Design, Synthesis, Characterization and Complexation Studies of Novel Vanadophiles: Calix[4]pyrrole Hydroxamic Acids

Kejal P. Jayswal^a and Jigar R. Patela,^b*

^a Department of Chemistry, School of Sciences, Gujarat University, Ahmedabad-380009, Gujarat, India.
^b Navrang Chemicals, L78-GIDC, Odhav, Ahmedabad, Gujarat, India.
* Corresponding author: E-mail: jigarvirdia@gmail.com, Tel.: +91-9879290447

Abstract
New four armed calix[4]pyrrole bearing four hydroxamic acid groups (C4PHA) have been synthesized by reacting partially reduced mesotetramethyl-mesotetra (p-nitrophenyl) calix[4]pyrrole with different aromatic acid chlorides (benzoyl chloride, p-nitrobenzoyl chloride, cinnamoyl chloride, phenyl acetyl chloride and p-chlorobenzoyl chloride) at low temperature. Synthesized compounds were characterized by elemental analysis, FT-IR, NMR and Mass data. Extraction studies showed that synthesized ligands exhibit high affinity and selectivity for vanadium(V), especially 3e. Thus, various significant extraction parameters like pH, concentration of vanadium(V), reagent (ligand) concentration and solvent effects were optimized for 3e. The results of extraction studies with 3e, (using optimized procedure) were very encouraging, hence, the extraction experiments were further extended to natural and industrial samples in presence of diverse ions. The stoichiometry of vanadium-C4PHA (3e) complex was determined by slope-ratio method using UV-Visible spectrophotometry and the results were validated by ICP-OES analysis. Transportation studies of vanadium(V) across a liquid membrane containing C4PHA (3e) in a three-phase system were carried out in a specially fabricated glass assembly under controlled conditions and the mechanism of metal-ion transport has been explained.

Keywords: Calix[4]pyrrole, hydroxamic acid, vanadium, liquid-liquid extraction.