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Synthesis of new imine compounds bearing indole and 1,3,4-thiadiazole moieties: Spectral properties, DFT studies, tautomerism and bond analysis     
Yazarlar
Sevil Özkınalı
Hitit Üniversitesi, Türkiye
Doç. Dr. Muhammet Serdar ÇAVUŞ Doç. Dr. Muhammet Serdar ÇAVUŞ
Kastamonu Üniversitesi, Türkiye
Tuğçe Tosun
Prof. Dr. Nesrin ŞENER Prof. Dr. Nesrin ŞENER
Kastamonu Üniversitesi, Türkiye
Prof. Dr. Mahmut GÜR Prof. Dr. Mahmut GÜR
Kastamonu Üniversitesi, Türkiye
Prof. Dr. İzzet ŞENER Prof. Dr. İzzet ŞENER
Kastamonu Üniversitesi, Türkiye
Özet
This study presents the synthesis of two series of indole derivatives linked with thiadiazole rings, derived from 5-styryl-1,3,4-thiadiazol-2-amine in combination with indole-3-carboxaldehyde and indole-5-carboxaldehyde. The chemical structures of the synthesized compounds were characterized using various spectroscopic techniques, including UV–VIS, FT-IR, 1H-NMR, 13C-NMR, and mass spectrometry. The experimental data obtained from FT-IR and UV–Vis analyses were compared with theoretical results calculated at the B3LYP/6–311++G(2d,2p) level of density functional theory (DFT). The effect of the spatial position of the substituents on the electronic and spectral properties of the compounds was systematically investigated. Additionally, QTAIM and IRI analyses was conducted to elucidate the effects of intramolecular interactions on the σ and π bond characteristics. The impact of substituents on bond strength and bond order was assessed through various methodologies, including intrinsic bond strength index and calculations of Fuzzy, Laplacian, Wiberg, and Mayer bond orders. The findings highlight that the methoxy‑substituted compounds exhibit lower HOMO-LUMO energy gaps compared to the nitro-substituted derivatives, indicating differences in stability and reactivity. Furthermore, the calculated bond orders reveal that a single approach is insufficient for interpreting bond strengths, emphasizing the importance of comprehensive analysis methods. With 1H-NMR, IR and UV–Vis spectroscopic data, it was determined that both indole-indoline and imine-enamine tautomeric forms were formed by proton migration along the N[sbnd]H and CH[dbnd]N groups in the indole, imine and thiadiazole rings. The existence of tautomeric structures was theoretically supported by calculating the transition state and relative enthalpy and Gibbs free energy values.
Anahtar Kelimeler
BOs | DFT | Indole | Schiff bases | Tautomerism | Thiadiazole
Makale Türü Özgün Makale
Makale Alt Türü SSCI, AHCI, SCI, SCI-Exp dergilerinde yayımlanan tam makale
Dergi Adı Journal of Molecular Structure
Dergi ISSN 0022-2860
Dergi Tarandığı Indeksler SCI-Expanded
Dergi Grubu Q2
Makale Dili İngilizce
Basım Tarihi 01-2025
Cilt No 1325
Sayı 1
Doi Numarası 10.1016/j.molstruc.2024.140901
Makale Linki https://doi.org/10.1016/j.molstruc.2024.140901