Synthesis, photophysical, and anion-sensing properties of quinoxalinebis(sulfonamide) functionalized receptors and their metal complexes.
We report the synthesis, characterization, and photophysical properties of a series of organic receptors and their corresponding ReI and RuII metal complexes as anion probes featuring bis(sulfonamide) interacting sites incorporating highly chromophoric pi-conjugated quinoxaline moieties. The interactions with various anions were extensively investigated. These probe molecules are capable of recognizing F-, OAc-, CN-, and H2PO4- with different sensitivities. The probe-anion interactions can be easily visualized via naked-eye colorimetric or luminescent responses. Probe 1 has the weakest acidic sulfonamide N-H protons and therefore simply forms hydrogen-bonding complexes with F-, OAc-, CN-, and H2PO4-. Probe 2 undergoes a stepwise process with the addition of F- and OAc-: formation of a hydrogen-bound complex followed by sulfonamide N-H deprotonation. Direct sulfonamide N-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 the addition of F-, CN-, or H2PO4-. However, only a genuine hydrogen-bound complex forms in the presence of the OAc- ion in a DMSO solution of probe 3 because of the subtle difference in the pKa values of sulfonamide N-H protons when probes 2 and 3 are compared. Coordination of probe 1 to a ReI center or probe 2 to a RuII center increases the intrinsic acidity of sulfonamide N-H protons and results in an enhanced sensitivity to anions.
Lin
Tzu-Pin
TP
Institute of Chemistry, Academia Sinica, Nankang, Taipei 115, Taiwan, Republic of China.
Chen
Chan-Yu
CY
Wen
Yuh-Sheng
YS
Sun
Shih-Sheng
SS
D000838:Anions; D009682:Magnetic Resonance Spectroscopy; D008670:Metals / Q000737:chemistry*; D008958:Models, Molecular; D010777:Photochemistry; D055585:Physical Phenomena; D010825:Physics; D013056:Spectrophotometry, Ultraviolet; D013449:Sulfonamides / Q000737:chemistry*
D000838:Anions; D008670:Metals; D013449:Sulfonamides