In the mid s, other groups of investigators joined the field of calixarene chemistry. In the same year another duo by the names of Niederl and Vogel did something similar with a para substituted resorcinol and they were the first to postulate a cyclic tetramer. He was able to freeze in a conformation by so called lower rim functionalization, replacing the hydroxyl groups by larger substituents.
Raman spectra of uranyl ion and its hydrolysis products in aqueous nitric acid. Evaluation of selective sorbents for the extraction of valuable metal ions Cs, Rb, Li, U from reverse osmosis rejected brine.