Sapelli Evandro, Brandão Tiago A S, Fiedler Haidi D, Nome Faruk
Departamento de Química, Universidade Federal de Santa Catarina, Florianópolis, SC 88040-900, Brazil.
J Colloid Interface Sci. 2007 Oct 1;314(1):214-22. doi: 10.1016/j.jcis.2007.05.049. Epub 2007 May 24.
Mixtures of Zn(II) and 8-hydroxyquinoline (8QOH) in a 1:2 proportion, in aqueous solutions, result in fast complexation, followed by precipitation. Addition of 0.05 M sodium dodecyl sulfate (SDS), N-dodecyl-N,N-dimethylammonio-1-propanesulfonate (SB3-12), N-hexadecyl-N,N-dimethylammonio-1-propanesulfonate (SB3-16) or Triton X-100 results in considerable retardation of precipitation. In the presence of SDS, SB3-12, SB3-16 and Triton X-100 the 8QOH chelates are only kinetically stable in solution and after 24 h, the precipitation is almost quantitative. Conversely, upon addition of the cationic surfactant hexadecyltrimethylammonium bromide (CTABr), the absorbance of the complex remains constant even after at least six months. The interaction of the ligand 8QOH (and of the (8QO)(2)Zn(II) complex) with the cationic surfactant was studied by ultraviolet and NMR spectroscopy and 8QOH has a pK(a)=9.05 in the presence of the cationic surfactant and the ligand intercalates in the micelle, being preferentially located near the headgroup of the micelle. Although the solubilization site of the (8QO)(2)Zn(II) complex is similar to that of 8QOH, the interaction of the aromatic moiety with the CTA(+) headgroup is much stronger, due to the increased electron density in the aromatic ring of the ligand. As a consequence of this interaction, sphere to rod transition and an increase in microscopic and macroscopic viscosity are observed.
在水溶液中，锌（II）与8 - 羟基喹啉（8QOH）以1:2的比例混合会导致快速络合，随后发生沉淀。添加0.05 M的十二烷基硫酸钠（SDS）、N - 十二烷基 - N,N - 二甲基铵 - 1 - 丙烷磺酸盐（SB3 - 12）、N - 十六烷基 - N,N - 二甲基铵 - 1 - 丙烷磺酸盐（SB3 - 16）或 Triton X - 100会使沉淀显著延迟。在SDS、SB3 - 12、SB3 - 16和Triton X - 100存在的情况下，8QOH螯合物在溶液中仅具有动力学稳定性，24小时后沉淀几乎是定量的。相反，添加阳离子表面活性剂十六烷基三甲基溴化铵（CTABr）后，即使至少六个月后，络合物的吸光度仍保持恒定。通过紫外光谱和核磁共振光谱研究了配体8QOH（以及(8QO)₂Zn(II)络合物）与阳离子表面活性剂的相互作用，发现在阳离子表面活性剂存在下8QOH的pKₐ = 9.05，并且配体插入胶束中，优先位于胶束的头基附近。尽管(8QO)₂Zn(II)络合物的增溶位点与8QOH相似，但由于配体芳环中电子密度增加，芳环部分与CTA⁺头基的相互作用要强得多。这种相互作用导致了从球形到棒状的转变以及微观和宏观粘度的增加。
