Fingerprint characterization of M-EDTA complexes and iron compounds using terahertz time-domain spectroscopy

Abstract Terahertz time-domain spectroscopy (THz-TDS) provides a novel approach for the coordination compounds characterization. In this paper, the THz absorption spectra of iron complexes and M-EDTA (M = Cd2+, Cu2+, Ni2+, Co2+, Fe2+, Fe3+, Mn2+, Cr3+) complexes were investigated. Comparing to the infrared (IR) spectra of those compounds, the THz spectra can provide unique chemical and intermolecular vibrational information. The M − O and M − N vibrational modes in the THz-TDS spectra of M-EDTA complexes reveal the vibrational information of intermolecular interactions. Characteristic absorption bands in the THz spectra of various complexes and ligands are observed. THz absorption spectra of iron complexes and different ligands exhibited characteristic absorption bands in 0–2.2 THz region. These characteristic bands can be used to characterize and identify different complexes and ligands. The molecular vibrational information in the THz spectral band provides the unique fingerprint for further study of coordination compounds identification and structure characterization.