Comparative analysis of nonlinear optical properties in santalin A and santalin B: a density functional theory approach

Abstract This study investigates the non-linear optical (NLO) properties of Santalin A and Santalin B using density functional theory (DFT) at the B3LYP/6-311G+(d,p) level of theory, marking the first computational exploration of these properties for Santalin compounds. The comparative analysis reveals distinct differences in the physicochemical and electronic properties of the two compounds, influencing their potential applications. Santalin A, characterized by a tightly bound highest occupied molecular orbital (HOMO), a larger band gap, and higher ionization potential, exhibits greater stability, making it suitable for applications requiring resistance to electronic changes, such as insulation or semiconductor roles. Its higher dipole moment (7.04) and polarizability (8.01 × 10 −40 C 2 m 2 J −1 ) suggest it could be more effective in advanced NLO applications, such as optical switching and second-harmonic generation. In contrast, Santalin B demonstrates higher reactivity with a less negative HOMO (−4.701 eV), a smaller band gap (2.040 eV), and greater electron affinity (2.66), indicating its potential for applications requiring enhanced conductivity, electron transfer, and flexibility, such as in organic electronics. Both compounds show notable NLO responses; Santalin A and B both exhibit remarkable nonlinear optical (NLO) properties, with Santalin A showing a higher dipole moment (7.0477 Debye vs. 6.53 Debye), greater anisotropic polarizability (48.55 × 10 −39 C 2 m 2 J −1 vs. 37.12 × 10 −39 C 2 m 2 J −1 ), and slightly stronger hyperpolarizability (1.13 × 10 −50 C 3 m 3 J −2 vs. 1.06 × 10 −50 C 3 m 3 J −2 ). Both molecules have similar second-order hyperpolarizabilities ( γ ), with Santalin A at −6.66753 × 10 −61 C 4 m 4 J −3 and Santalin B at −6.76983 × 10 −61 C 4 m 4 J −3 , highlighting their potential for advanced NLO applications. However, Santalin A exhibits slightly more pronounced properties. The findings emphasize the importance of tailoring material selection based on specific application needs, with Santalin A being more suited for stability-driven contexts and Santalin B excelling in environments that demand high reactivity and conductivity.