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Abstract Our interest in the design of heavy pnictogen‐based Lewis acids for anion trafficking across biological membrane mimics has led us to investigate trivalent bismuthenium cations as chloride anion transporters. Here, we describe two chlorodiarylbismuthines, elaborated on aperi‐substituted naphthalene backbone and stabilized by an adjacent thio‐ or seleno‐ether functionality that engages the bismuth center in a Ch→Bi interaction (Ch=chalcogen). These new derivatives are stable in aqueous environment and readiliy transport chloride anions across the membrane of phospholipid‐based vesicles loaded with KCl. In addition to establishing the use of such motifs in anion transport, this investigation shows that the Lewis acidity, lipophilicity, and thus chloride transport properties depend on the nature of the chalcogen.
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Abstract To augment the fluoride binding ability of Lewis acidic stiboranes, we have synthesized and characterized a SbVderivative (PhSbF2((o‐(NH(2,6‐C6H3F2)C6H4)2,3) featuring diarylamine groups installed in proximity to the antimony center and poised to engage Sb‐bound fluoride anions in hydrogen bonding interactions. A competition experiment between3and Ph3SbF2(4) along with calculations show that the fluoride ion affinity of3is superior to that of4.more » « less
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Organoantimony Lewis acids have been coveted for their ability to bind hard anions like fluoride in competing media. Herein, we describe the synthesis of a phenyl dithienostibole (1) in which the antimony(III) center is embedded within a planar dibenzodithiophene chromophore. Compound1reacts witho‐chloranil to form the corresponding catecholatostiborane (2); it also reacts withtert‐butyl peroxide in the presence of perfluoropinacol to form the corresponding pinacolatostiborane (3). Compound2was investigated as a platform for anion binding. UV–vis titrations in CH2Cl2afforded an association constant greater than 107 M−1pointing to the high fluoridophilicity of this new system. Density functional theory calculations highlight the role played by theσ*(Sb‐Cphenyl) orbital in imparting Lewis acidity to the antimony center of2.more » « less
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Here we present a new method to monitor fluoride transmembrane transport into liposomes using a europium( iii ) complex. We take advantage of the long emission lifetime of this probe to measure the transport activity of a fluorescent transporter. The high sensitivity, selectivity, and versatility of the assay allowed us to study different types of fluoride transporters and unravel their mechanisms of action.more » « less
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With our continuing interest in the chemistry of cationic boranes, we have synthesizedthe tetrafluoroborate salt of 1-dimesitylboron-4-(N-methyl-9-acridinium)-phenylene which acts as a turn-on fluoride anion sensor, visibly changing from yellow to orange upon binding fluoride. To understand this reactivity, we spectroscopically and computationally analyzed the cation and triarylfluoroborate adduct. UV-vis spectroscopy and TD-DFT revealed the basis of the color change to be a red shift in a low-energy absorption band resulting from intramolecular charge-transfer. Electrochemical studies were undertaken to further probe this system. Cyclic voltammetry indicated a reversible one-electron reduction for the cation and a cathodic shift of -0.12 V in the first reduction wave upon fluoride binding. Chemical reduction of the cation yielded the acridine borane radical which was verified by EPR spectroscopy.more » « less
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We describe the synthesis of [ o -Ph 2 P(O)(C 6 H 4 )SbPh 3 ] + ([2] + ), an intramolecularly base-stabilized stibonium Lewis acid which was obtained by reaction of [ o -Ph 2 P(C 6 H 4 )SbPh 3 ] + with NOBF 4 . This cation reacts with fluoride anions to afford the corresponding fluorostiborane o -Ph 2 P(O)(C 6 H 4 )SbFPh 3 , the structure of which indicates a strengthening of the PO → Sb interaction. When deployed in fluoride-containing POPC unilamellar vesicles, [2] + behaves as a potent fluoride anion transporter whose activity greatly exceeds that of [Ph 4 Sb] + .more » « less
