DFT/TDDFT insight into the impact of ring size of the NHC chelating unit of high effective phosphorescent Platinum (II) complexes

Abstract

Uncovering the photodeactivation mechanisms of unique N‐heterocyclic carbene (NHC)‐based transition metal complexes is favorable for designing more high‐efficiency phosphorescent materials. In this work, four bidentate platinum (II) complexes with NHC‐chelate are investigated by the density functional theory (DFT) and time‐dependent density functional theory (TDDFT) to probe into how the ring size of NHC‐chelate unit influences on electronic structures and the phosphorescent properties. To illustrate the photodeactivation mechanisms clearly, three significant photodeactivation processes (radiative decay process, temperature‐independent and temperature‐dependent nonradiative decay processes) were taken into consideration. We stated that radiative decay rate constants kr slightly increased with declined number of NHC‐chelate ring, owing to the gradually larger SOC matrix elements between the T1 state and Sn states. Combining the temperature‐independent with temperature‐dependent nonradiative decay processes, the nonradiative decay rate knr is Pt‐4 (five‐membered) < Pt‐3 (six‐membered) < Pt‐2 (seven‐membered) < Pt‐1 (eight‐membered). The calculated results testify that the decrease of size of the NHC chelating unit is a reliable insurance to improve the quantum yield. The designed complex Pt‐4 with five‐membered NHC‐ring can serve as a highly efficient phosphorescent material in the future. The results indicated controlling the ring size of NHC‐chelate is a feasible method to tune phosphorescence properties of Pt (II) complexes.

Insight into Coordination of Uranyl Ions with N,N′‐bis(2‐five‐membered heterocyclidene)‐1,8‐anthradiamines

“…The five‐membered heterocycles containing atoms N and O coordinating with metals are also frequently reported. For example, Yan X et al reported the impact of ring size of the NHC chelating unit of high effective phosphorescent Platinum (II) complexes, among which the designed complex Pt‐4 with five‐membered NHC‐ring can serve as a highly efficient phosphorescent material in the future . Wu N et al synthesized and characterized three cyclometalated iridium (III) complexes containing monodentate five‐membered heterocyclic ligands and demonstrated that these complexes can act as novel dual‐mode light‐mediated anticancer agents …”

Computational insights into the coupling mechanism of benzoic acid, phenoxy acetylene and dihydroisoquinoline catalyzed by silver ion as polarizer and stabilizer

“…The popular meta-GGA M06-L functional [20][21][22][23] was selected to study the entire reaction mechanism because the coupling of benzoic acid and phenyl alkynyl ether, the initial process of this reaction system, was catalyzed by Ag + . The highly parameterized M06-2X functional [24][25][26][27][28] was also employed to describe the coupling of the following coupling reaction of the generated α-acyloxy enol ester and dihydroisoquinoline without transition metals, and was compared with the M06-L results. Both the M06-L [29][30][31] and M06-2X [32,33] functionals can obtain reliable relative energies in describing noncovalent interactions.…”