科研之友
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摘要
We herein report a theoretical study using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods to investigate Cu(I) complexes with 2-(2'-pyridyl/quinolyl)imidazole and bis[2-(diphenylphosphino)phenyl]ether mixed ligands. Based on the experimental data for complexes 1 and 2, we first benchmarked different functionals with different HF% and found B3PW91 to be the optimal functional for this system. The computational results indicate that complex 1, with a pyridyl unit, has a much larger radiative decay rate (k(r)) than complex 2, which has a quinolyl unit. This difference is presumably due to higher HOMO electronic distribution in the d(x-)(y)(2)(2) orbital, which leads to a markedly shortened Cu-N-2 bond, enhancing the metal-ligand interaction. However, a much smaller experimental value was found for the non-radiative decay rate (k(nr)) in complex 2, rendering 1 a slightly weaker emitter than 2. We conclude that the difference is due to more effective suppression of deformation when the quinolyl unit is used instead of pyridyl. We sought to increase the photoluminescence quantum yield (PLQY) through modifying the ligand on complex 2, with the goal being to keep the small k(nr) value while simultaneously increasing k(r). The computational results indicate that our designed complexes 2a-2c, which possess modified ligands with electron-donating or withdrawing alkyl substituents on N-3, increased the distributions of d(x-)(y)(2)(2) and decreased that of the d(yz) compared to 2. Their coordinating abilities were therefore enhanced, with the k(r) values being 134, 22.70, and 0.16 times that of 2 for 2a, 2b and 2c, respectively. Higher PLQYs were achieved in 2a and 2b with the addition of electron-donating alkyl substituents on the ligands, which yielded complexes with significantly shortened Cu-N-2 bonds and enhanced metal-ligand interaction. This investigation on the microscopic mechanism of the photoluminescent properties of these complexes can provide useful knowledge for experimentalists.
- 出版日期2017-6
- 单位吉林大学
