Fluorescent, Siderophore-Based Chelators. Design and Synthesis of a Trispyrenyl Trishydroxamate Ligand, an Intramolecular Excimer-Forming Sensing Molecule Which Responds to Iron(III) and Gallium(III) Metal Cations

Abstract

Two pyrene-labeled hydroxylamines, 5-Bn and 5-Bz, O-protected with the benzyl and the benzoyl group, respectively, have been prepared for the generation of siderophore-based new chelators incorporating both the pyrene chromophore and the hydroxamic acid functionality. 5-Bz formed the starting point toward the synthesis of the tripod-shaped trishydroxamate, 1. That trichromophoric ligand displays remarkable fluorescence emission properties (dual emission: "monomer" and excimer type) which are markedly and selectively modified by binding Fe(NO(3))(3) and Ga(NO(3))(3). Ferric ions induce a quasi total quenching of the pyrene fluorescence, whereas the nonquenching Ga(III) cations are observed to affect the value of the excimer-to-monomer fluorescence intensity ratio. Ethylenediaminetetraacetic acid (EDTA) competition reactions yielded an estimated value of 3.8 for log K of the complex LFe in methanol/water (80/20 v/v), where K = ([LFe][H(+)](3))/([LH(3)][Fe(3+)]) and L is the ligand in its totally deprotonated form. Compound 1 is the prototype of a new class of photoresponsive molecular systems which could act as sensitive probes for metal cation detection and recognition.

Calcein as a Fluorescent Probe for Ferric Iron

“…Some fluorescent probes become available for iron(III) (32,33). A fluorescent form of desferrioxamine B has been synthesized.…”

Siderophore-based detection of Fe(iii) and microbial pathogens

“…A wealth of literature pertaining to the design, synthesis, and application of siderophore analogs exists, [59][60][61][62][63][64][65][66][67][68][69][70][71][72] some of which has been reviewed recently, 18 and we note that a number of these molecules are fluorescent Fe(III) sensors. [65][66][67][68][69][70][71][72] …”

Recent Achievements on Siderophore Production and Application

“…effective diagnosis of certain disease states. Among the various methods known for the estimation of Fe(III) [195][196][197], fluorescent probes combined with siderophores (or analogues) or fluorescent siderophores have been actively investigated because of the rapid response rates and high sensitivity [198][199][200][201][202][203][204]. The sensors use different electrochemical properties of the complexes formed between the siderophores-flourescent probes and the metal to detect the iron content.…”