by DFT. The excied geometries have been optimized by ab initio CIS/6-31G.. The absorption and emission spectra were predicted by TD-DFT.1. The optimized structures indicated that the bond lengths also become more average with benzene ring increasing in the same transverse system, the bond length differences decrease between the ground and excited state with the conjugation lengths increasing. Next, the energy level calculation results show that HOMO energy level increase and LUMO energy level decrease with increasing phenyl rings, leading to the HOMO-LUMO energy gaps minish gradually. Due to the introduction of oxadisilole ring, the LUMO energy level further decreases with oxadisilole ring increasing. The strongest absorption and emission peaks are assigned to HOMO→LUMOπ-π* excitation character arising from S0→S1 electronic transition. The twelve oxadisilole-substituted acenes have comparatively small and similar reorganization energy, thus each oxadisilole-substituted acenes can be used as efficient and balanced carrier transport material.2. The electronic structure and absorption characters of 5-(2-pyridyl) pyrazole boron complexes, namely, 2a, 2c, 2a'and 2c'were theoretically studied using density functional theory (DFT). The optimized results show that the four compounds are four-coordinate organic compounds with C1 symmetry. The boron atom has a typical tetrahedral geometry with the adjacent atoms. In 2a and 2c, the phenyl ring is functioned as a hole transport group and the pyridyl ring as a electron transport group. In 2a'and 2c', the hole transport groups are phenyl and pyrazole ring and the electron transport groups are still pyridyl rings. The main transitions assigned to the intraligandπ→π* character.