Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, 01328 Dresden, Germany.
Radiochemistry and Radioecology, Technical University Dresden, 01062 Dresden, Germany.
Molecules. 2022 Jun 24;27(13):4067. doi: 10.3390/molecules27134067.
Although 2-phosphonobutane-1,2,4,-tricarboxylic acid, PBTC, has manifold industrial applications, relevant and reliable data on the protonation of PBTC are poor. However, these data are critical parameters for ascertaining PBTC speciation, especially with regard to a sound structural and thermodynamic characterization of its metal ion complexes. A rigorous evaluation of pH-dependent H, C, and P chemical shifts along with accessible scalar spin-spin coupling constants () was performed in order to determine the p values of PBTC in 0.5 molal NaCl aqueous solution by means of nuclear magnetic resonance (NMR) spectroscopy. The phosphonate group revealed p values of 0.90 ± 0.02 and 9.79 ± 0.02, and the p values associated with the carboxylic groups are 3.92 ± 0.02, 4.76 ± 0.03, and 6.13 ± 0.03. Supported by DFT-calculated structures revealing strong intramolecular hydrogen bonding, the sequence of deprotonation could be unambiguously determined.
尽管 2-膦丁烷-1,2,4,三羧酸（PBTC）具有多种工业应用，但关于 PBTC 的质子化的相关且可靠的数据却很少。然而，这些数据是确定 PBTC 形态的关键参数，特别是对于其金属离子配合物的合理结构和热力学特性的描述。通过核磁共振（NMR）光谱法，我们对 pH 值依赖性的 H、C 和 P 化学位移以及可及的标量自旋-自旋耦合常数（）进行了严格的评估，以便确定 PBTC 在 0.5molal NaCl 水溶液中的 p 值。结果表明，膦酸基团的 p 值为 0.90 ± 0.02 和 9.79 ± 0.02，而羧酸基团的 p 值分别为 3.92 ± 0.02、4.76 ± 0.03 和 6.13 ± 0.03。由 DFT 计算的结构证实了强烈的分子内氢键的存在，因此可以明确确定去质子化的顺序。
