A Novel Ferrocenyl Naphthoquinone Fused Crown Ether as a Multisensor for Water Determination in Acetonitrile and Selective Cation Binding

Abstract

A multisensor which is based on a novel multifunctional triad molecule, ferrocenyl naphthoquinone fused crown ether (Fc-cnq) bearing ferrocene, quinone, and crown ether functional groups together, was synthesized and characterized in this study. Sensing performance of a trace amount of water and the selective cation binding capabilities of this multisensor were carried out by the electrochemical, spectroelectrochemical, and spectrophotometric titration techniques in acetonitrile (CH3CN). It was shown that the potential separation (E((Fc))1/2 - E((2))1/2) between the second reduction of naphthoquinone and the oxidation processes of ferrocene in the triad molecule Fc-cnq was proportional to the amount of water due to the hydrogen-bonding interactions between water and the doubly reduced species (Fc-cnq(2-)). This property enabled Fc-cnq to detect the trace amount of water in CH3CN. The half-wave potential (E((Fc))1/2) of the ferrocene in Fc-cnq was used as an internal reference potential, and it defined the accuracy of the detection. In addition, by using the UV-vis spectrophotometric titration technique in CH3CN, it was also shown that the Fc-cnq multisensor could bind Ba(2+) and Ca(2+) cations selectively. We proposed that the intramolecular charge-transfer (CT) transition which occurred between the donor ferrocene and the acceptor naphthoquinone was the principle mechanism for the selective binding property of this multisensor. Quantum chemical calculations were also performed to investigate optical and electronic properties of the Fc-cnq molecule.

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“…It is quite noticeable that even though there are some fluctuations in the standard potential of the electrode in ACN or DCM, it could be said that the potential of the developed biosensor is not significantly changed. It can therefore be deduced that AQ-modified MWCNT electrode can be used for the determination of the trace amount of water in the aprotic media (Dağdevren et al 2015).…”

Beryllium ion sensing through the ion pair formation between the electrochemically reduced ferrocenyl naphthoquinone radicals and $$\hbox {Be}^{2+}$$ ions

“…The processes are similar to typical CVs of benzoquinone, naphthoquinone, and ferrocene derivatives in aprotic organic solvents without water and acidic ingredients. 4,5,[39][40][41] On the other hand, the electrochemistry of Fc-cnq-1b is similar to that of Fc-cnq-1a under the same conditions ( Figure 2B). Compared to the CVs of Fc-cnq-1a (blue line) and Fc-cnq-1b (red line) in Figure 3, the first reduction potential of Fc-cnq-1a shifted to the cathodic region because of more electron-donating oxygen atoms in case of Fccnq-1a.…”

“…The first chemically reversible process at E 1 yields a monoanion radical (semiquinone) product and the second generally at least quasi-reversible process at a more negative potential, E 2 , produces dianion species at customary scan speeds. [1][2][3][4][5] The potentials of these reductions depend on the polarity of solvents, the nature of the supporting electrolyte and the presence of acidic additives, reflecting respectively non-specific solvation energies, ion-pairing and protonation. [1][2][3][4][5] Few studies have been devoted to exploring the ion-pair formation processes between the electrochemically reduced quinones and the cationic species, including some alkali metals and alkaline earth metal cations in aprotic solvents.…”

“…[1][2][3][4][5] The potentials of these reductions depend on the polarity of solvents, the nature of the supporting electrolyte and the presence of acidic additives, reflecting respectively non-specific solvation energies, ion-pairing and protonation. [1][2][3][4][5] Few studies have been devoted to exploring the ion-pair formation processes between the electrochemically reduced quinones and the cationic species, including some alkali metals and alkaline earth metal cations in aprotic solvents. [6][7][8][9] For these studies, some well-known electrochemical methods such as cyclic voltammetry (CV) and pulse-electrolysis stopped-flow were used to explore the mechanistic aspects of the electrochemical reduction of quinones in the presence of metal ions such as Na + , Mg +2 and Ba +2 .…”

“…In this study, firstly, we investigated the ion pair formation between the electrochemically reduced monoanion radicals/dianion products (Fc-cnq-1a • − /Fc-cnq-1b • − and Fc-cnq-1a 2− /Fc-cnq-1b 2− ) of ferrocenyl naphthoquinones (Fc-cnq-1a and Fc-cnq-1b) and several metal ions (Li + , Na + , K + , Cs + , Be 2+ , Mg 2+ , Ca 2+ , Ba 2+ , Ni 2+ , Zn 2+ , Cu 2+ and Co 2+ ) by cyclic voltammetry, square wave voltammetry (SWV) and in situ spectroelectrochemistry in a thin layer cell. The reasons behind choosing the ferrocenyl naphthoquinone fused crown ether Fc-cnq-1a and model compound Fc-cnq-1b without crown ether unit in the molecular structure ( Figure 1) are as follows: (1) the naphthoquinone skeletal structure provides electron transfer processes with tunable redox potential in the presence of metal ions along with thermal and chemical stability; 4,[10][11][12][13][14] (2) ferrocene unit in the molecular structure of Fc-cnq-1a and Fc-cnq-1b displays well-known one-electron reversible oxidation process which can serve as an internal electrochemical standard to evaluate ion pair formation; (3) the crown ether unit not only makes the compound Fc-cnq-1a highly soluble but also provides information about the ion pair formation mechanism only taking place between the reduced naphthoquinone products and metal ions, although it is capable of complex formation with proper metal ions; (4) the naphthoquinone fused crown ether Fc-cnq-1a as a triad molecule shows intramolecular charge-transfer (ICT) transition between the ferrocenyl donor and the naphthoquinonyl acceptor center [e π (HOMO-Fc) → e π * (LUMO-cnq)] at near IR region, which renders monitoring spectral changes of the molecules during the electrolysis in thin layer cell, thereby understanding the ion pair formation reaction.…”