Tuning the emission properties of cyclometalated platinum(II) complexes by intramolecular electron-sink/arylethynylated ligands and its application for enhanced luminescent oxygen sensing
作者:Wanhua Wu、Wenting Wu、Shaomin Ji、Huimin Guo、Peng Song、Keli Han、Lina Chi、Jingyin Shao、Jianzhang Zhao
DOI:10.1039/c0jm01794a
日期:——
We have synthesized five novel cyclometalated Pt(II) complexes (aryl-ppy)Pt(acac) (ppy = 2-phenyl pyridine, aryl = N-butyl naphthalimide (NI) ethynylene for Pt-1, N-butyl naphthalimide (NI)–CH2 –CO– for Pt-2, 4-cyanophenyl – CH2 – CO– for Pt-3, naphthal ethynylene for Pt-4 and naphthal-diketo for Pt-5). For the first time, π-conjugation of the ppy ligands was extended via the CC bond. Deep red/near IR emission (638 nm–700 nm) was observed for the complex containing naphthalimide ethynylene subunit (Pt-1), whereas the close analogue Pt-2 (in which the linker between the NI and the ppy subunit is a –CH2CO– group) shows a relatively blue-shifted emission (540 nm–570 nm) but much longer luminescent lifetime (τ = 25.5 μs) than Pt-1 (τ = 6.6 μs). Simultaneous fluorescence/phosphorescence emissions were observed for Pt-1 and Pt-2, but other complexes show sole phosphorescent emission. The red-shifted phosphorescence of the complexes compared to the model complex ppyPt(acac) (486 nm) was attributed to either the significant electron-sink effect of the NI fragment (Pt-1) (for which the electron withdrawing effect is stronger than the previously reported fluoren-9-one), or the extended π-conjugation of the ppy ligand (via CC bond) (e.g.Pt-4). The substantial tuning of the emission color and the luminescent lifetimes (0.86 μs–25.5 μs) of the complexes were rationalized by theoretical calculations (DFT/TDDFT), i.e. the emissive triplet excited states were assigned as the normal 3MLCT state (give smaller τ values) or the novel ligand-localized 3IL emissive state (give larger τ values). With tuning the luminescent lifetimes, the luminescent O2 sensitivity of the complexes was improved by 117-fold (Stern–Volmer quenching constants KSV = 0.234 Torr−1 for Pt-2vs. KSV = 0.002 Torr−1 for Pt-5).
我们合成了五种新型的环金属化铂(II)配合物(aryl-ppy)Pt(acac)(ppy = 2-苯基吡啶,aryl = N-丁基萘啶胺(NI)乙炔基用于Pt-1,N-丁基萘啶胺(NI)–CH2 –CO–用于Pt-2,4-氰基苯 – CH2 – CO–用于Pt-3,萘乙炔基用于Pt-4,萘-双酮用于Pt-5)。首次通过CC键扩展了ppy配体的π-共轭。含有萘啶胺乙炔基子单元(Pt-1)的配合物显示出深红色/近红外发射(638 nm–700 nm),而其近似物Pt-2(其中NI与ppy子单元之间的连接基团是–CH2CO–)则显示出较蓝移的发射(540 nm–570 nm),但其荧光寿命(τ = 25.5 μs)明显长于Pt-1(τ = 6.6 μs)。Pt-1和Pt-2同时观察到了荧光/磷光发射,但其他配合物仅显示磷光发射。与模型配合物ppyPt(acac)(486 nm)相比,配合物的红移磷光被归因于NI片段的显著电子吸引效应(Pt-1),其电子吸引效果强于之前报道的9-氟烯酮,或是ppy配体的扩展π-共轭(通过CC键)(如Pt-4)。通过理论计算(DFT/TDDFT)解释了配合物发射颜色和荧光寿命(0.86 μs–25.5 μs)的显著调节,即发光的三重激发态被归类为常规的3MLCT状态(给出较小的τ值)或新型的配体局域的3IL发光态(给出较大的τ值)。通过调节荧光寿命,配合物的荧光O2敏感性提升了117倍(Stern–Volmer淬灭常数KSV = 0.234 Torr−1对于Pt-2,相较于KSV = 0.002 Torr−1对于Pt-5)。