The synthesis of tetraamino derivative of thiacalixarene and its acid base property was carried out using ultraviolet (UV) spectroscopy. It was found that the properties of thiacalixarenes and calixarenes were different due to the substitution of methylene bridge groups with sulfur atoms. The pH distribution regions of several acidic or basic forms of thiacalixerene were also determined. It was stated that the determination of pH distribution region of the neutral form was important to the synthesis of thiacalixarene.
Hu, X., Xia, N., Ye, F., Ren, J., & Shi, X. (2004). Synthesis of tetraamino derivative of thiacalixarene and its acid-base property studied by UV spectroscopy. Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy, 60(7), 1427–1430. https://doi.org/10.1016/j.saa.2003.07.007