Abstract The 5-Methyl-2-thiophenecarboxaldehyde (MTC) and its derivatives present a wide range of biological activities. In this regard a combined experimental and theoretical analysis for MTC and its derivatives can help to understand the electronic factors involved in the mode of action in biological systems. In the present work we used FT-IR and UV–vis techniques to investigate the spectroscopic properties of MTC. The conformational and vibrational analyses were theoretically explored using DFT calculation at DFT/B3LYP/6–311++G(d,p) level. A full electronic analysis of compound was performed using TD-DFT/B3LYP/6–311++G(d,p) calculations in gas phase and in ethanol solvent with the CPCM model. The NLO parameters (β, γ and χ(3)) and FMO energies for MTC were calculated at the same level of theory. The relation between linear polarizability (α) and refractive index (n) were used to describe the polarization behavior of MTC in ethanol solvent. Our results indicate that MTC can be considered as a candidate to microscopic third−order NLO material.

中文翻译：

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5-METHYL-2-THIOPHENECARBOXALDEHYDE：实验和 TD/DFT 研究

摘要 5-甲基-2-噻吩甲醛（MTC）及其衍生物具有广泛的生物活性。在这方面，对 MTC 及其衍生物的实验和理论分析相结合，可以帮助理解生物系统中作用模式所涉及的电子因素。在目前的工作中，我们使用 FT-IR 和 UV-vis 技术来研究 MTC 的光谱特性。在 DFT/B3LYP/6–311++G(d,p) 水平上使用 DFT 计算从理论上探索了构象和振动分析。使用 TD-DFT/B3LYP/6–311++G(d,p) 计算在气相和乙醇溶剂中使用 CPCM 模型对化合物进行全电子分析。MTC 的 NLO 参数（β、γ 和 χ(3)）和 FMO 能量是在相同的理论水平下计算的。线性极化率 (α) 和折射率 (n) 之间的关系用于描述 MTC 在乙醇溶剂中的极化行为。我们的结果表明 MTC 可以被认为是微观三阶 NLO 材料的候选者。