Optical spectra of the CoCl2/PEG systems

Abstract UV–VIS absorption spectra of the cobalt chloride (CoCl2) in poly(ethylene glycol) (PEG) were measured and analyzed. Six different PEG average molecular weight (chain length) have been used. The study was performed to determine changes in the symmetry species of the Co-complex ions formed in these systems. All recorded spectra belong to the tetrahedral-like, tetrachloro, Td, [Co2+4Cl−]2− and trichloro, C3v, [Co2+3Cl−O2−]3− Co-complexes. The Co-coordination has been studied in dependence on the PEG type (chain length and phase) and an added co-solvent. These spectra have been subsequently deconvoluted into their components. A new mechanism of the (pseudo)tetrahedral Co-complexes formation in PEG is proposed. A doubt is raised concerning the old assignment of two of the components of the tetrahedral Co-complexes spectra around 16,000 cm−1.