FT-IR, FT-Raman, NMR spectra, and molecular structure investigation of 2,3-dibromo-N-methylmaleimide: A combined experimental and theoretical study

In the present work, the experimental and theoretical vibrational spectra and chemical shifts of 2,3-dibromo-N-methylmaleimide (2,3DBrNMM, C5H3NO2Br2) were studied. FT-IR and FT-Raman spectra of 2,3DBrNMM in the solid phase were recorded in the region 4000–4400 cm−1 and 3500–3550 cm−1, respectively. The structural and spectroscopic data of the molecule in the ground state were calculated by using Hartree-Fock and density functional method (B3LYP) with the 6-31G(d), 6-31G(d,p), 6-31+G(d,p), 6-31++G(d,p), 6-311G(d), 6-311G(d,p), 6-311+G(d,p) and 6-311++G(d,p) basis sets. The scaled values have been compared with experimental FT-IR and FT-Raman spectra. The observed and calculated frequencies are found to be in good agreement. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. 13C NMR, 1H NMR and DEPT spectra were recorded. 13C NMR and 1H NMR chemical shifts were calculated by using HF and B3LYP methods with 6-311++G(d,p) basis sets. The optimized geometric parameters (bond lengths and bond angles) were given corresponding experimental values of maleimide and 3-benzoylmethyl-2-chloro-N-methylmaleimide molecules.