A Photoresponsive Receptor with a 105 Magnitude of Reversible Anion‐Binding Switching. Issue 26 (5th April 2022)

• Record Type: Journal Article
• Authors: Einkauf, Jeffrey D.; Bryantsev, Vyacheslav S.; Moyer, Bruce A.; Custelcean, Radu
• Is Part Of: Chemistry. Volume 28:Issue 26(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-04-05
• Subjects: anions -- guanidines -- photoswitches -- separations -- sulfate; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202200719
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: In a leap toward anion separation that uses only energy input for binding and release cycles, we report herein a new class of photoswitchable anion receptors featuring a diiminoguanidinium functionality that displays a change of more than five orders of magnitude in switched‐off binding strength towards sulfate, a representative oxyanion, upon photoirradiation with UV light. The ( E, E )‐2‐pyridyl‐diiminoguanidinium cation, synthesized as the triflate salt, binds sulfate with extraordinary strength in [D6 ]DMSO owing to its bidentate guanidinium hydrogen bonding, which can chelate the O−S−O edge of sulfate. Upon photoisomerization to the Z, Z isomer, the anion‐binding site is essentially shut off by intramolecular hydrogen bonds to the 2‐pyridyl substituents, as shown by anion‐binding titrations, theoretical calculations, and X‐ray structural analysis. This approach will allow the development of advanced anion‐separation cycles that use only energy input and generate no chemical waste, and thus address challenging chemical separation problems in a more sustainable way. Abstract : A highly efficient anion receptor with photoswitchable functionality based on a new photoresponsive chromophore is introduced. Upon photoirradiation with UV light, ( E, E )‐2‐pyridyl‐diiminoguanidinium displays a switched‐off change in binding strength towards sulfate of more than five orders of magnitude. In DMSO, the open E, E form binds sulfate with extraordinary strength through chelating guanidinium hydrogen bonds. Upon photoisomerization to the Z, Z isomer, the anion‐binding site is shut off by intramolecular hydrogen bonds to the 2‐pyridyl substituents, thereby releasing the bound sulfate.