Chatterjee Aninda, Maity Banibrata, Ahmed Sayeed Ashique, Seth Debabrata
Department of Chemistry, Indian Institute of Technology Patna , Patna 800013, Bihar, India.
J Phys Chem B. 2014 Nov 6;118(44):12680-91. doi: 10.1021/jp506786m. Epub 2014 Oct 22.
In this work we report the photophysics and rotational diffusion of a hydrophilic solute 7-(N,N'-diethylamino)coumarin-3-carboxylic acid (7-DCCA) in four protic solvents: poly(ethylene glycol), ethylene glycol, tetraethylene glycol, and glycerol, with variation of temperature. The cumulative effect of polarity, viscosity, and structural features of these solvents, as well as specific solute-solvent interaction on the photophysical properties of 7-DCCA was discussed. We observed significant differences in both steady-state and time-resolved emission properties. Estimation of activation energy of viscous flow and activation energy of nonradiative decay reinforce our assumption of a cumulative effect. It was observed that, in all solvents, H-bonding interactions are mainly responsible for changing the spectral properties. Study of rotational relaxation behavior demonstrates superstick boundary condition to be operative in ethylene glycol. It is due to the H-bonding interaction between 7-DCCA and ethylene glycol. Similarly, stick boundary condition is followed in case of tetraethylene glycol at 278 K and further from 293 K. Convergence to the stick boundary is observed in case of poly(ethylene glycol). These changes can be attributed to the change in structural organization in both poly(ethylene glycol) and tetraethylene glycol.
在本工作中，我们报道了亲水性溶质7-(N,N'-二乙氨基)香豆素-3-羧酸（7-DCCA）在四种质子溶剂：聚乙二醇、乙二醇、四甘醇和甘油中随温度变化的光物理性质和旋转扩散。讨论了这些溶剂的极性、粘度和结构特征以及特定的溶质-溶剂相互作用对7-DCCA光物理性质的累积影响。我们观察到稳态和时间分辨发射性质都存在显著差异。粘性流动活化能和非辐射衰变活化能的估计强化了我们关于累积效应的假设。据观察，在所有溶剂中，氢键相互作用是改变光谱性质的主要原因。旋转弛豫行为的研究表明，在乙二醇中，超粘性边界条件起作用。这是由于7-DCCA与乙二醇之间的氢键相互作用。同样，在278 K时四甘醇以及293 K及更高温度下遵循粘性边界条件。在聚乙二醇中观察到向粘性边界的收敛。这些变化可归因于聚乙二醇和四甘醇中结构组织的变化。
