Theoretical Studies on Phosphorescent Materials: The Conjugation-Extended PtII Complexes

Abstract

A theoretical study on the Pt II complex A based on a dimesitylboron (BMes 2 )-functionalized [Pt(C^N)(acac)] (C^N ¼ 2phenyl-pyridyl, acac ¼ acetylaceton) complex, as well as three conjugation-extended analogues of the methylimidazole (C*) ligand BMes 2 -[Pt(C^C*)(acac)] complexes B-D is performed. Their theoretical geometries, electronic structures, emission properties, and the radiative decay rate constants (k r ) were also investigated. The energy differences between the two highest occupied orbitals with dominant Pt d-orbital components (Ddd occ ) of D both at the ground and excited states are the smallest of all. Compared with B, the charge transfer in D possesses a marked trend towards the extended conjugated group, while C changed inconspicuously. The lowest-lying absorptions and the phosphorescence of them can be described as a mixed metal-to-ligand charge transfer (MLCT)/intra-ligand p-p* charge transfer (ILCT) and 3 MLCT/ 3 ILCT, respectively. The variation of charge transfer properties induced by extended conjugation and the radiative decay rate constants (k r ) calculated revealed that D is a more efficient blue phosphorescence material with a 497 nm emission transition.

A promising strategy for increasing phosphorescent quantum yield: The ligand 10‐cyclic chelate of the tetradentate Pt(II) complex

“…Besides, previous studies have shown that the SOC between the lowest triple excited state and the ground state is another temperatureindependent factor affecting the non-radiative rate constant. [54][55][56][57] The stronger the SOC effect is, the more easily the excited state will return to the ground state in the form of intersystem transition, causing the phosphorescence quenching. According to Table 7, the value of SOC between the lowest triple excited state and the ground state of Pt-C10 is 94.52 cm À1 , which is smaller than that of Pt-C11 (100.37 cm À1 ) and has a smaller Huang-Rhys factor.…”

Theoretical investigation on the effect of ancillary ligand modification for highly efficient phosphorescent platinum(ii) complex design

“…They are heavy metal atoms that can induce strong spin-orbit coupling (SOC) and promote an effective intersystem crossing (ISC), which results in higher quantum efficiency. [7][8][9][10][11] Platinum which has the second largest SOC constant, tends to form planar structure due to the d 8 electron conguration of the Pt(II) ion. The ligand of cyclometalated Pt(II) complexes can be designed as bidentate, tridentate and tetradentate.…”

A theory study based on DFT/TD‐DFT for a series of Ir(III) complexes with the low‐efficiency roll‐off and the high‐inter‐system crossover rate properties

“…Among heavy metal complexes, Ir(III) complexes excel in inducing strong spin-orbit coupling (SOC), promoting efficient inter-system crossover (ISC), and achieving heightened quantum efficiency. SOC can be boosted by introducing heavy atoms or altering electronic configurations from single to triplet states [15][16][17][18][19]. In summary, leveraging the effectiveness of (mdp) 2 Ir(acac)-where mdp represents 4-methyl-2,5-diphenylpyridine and acac stands for acetylacetone-as demonstrated by density functional theory (DFT) and time-dependent density functional theory (TD-DFT), we adopted it as a reference to systematically devise a series of Ir(III) complexes [20].…”