Quantum chemical studies of molecular structure, vibrational spectra and nonlinear optical properties of p-iodoaniline and p-bromoaniline

• Published in: Journal of molecular structure 2020-12, Vol.1222, p.128939, Article 128939
• Main Authors: John, Nimmy L., Abraham, Sunila, Sajan, D., Sarojini, B.K., Narayana, B.
• Format: Article
• Language: English
• Subjects: Density functional theory; Hirshfield surface; Normal coordinate analysis; Second harmonic generation; Vibrational spectra; Z-scan
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2020.128939

•Binding energies of optimized dimers of para-haloaniline by Counterpoise method.•Hydrogen bonded, halogen bonded and π- π stacked intermolecular interactions.•Simulated and experimental vibrational spectra with PED calculation.•Comparison of Intra and intermolecular interactions in the stable dimers.•Hyperpolarizability,2PA coefficient, NLO response and optical limiting property. Quantum chemical computations of monomer and dimer molecules of para-Iodoaniline (p-IA) and para-Bromoaniline (p-BA) were performed at best suitable DFT/WB97XD levels of theory using LANL2DZ basis set through Gaussian 09 program in addition to experimental z-scan and spectroscopic characterization. Molecular structure analysis reveals halogen/ hydrogen bonded interactions such as NH…X, CX…N and CH…N as well as π- π stacked intermolecular interactions to form the dimer with high binding energy (28.2979 kJ/mol) and stability. The order of planarity p-IA> p-BA is also identified. NBO predicts that the strength of intermolecular interaction in p-IA >p-BA and intramolecular interaction in p-BA >p-IA. The FT-IR and FT-Raman spectra also supports greater planarity and intermolecular interactions in p-IA compared to p-BA. The presence of higher π*(C15C16) → π*(C2C3) stacked intermolecular interaction energy (20.18 kJ/mol) enhances the NLO activity of p-IA. The FMO's and NBO analyses predict the delocalization of electrons within the phenyl ring of the molecules due to the strong ICT interaction between the lone pair of N and π*(CC) orbitals at high stabilization energy. Hirshfeld surface map and 2D fingerprint plot analysis confirm the stability and interactions within the compounds. First order hyperpolarizability values corresponding to p-IA and p-BA were computed which are 5.1 and 3.6 times that of urea. Third order optical nonlinearity was measured by the means of the open aperture z-scan technique .The calculated values of 2PA coefficient β =4.3 × 10−11 m/W in p-IA and β =2.4 × 10−11 m/W in p-BA reveal that the p-IA is a better optical limiter than p-BA crystal.