Computational and spectroscopic studies of biologically active coumarin‐based fluorophores

• Published in: Luminescence (Chichester, England) Vol. 36; no. 3; pp. 769 - 787
• Main Authors: S., Chandrasekhar, H.R., Deepa, Melavanki, Raveendra, Basanagouda, Mahanthesh M., Mogurampelly, Santosh, J, Thipperudrappa
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.05.2021
• Subjects: Biological activity; Chemical compounds; Computer applications; Coumarin; Density functional theory; dipole moment; Dipole moments; Doppler effect; Fluorescence; Fluorophores; Mathematical analysis; Molecular interactions; Molecular orbitals; Molecular structure; Polarity; Red shift; solvatochromic shift; Solvents; Vibrational spectra; solvatochromic shift; fluorescence; dipole moment; coumarin; density functional theory
• DOI: 10.1002/bio.4002
• ISSN: 1522-7235

We used density functional theory (DFT) calculations to examine the various molecular properties of two coumarin derivatives, namely 4‐(5‐amino‐[1,3,4]thiadiazol‐2‐ylsulfanylmethyl)‐7‐methyl‐chromen‐2‐one and 4‐(5‐amino‐[1,3,4]thiadiazol‐2‐ylsulfanylmethyl)‐7‐methoxy‐chromen‐2‐one at different levels of theory and basis sets. The calculated highest occupied molecular orbital and lowest unoccupied molecular orbital energies revealed that the investigated molecules were chemically active with a tendency for molecular interactions. The theoretical vibrational frequencies of these molecules were found to be consistent with the experimentally obtained frequencies. Moreover, solvatochromic measurements indicated no significant change in absorption spectral peak by varying the polarity of solvent. Under the same conditions we found that there was a red shift of 39 nm in the fluorescence spectral peak with increase in solvent polarity. The solvatochromic data were used to estimate excited dipole moments and the change in dipole moment was interpreted based on resonance structure of molecules. Optimized molecular geometry, infrared stretching vibrations and HOMO–LUMO energies were obtained using density functional theory. The experimental results of solvent effect were investigated using the Lippert–Mataga and Reichardt methods, and Catalán polarity scales. A double linear correlation of spectral properties with ETN was observed.