Syntheses and phosphorescent properties of blue emissive iridium complexes with tridentate pyrazolyl ligands
Syntheses and phosphorescent properties of blue emissive iridium complexes with tridentate pyrazolyl ligands
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DOI：
10.1021/ic800196s
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发表时间：
2008-08-18
影响因子：
4.6
通讯作者：
Haga, Masa-aki
中科院分区：
文献类型：
--
作者：
Yang, Lifen;Okuda, Furnio;Haga, Masa-aki
新型中性混合配体lr(N布尔AND C布尔AND N)(N布尔AND C)X配合物(N布尔AND C布尔AND N = 1,3 -二（3-甲基吡唑基）苯（bpzb）、1,5-二甲基-2,4-二（3-甲基吡唑基）苯（dmbpzb）和1,5-二氟-2,4-二（3-甲基吡唑基）苯（dfbpzb）；N布尔与C = 2-苯基吡啶（ppy）；和X = Cl或CN)的合成和表征。配合物lr(dmbpzb)(ppy)Cl的x射线单晶结构表明，在dmbpzb的N布尔与C布尔与N配体中，ppy配体中的氮原子占据了碳原子的反位，其lr-C键长为1.94(1)埃，配位碳原子占据了氯的反位。电化学数据表明，配合物在与0.9 V相似的+0.5电位范围内表现出lr（III/IV）氧化过程，在-2.6 V和-3.0 V左右分别表现出对Fc(0)/Fc（+）的不可逆还原。所有的lr（III）配合物在室温下都不发出磷光，尽管在77 K时表现出强烈的磷光，0-0跃迁中心在450 nm左右，寿命为3-14 μ s。DFT计算表明，HOMOs主要定位在铱5d pi和氯p pi*轨道上，而lumo主要来自ppy配体pi*轨道。磷光是由(LC)-L-3与(MLCT)-M-3和(XLCT)-X-3混合产生的。lr(dfbpzb)(ppy)Cl的温度相关寿命测量表明，存在一个低活化能（1720 cm(-1)）和高频因子(2.3 × 10（13) s(-1)）的热失活过程。一个不受限制的密度泛函理论表明，在dd态中，lr-N（吡唑基）键长都显著增加，其存在能量与磷光态几乎相同。基于T-1和S-0态势能面的彻底分析使我们能够确定导致这种热失活的反应途径。计算的活化能为1600，近似于1800 cm(-1)，与观测值非常吻合。
Novel neutral mixed-ligand lr(N boolean AND C boolean AND N)(N boolean AND C)X complexes (N boolean AND C boolean AND N = 1, 3-bis (3-methylpyrazolyl)benzene (bpzb), 1,5-dimethyl-2,4-bis(3-methylpyrazolyl)benzene (dmbpzb), and 1,5-difluoro-2,4-bis(3-methylpyrazolyl)benzene (dfbpzb); N boolean AND C = 2-phenyl pyridine (ppy); and X = Cl or CN) have been synthesized and characterized. An X-ray single-crystal structure of the complex lr(dmbpzb)(ppy)Cl shows that the nitrogen atom in the ppy ligand occupied the trans position to the carbon atom in the tridentate N boolean AND C boolean AND N ligand of dmbpzb with the lr-C bond length of 1.94(1) angstrom, whereas the coordinating carbon atom occupied the trans position of chlorine. Electrochemical data show that the complexes exhibit an oxidation lr(III/IV) process in the potential range of +0.5 similar to 0.9 V and two irreversible reductions at approximately -2.6 and -3.0 V against Fc(0)/Fc(+), respectively. All of the lr(III) complexes do not emit phosphorescence at room temperature, although strong phosphorescence is exhibited at 77 K with the 0-0 transition centered at around 450 nm and lifetimes of 3-14 mu s. DFT calculations indicate that the HOMOs are mainly localized on iridium 5d pi and chlorine p pi*, whereas the LUMOs are mainly from the ppy ligand pi* orbitals. The phosphorescence originates from a (LC)-L-3 state mixed with the (MLCT)-M-3 and (XLCT)-X-3 ones. Temperature-dependent lifetime measurements of lr(dfbpzb)(ppy)Cl reveal the existence of a thermal deactivation process with a low activation energy (1720 cm(-1)) and very high frequency factor (2.3 x 10(13) s(-1)). An unrestricted density functional theory indicates that the dd state, in which both the lr-N (pyrazolyl) bond lengths increase considerably, exists almost at the same energy as that for the phosphorescent state. A thorough analysis based on the potential energy surfaces for the T-1 and S-0 states allows us to determine the reaction pathway responsible for this thermal deactivation. The calculated activation energies of 1600 similar to 1800 cm(-1) are in excellent agreement with the observed values.