Quantum chemical studies, natural bond orbital analysis and thermodynamic function of 2,5-dichlorophenylisocyanate

• The FT-IR and FT-Raman spectra of 2,5-dichlorophenylisocyanate were analyzed.
• DFT calculations were carried out for 2,5-dichlorophenylisocyanate at B3LYP method.
• MEP surface provide information about donor and acceptor atoms in the molecule.
• Charge transfer characteristics were examined by HOMO–LUMO and NBO analysis.
• Thermodynamic properties were determined at different temperatures.

In this work, vibrational spectral analysis on the solid state of 2,5-dichlorophenylisocyanate have been investigated both the experimental and theoretical vibrational data indicate the presence of various functional groups within the title of molecule. The equilibrium geometry, bonding features, harmonic vibrational frequencies, infrared and Raman intensities have been calculated with the help of density functional theory methods. The assignments of the vibrational spectra have been carried out with the help of normal coordinate analysis following the scaled quantum mechanical force field calculations. The first hyperpolarizability (βtot) of this noval molecular system and related properties (μ, α and Δα) are calculated using B3LYP/6-31+G(d) and B3LYP/6-311++G(d,p) method on the finite-field approach. Second order perturbation energies and electron density in the bonding and anti-bonding orbitals are discussed on the basis of NBO analysis. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule.

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