Elsevier

Chemical Physics Letters

Volume 584, 1 October 2013, Pages 165-171
Chemical Physics Letters

Fluorescent recognition of Fe3+ ion with photoinduced electron transfer (PET) sensor

https://doi.org/10.1016/j.cplett.2013.08.029Get rights and content

Highlights

  • We synthesized a fluorescence receptor (2) and report it as a photoinduced electron transfer (PET) cation sensor.

  • The association constant (K) of receptor (2) with Fe3+ ions was calculated at 1.4 ± 0.2 × 104 M−1.

  • The 1:1 stoichiometry of the host guest relationship was realized from the Job’s plot.

Abstract

We synthesized a fluorescence receptor 2,2-(pyridine-2,6-diylbis(azanediyl))bis(methylene)diphenol (2) and report it as a photoinduced electron transfer (PET) cation sensor that is capable of indicating the presence of Fe3+ ion via a fluorescence signal. It was observed that fluorescence intensity changes and quenched. The association constant (Ka) of receptor (2) with Fe3+ ions was calculated from Benesi–Hildebrand and Scatchard Plot at 1.60 and 1.30 × 104 M−1 respectively.

Introduction

In recent years the development of fluorescent receptors for the detection of cation is the attractive research area in the field of supramolecular chemistry because of it’s use in material science and biology [1], [2], [3]. The development of molecular systems capable of signaling different guest molecules or ions have been energetic areas of modern research [4], [5], [6]. One of the most frequently utilized design processes for fluorescence signaling system is the development of three-component system with a fluorophore-spacer-receptor architecture containing components that are selected such that the communication between the fluorophore and receptor leads to quenching of the fluorescence of the system. In the presence of a guest, the communication between the terminal moieties, which is responsible for fluorescence quenching, gets cut off, thus leading to the recovery of the fluorescence of the system. This is commonly referred to as ‘off–on’ fluorescence signaling of a guest. Interestingly, the off–on fluorescence signaling systems for the transition-metal ions, which are well-known for their fluorescence quenching abilities, have been developed only very recently [7], [8].

Among the transition metal ions Fe3+ is having much importance as it plays a crucial role in the growth and progress of living systems. For example numerous enzymes use iron as a catalyst for oxygen metabolism, electron transfer as well as DNA and RNA synthesis. Both its lack and excess in the body can cause serious diseases [9], [10], [11], [12].

In the present letter, we prepared a simple and efficient fluorogenic receptor 2 containing the two amine and two hydroxyl fragment (Scheme 1). It was found that the compound selectively complexes with Fe3+ ions in semi aqueous solution, resulting in a significant fluorescence quenching.

Section snippets

Reagents

All spectroscopy grade chemicals and solvents were used without further purification. The fluorescence and UV–visible spectra were recorded on Fluoromax-4 Spectrofluorometer and Shimadzu UV-24 500 with 5 nm slit of fluorescence and the nitrate salt of metal were used in the letter. Ultrapure water with a Millipore Purification System (Milli-Q water) was used throughout the analytical experiments. 1H NMR spectra were recorded on a Varian NMR mercury system 300 spectrometer operating at 300 MHz in

Synthesis of receptor 2

Compound 1 was synthesized by reacting one mole of 1,2-diaminopyridine with two moles of 2-hydroxy benzaldehyde in methanol with stirring for 3 h. Compound 1 was obtained with quantitative yield. Receptor 2 was obtained from compound 1 by reduction under NaBH4 with good yield (Scheme 1). The synthesized receptors were characterized by melting point, IR, 1H NMR, 13C NMR and mass spectroscopic methods. The spectral investigation gave consistent data of structure of both.

Fluorescence studies of receptors 2

The solvent ratio CH3OH/H2O

Conclusion

In summary, we have synthesized the selective and sensitive fluorescent chemical sensor that is, receptor 2 for the detection of Fe3+ ions in CH3OH/H2O (70:30, v/v) solvent system. The addition of Fe3+ gave rise to major fluorescent colour change, which can be easily seen by the naked eye under UV irradiation. Furthermore, our sensor is not affected by the common interference of other ions. The 1:1 stoichiometry of the host guest relationship was realized from the Job’s plot and the association

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