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.
Inorg Chem. 2011 Nov 21;50(22):11446-60. doi: 10.1021/ic201254w. Epub 2011 Oct 26.
[C(^)NPt(acac)] (C(^)N = cyclometalating ligand; acac = acetylacetonato) complexes in which the naphthalimide (NI) moiety is directly cyclometalated (NI as the C donor of the C-Pt bond) were synthesized. With 4-pyrazolylnaphthalimide, isomers with five-membered (Pt-2) and six-membered (Pt-3) chelate rings were obtained. With 4-pyridinylnaphthalimide, only the complex with a five-membered chelate ring (Pt-4) was isolated. A model complex with 1-phenylpyrazole as the C(^)N ligand was prepared (Pt-1). Strong absorption of visible light (ε = 21,900 M(-1) cm(-1) at 443 nm for Pt-3) and room temperature (RT) phosphorescence at 630 nm (Pt-2 and Pt-3) or 674 nm (Pt-4) were observed. Long-lived phosphorescences were observed for Pt-2 (τ(P) = 12.8 μs) and Pt-3 (τ(P) = 61.9 μs). Pt-1 is nonphosphorescent at RT in solution because of the acac-localized T(1) excited state [based on density functional theory (DFT) calculations and spin density analysis], but a structured emission band centered at 415 nm was observed at 77 K. Time-resolved transient absorption spectra and spin density analysis indicated a NI-localized intraligand triplet excited state ((3)IL) for complexes Pt-2, Pt-3, and Pt-4. DFT calculations on the transient absorption spectra (T(1) → T(n) transitions, n > 1) also support the (3)IL assignment of the T(1) excited states of Pt-2, Pt-3, and Pt-4. The complexes were used as triplet sensitizers for triplet-triplet-annihilation (TTA) based upconversion, and the results show that Pt-3 is an efficient sensitizer with an upconversion quantum yield of up to 14.1%, despite its low phosphorescence quantum yield of 5.2%. Thus, we propose that the sensitizer molecules at the triplet excited state that are otherwise nonphosphorescent were involved in the TTA upconversion process, indicating that weakly phosphorescent or nonphosphorescent transition-metal complexes can be used as triplet sensitizers for TTA upconversion.
[C(^)NPt(acac)]（C(^)N=环金属化配体；acac=乙酰丙酮酸盐）配合物，其中萘酰亚胺（NI）部分直接环金属化（NI 作为 C-Pt 键的 C 供体）。使用 4-吡唑基萘酰亚胺，获得了具有五元（Pt-2）和六元（Pt-3）螯合环的异构体。使用 4-吡啶基萘酰亚胺，仅分离出具有五元螯合环的配合物（Pt-4）。制备了以 1-苯基吡唑为 C(^)N 配体的模型配合物（Pt-1）。在 443nm 处观察到可见光（ε=21900M(-1)cm(-1)）和室温（RT）磷光（Pt-2 和 Pt-3 在 630nm 处或 Pt-4 在 674nm 处）的强吸收。观察到 Pt-2（τ(P)=12.8μs）和 Pt-3（τ(P)=61.9μs）的长寿命磷光。由于 acac 局域 T(1)激发态[基于密度泛函理论（DFT）计算和自旋密度分析]，Pt-1 在溶液中在 RT 下是非磷光的，但在 77K 时观察到中心位于 415nm 的结构化发射带。时间分辨瞬态吸收光谱和自旋密度分析表明，复合物 Pt-2、Pt-3 和 Pt-4 具有 NI 局域内配体三重态激发态((3)IL)。瞬态吸收光谱（T(1)→T(n)跃迁，n>1）的 DFT 计算也支持 Pt-2、Pt-3 和 Pt-4 的 T(1)激发态的(3)IL 分配。这些配合物被用作三重态-三重态湮灭（TTA）基上转换的三重态敏化剂，结果表明 Pt-3 是一种有效的敏化剂，上转换量子产率高达 14.1%，尽管其磷光量子产率仅为 5.2%。因此，我们提出处于三重态激发态的敏化剂分子即使是非磷光的，也参与了 TTA 上转换过程，这表明弱磷光或非磷光过渡金属配合物可用作 TTA 上转换的三重态敏化剂。
