Interaction of calix[4]arene derivatives towards anions and organic molecules

Abstract

Two new compounds, 25,27-N,N'-di-((2-ethoxy)benzyl)ethylenediamine-p-tert-butylcalix[4]arene (5a) and 25,27-di-(4-pyridylmethoxy)-p-tert-butylcalix[4]arene (6) have been synthesized. 1H-NMR titration experiments in chloroform-d or methanol-d4 were used to investigate the hydrogen bonding interaction. Complexation studies of diaza benzo crown p-tert-butylcalix[4]arene containing ethylene, propylene and butylene linkages (linkages (ligands (5a), (5b) and (5c), respectively) were carried out with various anions such as chloride, bromide, iodide, nitrate, carbonate, sulfate and phosphate. The complexation induced shift could not be observed. Ligand (6) containing hydrogen bond acceptors was investigated the hydrogen bonding interaction towards neutral molecules containing a wide varieties of hydrogen bond donors such as 1,3-dialdehyde-crown-p-tert-butylcalix[4]arene (ligand (2-1) and (2-2)), acetylacetone, 1,2-diaminoethane, 2,6-diaminopyridine, catechol, resorcinol, hydroquinone, phthalic acid, isophthalic acid and terephthalic acid. Ligand (6) was able to form complexes with catechol, resorcinol (log K > 20.8) and phthalic acid (log K = 5.41) in 1:4, 1:1 and 1:1 fashions, respectively. Comparison studie between catechol and phthalic acid suggested that ligand (6) formed a stronger complex with phthalic acid. In addition, the possible structures in the solutions of (6) catechol, (6) resorcinol and (6) phthalic acid were deduced from NOESY and ROESY.