Molecular structure, vibrational, UV and NBO analysis of 4-chloro-7-nitrobenzofurazan by DFT calculations

In the present work, we reported a combined experimental and theoretical study on molecular structure, vibrational spectra and NBO analysis of 4-chloro-7-nitrobenzofurazan (NBD-Chloride). The FT-IR (400–4000 cm−1) and FT-Raman spectra (50–4000 cm−1) of NBD-Chloride were recorded. The molecular geometry, harmonic vibrational frequencies and bonding features of NBD-Chloride in the ground-state have been calculated by using the density functional B3LYP method with 6-311++G (d, p) as higher basis set. The energy and oscillator strength calculated by time-dependent density functional theory (TD-DFT) result in DMSO and CDCl3 solvents complements with each other. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Finally the calculation results were applied to simulate infrared and Raman spectra of the title compound which show good agreement with observed spectra.

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► Molecular geometry and vibrational frequencies of NBD-Chloride were calculated.
► The calculated DFT results were compared with both FTIR and FT-Raman data.
► The detailed study on natural bond orbital analysis was reported.
► TD-DFT calculations were also carried out for different solvents.
► NBD-Chloride was mainly used in protein labeling reagent.