Molecular Structure, Vibrational Spectroscopic, Electronic Properties and Chemical Stability of p-n-Alkylbenzoic Acids (nBAC) - a Comparison Using DFT and HF Methods
S. Prasad, D. Ojha
School of Physics, Sambalpur University, Jyoti Vihar-768 019, Sambalpur, Odisha, India
Received: March 10, 2018
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The molecular structure and vibrational spectra of homologous series of nematogenic p-n-alkylbenzoic acids (nBAC) with 4 (4BAC), 5 (5BAC), 6 (6BAC), 7 (7BAC), 8 (8BAC) and 9 (9BAC) carbon atoms in the alkyl chain have been investigated using the density functional Becke3-Lee-Yang-Parr (B3LYP) level with the basis set 6-31++G(d.p) and the Hartree-Fock with the same basis set. The computations have been carried out for all the molecules but detailed results have been reported only for 9BAC molecule. However, the salient features of others have also been reported. The observed vibrational spectra have been resolved and assigned in detail for comparison with the molecules. These results indicate that DFT and HF values are slightly different at both the levels. A comparison of electronic properties such as HOMO (EHOMO), LUMO (ELUMO) energies, energy gap (Eg), ionization potential (I), electron affinity (A), electro negativity (i), chemical hardness (η), electronic chemical potential (μ), electrophilicity index (ω), and softness (S) has been made. It has been observed that the substitution of additional alkyl group has a profound control on energy band gap, and the conductivity of molecules.

topics: vibrational spectra, nematogens, DFT and HF methods