TY - JOUR
T1 - Octamethyl-octaundecylcyclo[8]pyrrole
T2 - A promising sulfate anion extractant
AU - Eller, Leah R.
AU - Stȩpień, Marcin
AU - Fowler, Christopher J.
AU - Jeong, Tae Lee
AU - Sessler, Jonathan L.
AU - Moyer, Bruce A.
PY - 2007/9/12
Y1 - 2007/9/12
N2 - The diprotonated form of an organic-solubilized cyclo[8]pyrrole derivative, bearing eight undecyl chains on the β-pyrrolic positions, was found to extract sulfate anion effectively from neutral aqueous media into a toluene organic phase. The kinetics of sulfate anion exchange between the two phases were found to be exceedingly slow in the absence of the phase-transfer catalyst, Aliquat 336-nitrate (A336N), but appreciable in its presence. The bisnitrate anion bound form of this cyclo[8]pyrrole could be generated in situ by subjecting the toluene phase containing initially 0.5 mM of the sulfate anion bound form and 0.1 mM trioctylamine (TOA) to successive equilibrations with aqueous 0.1 M HNO3 until sulfate was no longer detected in the aqueous phase. This bisnitrate complex, when studied as a 0.5 mM solution in toluene in the presence of 0.1 mM (TOAH)+(NO3-), was also found to be an effective extractant for sulfate anion. DSO4 values of 0.001 and 1000 were observed at 1 M NaNO3(aq) and 0.3 mM NaNO3(aq), respectively, and the logarithm of the conditional exchange constant, log(K'exch), was calculated to be 4.9±0.4. The present cyclo[8]pyrrole system is thus noteworthy as being the first synthetic receptor that displays a high selectivity for sulfate anion in the presence of excess nitrate under conditions of solvent extraction.
AB - The diprotonated form of an organic-solubilized cyclo[8]pyrrole derivative, bearing eight undecyl chains on the β-pyrrolic positions, was found to extract sulfate anion effectively from neutral aqueous media into a toluene organic phase. The kinetics of sulfate anion exchange between the two phases were found to be exceedingly slow in the absence of the phase-transfer catalyst, Aliquat 336-nitrate (A336N), but appreciable in its presence. The bisnitrate anion bound form of this cyclo[8]pyrrole could be generated in situ by subjecting the toluene phase containing initially 0.5 mM of the sulfate anion bound form and 0.1 mM trioctylamine (TOA) to successive equilibrations with aqueous 0.1 M HNO3 until sulfate was no longer detected in the aqueous phase. This bisnitrate complex, when studied as a 0.5 mM solution in toluene in the presence of 0.1 mM (TOAH)+(NO3-), was also found to be an effective extractant for sulfate anion. DSO4 values of 0.001 and 1000 were observed at 1 M NaNO3(aq) and 0.3 mM NaNO3(aq), respectively, and the logarithm of the conditional exchange constant, log(K'exch), was calculated to be 4.9±0.4. The present cyclo[8]pyrrole system is thus noteworthy as being the first synthetic receptor that displays a high selectivity for sulfate anion in the presence of excess nitrate under conditions of solvent extraction.
UR - http://www.scopus.com/inward/record.url?scp=34548735368&partnerID=8YFLogxK
U2 - 10.1021/ja074568k
DO - 10.1021/ja074568k
M3 - Article
AN - SCOPUS:34548735368
SN - 0002-7863
VL - 129
SP - 11020
EP - 11021
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 36
ER -