| Electronic, Aromatic, and Structural Effects in Thiophene N-oxide analogs |
| کد مقاله : 1038-ICOC |
| نویسندگان |
|
زینب محمدپور ضیائی *1، مسعود مختاری2 1دانشجو 2هیات علمی |
| چکیده مقاله |
| Thiophene N-oxide derivatives are a significant subgroup of sulfur-containing heteroaromatic compounds with altered electronic and aromatic properties. N-oxidation modifies the electron-donating capacity of sulfur, disrupts π-electron delocalization, and impacts ring aromaticity. Because thiophene is typically more aromatic and stable than furan, understanding the impact of N-oxidation on its structure and reactivity is crucial for predicting chemical behavior and creating functional thiophene-based materials [1,2]. The structural and electronic properties of thiophene N-oxide derivatives were analyzed through DFT calculations at the B3LYP/6-311++G** level. Aromaticity was assessed using NICS(0), NICS(1), and NICS(1)zz indices, along with HOMA values. Frontier molecular orbital energies and HOMO-LUMO gaps were also examined. The analysis of molecular orbitals (MOs) included calculating the percentage of carbon atoms in the HOMO orbital through C2 population analysis . N-oxidation resulted in a noticeable decrease in aromaticity in all studied thiophene derivatives. NICS and HOMA values, along with other aromaticity criteria, clearly demonstrate a decrease in aromaticity compared to thiophene. Specifically, the N+–O– dipole enhanced electron polarization within the structure, resulting in decreased electron density within the ring. Subsequently, with the assistance of molecular orbital analysis, the impact of the N-oxide group on the reactivity of these compounds was explored. It was noted that the N-oxide group alters the distribution of electron density on the carbon atoms of the ring, consequently enhancing the reactivity of C–H bonds with higher electron density to facilitate direct arylation reactions. Thiophene N-oxide analogs (Scheme 1) exhibit reduced aromaticity and modified electronic properties compared to the original thiophene molecule. These findings lay the groundwork for understanding and predicting the behavior of oxidized sulfur-containing heterocycles in both synthetic and materials chemistry. |
| کلیدواژه ها |
| Thiophen N-oxide, Nucleus Independent Chemical Shift (NICS), Reactivity |
| وضعیت: پذیرفته شده |