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<p>Substituted chalcone derivatives are attractive candidates for nonlinear optical (NLO) applications owing to their extended π-conjugation and tunable donor–π–acceptor architecture. A comprehensive experimental and theoretical investigation has been carried out on four substituted chalcone derivatives—C2SC, C3NC, C3BC, and CB—to elucidate the influence of substituent-induced electronic effects on their structural, optical, and nonlinear optical (NLO) properties. Structural confirmation was achieved through single-crystal X-ray diffraction and spectroscopic analyses. UV–Visible spectroscopy reveals high transparency in the visible region with optical band-gap energies exceeding 3.0&#xa0;eV, indicating suitability for photonic applications. Density functional theory (DFT) calculations performed at the B3LYP/6–311 +  + G(d,p) level provide detailed insight into frontier molecular orbitals, global reactivity descriptors, dipole moments, polarizability, and hyperpolarizability, establishing clear structure–property relationships. Theoretical analysis shows that strong electron-withdrawing and heteroatom substituents significantly modulate intramolecular charge transfer (ICT), HOMO–LUMO energy gaps, and nonlinear polarization. Among the studied compounds, C3NC exhibits the largest dipole moment (6.426 D) and first hyperpolarizability (βₜₒₜ = 350.32 × 10⁻<sup>30</sup> esu), confirming enhanced ICT driven by the nitro group. Experimental Z-scan measurements demonstrate pronounced third-order NLO behavior, with C2SC displaying the highest nonlinear absorption coefficient (β = 26.9 × 10⁻<sup>5</sup>&#xa0;cm W⁻<sup>1</sup>), third-order susceptibility (χ<sup>3</sup>), and the lowest optical limiting threshold, attributed to sulfur-induced polarizability and efficient charge redistribution. Thermal analysis further confirms good thermal stability of all compounds, with decomposition temperatures above ~ 280&#xa0;°C. Overall, the combined experimental and theoretical results demonstrate that substituent-controlled electronic structure, molecular asymmetry, and charge-transfer efficiency play a decisive role in governing the nonlinear optical response of chalcone derivatives. The present study identifies C2SC as a promising candidate for third-order NLO and optical limiting applications, while C3NC shows strong potential for charge-transfer-driven nonlinear polarization, highlighting substituted chalcones as viable materials for advanced photonic and optoelectronic devices.</p>

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Structure-dependent second- and third-order nonlinear optical properties of substituted chalcone crystals: a comparative experimental and computational study

  • 期刊论文

  • 发表日期：

    2026年7月22日

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  • Anita R. Nandurkar,
  • Neelamma B. Gummagol,
  • Anita Shettar,
  • Parutagouda Shankaragouda Patil

摘要

Substituted chalcone derivatives are attractive candidates for nonlinear optical (NLO) applications owing to their extended π-conjugation and tunable donor–π–acceptor architecture. A comprehensive experimental and theoretical investigation has been carried out on four substituted chalcone derivatives—C2SC, C3NC, C3BC, and CB—to elucidate the influence of substituent-induced electronic effects on their structural, optical, and nonlinear optical (NLO) properties. Structural confirmation was achieved through single-crystal X-ray diffraction and spectroscopic analyses. UV–Visible spectroscopy reveals high transparency in the visible region with optical band-gap energies exceeding 3.0 eV, indicating suitability for photonic applications. Density functional theory (DFT) calculations performed at the B3LYP/6–311 +  + G(d,p) level provide detailed insight into frontier molecular orbitals, global reactivity descriptors, dipole moments, polarizability, and hyperpolarizability, establishing clear structure–property relationships. Theoretical analysis shows that strong electron-withdrawing and heteroatom substituents significantly modulate intramolecular charge transfer (ICT), HOMO–LUMO energy gaps, and nonlinear polarization. Among the studied compounds, C3NC exhibits the largest dipole moment (6.426 D) and first hyperpolarizability (βₜₒₜ = 350.32 × 10⁻30 esu), confirming enhanced ICT driven by the nitro group. Experimental Z-scan measurements demonstrate pronounced third-order NLO behavior, with C2SC displaying the highest nonlinear absorption coefficient (β = 26.9 × 10⁻5 cm W⁻1), third-order susceptibility (χ3), and the lowest optical limiting threshold, attributed to sulfur-induced polarizability and efficient charge redistribution. Thermal analysis further confirms good thermal stability of all compounds, with decomposition temperatures above ~ 280 °C. Overall, the combined experimental and theoretical results demonstrate that substituent-controlled electronic structure, molecular asymmetry, and charge-transfer efficiency play a decisive role in governing the nonlinear optical response of chalcone derivatives. The present study identifies C2SC as a promising candidate for third-order NLO and optical limiting applications, while C3NC shows strong potential for charge-transfer-driven nonlinear polarization, highlighting substituted chalcones as viable materials for advanced photonic and optoelectronic devices.