Spectroscopic analysis (FT-IR/FT-Raman) and molecular structure investigation on m-fluoronitrobenzene using hybrid computational calculations.

In the present investigation, the FT-IR/FT-Raman spectra of the m-fluoronitrobenzene (m-FNBZ) are recorded. The fundamental frequencies are assigned and the computational calculations are performed by DFT (B3LYP, B3PW91 and MPW1PW91) methods with 6-31++G(d,p) and 6-311++G(d,p) basis sets and the corresponding results are tabulated. The computed values of frequencies are scaled by using suitable factors. The distortion of the structure of the compound due to the substitutions of Fl and NO(2) is investigated. The alternation of the vibrational pattern of the pedestal molecule related to the substitutions is analyzed. A study on the electronic properties; absorption wavelengths, excitation energy, dipole moment and frontier molecular orbital energies, are performed by time dependent DFT (TD-DFT) approach. The electronic structure and the assignment of the absorption bands in the electronic spectra of steady compounds are discussed. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Besides frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) was performed. Mulliken charges of the m-FNBZ molecule was also calculated and interpreted. The thermodynamic properties (heat capacity, entropy, and enthalpy) of the title compound at different temperatures were calculated in gas phase.