An interesting coordination complex formed between the azo dye Sudan Red G and cobalt ion

In this study, the synthesis, spectroscopic analysis (Raman and infrared) and crystal structure of compound denominated [Co(SRG)2]·CH3CH2OH have been investigated, were SRG is 1-(2-methoxyphenyl-azo)-2-naphthol or simply Sudan Red G and CH3CH2OH is one molecule of ethanol. The repeating unit is formed by the presence of an adduct complex constituted by two SRG ligands coordinated to the cobalt ion in a slightly distorted octahedral geometry. The other building block consists of a molecule of ethanol, which was used as the reaction solvent. The spectroscopic analysis provided important information related to coordination and formation of molecular complex through its mains bands. In the Raman spectrum the presence of marker bands as in at 1224 cm−1 ascribed to the binder SRG [δ(NH) + ν(COC) + δ(CH) + ν(CC)] were displaced in the complex formed to 1232 cm−1 due to the loss of the proton from the azo group and the formation of a bond between the oxygen of the ether group with the metal ion. In the infrared spectrum the bands at 653/489 cm−1 and 622/528 cm−1 were attributed to [ν(CoO) + νCC)] and [νCoN + νCC] characteristic of the metal–ligand bond.