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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >The substituent effect of 2-R-o-carborane on the photophysical properties of iridium(III) cyclometalates
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The substituent effect of 2-R-o-carborane on the photophysical properties of iridium(III) cyclometalates

机译：2-R-o-碳环烷的取代基对铱（III）环金属盐的光物理性质的影响

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摘要

A family of heteroleptic iridium(III) cyclometalates, [4-(2-RCB) ppy](2)Ir(acac) (3c-3g; CB = o-carboran-1-yl; ppy = 2-phenylpyridinato-C-2, N; acac = acetylacetonate; R = Pr-i (3c), Bu-i (3d), Ph (3e), CF3C6H4 (3f), C6F5 (3g)) with various 2-R substituted o-carboranes at the 4-position in the phenyl ring of the ppy ligand, were prepared. The X-ray crystal structure of all complexes, including 3a (R = H) and 3b (R = Me), showed that while the carboranyl C-C bond distance increases with the increasing steric effect of the 2-R substituent (3a-3d), the bond distance is more likely to be influenced by the electronic effect of the substituent for the 2-aryl substituted complexes (3e-3g). The absorption and emission bands of all complexes were red-shifted with respect to those of the parent (ppy)(2)Ir(acac) (4). While 3a-3d exhibited intense green phosphorescence with good quantum efficiency in toluene (Phi(PL) = 0.17-0.47), the complexes were poorly emissive in THF (Phi(PL) < 0.004). In a PMMA film, however, 3a-3d became substantially emissive (FPL = 0.11-0.14, 8 wt% Ir), albeit less emissive than 4 (Phi(PL) = 0.15). In contrast, the 2-aryl substituted 3e-3g were almost non-emissive in both the solution and solid states. All complexes underwent facile carborane-centered, electrochemical reduction (E-onset = -2.01 to -1.22 V). The potential values of these reductions increased with increases in the electron accepting ability of the 2-R group (H < alkyl < aryl) and were largely shifted anodically with respect to those of 4 and 5-carborane substituted complexes. This reduction behavior of 3a-3g implies that the LUMO contribution of 2-R-o-carborane units increases through the substitution at the 4-position of the ppy ligand and is influenced by the nature of the 2-R group, which may be responsible for facile carboranyl C-C bond variation leading to efficient quenching of the emissive excited states.
机译：杂芳族铱（III）环金属化物家族，[4-（2-RCB）ppy]（2）Ir（acac）（3c-3g; CB =邻氨基甲酸酯-1-基; ppy = 2-苯基吡啶基-C- 2，N; acac =乙酰丙酮; R = Pr-i（3c），Bu-i（3d），Ph（3e），CF3C6H4（3f），C6F5（3g）），在其末端带有各种2-R取代的邻碳氢化合物。制备了ppy配体的苯环中的4-位。所有配合物的X射线晶体结构，包括3a（R = H）和3b（R = Me），都表明，尽管碳硼烷基CC键的距离随着2-R取代基（3a-3d）的空间效应的增加而增加。 ，键距更可能受2-芳基取代的配合物（3e-3g）的取代基的电子效应影响。所有配合物的吸收带和发射带相对于母体（ppy）（2）Ir（acac）（4）发生了红移。尽管3a-3d在甲苯中表现出强烈的绿色磷光并具有良好的量子效率（Phi（PL）= 0.17-0.47），但配合物在THF中的发射却很差（Phi（PL）<0.004）。然而，在PMMA膜中，尽管3a-3d的发射率小于4（Phi（PL）＝ 0.15），但3a-3d变得基本上发射（FPL ＝ 0.11-0.14，8wt％Ir）。相反，在溶液和固态下，被2-芳基取代的3e-3g几乎不发光。所有络合物均经过以碳硼烷为中心的简便电化学还原（E起始= -2.01至-1.22 V）。这些还原的电势值随2-R基团的电子接受能力的增加而增加（H <烷基<芳基），并且相对于4和5-碳环烷取代的配合物而言，在很大程度上发生了阳极移位。 3a-3g的这种还原行为表明2-Ro-碳环单元的LUMO贡献通过在ppy配体的4位上的取代而增加，并且受2-R基团的性质影响，这可能是由于轻度的碳硼烷基CC键变化导致发射激发态的有效猝灭。

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