Hydrogen bond strengthening induces fluorescence quenching of PRODAN derivative by turning on twisted intramolecular charge transfer.
Hydrogen bond strengthening induces fluorescence quenching of PRODAN derivative by turning on twisted intramolecular charge transfer.
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DOI：
10.1016/j.saa.2017.06.029
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发表时间：
2017-12
期刊：
影响因子：
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通讯作者：
Yonggang Yang;Donglin Li;Chaozheng Li;Yufang Liu;Kai Jiang
中科院分区：
文献类型：
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作者：
Yonggang Yang;Donglin Li;Chaozheng Li;Yufang Liu;Kai Jiang
研究人员提出了氢键(HB)对6-丙酰-2-二甲氨基萘(PRODAN)及其衍生物荧光的不同影响机制。在此，激发态跃迁和动力学分析证实了Pd(由3-羟基-2，2-二甲基丙烷取代的丙烷衍生物)的荧光是从平面分子内电荷转移(PICT)态而不是扭曲分子内电荷转移(TICT)态发出的，因为从TICT态到扭曲基态(T-S0)的荧光发射和表面跃迁是被禁止的。而Pd-(甲醇)2的分子内Hb(Intra-Hb)和分子间Hb(InterHb)的增强使TICT向T-S0态的表面跃迁和外转换到平面基态的路径变得顺畅，从而减小了两态的能量差。这种平滑使Pd-(甲醇)2的荧光状态转变为TICT状态，在TICT状态下不发生荧光发射，而是发生表面跃迁，导致Pd在甲醇溶剂中的部分荧光猝灭。这一结论不同于以往的相关报道。此外，Pd-甲醇在PICT状态下的Hb间增强导致了Hb内的裂解，与Pd相比，荧光红移了54 nm。对于Pd-(甲醇)2，这个红移增加到66 nm，以加强一个Hb内和两个Hb间。在PICT状态下，Pd-甲醇和Pd-(甲醇)2的偶极矩分别比Pd增加约10.3d和8.1D。Hb内和Hb间的协同作用通过开启TICT态和荧光红移导致Pd在甲醇溶剂中的部分猝灭。本工作合理地描述了Pd在甲醇溶剂中的荧光红移和部分猝灭现象，为研究具有较好光谱特性的分子的光谱性质提供了理论依据。
Researchers have proposed different effective mechanisms of hydrogen bonding (HB) on the fluorescence of 6-propionyl-2-dimethylaminonaphthalene (PRODAN) and its derivatives. Herein, excited state transition and dynamics analysis confirm that the fluorescence of PD (a derivative of PRODAN with ethyl replaced by 3-hydroxy-2,2-dimethylpropan) emits from the planar intramolecular charge transfer (PICT) state rather than twist ICT (TICT) state, because the fluorescence emission and surface hopping from the TICT state to the twist ground (T-S0) state is energy forbidden. Nevertheless, the strengthening of intramolecular-HB (intra-HB) and intermolecular-HB (inter-HB) of PD-(methanol)2smooth the pathway of surface hopping from TICT to T-S0state and the external conversion going to planar ground state by decreasing the energy difference of the two states. This smoothing changes the fluorescence state of PD-(methanol)2to the TICT state in which fluorescence emission does not occur but surface hopping, leading to the partial fluorescence quenching of PD in methanol solvent. This conclusion is different from previous related reports. Moreover, the inter-HB strengthening of PD-methanol in PICT state induces the cleavage of intra-HB and a fluorescence red-shift of 54 nm compared to PD. This red-shift increases to 66 nm for PD-(methanol)2for the strengthening of the one intra-HB and two inter-HBs. The dipole moments of PD-methanol and PD-(methanol)2respectively increase about 10.3D and 8.1D in PICT state compared to PD. The synergistic effect of intra-HB and inter-HB induces partial quenching of PD in methanol solvent by turning on the TICT state and fluorescence red-shift. This work gives a reasonable description on the fluorescence red-shift and partial quenching of PD in methanol solvent, which will bring insight into the study of spectroscopic properties of molecules owning better spectral characteristics.