D-A-D/A chalcones with tunable optical characteristics: Synthesis, photophysical, electrochemical and theoretical investigations

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Vol. 451; p. 115511
• Main Authors: Nair, Ajil R., Raksha, C., Heera, R., Gayathri Mohan, M., Manoj, P., Sivan, Akhil
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-06-2024
• Subjects: Chalcone; CIE-chromaticity diagram; DFT; Donor-acceptor–donor; HOMO-LUMO; Optical bandgap; Photoluminescence; Optical bandgap; DFT; HOMO-LUMO; Photoluminescence; Donor-acceptor–donor; CIE-chromaticity diagram; Chalcone
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/j.jphotochem.2024.115511

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•An interrogation into simple chalcones' optical and electronic properties by altering the chemistry of their skeleton is carried out.•The effects of the substituents (electron donating group/EDG or electron withdrawing group/EWG) on the chalcone skeleton are reflected in computational, photophysical and electrochemical results.•Computational calculations of a few selected chalcones (3a-f, 4g, 5h and 6i) are done to ensure the possibility of tuning the bandgap via altering the aldehyde ring/altering substitution on aldehyde-ring.•The chalcones 6a-f and 6i are the best-performing set in terms of photophysical results in CHCl3 solvent.•6d displayed the highest quantum yield of 41.28 %, and 6c had the maximum fluorescence lifetime of 24.5 ns in solid-state.•The HOMO (−6.58 to −5.87 eV)/LUMO (−3.04 to −2.51 eV) energy values of all chalcones were estimated from the recorded cyclic voltammogram.
Herein, we aimed to study four sets/25 derivatives (3a-f, 4a-e, 4g, 5a-e, 5h, 6a-f and 6i) of simple chalcone’s optical and electrochemical properties by altering the chemistry in the chalcone skeleton. The design of chalcone derivatives for the current study was made by creating donor–acceptor-donor/acceptor (D-A-D/A) or push–pull effect in the chalcone backbone. Based on the designed structures, the desired compounds were synthesised by Claisen-Schmidt condensation reaction from four aromatic ketones (1a-d) and seven aromatic aldehydes (2a-i) with 75–94 % yield. Our research interest is to investigate the tunable optical behaviour of these chalcones by varying the combinations of aldehydes and ketones. By doing so, the π-electrons push–pull effect experienced in the chalcone skeleton may vary by default. The theoretical studies of a few selected chalcone derivatives were performed to validate the planned hypothesis using Gaussian 09 W software. All the optimised structures were visualised using GaussView 5.0. DFT (Density Functional Theory) with the B3LYP method and 6–31 + g(d) basis set were used to explain the structure of the selected chalcones via optimisation and FMOs (Frontier Molecular Orbitals). In CHCl3 solvent, the effects of the absorption and emission results elucidate the effects of the substituents (electron donating group/EDG or electron withdrawing group/EWG) in the aldehyde ring on the optical properties of the chalcones. The compound’s emission colour position in the Commission Internationale de l'Eclairage (CIE) chromaticity colour space guarantees its ability to emit visible light in different colour ranges. Among the four chalcone sets, the chalcones 6a-f and 6i exhibited better photophysical results in the CHCl3 solvent. Hence, the solid-state photophysical characteristics of the same set of chalcones were investigated and recorded in the present work. The chalcone 6d displayed the highest quantum yield of 41.28 %, and 6c had the maximum fluorescence lifetime of 24.5 ns. The chalcone family members are already proven candidates for various applications in multidisciplinary fields; the results produced here may aid future researchers in finding more applications by utilising the recorded properties.