New Polymerizable Tetraaza Macrocycle Containing Two Acridine Units for Selective Fluorescence Sensing of Metal Ions

Abstract

A new fluorescent bis(acridino)-macrocycle containing two allyl groups was synthesized and photophysically studied. Studies were carried out on metal ion recognition and selectivity-influencing effects including the determination of the relevant thermodynamic constants as logK and pKa. The proposed sensor molecule is recommended for the development of Zn2+-selective optochemical analyzers based on covalently immobilized ionophores as it has a unique pH-independent metal ion recognition ability, which is not influenced by anions and other potentially occurring metal ions in biological samples.

A cuvette-compatible Zn2+ sensing tool for conventional spectrofluorometers prepared by copolymerization of macrocyclic fluoroionophores on quartz glass surface

“…Aqueous solutions (2 ml, 50 mmol•l −1 ) of 24 metal salts and those of tetrabutylammonium (sterically shielded cation, which cannot be complexed) salts of The largest change in fluorescence was caused by Zn 2+ , followed by Cd 2+ and Pb 2+ as competing ions similarly to preliminary studies on the parent ionophore in acetonitrile [38]. This competition was expected as these metal ions have a very similar chemical character.…”

“…Chemicals were purchased from Sigma-Aldrich Corporation (USA, owned by Merck, Germany) and used without further purification unless otherwise noted. The applied sensor molecule (figure 1) was prepared as reported [38].…”

“…In the case of covalently immobilized sensor molecules inside the membrane, both the polarity of the membrane and the decreased conformational flexibility of them can be manifested in an altered selectivity compared to that of the corresponding ones in solution. That is why, studies on selectivity were carried out in a similar manner as reported previously for the parent ionophore dissolved in acetonitrile [38].…”

“…The main purpose of the reported work was to create a non-device-specific spectrophotometric cuvettecompatible tool with a covalently attached sensor layer on its surface to enable an easy conversion of any spectrofluorometers to ion-selective sensors. We report herein the development of a quartz glass surface-bonded direct-type optode membrane by the copolymerization of a recently reported fluorescent macrocycle [38]. This fluorescence macrocycle contains two allyl groups, which provide opportunity for photo-copolymerization with acrylamide, (2-hydroxyethyl)methacrylate and triethylene glycol dimethacrylate on a glass surface modified by a silanizing agent in a rapid method, which can be carried out in ordinary conditions by using only UV-radiation for radical initiation.…”

Two Acridone Units in One Crown Ether

“…The acridinium cation can only be present in excited state attributed to an intramolecular proton transfer, unless an anion is complexed by the macrocycle [17,18]. Moreover, in the fully protonated state a strong electrostatic repulsion takes place, which also prevents the acridines to accept a proton [15,17,18]. In contrast, if O-atoms are also parts of the macroring as nucleophile centers, coordination of cations is preferred [15,19,20] and anions are not complexed even in partially protonated forms of the macrocycles [15,19].…”