Amino acid-based squaramides for anion recognition

Elmes, Robert B. P.; Jolliffe, Katrina A.

doi:10.1080/10610278.2014.976221

Cited by 25 publications

(13 citation statements)

References 26 publications

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“…From our work on squaramides we are familiar with the self-assembly/aggregation of these molecules due to bidirectional H-bonding interactions in addition to π-π stacking brought about by the aromatic cyclobutenedione ring (Elmes et al, 2013, 2014, 2015; Busschaert et al, 2014; Elmes and Jolliffe, 2014; Qin et al, 2016; Marchetti et al, 2018). Moreover, we have also gained considerable experience working with the naphthalimide fluorophore which has fluorescence properties that are highly dependent upon aggregation (Elmes and Gunnlaugsson, 2010; Elmes et al, 2012; Ryan et al, 2012, 2015; Ao et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Squaramide—Naphthalimide Conjugates as “Turn-On” Fluorescent Sensors for Bromide Through an Aggregation-Disaggregation Approach

et al. 2019

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The syntheses of two new squaramide-naphthalimide conjugates ( SQ1 and SQ2 ) are reported where both compounds have been shown to act as selective fluorescence “turn on” probes for bromide in aqueous DMSO solution through a disaggregation induced response. SQ1 and SQ2 displayed a large degree of self-aggregation in aqueous solution that is disrupted at increased temperature as studied by 1 H NMR and Scanning Electron Microscopy (SEM). Moreover, the fluorescence behavior of both receptors was shown to be highly dependent upon the aggregation state and increasing temperature gave rise to a significant increase in fluorescence intensity. Moreover, this disaggregation induced emission (DIE) response was exploited for the selective recognition of certain halides, where the receptors gave rise to distinct responses related to the interaction of the various halide anions with the receptors. Addition of F − rendered both compounds non-emissive; thought to be due to a deprotonation event while, surprisingly, Br − resulted in a dramatic 500–600% fluorescence enhancement thought to be due to a disruption of compound aggregation and allowing the monomeric receptors to dominate in solution. Furthermore, optical sensing parameters such as limits of detection and binding constant of probes were also measured toward the various halides (F − , Cl − , Br − , and I − ) where both SQ1 and SQ2 were found to sense halides with adequate sensitivity to measure μM levels of halide contamination. Finally, initial studies in a human cell line were also conducted where it was observed that both compounds are capable of being taken up by HeLa cells, exhibiting intracellular fluorescence as measured by both confocal microscopy and flow cytometry. Finally, using flow cytometry we were also able to show that cells treated with NaBr exhibited a demonstrable spectroscopic response when treated with either SQ1 or SQ2 .

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Section: Introductionmentioning

confidence: 99%

Squaramide—Naphthalimide Conjugates as “Turn-On” Fluorescent Sensors for Bromide Through an Aggregation-Disaggregation Approach

et al. 2019

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“…For example, it has been reported that the pKa's of the hydrogen bonding donor protons affects directly the halide‐binding affinities of anion receptors with an inverse correlation . Furthermore, with a suitable geometry such as the tripodal conjugation, some powerful anion receptors have been developed by these approaches .…”

Section: Resultsmentioning

confidence: 99%

Tripodal Squaramide Derivative as a Neutral Chloride Ionophore for Whole Blood and Sweat Chloride Measurement

Fan¹,

Xu²,

Feng³

et al. 2020

Electroanalysis

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A tripodal squaramide derivative was synthesized and characterized as a new neural ionophore for chloride ion. Squaramide based compounds are known to be better hydrogen bonding receptors than urea derivatives because they donate four hydrogen bonds to anions, while the tripodal structure provides a 3D geometry optimum for spherical anion complexation. The ionophore demonstrated high selectivity over salicylate and heparin that are major interferences for chloride measurement in biological samples with direct potentiometric method. The new ionophore based solid‐contact electrodes were fabricated and showed the measuring range of 10−5 to 1 M chloride ion in the presence of 1 mM of salicylate and heparin with near Nernstian slope of 55 mV/decade. The sensor was successfully applied for the chloride measurement in undiluted heparinized whole blood and artificial sweat samples with our clinical analyzer.

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“…Recently, we and others have reported that functionalized α–amino acids are a suitable platform for the construction of salt receptors since their framework allows for easy introduction of specific binding domains that might lead to cooperative binding of ion pairs in some cases [33,34,35,36]. Very recently, we have demonstrated that 3-aminobenzoic acid functionalized with arylthiourea and 18-aza-crown-6-ether acting as anion and cation binding units, respectively, also offer a promising platform for obtaining effective ion pair receptors [30,37].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Substitution Pattern on Binding Ability in Regioisomeric Ion Pair Receptors Based on an Aminobenzoic Platform

et al. 2019

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A series of ditopic ion pair receptors equipped with 4-nitrophenylurea and 1-aza-18-crown-6-ether linked by ortho-(1), meta-(2), and para-(3) substituted benzoic acid were readily synthesized in three steps from commercially available materials. The binding properties of these regioisomeric receptors were determined using UV-vis and 1H NMR spectroscopy in MeCN and in the solid state by single-crystal X-ray diffraction crystallography. The solution studies revealed that, apart from carboxylates, all the anions tested formed stronger complexes in the presence of sodium cations. Receptors 2 and 3 were found to interact with ion pairs with remarkably higher affinity than ortho-substituted 1. 1H NMR titration experiments showed that both urea NH protons interacted with anions with comparable strength in the case of receptors 2 and 3, but only one of the NHs was effective in anion binding in the case of receptor 1. X-ray analysis of the crystal structure of receptor 1 and 1·NaPF6 complex showed that binding was hampered due to the formation of an intramolecular hydrogen bond. Analysis of the crystal structures of 2·NaBr and 3·NaBr complexes revealed that proper mutual orientation of binding domains was responsible for the improved binding of the sodium salts.

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Amino acid-based squaramides for anion recognition

Cited by 25 publications

References 26 publications

Squaramide—Naphthalimide Conjugates as “Turn-On” Fluorescent Sensors for Bromide Through an Aggregation-Disaggregation Approach

Squaramide—Naphthalimide Conjugates as “Turn-On” Fluorescent Sensors for Bromide Through an Aggregation-Disaggregation Approach

Tripodal Squaramide Derivative as a Neutral Chloride Ionophore for Whole Blood and Sweat Chloride Measurement

The Effect of Substitution Pattern on Binding Ability in Regioisomeric Ion Pair Receptors Based on an Aminobenzoic Platform

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