Copper 10-Phenanthroline Lab Report

The electrochemical behaviour of copper-1,10-phenanthroline (phen) complex in aqueous and in water-acetone mixed solutions was studied by CV-thin layer spectroelectrochemistry. In aqueous solution, [Cu(II)(phen)2]2+ complex electrochemically reduced to [Cu(I)(phen)2H2O]+ with maximum absorption at 405nm, and followed by a reversible chemical reaction. The formal potential, E0=0.078V, the number of electron transferred, n=1.0, and the equilibrium constant of the following chemical reaction, K=0.107 (0.005), were determined. In water-acetone mixed solution, [Cu(II)(phen)2]2+ reduced to [Cu(I)(phen)2]+ with maximum absorption at 435 nm.

Keywords: CV-thin layer spectroelectrochemistry; copper-1,10-phenanthroline complex

1. INTRODUCTION

Copper,

EXPERIMENTAL

2.1. Chemicals and solutions

CuSO4·5H2O, 1,10-phenanthroline and other reagents are all analytical pure. All solutions were prepared with MilliQ water. The solutions were deaerated with high-pure nitrogen for 15min before use.

2.2. Apparatus

Spectroelectrochemical experiments were carried out on Perkin-Elmer Lambda 25 UV/VIS spectrometer (made in USA) and CHI620B (made in China) with homemade long optical path length thin layer cell (LOPTLC, thickness of the thin layer is 0.020 cm) [11]. A graphite carbon slice served as working electrode, a platinum wire as auxiliary electrode and a Ag/AgCl (KCl saturated) as reference electrode. All potentials are reported with respect with this reference electrode.

Graphite carbon electrode was polished to a mirror-like surface with 1.0, 0.3 and 0.05 micron α-alumina powder in sequence and washed in supersonic for one minute before use.

3. RESULTS AND DISCUSSION

3.1 Cyclic voltammetric studies of copper-phen

The reduction peak potential shifts to negative direction with scan rates (average 53 mV for 10 times of scan rate), and the ratio of peak currents, ipa/ ipc, goes up to 1 with the increase of scan rates, as shown in Fig.2. The results indicate that there is a reversible following chemical reaction [9] in the reduction process.

Figure 1. The CVs of copper-phen complex with different mol ratios in 0.2 mol/L NaAc-HAc buffer solution (pH=4.4). scan rate:60 mV/s; mol ratio of copper to phen: 1, 1:1; 2, 1:1.5; 3, 1: 2.The dot line: background; The dash line: CuSO4 solution without phen.

Figure 2. The CVs of Cu-phen complex at different scan rates. Scan rate (V/s): 1, 0.03; 2, 0.02; 3, 0.01; 4, 0.008; 5, 0.004; 6, 0.002.Other conditions are the same as in Fig.1.

3.2 Potential-step thin-layer spectroelectrochemical study of