Electrocatalytic reduction of carbon dioxide induced by bis(N-R-2-hydroxy-1-naphthaldiminato)-copper(II) (R = n-octyl, n-dodecyl): Magnetic and theoretical studies and the X-ray structure of bis(N-n-octyl-2-hydroxy-1-naphthaldiminato)-copper(II) |
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Authors: | A Ríos-Escudero F Caruso D Venegas-Yazigi LJ Todaro GI Cárdenas-Jirón J Costamagna |
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Institution: | a Faculty of Chemistry and Biology, Universidad de Santiago de Chile, Casilla 40, Correo 33, Santiago, Chile b Istituto di Chimica Biomolecolare, CNR, P.le Aldo Moro, 5, 00185, Rome, Italy c CIMAT, Faculty of Chemical and Pharmaceutical Sciences, Universidad de Chile, Santiago, Chile d Department of Chemistry, Hunter College, New York, USA |
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Abstract: | Copper(II) complexes of n-alkyl-2-hydroxy-1-naphthaldimine Schiff bases (with n-alkyl: n-octyl, and n-dodecyl) have been synthesized, to study steric and electronic effects of long alkyl chain substituents on their structure and properties. These complexes have been characterized with FT-IR, UV-Vis, magnetic susceptibility and cyclic voltammetry both in nitrogen and carbon dioxide atmosphere. Metal-ligand coordination is inferred from the shifting of the νC N stretching vibration mode in the 1610-1620 cm−1 region when compared to that of the free ligand. The UV-Vis spectra show one band around 640 nm typical for square planar Cu(II) complexes. Results obtained from cyclic voltammetry indicate electrocatalytic reduction of carbon dioxide around −0.90 V (versus Ag/AgCl). Bis(N-n-octyl-2-hydroxy-1-naphthaldiminato)-copper(II) has been studied with X-ray diffraction. The molecular structure shows the copper atom in a planar environment and the n-octyl chains having thermal disorder. The crystal packing shows stacked units intermolecularly separated by 3.33 Å, probably due to π-π interactions between naphthyl groups, and Cu-O and O-O separations of 3.95 and 3.42 Å, respectively. The magnetic susceptibility data between 10 and 300 K are indicative of diluted paramagnetic behavior. Density functional theory calculations of spin density for the n-octyl complex shows the unpaired electron localized along the planar CuO2N2 moiety. The calculated electrostatic potential show electron rich regions on the oxygen atoms. |
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Keywords: | Copper complexes Cyclic voltammetry Crystal structure Magnetic properties Theoretical study |
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