Department of Chemistry and Institute for Molecular Science and Fusion Technology , Kangwon National University , Chuncheon , Gangwon 24341 , Republic of Korea.
Inorg Chem. 2019 Feb 18;58(4):2454-2462. doi: 10.1021/acs.inorgchem.8b03005. Epub 2019 Jan 29.
A series of triphenylamine (TPA)-containing salen-Al assembly dyads, [salen(3- tBu-5-R)Al(OCH- p-N(CH))] [salen = N, N'-bis(salicylidene)ethylenediamine; R = H (D1), tBu (D2), Ph (D3), OMe (D4), and NMe (D5)], were prepared in good yield (50-80%) and fully characterized by NMR spectroscopy and elemental analysis. Both the UV/vis absorption and photoluminescence (PL) spectra of D1-D4, except for D5, in a tetrahydrofuran solution exhibited dual patterns, which are assignable to the salen-Al-centered π-π* transition (low-energy region) and the TPA-centered π-π* transition (high-energy region). In particular, the emission spectra of the dyads displayed interesting dual-emissive patterns via a significant intramolecular energy transfer (IET) process between the salen-Al moiety and TPA group. Notably, this IET process was systematically tuned by varying the substituents and dominantly observed in the rigid state. More interestingly, compared to the salen-Al complexes (A1-A4) without the TPA group, D1-D4 exhibited enhanced quantum efficiencies. Time-dependent density functional theory calculations on the S-optimized structures of D1-D5 further supported these experimental results by indicating the existence of independent transition states between the salen-Al moiety and TPA group in the assembly dyads. The present study reports the first example of salen-Al complexes bearing electron-rich TPA moieties.
一系列含三苯胺（TPA）的席夫碱-铝组装二聚体，[席夫碱（3-tBu-5-R）铝（OCH-p-N（CH））] [席夫碱=salen=N，N'-双（水杨醛亚胺）乙二胺；R=H（D1），tBu（D2），Ph（D3），OMe（D4）和NMe（D5）]，以良好的产率（50-80%）制备，并通过 NMR 光谱和元素分析进行了充分的表征。除 D5 外，D1-D4 在四氢呋喃溶液中的紫外/可见吸收和光致发光（PL）光谱均表现出双重模式，可归因于席夫碱-铝中心的π-π跃迁（低能区）和 TPA 中心的π-π跃迁（高能区）。特别是，二聚体的发射光谱通过席夫碱-Al 部分和 TPA 基团之间的显著分子内能量转移（IET）过程显示出有趣的双重发射模式。值得注意的是，通过改变取代基，可以系统地调节这种 IET 过程，并且在刚性状态下主要观察到这种过程。更有趣的是，与没有 TPA 基团的席夫碱-铝配合物（A1-A4）相比，D1-D4 表现出增强的量子效率。对 D1-D5 的 S 优化结构进行的时间相关密度泛函理论计算进一步通过表明在组装二聚体中席夫碱-Al 部分和 TPA 基团之间存在独立的过渡态，支持了这些实验结果。本研究报道了首例含有富电子 TPA 部分的席夫碱-铝配合物。
