Modulating the blue shift of phosphorescence with fluorine-free group in iridium (Ⅲ) complexes
Abstract
In this work, iridium complexes 1–8 bearing bipyridine or pyridine-pyrimidine main ligand and picolinate ancillary ligand have been designed by varying the position of –OCH3 and phenyl groups at the ligands aiming at finding a better choice to design blue phosphors. The results indicate that an appropriate combination of –OCH3 and pyridine-pyrimidine ligand makes the emission wavelength a noticeable blue-shift. Moreover, the further introduction of phenyl group shifts the emission wavelength to a shorter region. In terms of the radiative decay rate constant (kr), the position of –OCH3 has a slight influence on it, but the introduction of phenyl group is conductive to enhancing this value. In particular, the 7 has the largest kr among the designed complexes up to 7.68 × 105 s‑1. As for the non-radiative process, 1–6 have high barriers between 3MLCT and 3MC, indicating the difficulty of electron relaxation to the non-emissive 3MC structure. There is no transition state of 3MLCT↔3MC is found for 7 and 8 bearing pyridine-pyrimidine ligand. However, the barriers of all complexes for the S0/3MC minimum energy crossing point reaction are high, which is in favor of avoiding the system relaxes to the S0 geometry by non-radiative path.
- Publication:
-
Journal of Luminescence
- Pub Date:
- June 2019
- DOI:
- 10.1016/j.jlumin.2019.03.011
- Bibcode:
- 2019JLum..210..479G
- Keywords:
-
- Radiative decay rate constant;
- Non-radiative process;
- S<SUB loc="post">0</SUB>/<SUP loc="pre">3</SUP>MC minimum energy crossing point