title: Squaramide hydroxamate-based chemidosimeter responding to iron(III) with a fluorescence intensity increase.
abstract: The synthesis and in vitro evaluation of a squarate hydroxamate-coumarin conjugate, 12, as a chemodosimeter for Fe(III) and other oxidants, such as Cr(VI) and Ce(IV), is described. As 12 was originally designed to become a chelation-enhanced fluorescence (CHEF)-type sensor for Fe(III), the competence of the squarate diamide platform to relay a CHEF response was demonstrated using a zinc-binding, cyclen-substituted squarate coumarin amide. Due to a photo electron transfer process, 12 possesses a low fluorescence yield. Upon exposure of 12 to Fe(III) (or other oxidants), an irreversible 9-fold fluorescence intensity increase is observed as the result of an oxidation/hydrolysis reaction. The (aminomethyl)coumarin portion of 12 is oxidized to an iminocoumarin that hydrolyzes to produce a highly fluorescent coumarinaldehyde. Fe(III) acts as a catalyst in this transformation, thereby enhancing the sensitivity of the system for the detection of Fe(III) down to 1 ppm in aqueous buffer solution. The identities of the major reaction products between 12 and Fe(III) were proven by independent synthesis.
authors.affiliation: Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269-3060, USA.
authors.forename: Nathaniel C
authors.initials: NC
authors.lastname: Lim
authors.forename: Svetlana V
authors.initials: SV
authors.lastname: Pavlova
authors.forename: Christian
authors.initials: C
authors.lastname: Brückner
mesh_terms: D005290:Ferric Compounds / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D006877:Hydroxamic Acids / Q000737:chemistry*; D015394:Molecular Structure; D013053:Spectrophotometry
chemical_list: D005290:Ferric Compounds; D005456:Fluorescent Dyes; D006877:Hydroxamic Acids; C074579:iron (III) hydroxamate