Study of complex formation in Al(III)-thiocyanate-water system via Raman spectra and factor analysis

Interaction between Al(III) and SCN- ion in aqueous solutions has been inve stigated using Raman spectroscopy. Eleven solutions with the SCN/Al(III) mo lar ratio from 0.5 to 10, have been studied. The systems of overlapped spec tra in the v(CS) and v(CN) regions are analyzed by the methods of factor an alysis. Spectra in the v(CN) and v(CS) regions have been reproduced using t he first four and the first three vectors, respectively. The band areas in the v(CN) region have been determined by deconvolution and used for quantit ative determination of species in solution. It is shown that the molar scat tering coefficient of v(CN) is the same for all the species. The quantitati ve measurements of the Raman band intensity variation has revealed that Al( NCS)-(H2O)(5)(2+). Al(NCS)(2)(H2O)(4)(+) and the two neutral, structurally different Al(NCS)(3)(H2O)(3) complexes are formed. The Al(NCS)(H2O)(5)(2+) complex is present in the solutions with R less than or equal to 1, while t he Al(NCS)(2)(H2O)(4)(+) appears in all the solutions with R greater than o r equal to 1. The neutral complexes are present for R greater than or equal to 4. In all the complexes, SCN is coordinated through nitrogen as a termi nal ligand. (C) 2001 Elsevier Science Ltd. All rights reserved.