Synthesis, Photophysical, and Anion-Sensing Properties of Quinoxalinebis(sulfonamide) Functionalized Receptors and Their Metal Complexes

Abstract

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.

Dithieno[3,2-a:2′,3′-c]phenazine-based chemical probe for anions: a spectroscopic study of binding

“…We 29,30 and others [31][32][33][34][35] have reported the use of sulfonamide groups to detect a wide range of anions. In this paper, we report on the preparation of the compound N,N'- (2,5-…”

Chromo- and Fluorogenic Organometallic Sensors

“…The bis (sulfonamide) complex 5n (Fig. 5) also exhibits considerable colorimetric change on the introduction of F À , CN À and OAc À , attributed to a de-protonation which is exacerbated by the Lewis acidity of the metal and can be used to modulate the amidic pK a [61].…”

Polypyridyl-imidazole based smart Ru(II) complex mimicking advanced Boolean and Fuzzy logic functions

“…The NH proton in the imidazole ring in resulting complex became sufficiently acidic to interact with the incoming anion either by hydrogen http://dx.doi.org/10.1016/j.ica.2016.02.041 0020-1693/Ó 2016 Elsevier B.V. All rights reserved. bonding interaction or by complete proton transfer [42,[55][56][57][58][59][60][61][62][63]. Consequently, the optical properties of the complex have been modulated to a great extent with the variation of both anionic and cationic inputs.…”