Tuning the Emission Lifetime in Bis-cyclometalated Iridium(III) Complexes Bearing Iminopyrene Ligands

Bis-cyclometalated Ir­(III) complexes with
the general formula Ir­(ppz)2(X^NPyrene), where ppz = 1-phenylpyrazole
and X^NPyrene is
a bidentate chelate with X = N or O, are reported. Modifications on
the ancillary ligand containing pyrene drastically affect the emission
lifetimes observed (0.329 to 104 μs). Extended emission lifetimes
in these complexes compared to model complexes result from reversible
electronic energy transfer or the observation of dual emission containing
along-lived pyrene ligand-centered triplet (3LC) component.
A combination of steady-state and time-resolved spectroscopic techniques
are used to observe reversible electronic energy transfer in solution
between the iridium core and pyrene moiety in the complex [Ir­(ppz)2(NMe^NCH2Pyr)]­[PF6]
(2), where NMe^NCH2Pyr = N-(pyren-1-ylmethyl)-1-(pyridin-2-yl)­ethaneimine. Studies
on [Ir­(ppz)2(NMe^NCH2Pyr)]­[PF6] in a poly­(methyl methacrylate) (PMMA) film reveal that reversible
energy transfer is no longer effective, and instead, dual emission
with a long-lived 3LC component from pyrene is observed.
Dual emission is observed in additional cyclometalated iridium complexes
bearing pyrene-containing ancillary ligands N^NPyrene and O^NPyrene
when the complexes are dispersed in a PMMA film.

本文报道了通式为Ir(ppz)₂(X^NPyrene)的双环金属化铱(III)配合物，其中ppz为1-苯基吡唑（1-phenylpyrazole），X^NPyrene为X=N或O的双齿螯合配体。含芘的辅助配体上的修饰会显著改变所观测到的发射寿命（0.329至104 μs）。相较于模型配合物，此类配合物具有更长的发射寿命，这源于可逆电子能量转移，或是观测到包含长寿命芘配体中心三重态（³LC）组分的双发射现象。研究人员采用稳态与时间分辨光谱联用技术，在溶液中观测了配合物[Ir(ppz)₂(NMe^NCH₂Pyr)][PF₆]（2，其中NMe^NCH₂Pyr为N-(芘-1-基甲基)-1-(吡啶-2-基)乙亚胺）中铱核心与芘官能团之间的可逆电子能量转移。对聚甲基丙烯酸甲酯（poly(methyl methacrylate), PMMA）薄膜中的[Ir(ppz)₂(NMe^NCH₂Pyr)][PF₆]进行的研究表明，可逆能量转移不再有效，取而代之的是观测到源自芘的长寿命³LC组分的双发射。当此类配合物分散于PMMA薄膜中时，在其他带有含芘辅助配体N^NPyrene和O^NPyrene的环金属化铱配合物中也观测到了双发射现象。