Experimental and theoretical studies on Sudan Red G [1-(2-methoxyphenylazo)-2-naphthol] and its Cu(II) coordination compound

The molecular structure, natural bond orbital (NBO) analysis and vibrational studies of Sudan Red G {(SRG), [1-(2-methoxyphenylazo)-2-naphthol]} have been investigated using Density Functional Theory (DFT) calculations. To investigate the tautomeric stability, optimisation calculations at the Hartree–Fock (HF) and DFT/B3LYP levels were performed for the azo (OH) and hydrazo (NH) forms of the title compound. FT-IR, FT-Raman and electronic absorption spectra of SRG have recorded and analysed. We have compared the calculated IR and Raman wavenumbers with the observed data. l copper(II) coordination compound with Sudan Red G was synthesised and characterised by analytical, spectroscopic (FT-IR and electronic absorption spectra) and single-crystal X-ray diffraction methods. The X-ray structure of the prepared coordination compound indicated that it crystallised in a dimeric form as [Cu2(SRG)4·2O0.5] that consists of facial geometric isomer. In the coordination compound, the Cu(II) atoms have a distorted octahedral geometry.