Entry of chiral phthalimides with significant second order nonlinear optical and piezoelectric properties

Abstract

Three new chiral phthalimides have been synthesized and characterized. Phthalimides (1–3) possess an acentric structure as revealed by structural investigation. Compounds 1 and 2 crystallize in an orthorhombic system with the space group P2₁2₁2₁, however the monoclinic system with the chiral space group P2₁ is observed for 3. The presence of C–H⋯O hydrogen bonds in 1–3 facilitates the construction of several supramolecular structures. Helical structural motifs are also observed. The maximum value of hyperpolarizability (β), 159.9446 × 10⁻³⁰ esu calculated for compound 3 is several times greater than that of urea. On the other hand 1 and 2 have hyperpolarizabilities of 10.8063 × 10⁻³⁰ and 121.9519 × 10⁻³⁰ esu, respectively. The polycrystalline samples of 1–3 were assessed for a second-harmonic generation response, which was found to be 8.8, 10.2 and 9.7 mV respectively. Further, compounds 1–3 showed d₃₃ values of 0.93, 1.97 and 1.88 pC N⁻¹ respectively. The present investigation demonstrates chiral phthalimides as effective contenders for nonlinear optical and piezoelectric properties.