Majumdar Poulomi, Cui Xiaoneng, Xu Kejing, Zhao Jianzhang
State Key Laboratory of Fine Chemical, School of Chemical Engineering, Dalian University of Technology, Dalian, 116024, P.R. China.
Dalton Trans. 2015 Mar 7;44(9):4032-45. doi: 10.1039/c4dt03373f.
A rhodamine moiety was used for the preparation of trans bis(tributylphosphine) Pt(II) bisacetylide complexes (RH-BDPY-Pt-1 and RH-BDPY-Pt-2, with two different Bodipy acetylide ligands), which show acid/base-switchable photophysical properties. The rhodamine moiety undergoes reversible spirolactam ↔ opened amide structure transformation in the presence of an acid/base. Bodipy ligands are responsible for strong visible light-harvesting. The photophysical properties of the Pt(II) complexes were studied with steady state UV-Vis absorption, luminescence spectra, nanosecond transient absorption spectroscopy, electrochemical characterization and DFT/TDDFT computations. In the absence of an acid, the complexes show the absorption of Bodipy ligands at 580 nm and 500 nm, respectively. Both complexes show fluorescence. A minor phosphorescence band was observed for RH-BDPY-Pt-1. In the presence of trifluoroacetic acid (TFA), the spirolactam → opened amide transformation occurred and the absorption of the rhodamine moiety at 570 nm appeared; colour changes were observed for the solutions of the complexes. Moreover, the fluorescence of the complexes was switched on. Long-lived triplet excited states were observed for the two complexes (35 μs and 423 μs, respectively, in dichloromethane). Upon the addition of TFA, the triplet state lifetime of RH-BDPY-Pt-1 was substantially prolonged to 80 μs from 35 μs (the triplet state of RH-BDPY-Pt-1 is localized on the Bodipy moiety); for RH-BDPY-Pt-2, however, the triplet state is switched from the Bodipy-confined triplet state to a triplet state delocalized on the Bodipy and rhodamine moiety. Thus both the singlet excited state and the triplet state of the Pt(II) complexes were switched upon the addition of an acid. The photophysical properties were rationalized with DFT/TDDFT calculations. These results on tuning of the photophysical properties of Pt(II) complexes with a rhodamine moiety may be useful for designing external stimuli-activatable transition metal complexes.
罗丹明部分用于制备反式双（三丁基膦）铂（II）双乙炔配合物（RH-BDPY-Pt-1和RH-BDPY-Pt-2，带有两种不同的Bodipy乙炔配体），这些配合物表现出酸/碱可切换的光物理性质。罗丹明部分在酸/碱存在下会发生可逆的螺内酰胺⇔开环酰胺结构转变。Bodipy配体负责强烈的可见光捕获。通过稳态紫外可见吸收、发光光谱、纳秒瞬态吸收光谱、电化学表征和密度泛函理论/含时密度泛函理论计算研究了铂（II）配合物的光物理性质。在没有酸的情况下，配合物分别在580 nm和500 nm处显示Bodipy配体的吸收。两种配合物均显示荧光。观察到RH-BDPY-Pt-1有一个较弱的磷光带。在三氟乙酸（TFA）存在下，发生了螺内酰胺→开环酰胺转变，罗丹明部分在570 nm处出现吸收；观察到配合物溶液的颜色变化。此外，配合物的荧光被开启。观察到两种配合物都有长寿命的三重激发态（在二氯甲烷中分别为35 μs和4μs）。加入TFA后，RH-BDPY-Pt-1的三重态寿命从35 μs大幅延长至80 μs（RH-BDPY-Pt-1的三重态定域在Bodipy部分）；然而，对于RH-BDPY-Pt-2，三重态从Bodipy限制的三重态转变为定域在Bodipy和罗丹明部分的三重态。因此，加入酸后，铂（II）配合物的单重激发态和三重态都发生了切换。通过密度泛函理论/含时密度泛函理论计算对光物理性质进行了合理解释。这些关于用罗丹明部分调节铂（II）配合物光物理性质的结果可能有助于设计外部刺激可激活的过渡金属配合物。
