| Abstract
| - A series of colorimetric and fluorescence organic and metal complex probes containing a quinoxalinebis(sulfonamide) moiety for inorganic anions have been synthesized and characterized. The photophysical properties and the interactions between anions and probe molecules are explored.
- We report the synthesis, characterization, and photophysical properties of a series of organic receptors and theircorresponding ReI and RuII metal complexes as anion probes featuring bis(sulfonamide) interacting sites incorporatinghighly chromophoric π-conjugated quinoxaline moieties. The interactions with various anions were extensivelyinvestigated. These probe molecules are capable of recognizing F-, OAc-, CN-, and H2PO4- with differentsensitivities. The probe−anion interactions can be easily visualized via naked-eye colorimetric or luminescentresponses. Probe 1 has the weakest acidic sulfonamide N−H protons and therefore simply forms hydrogen-bondingcomplexes with F-, OAc-, CN-, and H2PO4-. Probe 2 undergoes a stepwise process with the addition of F- andOAc-: formation of a hydrogen-bound complex followed by sulfonamide N−H deprotonation. Direct sulfonamideN−H deprotonation occurs upon the addition of CN-, while only a hydrogen-bound complex forms with the H2PO4-ion for probe 2 in a dimethyl sulfoxide (DMSO) solution. Similar probe−anion interactions occur in probe 3 with theaddition of F-, CN-, or H2PO4-. However, only a genuine hydrogen-bound complex forms in the presence of theOAc- ion in a DMSO solution of probe 3 because of the subtle difference in the pKa values of sulfonamide N−Hprotons when probes 2 and 3 are compared. Coordination of probe 1 to a ReI center or probe 2 to a RuII centerincreases the intrinsic acidity of sulfonamide N−H protons and results in an enhanced sensitivity to anions.
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