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DFT/TDDFT insight into the impact of ring size of the NHC chelating unit of high effective phosphorescent Platinum (II) complexes
Author(s) -
Yan Xi,
Li Wenqian,
Zhang Huize,
Cai Wanlin,
Wang Jian,
Shen Wei
Publication year - 2018
Publication title -
applied organometallic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.53
H-Index - 71
eISSN - 1099-0739
pISSN - 0268-2605
DOI - 10.1002/aoc.4467
Subject(s) - phosphorescence , time dependent density functional theory , chemistry , density functional theory , platinum , ring (chemistry) , carbene , chelation , quantum yield , photochemistry , computational chemistry , catalysis , inorganic chemistry , organic chemistry , physics , fluorescence , quantum mechanics
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 k r slightly increased with declined number of NHC‐chelate ring, owing to the gradually larger SOC matrix elements between the T 1 state and S n states. Combining the temperature‐independent with temperature‐dependent nonradiative decay processes, the nonradiative decay rate k nr 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.