Dansylated Polyamines as Fluorescent Sensors for Metal Ions: Photophysical Properties and Stability of Copper(II) Complexes in Solution

Abstract

Protonation and the Cu II complexation constants of the dansylated polyamines N-dansylethylenediamine (1), N-dansyldiethylenetriamine (2), N-dansyltriethylenetetramine (3), N'-[2-(dansylamino)ethyl]diethylenetriamine (4), and tris(2-dansylaminoethyl)amine (5) were determined by glass-electrode potentiometry in MeOH/H 2 O 9 :1 (v/v) solution. For ligands 3 and 4, the determinations were also performed in aqueous solution. The complexes formed by these ligands in neutral form correspond to those observed for the analogous unsubstituted monoprotonated amines, whereas, when the ligands are deprotonated at the sulfonamide moiety, the species parallel those of the corresponding amines. The molecular structures of the complexes were deduced from the VIS absorption spectra. The crystal structure of the [CuL 2 H À2 ] complex 6 of ligand 1 (L) was determined by X-ray diffraction. The study of the photophysical properties of the ligands 3 ± 5 showed that they are good fluorescent sensors for copper(II), which induced fluorescence quenching. Time-resolved fluorescence measurements allowed us to clarify the sensing mechanism. The pH dependence of the quenching effect demonstrated that it occurs for all Cu 2 complexes, even for species in which the sulfonamide moiety is not deprotonated. Sensing of Cu 2 was compared with that of other metal ions (Co 2 , Ni 2 , Zn 2 , Cd 2 , Hg 2 ), and selectivity was studied as a function of pH. Ligands 3 and 4 were found to be selective chemosensors for Cu 2 in weakly acidic solution (pH ca. 4 ± 5).1. Introduction. ± The need of sensors for different target analytes is wellrecognized and has already stimulated considerable research devoted to the preparation of sensitive and selective sensory devices. Fluorescent chemosensors are of particular interest because of their high sensitivity and selectivity [1] in the detection of metal ions [2], anions [3], and organic bioactive molecules [4].The increasing awareness of the detrimental role that certain transition-metal ions play in human health (see, e.g., [5]) has stimulated the development of transition metal ion sensors for applications in environmental sciences, medical diagnostics, and food technology. For these reasons, many fluorescent sensors for these metal ions have been lately synthesized and characterized [1] [2] [6].In this context, we used N-dansylethylenediamine 1 ) (1) and N-dansyldiethylenetriamine 1 ) (2) ( Fig. 1; dansyl [5-(dimethylamino)naphthalen-1-yl]sulfonyl) as compo-

Dansyl-based fluorescent films prepared by chemical and electrochemical methods: cyclic voltammetry, afm and spectrofluorimetry characterization

“…The dansyl fluorophore exhibits intense absorption bands in the near UV and a strong fluorescence in the visible region with high emission quantum yields. 12 These characteristics, together with the synthetic flexibility of the sulfonyl group, have led the dansyl fluorophore to be a core-structure present in many fluorescent sensors and labels for the detection of both metal cations [13][14][15] and anions, 16,17 as well as in larger supramolecular structures such as dendrimers. 18,19 The present paper describes the preparation of fluorescent films of a dansyl fluorophore immobilized on a polymer substrate.…”

Toward Wearable Sensors: Fluorescent Attoreactor Mats as Optically Encoded Cross‐Reactive Sensor Arrays

“…Here, we use fluorophore‐polyamines (e.g. dansyl‐polyamines)6 that bind metal ions while displaying a change in fluorescence. Figure 2 shows three polyurethane nanofibers: Two are doped with triethylenetetramine (4N) and one with dansyl chloride (bottom left→top right), forming two fluorescent attoreactors.…”

A selective fluorescent sensor for Cu2+ and its immobilization on CPG beads

“…The system is based on the well precedented dansyl-dien derived sensors [6] but represents a novel molecular structure with a secondary amine group for conjugation by reaction with alkyl halide functions. Preparation of the dansyl derived fluorescent sensor (1) was accomplished in four steps as outlined in Scheme 1.…”

“…The UV-Vis behavior of 1 is comparable to that of related dansyl-based sensors [6]. A decrease of intensity at the 210 nm maximum and increase of intensity at 230 is observed upon addition of up to 1 equivalent of Cu(II) (Fig.…”

“…Yield: 0.1 g In the fluorescence spectrum 3 of 1 (Fig. 2), an emission maximum is observed at 558 nm (excitation at 343 nm), which is typical for compounds containing the dansyl chromophore [6,8]. The emission intensity of 1 is strongly decreased upon addition of 0-1 equivalents copper ions.…”