Antiradical Properties of trans -2-(4-substituted-styryl)-thiophene
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ORIGINAL ARTICLE
Antiradical Properties of trans-2-(4-substituted-styryl)-thiophene Anamika Gusain 1 & Naresh Kumar 1 & Jagdeep Kumar 1 & Gunjan Pandey 1 & Prasanta Kumar Hota 1 Received: 25 May 2020 / Accepted: 5 October 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract 2-substituted thiophene compounds with electron donating and electron withdrawing p-phenyl substitution were synthesized and studied their radical scavenging properties using DPPH assay and DFT method. It is shown that p-hydroxy and p-amino phenyl substituted compound exhibit radical scavenging activity. From DFT and radical scavenging studies, a correlation between IC50 with the bond dissociation enthalpy, proton affinity, ground state dipole moment and optical band gap of compound is found. Compounds 1–3 with electron withdrawing substituent (NO2, CN, Cl) do not show any radical scavenging properties, whereas compounds 6–7 with electron donating substituent (OH, NH2) show antiradical properties. Further, the antiradical activity is reduced drastically by replacing the -OH and -NH2 with methoxy and -N-alkylating group respectively in 6 and 7. The compound with p-hydroxy phenyl substitution, exhibits stronger antiradical activity as compared to the p-amino phenyl substitution due to smaller O-H bond dissociation energy as compared to the N-H bond. From DPPH and DFT studies, it is suggested that the radical scavenging activity in 2-substituted thiophene is occurred through proton transfer mechanism. The other possible SET, SPLET mechanisms are also corroborated. Keywords Antioxidant ability . Thiophene . Phenol . Stilbene . Absorption . Fluorescence . Density functional theory . Bond dissociation energy . Ionization energy . Proton affinity
Introduction Radical scavengers are active molecules, which play important role in many area of chemistry, biology and material science such as in food storage, cosmetic, pharmaceuticals, oil, rubber, Anamika Gusain and Naresh Kumar contributed equally to this work. Highlights Thiophene compounds with p-hydroxy and p-amino phenyl substitutent, exhibit antiradical activity with IC50 range from 45 μM to 165μM . The activity is comparable to vitamin E (IC50 : 26 μM) Correlation between the anti-radical activity with the ground state dipole moment, bond dissociation enthalpy, ionization potential and proton affinity of thiophene compound is elucidated. In thiophene compounds, the radical scavenging activity is predominantly occurred through hydrogen atom transfer mechanism. The other possible mechanisms such as SET, SPLET are also discussed. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10895-020-02629-5) contains supplementary material, which is available to authorized users. * Prasanta Kumar Hota [email protected] 1
Department of Chemistry, School of Sciences, Hemvati Nandan Bahuguna Garhwal University, Srinagar (Garhwal), Uttarakhand 246174, India
petroleum products and in electronic device applications [1–4]. Some of the well
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