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Issue 20, 2015
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An X-ray absorption spectroscopy investigation of the coordination environment of electrogenerated Ni(II)-pseudohalide complexes arising from the anodic polarization of Ni electrodes in DMSO solutions of NCO, NCS and NCSe ions

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Abstract

X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) were used to provide direct information in solution on the coordination state of electrogenerated products from anodically polarized nickel electrodes in pseudohalide-ion-containing dimethyl sulfoxide (DMSO) solvent (i.e. NCX, X = O, S, Se) in the presence of a supporting electrolyte of tetrabutylammonium perchlorate (TBAP). Electrogenerated solutions and model solutions representative of the chemical speciation in electrolyzed systems (prepared by mixing Ni(II) and pseudohalide ion solutions in DMSO), were also examined. In general for Ni(II) interacting with NCS and NCSe, the complex ion generated appears to be 6-coordinate [Ni(NCX)(DMSO)5]+, while EXAFS/XANES data of the Ni/cyanate system suggest an average coordination number of 5, which in reality is due to the electrogenerated solution containing a mixture of 4 coordinate (tetrahedral) [Ni(NCO)4]2− and octahedral [Ni(DMSO)6]2+ species. These observations of the octahedral geometry for the Ni(II)/thiocyanate and Ni(II)/selenocyanate systems and 5-coordinate geometry in the Ni(II)/cyanate systems (being electrogenerated products of anodic polarisation of Ni in the DMSO-supported pseudohalide ion electrolytes) agree with the differences in colour observed between samples. EXAFS/XANES measurements combined with IR spectroelectrochemical analyses of solutions provide a versatile way of analyzing these electrochemical systems without the need for isolating compounds from the electrolyte.

Graphical abstract: An X-ray absorption spectroscopy investigation of the coordination environment of electrogenerated Ni(ii)-pseudohalide complexes arising from the anodic polarization of Ni electrodes in DMSO solutions of NCO−, NCS− and NCSe− ions

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Publication details

The article was received on 20 Nov 2014, accepted on 26 Jan 2015 and first published on 26 Jan 2015


Article type: Paper
DOI: 10.1039/C4RA14940H
Author version available: Download Author version (PDF)
Citation: RSC Adv., 2015,5, 15709-15718
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    An X-ray absorption spectroscopy investigation of the coordination environment of electrogenerated Ni(II)-pseudohalide complexes arising from the anodic polarization of Ni electrodes in DMSO solutions of NCO, NCS and NCSe ions

    K. H. K. L. Alwis, B. Ingham, M. R. Mucalo, P. Kappen and C. Glover, RSC Adv., 2015, 5, 15709
    DOI: 10.1039/C4RA14940H

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