Cyclic voltammetry data of polypyridine ligands and Co(II)-polypyridine complexes

The data presented in this article is related to the research article entitled “Electrochemical and electronic properties of a series of substituted polypyridine ligands and their Co(II) complexes” (Ferreira et al., 2019). This data article presents electrochemical data of five polypyridine ligands, as well as of the three redox couples of each of their corresponding five polypyridine-containing Co(II) complexes. All complexes exhibit two Co-based redox couples (CoIII/II and CoII/I), as well as a ligand-based reduction of the Co(I) complex.


a b s t r a c t
The data presented in this article is related to the research article entitled "Electrochemical and electronic properties of a series of substituted polypyridine ligands and their Co(II) complexes" (Ferreira et al., 2019). This data article presents electrochemical data of five polypyridine ligands, as well as of the three redox couples of each of their corresponding five polypyridinecontaining Co(II) complexes. All complexes exhibit two Co-based redox couples (Co III/II and Co II/

Subject area
Chemistry More specific subject area Electrochemistry Type of data Table, text file, graph, figure How data were acquired BAS 100B/W electrochemical analyzer (Electrochemical studies).

Data format
Raw and analyzed.
Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/dib its suitability to act as a redox mediator, to be used in dye-sensitized solar cells (DSSC) [2][3][4].
Figs. 3-8 (0.10 V s À 1 scans from [1]), with the data summarized in Tables 1-5. The redox events are the Co III/II redox couple (peak 1), the Co II/I redox couple (peak 2) and the ligand reduction peak (peak 3), as well as an irreversible peak at ca. 1.63 V vs FcH/FcH þ (preliminary assigned to anionic nitrate oxidation). The data obtained in this data article, compares well with available published data on some of the redox events for some of the complexes, namely complex 1 [5][6][7][8][9][10], complex 2 [11][12][13] and complex 5 [11]; obtained under different experimental conditions (different solvents, scan rates Cyclic voltammograms of ca. 0.002 mol dm À 3 or saturated solutions of the free ligands 1a-5a, at the indicated scan rates (0.10 V s À 1 top left for the comparative graph and 0.05-0.50 V s À 1 for all other graphs). The reduction peak of ligand 5a is chemically (i pa /i pc ¼ 0.9) and electrochemically (ΔEp ¼ E pa -E pc ¼ 0.088 V) reversible at all scan rates above 0.05 V s À 1 , while the reduction of free ligands 2a-5a 1a -4a is irreversible at low scan rates.
, at scan rates of 0.05 V s À 1 (lowest peak current) À 5.00 V s À 1 to 5.00 V s À 1 (highest peak current). All scans were initiated in the positive direction from 1 V. Data is summarized in Table 1.  , at scan rates of 0.05 V s À 1 (lowest peak current) À 5.00 V s À 1 to 5.00 V s À 1 (highest peak current). All scans were initiated in the positive direction from 1 V. Data is summarized in Table 2. , at scan rates of 0.05 V s À 1 (lowest peak current) À 5.00 V s À 1 to 5.00 V s À 1 (highest peak current). All scans were initiated in the positive direction from 1 V. Data is summarized in Table 3. Fig. 7. Cyclic voltammograms of [Co(4,4 0 -t Bu-bpy) 2 ](NO 3 ) 2 (complex 4), at scan rates of 0.05 V s À 1 (lowest peak current)À 5.00 V s À 1 to 5.00 V s À 1 (highest peak current). All scans were initiated in the positive direction from 1 V. Data is summarized in Table 4. , at scan rates of 0.05 V s À 1 (lowest peak current) À 5.00 V s À 1 to 5.00 V s À 1 (highest peak current). All scans were initiated in the positive direction from 1 V. Data is summarized in Table 5. Table 1 Electrochemical data (potential in V vs FcH/FcH þ and current in A) obtained in CH 3 CN for ca. 0.002 mol dm À 3 of [Co(tpy) 2 ] (NO 3 ) 2 (complex 1), at indicated scan rates in V s À 1 . Peak 1 is the Co III/II redox couple, peak 2 the Co II/I redox couple and peak 3 the ligand reduction peak.Pl   Table 3 Electrochemical data (potential in V vs FcH/FcH þ and current in A) obtained in CH 3 CN for ca. 0.002 mol dm À 3 of [Co(4,4'-Mebpy) 2 ](NO 3 ) 2 (complex 3), at indicated scan rates in V s À 1 . Peak 1 is the Co III/II redox couple, peak 2 the Co II/I redox couple and peak 3 the ligand reduction peak. and supporting electrolytes). The linear responses obtained for the graphs of the peak currents vs the square root of the scan rate, for three main redox events in the CV of complex 1 (see Fig. 4), are in agreement with the Randles-Sevcik equation [14].

Experimental design, materials, and methods
Electrochemical studies, by means of cyclic voltammetry (CV), were performed at 25°C on a BAS 100B/W electrochemical analyser under inert conditions as described previously [1]. The concentration of the analyte was 0.002 mol dm À 3 or saturated. The solvent was dry acetonitrile and the  Table 4 Electrochemical data (potential in V vs FcH/FcH þ and current in A) obtained in CH 3 CN for ca. 0.002 mol dm À 3 of [Co(4,4'-t Bubpy) 2 ](NO 3 ) 2 (complex 4), at indicated scan rates in V s À 1 . Peak 1 is the Co III/II redox couple, peak 2 the Co II/I redox couple and peak 3 the ligand reduction peak.  6 ]). A three-electrode cell comprising of a glassy carbon (surface area 7.07 Â 10 À 6 m 2 ) working electrode, Pt auxiliary electrode and a Ag/Ag þ (0.010 mol dm À 3 AgNO 3 in CH 3 CN) reference electrode [15], mounted on a Luggin capillary [16] was used.

Acknowledgments
This work has received support from the South African National Research Foundation (Grant numbers 113327 and 96111) and the Central Research Fund of the University of the Free State, Bloemfontein, South Africa.

Transparency document. Supporting information
Transparency document associated with this article can be found in the online version at https:// doi.org/10.1016/j.dib.2018.12.043. Table 5 Electrochemical data (potential in V vs FcH/FcH þ and current in A) obtained in CH 3 CN for ca. 0.002 mol dm À 3 of [Co(4,4'-OMebpy) 2 ](NO 3 ) 2 (complex 5), at indicated scan rates in V s À 1 . Peak 1 is the Co III/II redox couple, peak 2 the Co II/I redox couple and peak 3 the ligand reduction peak.