Electrochemical Studies of Betti Base and Its Copper(II) Complex by Cyclic and Elimination Voltammetry

The electrochemical behavior of Betti base 1-(α-amino benzyl)-2-naphthol (BB) and its copper(II) complex by cyclic and elimination voltammetry (EVLS) is reported in the present study. The cyclic voltammetric studies carried out at a glassy carbon working electrode, Ag/Ag+ reference electrode (0.01？M AgNO3 in acetonitrile) in DCM at 100？mV/sec, 200？mV/sec, and 400？mV/sec scan rates indicated a preceding chemical oxidation of the adsorbed BB species to form an iminium ion followed by formation of a carbanion via two-step quasireversible reduction. The suggested reaction mechanism has been supported by the elimination voltammetry. The CV and EVLS studies revealed Cu(II)BB complex to undergo a chemical or a surface reaction before electron transfer from the electrode at ？0.49 V to form Cu(I)BB species. The oxidation of Cu(I)BB species has been observed to be CV silent. 1. Introduction The study of chemistry of Betti base (Figure 1) started in the beginning of the 20th century, when Betti reported the synthesis of 1-(α-amino benzyl)-2-naphthol (Betti base, BB) [1]. Figure 1: Betti base (BB). BB and its derivatives have been extensively used as auxiliary in catalytic reactions, particularly in addition of diethylzinc to arylaldehyde [2] and various coupling reactions like Mizoroki-Heck, Suzuki-Miyaura and Sonogashira [3]. It is suggested that the role of auxiliary amino ligands in Pd catalyzed reactions is to stabilize the catalytically active Pd(0) species [4]. This observation calls for an exhaustive investigation of the redox property of the ligand. BB with –NH2 and –OH groups at 1 and 3 positions, respectively, is expected to act as an excellent ligand for coordination with transition metal ions, and Cu(II) complex with BB has been reported [5]. BB with sp3 hybridized carbon attached to phenyl ring, amine, and naphthol is expected to exhibit an interesting redox property. Cyclic voltammetry is an excellent technique to probe chemical changes that occur as a result of electron transfer. One of the strengths of the CV technique is in the identification of electrochemical reactions involving combinations of electron transfer and chemical reaction steps through proper analysis of CV curves recorded at various scan rates. Many mathematical models have been proposed to extract useful information from the CV data [6] and elimination voltammetry is one such model. Elimination voltammetry with linear scan (EVLS), an electrochemical method comprising the elimination of some particular currents from the measurements of linear scan voltammetry was first proposed by