Combined experimental and computational investigations of the fluorosolvatochromism of chromeno[4,3-b]pyridine derivatives: Effect of the methoxy substitution

Mohanad Shkoor; Vandana Thotathil; Raed M Al-Zoubi; Haw-Lih Su; Abdulilah Dawoud Bani-Yaseen

doi:10.1016/j.saa.2023.123210

Combined experimental and computational investigations of the fluorosolvatochromism of chromeno[4,3-b]pyridine derivatives: Effect of the methoxy substitution

Spectrochim Acta A Mol Biomol Spectrosc. 2023 Dec 15:303:123210. doi: 10.1016/j.saa.2023.123210. Epub 2023 Jul 27.

Authors

Mohanad Shkoor¹, Vandana Thotathil², Raed M Al-Zoubi³, Haw-Lih Su⁴, Abdulilah Dawoud Bani-Yaseen⁵

Affiliations

¹ Department of Chemistry & Earth Sciences, Faculty of Arts & Science, Qatar University, P.O. Box: 2713, Doha, Qatar. Electronic address: mshkoor@qu.edu.qa.
² Department of Chemistry & Earth Sciences, Faculty of Arts & Science, Qatar University, P.O. Box: 2713, Doha, Qatar.
³ Surgical Research Section, Department of Surgery, Hamad Medical Corporation, Doha, Qatar; Department of Biomedical Sciences, College of Health Sciences, QU-Health, Qatar University, Doha 2713, Qatar; Department of Chemistry, Jordan University of Science and Technology, P.O. Box 3030, Irbid 22110, Jordan.
⁴ Department of Nature Biotechnology, Nanhua University, Chiayi County 62249, Taiwan.
⁵ Department of Chemistry & Earth Sciences, Faculty of Arts & Science, Qatar University, P.O. Box: 2713, Doha, Qatar. Electronic address: abdulilah.baniyaseen@qu.edu.qa.

PMID: 37536243
DOI: 10.1016/j.saa.2023.123210

Abstract

Extensive research has been conducted on the spectral properties of chromeno[4,3-b]pyridine derivatives, owing to their potential applications in sensing, optoelectronic devices, and drug discovery. This study presents a comprehensive investigation into the fluorosolvatochromism of selected chromeno[4,3-b]pyridine derivatives, with a particular emphasis on the impact of methoxy substitution. Three derivatives were synthesized and subjected to spectral analysis: chromeno[4,3-b]pyridine-3-carboxylate (I) as the parent compound, and its 7-methoxy (II) and 8-methoxy (III) substituted derivatives.The UV-Vis absorption spectra of all derivatives exhibited a broad band with a maximum absorption wavelength that remained unaffected by the surrounding medium. However, distinct fluorescence properties were observed among them. Specifically, derivative II displayed notable fluorescence, while derivatives I and III exhibited no fluorescence properties. Furthermore, derivative II exhibited a fluorescence spectrum that is significantly influenced by the polarity of the medium. To investigate the fluorosolvatochromic behavior in depth, we conducted a comprehensive analysis using various neat solvents with different polarities and hydrogen bonding capabilities. The results obtained revealed a significant positive fluorosolvatochromism, with a bathochromic shift in the fluorescence spectrum as the solvent polarity increased. To understand how specific and non-specific interactions between the solute and the solvent affected the fluorosolvatochromism of II, we employed the four empirical scales model of Catalán. The obtained results demonstrated that intramolecular charge transfer played a crucial role in the fluorescence behavior of II. To provide a molecular-level explanation for the experimental spectral properties, we utilized the DFT and TD-DFT/B3LYP/6-31 + G(d) computational methods with the IEFPCM implicit solvation approach. The spectral differences between II and III were rationalized in terms of the frontier molecular orbitals (FMOs: the HOMO and LUMO), where distinct natures were observed among the examined derivatives. This study offers valuable insights into the impact of methoxy substitution on the physical and chemical properties of chromeno[4,3-b]pyridine derivatives, specifically concerning their spectral properties as elucidated by their fluorosolvatochromic behavior.

Keywords: Chromeno[4,3-b]pyridine; Coumarins; DFT and TD-DFT; Fluorosolvatochromism; Methoxy substituent; Solvation models.