Thiacalixarene-p-tetrasulfonate (TCAS) incorporated a trilanthanide(III) core to form a 3:2 Ln3TCAS2complex in aqueous solution. The self-assembly process was monitored at pH 9.5 and 7.4 by HPLC for all lanthanides except PmIII. Self-assembly took place in three steps. First, TCAS and LnIIIformed a 1:1 Ln1TCAS1complex. Second, two molecules of Ln1TCAS1condensed to form Ln2TCAS2. Finally, Ln2TCAS2reacted with additional LnIIIto form Ln3TCAS2. This self-assembly exhibited extremely slow kinetics and required 1–4 d to reach completion. Small amounts of minor species, including Ln1TCAS1, Ln2TCAS2, and Ln4TCAS2, were observed depending on the LnIIIspecies and pH. The generation of these species is controlled by factors such as the stability of the Ln-TCAS species, effect of coordinated water, and size of LnIII. XAFS spectra of aqueous Gd3TCAS2solutions established the solution structure of the tri-LnIIIcluster sandwiched by two TCAS ligands.
ASJC Scopus subject areas
- Inorganic Chemistry