BODIPY-Based Ratiometric Fluoroionophores with Bidirectional Spectral Shifts for the Selective Recognition of Heavy Metal Ions

Abstract

Two novel asymmetric BODIPY fluoroionophores with dipicolylamine (BDP-DPA, dipicolylamine: bis(pyridylmethyl)) and terpyridine (BDP-TPY) are described. These fluoroionophores display opposite wavelength responses on complexation with heavy metal ions. Furthermore, the fluorescence spectra vary depending on the ionic species. In particular, BDP-DPA shows a high affinity toward Cr 3+ and upon complexation, the fluorescence spectrum blue-shifts from 591 to 566 nm. In contrast, BDP-TPY preferentially binds to Zn 2+ and the fluorescence spectra red-shifts from 539 to 567 nm. BDP-TPY is the first example of asymmetric BODIPY with a pyridyl receptor at the 3 position showing redshifted fluorescence by complexation with metal ions. The concentration of each metal ion was successfully determined by ratiometric measurement. The wavelength-responses characteristics of these fluoroionophores could be very useful in the development of novel ratiometric fluoroionophores for metal ions.The conservation and protection of the natural environment from trace contaminants are becoming increasingly important, and in particular, heavy metals pose severe risks to human health and to the environment because of their toxicity.1 For instance, chromium (Cr) is a common heavy metal contaminant used throughout the world, and its compounds can have genotoxic effects on humans and increase the risk of lung cancer.2 It originates primarily from industrial uses, such as electroplating, metal finishing, and leather tanning.3 Zinc (Zn) is also one of the major heavy metal pollutants because of its widespread industrial applications in chemical and alloyed products, fabricated metal products, and paper products. 4 Zn compounds have hazardous effects not only on humans but also on fish and plants. 5 Currently, the most common analytical methods for heavy metals are atomic absorption spectrometry (AAS) and inductively coupled plasma (ICP) spectroscopy. 6,7 Although precise, these analytical instruments are expensive and often require complex sample preparation. In addition, they are not applicable to continuous on-site monitoring and measure only the total concentration of heavy metals. Therefore, an inexpensive and simple method is needed for determining levels of heavy metal ions, which is appropriate for monitoring industrial and environmental samples.Fluorescence spectroscopy is a desirable method for quantifying heavy metal ions because of its high sensitivity, operational simplicity, and versatile instrumentation.8 The design and development of novel fluoroionophores remain an active area of research, and various fluoroionophores for heavy metal ions have been reported. 911 In terms of sensitivity, fluoroionophores that exhibit ratiometric spectral changes induced by complexation with heavy metal ions are more favorable than those exhibiting only fluorescence enhancement ("turn-on") or fluorescence quenching ("turn-off"). Ratiometric fluoroionophores provide more detailed information about the analyte in a sample, as well as allowing reliable...

A highly selective multifunctional Zn‐coordination polymer sensor for detection of Cr (III), Cr (VI) ion, and TNP molecule

“…The small blue‐shifted fluorescence of compound 1 induced by Cr 3+ and Al 3+ ion can be explained by an intramolecular charge transfer (ICT) mechanism. When a fluorophore containing an electron donating group (e.g., carboxylate group) is coordinated to an ion, the carboxylate group loses its electron donating ability, and consequently ICT is inhibited and compound 1 exhibits the blue‐shifted fluorescence …”

Determination of Cadmium in Brown Rice Samples by Fluorescence Spectroscopy Using a Fluoroionophore after Purification of Cadmium by Anion Exchange Resin

“…The standard method for rice digestion is complicated and time-consuming. Therefore, we developed a simpler method with fluorescence spectroscopy using 0.1 M HCl solution ( Section 2.2 ) which was appropriate for the following purification and fluorescence determination steps [ 22 ]. The Cd concentrations in the rice extracts were determined by the standard and our methods ( Figure 3 ).…”

“…The fluoroionophore, 2,2′:6′,2′′-terpyridine-substituted BODIPY (BDP-TPY), designed in our laboratory, was synthesized according to a previously reported method [ 22 ]. The chemical structure of BDP-TPY is shown in Figure 1 .…”

“…The chemical structure of BDP-TPY is shown in Figure 1 . Since 2,2′:6′,2′′-terpyridine (TPY) acts as a heavy metal ion receptor, the fluorescence color of BDP-TPY changes upon binding of heavy metals to TPY [ 22 ]. A stock solution of BDP-TPY (2 μM) was prepared in acetonitrile.…”

Application of fluorescence spectroscopy using a novel fluoroionophore for quantification of zinc in urban runoff

“…The fluoroionophore designed in our laboratory was synthesized according to a previously described method (Hafuka et al, 2013). Milli-Q water (18.25 Mcm) was used to prepare all aqueous solutions.…”