Self-aggregation of Methylene Blue in aqueous medium and aqueous solutions of Bu4NBr and urea
Self-aggregation of Methylene Blue in aqueous medium and aqueous solutions of Bu4NBr and urea
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DOI：
10.1039/b005370h
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发表时间：
2000-01-01
影响因子：
3.3
通讯作者：
Talap, P
中科院分区：
文献类型：
--
作者：
Patil, K;Pawar, R;Talap, P
通过记录波长范围 550 至 700 nm 的电子光谱，研究了亚甲基蓝 [MB] (1x10(-6)-4x10(-4) M) 在水中以及 Bu4NBr (0.1-0.3 M) 和尿素 (0.1-4 M) 水溶液中的自聚集。光谱数据的分析产生了二聚体解离常数以及个体特征单体和二聚体光谱。通过首次应用激子模型，评估了二聚体中MB分子之间的相互作用能。此外，还获得了有关二聚体几何形状和二聚体中 MB 分子偶极子之间扭转角的信息。 MB 的尿素水溶液和 Bu4NBr 溶液也获得了类似的数据。显着的观察结果是，在尿素和 Bu4NBr 存在的情况下，二聚体几何形状从夹心型变为端对端型。据观察，除了涉及多极子的短程力外，对相互作用能的贡献主要来自范德华力和色散力。然而，MB 和水分子之间氢键相互作用的贡献却非常低。提出水结构效应和疏水相互作用是聚集现象的主要因素。
The self-aggregation of Methylene Blue [MB] (1x10(-6)-4x10(-4) M) in water and in aqueous solutions of Bu4NBr (0.1-0.3 M) and urea (0.1-4 M) has been investigated by recording electronic spectra in the wavelength range 550 to 700 nm. Analysis of the spectral data yielded the dimer dissociation constant, and individual characteristic monomer and dimer spectra. By applying the exciton model for the first time, the interaction energy between the MB molecules in the dimer species has been evaluated. Further, information about the dimer geometry and the twist angle between the dipoles of the MB molecules in the dimer species has been obtained. Similar data have also been obtained for solutions of MB in aqueous urea and Bu4NBr solutions. The significant observation is the change in the dimer geometry from sandwich type to end-on-end type in the presence of urea and Bu4NBr. It is observed that the contribution to the interaction energy is mainly from van der Waal's type and dispersion forces, in addition to short-range forces involving multipoles. However, the contribution from hydrogen-bonding interactions between MB and water molecules is found to be significantly low. It is proposed that water structural effects and hydrophobic interactions are the major factors in the phenomenon of aggregation.