英语翻译Luminescence Spectroscopy.The room-temperaturephotolumin

英语翻译
Luminescence Spectroscopy.The room-temperature
photoluminescence (PL) spectra of 1-5 inCH2Cl2 are shown
in Figure 3a,and the photoluminescent data are given in
Table 1.All of the complexes exhibit intense PL emission
with quantum efficiencies of 0.13-0.25 and emission lifetimes
of 0.75-2.7 μs.Complex 1 exhibits intense blue emissions
with vibronic fine structure at 457 and 486 nm,
corresponding to CIE (x = 0.18,y = 0.31).That is,the
emission of 1 is bluer than that of the already known complex
Ir(dfpy)(pic) (7)20 with CIE (x=0.16,y=0.33) (see Figures 3
and 4).The vibrational fine structure observed in the emission
spectra is the result of several overlapping satellite bands
that belong to different vibronic transitions.21 Generally,
emission bands from charge-transfer (CT) states are broad
and featureless,while ligand-centered (LC) states typically
give highly structured emissions.22 Thus,we can conclude
that the emission of 1 is mainly attributable to 3LC (πC∧N f
π*C∧N) and [dπ(Ir)fπ*C∧N] 3MLCT transitions.
It has been well demonstrated that the photophysical
properties of iridium(III) complexes,especially emission
color,are determined by the ligand structures.In our previous
report,15 we described the synthesis of a series of
cationic iridium(III) complexes [Ir(piq)2(N∧N)]þPF6
- (piq
=1-phenylisoquinoline),the emission wavelengths of which
could be significantly tuned from 586 to 732 nm.However,
all of these complexes are red-emitting materials.In the
present work,significant emission color tuning from blue
to deep red was realized (see Figure 4); the emission wavelength
could be tuned from 457 to 632 nm.That is,the
emission of these complexes is significantly red-shifted with
extension of the conjugated length of the N∧N ligands.
Moreover,the emission bands of 2-5 are broad and featureless.
Taken together with the results of theoretical calculations
(Table 2),we conclude that the emissions of 2-5 are
mainly attributable to [dπ(Ir) f π*N∧N] 3MLCT transitions
and 3[πC∧N f π*N∧N] LLCT transitions.
The low-temperature PL spectra of the complexes in
CH2Cl2 glass were recorded and are shown in Figure 3b.A
blue shift in the emission maxima of 20-30 nm on going
from fluid solution at room temperature to a rigid matrix at
77Kwas observed for 2-5.For typicalMLCTemitters,such
as the well-known [Ru(bpy)3]2þ complex and analogous
compounds,such a blue shift is usually in the range of
1000-2000 cm-1,and it is also in the same range for Ir(III)
cyclometalated compounds that are reported to be pure
MLCT emitters.23 For 2-5,the rather small blue shifts of

发光光谱研究.1－5在CH2Cl中的室温光致发光（PL）示于图3a,而光致发光数据在表1中给出.所有这些络合物都呈现强的PL发射,量子效率为0.13－0.25,发射寿命为0.75－2.7μs.络合物1呈现强的蓝光发射,在457和486nm处有电子振动的微细结构,对应于CIE（x＝0.18,y＝0.31）.也就是说,1的发射比已知的、具有CIE(x＝0.16,y＝0.33）的络合物Ir(dfpy)(pic)(7)20更蓝（见图3和4）.在发射谱中观察到的电子振动的微细结构是属于不同电子振动跃迁的若干重叠的附属谱带的结果21.一般来说,来自电荷传递（CT）状态的发射谱带是宽的,没有特色的,而以配体为中心的（LC）状态典型来说给出高度结构化的发射22.因此,我们可以得出结论,1的发射主要可归因于3LC（πC∧N→π*C∧N）和[dπ(Ir) →π*C∧N]3MLCT跃迁.
人们已很好地试验证实,铱（III）络合物的光物理性质,特别是发射颜色,由配体结构决定.在我们以前的报告中15,我们描述了一系列阳离子铱(III)络合物[Ir(piq)2(N∧N)]+PF6－
(piq=1-苯基异喹啉),它们的发射波长可以从586nm明显调谐到732nm.可是,所有这些络合物都是红光发射材料.在本研究中,实现了从蓝色到深红色的明显的发射颜色的调谐（见图4）；发射波长可从457nm调谐到632nm.也就是说,这些络合物的发射随着N∧N配体共轭长度的扩展明显红移了.而且,2－5的发射谱带是宽的,并且没有特色的.将这些理论计算结果（表2）放在一起,我们得出结论,2－5的发射主要可归因于[dπ(Ir) →π*C∧N]3MLCT跃迁和3[πC∧N→π*N∧N]LLCT跃迁.
这些络合物在CH2Cl2玻璃中的低温PL谱示于图3b.对于2－5来说,观察到了在从室温流体溶液进到77K下的刚性基质时,发射最大值的20－30nm的蓝移.对于典型的MLCT发射体,例如众所周知的[Ru(bpy)3]2+络合物或类似的化合物来说,这样的蓝移通常实在1000－2000cm－1的范围,而对于Ir（III）环金属化合物来说（据报道它们是纯MLCT发射体）,也是在此范围内23.对于2－5来说,小于1000cm－1的小蓝移反映了这些络合物的发射主要归因于MLCT跃迁.此蓝移是由室温下流体溶液的快速溶剂重组而引起的,这可以使CT状态在1发生前稳定化.