Anderson EL, Gingery NM, Boswell PG, Chen XV, Rábai J, Bühlmann P. Ion Aggregation and R
3N
+-C(R)-H···NR
3 Hydrogen Bonding in a Fluorous Phase.
J Phys Chem B 2016;
120:11239-11246. [PMID:
27723332 DOI:
10.1021/acs.jpcb.6b07299]
[Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Potentiometric selectivities show that in fluorous ion-selective electrode membranes the tetrabutylammonium ion binds to fluorophilic proton ionophores. For the ionophore bis[3-(perfluorooctyl)propyl](2,2,2-trifluoroethyl)amine, this type of interaction is confirmed by the effect of the ionophore on the ionic conductivity of perfluoro(perhydrophenanthrene) solutions of a fluorophilic NBu4+ salt. In this system, ion pairs, triple ions, and higher ionic aggregates dominate over single ions, and the ionophore increases the conductivity by favoring the formation of ion aggregates with a net charge. These observations are consistent with the formation of R3N+-C(R)-H···NR3 type hydrogen bonds between the nitrogen atom of the ionophore and the hydrogen atoms in the α position to the positively charged quaternary ammonium center of NBu4+. Similar interactions were observed in a number of crystalline phases. To date, observations of C-H···N type hydrogen bonds in liquid phases have been very few, and solution-phase N+-C-H···N type hydrogen bonds have not been reported previously. Interestingly, no interactions between NBu4+ and the more basic ionophore tridodecylamine were observed in conventional plasticized poly(vinyl chloride) membranes doped with the ionophore tridodecylamine, emphasizing the uniquely low polarity of fluorous phases.
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