1,8-Diamidocarbazoles: an easily tuneable family of fluorescent anion sensors and transporters

Abstract

The synthesis, structure and anion recognition properties of an extensive, rationally designed series of bisamide derivatives of 1,8-diaminocarbazole and 1,8-diamino-3,6-dichlorocarbazole are described. Despite simple structures and the presence of only three hydrogen bond donors, such compounds are remarkably strong and selective receptors for oxyanions in DMSO + 0.5%H2O. Owing to their carbazole fluorophore, they are also sensitive turn-on fluorescent sensors for H2PO4- and AcO-, with a more than 15-fold increase in fluorescence intensity upon binding. Despite relatively weak chloride affinity, some of the diamidocarbazoles have also been shown, for the first time, to be very active chloride transporters through lipid bilayers. The binding, sensing and transport properties of these receptors can be easily modulated by the usually overlooked variations in the length and degree of branching of their alkyl side arms. Overall, this study demonstrates that the 1,8-diamidocarbazole binding unit is a very promising and synthetically versatile platform for the development of fluorescent sensors and transporters for anions.

Advances in fluorescent and colorimetric sensors for anionic species

“…A series of bisamide derivatives of 1,8-diaminocarbazole and 1,8-diamino-3,6-dichlorocarbazole were described by Chmielewski and co-workers [34]. In particular, chemosensor 10 was found to have good affinity for oxoanions in DMSO/0.5 % H2O (K11 = 1.02 x 10 4 M -1 and K11 = 4.65 x 10 3 M -1 for H2PO4and AcO -, respectively).…”

Direct Monitoring of Bicarbonate Transport by Emission Spectroscopy

“…8,9 While the development of HCO3 − transporters was defined as "an interesting target with potential utility" by A. P. Davis, Sheppard, and Smith in 2006, 10 J. T. Davis, Gale, Quesada and co-workers reported in 2009 that a series of isophthalamides and the natural compound prodigiosin can act as Cl − /HCO3 − exchangers. 11 Since then, many different anion transporters have been shown to transport HCO3 − , of which the vast majority have urea, 12,13,14 thiourea, 15,16,17 squaramide, 18,19 amide, 11,20,21 or pyrrolic N-H groups 22,23 as H-bond donors. Phenyl rings with electron withdrawing substituents are often connected to these functional groups to increase the acidity of the N-H groups and improve both the affinity for anions and the rates of transport.…”

“…In most cases, a chloride selective electrode has been employed to study the efflux of Cl − from liposomes that were dispersed in a medium containing HCO3 − . 37,11,[13][14][15][16][17][18][19][21][22][23]33 The transport of Cl − out of the liposomes proceeds only if another anion is transported in the opposite direction, to balance the charge by an antiport process. From the observed efflux of Cl − it is then concluded that an influx of HCO3 − has occurred.…”

Transmembrane Anion Transport Promoted by Thioamides

“…Compound 6AT is an active transporter derived from a non-chlorinated carbazole core, which was found unable to deliver any active carrier in our previous investigations. 18 Experiments were also performed by suspending the vesicles in an external sulfate solution or an external mixture of sulfate and bicarbonate. These assays allow studying the impact of the anion composition of the external buffer on the observed chloride efflux.…”

“…1). 18 We envisaged the potential of this motif to prepare their thioamide derivatives and to explore their anion transport properties. Thioamides 1T-5T as well as amido-thioamides 5AT and 6AT were synthesized from the corresponding 1,8diamidocarbazoles by treatment with Lawesson's reagent and fully characterized (Fig.…”