Diclofenac (active ingredient of Voltaren) has a significant, multifaceted role in medicine, pharmacy, and biochemistry. Its physical properties and impact on biomolecular structures still attract essential scientific interest. However, its interaction with water has not been described yet at the molecular level. In the present study, we shed light on the interaction between the steric hindrance (the intramolecular N–H···O bond, etc.) carboxylate group (−CO₂^–) with water. Aqueous solution of sodium declofenac is investigated using attenuated total reflection-infrared (ATR-IR) and computational approaches, i.e., classical molecular dynamics (MD) simulations and density functional theory (DFT). Our coupled classical MD simulations, DFT calculations, and ATR-IR spectroscopy results indicated that the −CO₂^– group of the diclofenac anion undergoes strong specific interactions with the water molecules. The combined experimental and theoretical techniques provide significant insights into the spectroscopic manifestation of these interactions and the structure of the hydration shell of the −CO₂^– group. Moreover, the developed methodology for the theoretical analysis of the ATR-IR spectrum could serve as a template for the future IR/Raman studies of the strong interaction between the steric hindrance −CO₂^– group of bioactive molecules with the water molecules in dilute aqueous solutions.

中文翻译：

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抗炎药中羧酸基团的水合：ATR-IR和双氯芬酸钠水溶液的计算研究

双氯芬酸（Voltaren的活性成分）在医学，药学和生物化学中具有重要的多方面作用。它的物理性质和对生物分子结构的影响仍然吸引着重要的科学兴趣。但是，它与水的相互作用尚未在分子水平上描述。在本研究中，我们揭示了空间位阻（分子内N–H···O键等）之间的相互作用羧酸酯基团（-CO ₂ ^–） 与水。使用衰减全反射红外（ATR-IR）和计算方法（即经典分子动力学（MD）模拟和密度泛函理论（DFT））研究了十氯芬酸钠水溶液。我们的耦合经典MD模拟中，DFT计算，和ATR-IR光谱结果表明，-CO ₂ ^-基团的双氯芬酸阴离子的经过与水分子强烈的特异性相互作用。结合实验和理论技术，可以深入了解这些相互作用的光谱表现形式以及−CO ₂ ^–的水合壳的结构。团体。此外，所开发的方法的ATR-IR光谱的理论分析可作为将来IR模板的空间位阻之间的强相互作用/拉曼研究-CO ₂ ^-与水分子的生物活性分子的组中的稀水溶液解决方案。