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首页> 外文期刊>RSC Advances >Reduced fluorescence quenching of coumarin 102 at higher phenol mole fractions in cyclohexane-phenol and anisole-phenol solvent mixtures: role of competitive hydrogen bonding
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Reduced fluorescence quenching of coumarin 102 at higher phenol mole fractions in cyclohexane-phenol and anisole-phenol solvent mixtures: role of competitive hydrogen bonding

机译：在环己烷-苯酚和苯甲醚-苯酚混合溶剂中较高的苯酚摩尔分数下，香豆素102的荧光猝灭减少：竞争性氢键的作用

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Recently, we demonstrated that the fluorescence of coumarin 102 (C102) drastically quenches upon hydrogen bonding (H-bonding) with phenol in a non-polar solvent cyclohexane due to H-bond driven photoinduced electron transfer (PET) (J. Phys. Chem. A, 2013, 117, 3945-3953). However, the work was limited to low concentrations of phenol only, where predominately a 1 : 1 C102-phenol complex exists. Herein, we report an unusual fluorescence modulation of C102 over mole fractions of the H-bond donor (phenol) in the cyclohexane-phenol mixtures covering a higher range of mole fractions. We found that the fluorescence quantum yield (phi(f)) and fluorescence lifetime (tau(f)) of C102 first diminish steadily with increase in the concentration of phenol, but after a particular mole fraction (X-PhOH = 0.013) both the quantities (phi(f) and tau(f)) increase upon further increase in the phenol content. The results can be attributed to the competitive nature of the C102-phenol and the phenol-phenol H-bonding. Since the PET quenching operates through the H-bond between the C=O group of C102 and the HO- group of phenol, the H-bond may fail to attain an optimum geometry when the phenol is linked with other phenols via the H-bond. The variation of the C102-phenol H-bonding nature with the mole fraction of phenol was supplemented by FT-IR measurements. Similar unusual variation of the C102 fluorescence is observed in the phenol-anisole mixtures to a lesser extent, but is completely absent in the anisole-cyclohexane mixtures, where H-bonding is practically impossible.
机译：最近，我们证明了由于H键驱动的光致电子转移（PET），香豆素102（C102）的荧光在非极性溶剂环己烷中与苯酚进行氢键（H键）时急剧淬灭（J. （A，2013，117，3945-3953）。但是，这项工作仅限于低浓度的苯酚，主要存在1：1的C102-苯酚配合物。在本文中，我们报道了在环己烷-苯酚混合物中，C102在氢键供体（苯酚）的摩尔分数上具有异常的荧光调制，该摩尔分数涵盖了较高的摩尔分数范围。我们发现C102的荧光量子产率（phi（f））和荧光寿命（tau（f））首先随着苯酚浓度的增加而稳步下降，但是在特定的摩尔分数（X-PhOH = 0.013）之后，苯酚含量的进一步增加会增加phi（f）和tau（f）的数量。结果可以归因于C102-苯酚和苯酚-苯酚H键的竞争性质。由于PET淬灭是通过C102的C = O基团与苯酚的HO-基团之间的H键进行的，因此当酚通过H键与其他酚连接时，H键可能无法获得最佳的几何形状。通过FT-IR测量来补充C102-酚H键合性质随酚的摩尔分数的变化。在苯酚-茴香醚混合物中观察到的C102荧光类似异常变化程度较小，但在苯甲醚-环己烷混合物中完全不存在，而H键实际上是不可能的。

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