Analysis on linear and nonlinear optical properties of two Bisphenols with DFT approach: A comparative study

• Hyperpolarizability calculations on two Bisphenols using DFT method.
• Large value of dipole moment is identified due to large charge distribution.
• Contribution of off diagonal components of β for octupole which leads non zero SHG.
• Importance of diagonal β components for dipole which leads zero SHG.

Density functional theory (DFT) method with B3LYP functional has been employed for the polarizability (α) and first order hyperpolarizability (β) calculations of two Bisphenols (4,4′ thiodiphenol and 4,4′ sulfonyldiphenol). Correlation between the dipole moment, polarizability and charge distribution is analyzed extensively. The calculated octupolar over dipolar contribution ratio parameter ρ from the hyperpolarizability components gives rise to macroscopic second harmonic generation (SHG) phenomenon identifying with the dipole nature of 4,4′ thiodiphenol and the tendency towards the octupole nature of 4,4′ sulfonyldiphenol molecule. Discussions on the geometrical structures of both Bisphenol molecules have been extended based on the comparison of optimized gas phase with solid state geometrical parameters to explain the high coplanarity in 4,4′ sulfonyldiphenol molecule which leads to the extended π-conjugation. Theoretically predicted large value of SHG in 4,4′ sulfonyldiphenol and zero value in case of 4,4′ thiodiphenol are confirmed with Kurtz–Perry Powder technique.