Vázquez-Hernández Hazel, Esquivel Rodolfo O
Departamento de Química, Universidad Autónoma Metropolitana-Iztapalapa, Av. Ferrocarril San Rafael Atlixco 186, Colonia Leyes de Reforma, 09310, Mexico City, México.
Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, 18071, Granada, Spain.
J Mol Model. 2023 Jul 18;29(8):253. doi: 10.1007/s00894-023-05589-2.
In spite of the fact that molecular acidity is a fundamental physicochemical property of molecular systems, the vast majority of theoretical studies have focused attention on monoprotic acids and on the prediction of pKa's. Polyprotic acids, represent a challenge for electronic structure calculations since the multiple acidic sites result in a vast group of species with different conformations and reactivities. In this work, Information-theoretic (IT) concepts of localizability, order and uniformity are applied to the Citric Acid and its deprotonated species through the one-electron density functionals: Shannon entropy (S), Fisher information (I) and Disequilibrium (D), respectively. We pursue the goal of characterizing the acidity of the aforementioned species with the aim to associate the IT concepts to chemical features such as the polarizability of the protonated/deprotonated species, the liability of the acidic sites, atomic electrostatic potentials, covalent bonding. IT analyses looks very promising for future studies on the acidity of specific deprotonation-sites of polyprotic acids.
Density functional theory (DFT) calculations were performed with Gaussian 09 program. A sensitivity analysis of the IT-measures was performed for the citric acid and the citrate using B3LYP, B3PW91, BPW91, M05-2X, M06-2X and PBEPBE functionals with the 6-311++g(3df,2p), 6-311++g(d,p), 6.311+g(d,p) and aug-cc-pVDZ basis sets. The rest of the analysis was performed with the M05-2X/6-311+G(d,p) level of theory. Additionally, aqueous media was considered by use of the SMD solvent model. The IT-measures were calculated using a suite of programs developed in our laboratory jointly with the DGRID software package.
尽管分子酸度是分子体系的一种基本物理化学性质，但绝大多数理论研究都集中在一元酸以及pKa的预测上。多质子酸对电子结构计算来说是一项挑战，因为多个酸性位点会产生大量具有不同构象和反应性的物种。在这项工作中，通过单电子密度泛函，分别将信息论（IT）中的定域性、有序性和均匀性概念应用于柠檬酸及其去质子化物种：香农熵（S）、费舍尔信息（I）和不平衡度（D）。我们旨在表征上述物种的酸度，目的是将IT概念与诸如质子化/去质子化物种的极化率、酸性位点的活性、原子静电势、共价键等化学特征联系起来。IT分析对于未来多质子酸特定去质子化位点酸度研究看起来非常有前景。
使用高斯09程序进行密度泛函理论（DFT）计算。使用B3LYP、B3PW91、BPW91、M05 - 2X、M06 - 2X和PBEPBE泛函以及6 - 311++g(3df,2p)、6 - 311++g(d,p)、6.311+g(d,p)和aug - cc - pVDZ基组，对柠檬酸和柠檬酸盐进行IT测量的敏感性分析。其余分析使用M05 - 2X/6 - 311 + G(d,p)理论水平进行。此外，通过使用SMD溶剂模型考虑水相介质。IT测量使用我们实验室联合DGRID软件包开发的一套程序进行计算。
