2 research outputs found
Molecular Architecture and Symmetry Properties of 1,3-Alternate Calix[4]arenes with Orientable Groups at the Para Position of the Phenolic Rings
Two glycoclusters
constituted by four fully acetylated β-acetylmannosamine
residues linked through trimethylenethioureido spacers to a calix[4]arene
core and differing for the presence of methoxy or propoxy groups at
the lower rim were synthesized. One of the two compounds is fixed
in the 1,3-alternate geometry by the presence of the propoxy groups,
while the other is potentially free to assume one of the different
geometries allowed in calix[4]arene. Their similar NMR spectra in
chloroform clearly suggest the same 1,3-alternate geometry. Both compounds
were submitted to a conformational investigation with the DFT approach
at the standard B3LYP/6-31G(d) level. The two glycocalixarenes showed
a large conformational preference for the same geometry that put the
mannosamine moiety of one substituent close to the thioureido group
of the opposite substituent. This allows the formation of intramolecular
hydrogen bonds and originates a series of through-space close contacts.
A comparison with the NOESY maps evidence an excellent correspondence
between experimental and theoretical data, thus giving an experimental
validation of the highly symmetrical conformation that the two glycocalixarenes
assume in apolar solvents
Actinide–lanthanide co-extraction by rigidified diglycolamides
<p>Within the actinide and lanthanide co-extraction strategy, three rigidified diglycolamides, namely 2,6-bis (<i>N</i>-dodecyl-carboxamide)-4-oxo-4<i>H</i>-pyran (<b>1</b>), 2,6-bis-[<i>N</i>-(4-<i>tert</i>-butylphenyl)carboxamide]-4-oxo-4<i>H</i>-pyran (<b>2</b>), 2,6-bis[(<i>N</i>-docecyl-<i>N</i>-methyl)carboxamide]-4-methoxy-tetrahydro-pyran (<b>3</b>), were synthesized. Moreover, the effect of structural rigidification on Am(III) and Eu(III) extraction under different conditions was investigated. The carboxamide extractant <b>3</b> resembles the extracting behavior of <i>N,N,N</i>′,<i>N</i>′‐tetraoctyl diglycolamide (TODGA) in terms of efficiency and affinity within the lanthanide family, together with fast kinetics and satisfactory cation back-extraction. The presence of 1-octanol in the diluent mixture strongly affects the ligand stability. Moreover, despite the low extraction efficiency showed by <b>1</b> and <b>2</b>, all the three ligands exhibit a higher affinity for Am with respect to TODGA, resulting in a lower lanthanide/Americium separation factor, of around 4 for ligand <b>3</b> and close to 1 for ligands <b>1</b> and <b>2</b>.</p