Study of coordination and ligand structure in cobalt-EDTA complexes with vibrational microspectroscopy

摘要

Micro-Raman scattering experiments and micro-infrared absorption studies have been conducted on the cobalt-EDTA complexes [Co(H2O)H(2)EDTA]. 2H(2)O (I) and [Co(H2O)(6)](2+)[Co(H2O) HEDTA](2)(2-). 2H(2)O (II) (where HEDTA is the mono-protonated EDTA(4-) ligand anion, or HEDTA(3-), and EDTAH(2) is the di-protonated anion, or H(2)EDTA(2-), of the neutrally charged parent EDTA acid) that previously have been documented with respect to their structural chemistry. The two complexes have been found to exhibit vibrational spectra that allow one to differentiate them from one another. The vibrational data for the two compounds are discussed in relation to their structures, particularly with respect to subtle bonding differences of both the EDTA ligands and the coordinated and un-coordinated water molecules. Several vibrational assignments are proposed for both the EDTA and water molecules in the complexes for the variably protonated EDTA molecule. (C) 1998 Elsevier Science B.V. All rights reserved. [References: 16]