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高效增强含双吡咯亚甲基铱(III)配合物三重态光敏剂的可见光吸收及其在光氧化和三重态-三重态湮灭上转换中的应用。

Efficient enhancement of the visible-light absorption of cyclometalated Ir(III) complexes triplet photosensitizers with Bodipy and applications in photooxidation and triplet-triplet annihilation upconversion.

机构信息

State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, E-208 West Campus, 2 Ling Gong Road, Dalian 116024, China.

出版信息

Inorg Chem. 2013 Jun 3;52(11):6299-310. doi: 10.1021/ic302210b. Epub 2013 Jan 17.

Abstract

We report molecular designing strategies to enhance the effective visible-light absorption of cyclometalated Ir(III) complexes. Cationic cyclometalated Ir(III) complexes were prepared in which boron-dipyrromethene (Bodipy) units were attached to the 2,2'-bipyridine (bpy) ligand via -C≡C- bonds at either the meso-phenyl (Ir-2) or 2 position of the π core of Bodipy (Ir-3). For the first time the effect of π conjugating (Ir-3) or tethering (Ir-2) of a light-harvesting chromophore to the coordination center on the photophysical properties was compared in detail. Ir(ppy)2(bpy) (Ir-1; ppy = 2-phenylpyridine) was used as model complex, which gives the typical weak absorption in visible range (ε < 4790 M(-1) cm(-1) in region > 400 nm). Ir-2 and Ir-3 showed much stronger absorption in the visible range (ε = 71,400 M(-1) cm(-1) at 499 nm and 83,000 M(-1) cm(-1) at 527 nm, respectively). Room-temperature phosphorescence was only observed for Ir-1 (λ(em) = 590 nm) and Ir-3 (λ(em) = 742 nm). Ir-3 gives RT phosphorescence of the Bodipy unit. On the basis of the 77 K emission spectra, nanosecond transient absorption spectra, and spin density analysis, we proposed that Bodipy-localized long-lived triplet excited states were populated for Ir-2 (τT = 23.7 μs) and Ir-3 (87.2 μs). Ir-1 gives a much shorter triplet-state lifetime (0.35 μs). Complexes were used as singlet oxygen ((1)O2) photosensitizers in photooxidation. The (1)O2 quantum yield of Ir-3 (ΦΔ = 0.97) is ca. 2-fold of Ir-2 (ΦΔ = 0.52). Complexes were also used as triplet photosensitizer for TTA upconversion; upconversion quantum yields of 1.2% and 2.8% were observed for Ir-2 and Ir-3, respectively. Our results proved that the strong absorption of visible light of Ir-2 failed to enhance production of a triplet excited state. These results are useful for designing transition metal complexes that show effective strong visible-light absorption and long-lived triplet excited states, which can be used as ideal triplet photosensitizers in photocatalysis and TTA upconversion.

摘要

我们报告了增强金属铱配合物有效可见光吸收的分子设计策略。通过 -C≡C- 键将硼二吡咯甲烷 (Bodipy) 单元连接到 2,2'-联吡啶 (bpy) 配体上,制备了阳离子金属铱配合物,该配体位于间苯基 (Ir-2) 或 Bodipy π 核的 2 位 (Ir-3)。首次详细比较了光收集生色团与配位中心的 π 共轭 (Ir-3) 或键合 (Ir-2) 对光物理性质的影响。使用 Ir(ppy)2(bpy) (Ir-1;ppy = 2-苯基吡啶) 作为模型配合物,它在可见光区的吸收较弱 (ε < 4790 M(-1) cm(-1),在 400nm 以上的区域)。Ir-2 和 Ir-3 在可见光区的吸收要强得多 (ε = 71400 M(-1) cm(-1),在 499nm 处;83000 M(-1) cm(-1),在 527nm 处)。仅 Ir-1 (λ(em) = 590nm) 和 Ir-3 (λ(em) = 742nm) 观察到室温磷光。Ir-3 给出了 Bodipy 单元的室温磷光。基于 77K 发射光谱、纳秒瞬态吸收光谱和自旋密度分析,我们提出 Ir-2 (τT = 23.7μs) 和 Ir-3 (87.2μs) 中存在 Bodipy 局域长寿命三重态激发态。Ir-1 的三重态寿命要短得多 (0.35μs)。配合物在光氧化中用作单线态氧 ((1)O2) 光敏剂。Ir-3 (ΦΔ = 0.97) 的 (1)O2 量子产率约为 Ir-2 (ΦΔ = 0.52) 的 2 倍。配合物也被用作三重态光敏剂用于 TTA 上转换;观察到 Ir-2 和 Ir-3 的上转换量子产率分别为 1.2%和 2.8%。我们的结果证明,Ir-2 对可见光的强吸收并未能增强三重态激发态的产生。这些结果有助于设计具有有效强可见光吸收和长寿命三重态激发态的过渡金属配合物,这些配合物可作为光催化和 TTA 上转换中的理想三重态光敏剂。

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