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

• Quantum chemical parameters, FT-IR and FT-Raman spectra of Sudan Red G were reported using DFT method.
• The hydrogen bonding and the possible interactions were calculated by using NBO analysis.
• The new Cu(II) coordination compound was synthesised and crystal structure was determined.
• The spectroscopic analyses of Sudan Red G and its Cu(II) coordination compound are reported.

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.A novel 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.

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