Fluorescence quenching and bonding properties of some hydroxamic acid derivatives by iron(III) and manganese(II)

Abstract

Spectrophotometric investigations of highly fluorescent metal chelating molecules are of relevance due to their potential application in novel, selective fluorescence-based sensors. Benzene and naphthalene chromophores are highly fluorescent while hydroxamic acids are widely used as ligands for complexation of transition metals. In order to develop fluorescence probes, several phenyl derivatives of N-phenylbenzohydroxamic acid and an aminodihydroxamic acid linked with a naphthalene chromophore were synthesized and their selective ionophoric properties towards iron(III) and manganese(II) ions were investigated using fluorescence and absorption spectroscopy. Both methods confirm the formation of 1:1 and 1:2 complexes for iron(III) and a 1:1 complex for manganese(II). The complex that is formed depends on the concentration of the ligand and pH of the medium. The amino dihydroxamic acid exhibits a prominent selectivity towards iron(III) with a two-step 1:1 and 1:2 quenching mechanism at pH 3 and towards manganese(II) with a 1:1 quenching mechanism at a probe concentration of 1 x 10(-5) mol dm(-3) at pH 9.5 The logarithm of overall formation constants of 1:1 and 1:2 complexes of iron(III) were estimated as 3.30 and 9.05, respectively.

Iron(iii) selective molecular and supramolecular fluorescent probes

“…However, compound 17b in acetonitrile formed a neutral complex with iron(III) in the ratio (l7b) 3 : Fe 3+ and the fluorescence of the pyrene chromophore was quenched either due to electron transfer to the tris(hydroxamato)Fe(III) moiety, and/or energy transfer to the low-lying excited metal-centre. 58 Subsequently, De Costa and co-workers 59,60 However, probe 21 exhibited prominent selectivity towards iron(III) with a two-step 1 : 1 and 1 : 2 (L : M) quenching mechanism at pH 3.0 in methanol-water medium (1 : 1, v/v). 60 The proposed coordination mode is shown in Fig.…”

“…58 Subsequently, De Costa and co-workers 59,60 However, probe 21 exhibited prominent selectivity towards iron(III) with a two-step 1 : 1 and 1 : 2 (L : M) quenching mechanism at pH 3.0 in methanol-water medium (1 : 1, v/v). 60 The proposed coordination mode is shown in Fig. 2.…”

Detecting free hemoglobin in blood plasma and serum with luminescent terbium complexes

“…A possible reason may be the quenching effect of the central iron(III) ion, which is known to quench very efficiently luminescence of metal chelating molecules such as the porphyrin ligands of hemoglobin. 14,15 Therefore in the experiments performed, hemoglobin acts as a dark quencher for LTC luminescence and the quantification of the degree of hemolysis is limited to LTC luminescence quenching. Noticeably, the interaction between terbium complexes and hemoglobin induces a change in terbium luminescence lifetimes even at very small amounts of hemoglobin (o0.05 mg mL À1 ) (Fig.…”

A highly selective chemosensor for nickel(II) based on fluorescence quenching of a bispyrazole derivative

“…In recent years, many highly selective and sensitive fluorescent probes for metal ions have been reported [4][5][6][7][8][9][10]. Among these metal ions, nickel(II) ion is an essential micronutrient for animals and plants.…”