Highly Fluorescent Materials Derived from Ortho-Vanillin: Structural, Photophysical Electrochemical and Theoretical Studies

Poojary, Sachin and Acharya, Madhukara and Salam, Abdul Ajees Abdul and Kekuda, Dhananjaya and Nayak, Upendra and Kumar, Madan and Adhikari, Airody Vasudeva and Sunil, Dhanya (2019) Highly Fluorescent Materials Derived from Ortho-Vanillin: Structural, Photophysical Electrochemical and Theoretical Studies. Journal of Molecular Liquids, 275 (3). pp. 792-806. ISSN 0167-7322

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Small-molecule organic fluorophores are highly in demand attributed to their extensive prospective in material and biomedical applications. Particularly, luminescent π-conjugated organic molecules that possess an efficient solid-state emission are excellent candidates for optoelectronic devices. Focusing on high demand of organic fluorophores, we herein report the synthesis of three organic fluorescent materials derived from o-vanillin, viz. an ester (F1), an azine (F2) and an azo dye (F3). Interestingly, F2 exhibited very intense luminescence in its aggregate phase due to the restriction in intra-molecular rotation (RIR), as demonstrated by solution thickening studies. Further, its Single Crystal X-ray Crystallography (SCXRD) study suggested the existence of various intra and inter molecular interactions and gave evidences for locked intramolecular rotations of the benzene rings in the rigid conformation of the molecule. The bathochromic shift in fluorescence from solution to solid phase was confirmed by its thin-film emission spectrum, which evidences the formation of J-aggregates. The observed RIR, development of J-aggregates and high conjugation in F2 impart an excellent fluorescence in its aggregated state. Thin films of both F2 and F3 on ITO plates exhibited a bathochromic shift with a deep orange to red photoluminescence on UV excitation. Furthermore, the morphologicalcharacterization revealed the presence of clear dense grains in case of F2 and F3, while the DSC analysis indicated phase transitions of all the derivatives. As seen from dielectric measurement studies, the azo dye F3 exhibited the highest dielectric constant among the three derivatives. The electronic and photophysical data based on Density Functional Theory (DFT) and Time Dependent-DFT (TD-DFT) calculations are in agreement with the experimental results. All the above data clearly advocate that, the synthesized fluorophoric o-vanillin derivatives are excellent candidates for electro-optical devices.

Item Type: Article
Uncontrolled Keywords: Aggregation, Azine, Dielectric, DFT, Electrochemical, Fluorophore, X-ray Crystallography
Subjects: Engineering > MIT Manipal > Chemistry
Engineering > MIT Manipal > Physics
Depositing User: MIT Library
Date Deposited: 04 Feb 2019 07:13
Last Modified: 04 Feb 2019 07:13
URI: http://eprints.manipal.edu/id/eprint/153143

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