Optical properties of 3-substituted indoles.
Jagdeep Kumar1, Naresh Kumar1, Prasanta Kumar Hota1
1Department of Chemistry, School of Sciences, Hemvati Nandan Bahuguna Garhwal University Srinagar (Garhwal) Uttarakhand 246174 India p.hota@hnbgu.ac.in.
RSC Advances
|May 6, 2022
Summary
Ethenyl indoles with strong electron-withdrawing groups exhibit significant non-linear optical (NLO) properties due to charge transfer. Substituent choice critically influences NLO response, with p-nitrophenyl derivatives showing superior performance.
Area of Science:
- Organic Chemistry
- Materials Science
- Computational Chemistry
Background:
- Non-linear optical (NLO) materials are crucial for advanced photonic applications.
- Ethenyl indoles are a class of organic molecules with potential NLO properties.
- Understanding structure-property relationships is key to designing effective NLO materials.
Purpose of the Study:
- To investigate the optical and NLO properties of various p-phenyl substituted ethenyl indoles.
- To correlate molecular structure with observed NLO behavior.
- To explore the influence of solvent polarity on these properties.
Main Methods:
- Absorption and fluorescence spectroscopy were employed to study optical properties.
- Time-Dependent Density Functional Theory (TDDFT) was used for theoretical calculations.
- Varying solvent polarities were utilized to probe excited-state behavior.
Main Results:
- Ethenyl indoles display substituent-dependent NLO properties.
- Compounds with strong electron-attracting groups, like p-nitrophenyl, exhibit significant charge transfer and high NLO responses (e.g., β up to 115 × 10⁻³⁰ esu⁻¹ cm⁵).
- A highly dipolar excited state was observed for p-nitrophenyl substituted ethenyl indoles (μe: 18.2-27.1 D; Δμ: 9.4-17.8 D).
Conclusions:
- The NLO properties of ethenyl indoles are strongly influenced by the electronic nature of the p-phenyl substituent.
- Strong electron-withdrawing substituents enhance NLO response through charge transfer mechanisms.
- A correlation was established between NLO properties (β) and optical band gap, dipole moments, and charge transfer characteristics.
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