In-silico analysis of substituent effect on the static first order hyperpolarizability of electron donating mono substituted Chalcone derivatives.

Noncentrosymmetric π conjugated systems with suitable electron donor acceptor groups play a crucial role in material NLO activity. The influence of an electron donating mono substituent at the para position of the phenylene ring of chalcone was investigated as a resource for second harmonic generation. The geometrical optimization of 11 electron donating group substituted chalcones were performed using density functional theory at the B3LYP/6-311G(d,p) level and compared with experimental geometrical parameters of five reported chalcones. All the derivatives are transparent to visible radiation as shown by the electronic absorption spectra investigated by the TDDFT-CAM B3LYP/6-311G(d,p) method, and the maximum absorption wavelength was due to the πPhB → π* transition. The first order hyperpolarizability βtot, calculated using the CAM B3LYP/6-311G(d,p) method, increases with the electron donating ability of the substituent, and the largest βtot was observed for dimethylamino substituent. The Hammett substituent constant (σp) shows good linear correlation with β, λmax, and Egap in the ground state. The Brown constant (σp+) was better correlated indicating the polarization of carbonyl group in the excited state. Frontier molecular orbitals also reveal the valence electron excitation. Correlation of σp with various parameters was analyzed to assess the property interrelationship with electronic reorganization in the molecule. The electronic structures of molecular fragments were described in terms of natural bond orbital analysis, which shows intramolecular interactions.