Departamento de Química, Universidade Federal de Santa Catarina, Campus Universitário Trindade, CP 476, Florianópolis, SC, 88040-900, Brazil.
Núcleo de Pesquisas em Ciências Exatas e Tecnológicas, Universidade de Franca, Franca, SP, Brazil.
Phys Chem Chem Phys. 2023 Jun 7;25(22):15518-15530. doi: 10.1039/d3cp01175e.
To control biochemical processes, non-covalent interactions involving cations are activated by protons or electrons. In the present study, the bonding situation between: (i) carboxylic acid or (ii) ferrocene-functionalized crown ether derivatives and cations (Li, Na or K) has been elucidated and, mainly, tuned by the substitution of hydrogen atoms by electron donor (-NH) or acceptor (-NO) groups. The deprotonation of the carboxyl groups improves the interaction with the cations through more favorable electrostatic O⋯cation interactions. Reducing the ferrocene structures favors cationic recognition supported by a less unfavorable iron⋯cation binding. The receptors preferably interact with smaller cations because of more attractive electrostatic and orbital (σ or π) O⋯cation interactions. The presence of electron donor or acceptor groups in the carboxylic acid-functionalized crown ethers promotes less attractive interactions with the cations, mainly due to the less favorable electrostatic O⋯Na interactions. The -H → -NH substitution in the ferrocene framework favors the cationic recognition. It is based on the strengthening of the electrostatic and σ O⋯Na and HN⋯Na bonds. The (i) absence of repulsive electrostatic iron⋯cation interactions, or (ii) the presence of oxygen atoms with large electron density, ensures carboxylic acid-functionalized crown ethers have more favorable interactions with cations than ferrocene compounds. Therefore, this work has demonstrated how cation recognition can be improved by structural changes in carboxylic acid- or ferrocene-functionalized crown ethers and has shown that the carboxylic acid molecules appear to be better candidates for cation recognition than ferrocene derivatives.
为了控制生化过程，涉及阳离子的非共价相互作用通过质子或电子被激活。在本研究中，阐明了（i）羧酸或（ii）二茂铁功能化冠醚衍生物与阳离子（Li、Na 或 K）之间的键合情况，并通过用电子供体（-NH）或受体（-NO）基团取代氢原子来主要调整这种键合情况。羧酸基团的去质子化通过更有利的静电 O⋯阳离子相互作用改善了与阳离子的相互作用。减少二茂铁结构有利于通过不太不利的铁⋯阳离子结合来支持阳离子识别。由于更有吸引力的静电和轨道（σ 或 π）O⋯阳离子相互作用，受体更喜欢与较小的阳离子相互作用。羧酸功能化冠醚中存在供电子或受电子基团会促进与阳离子的吸引力降低，主要是由于静电 O⋯Na 相互作用不太有利。在二茂铁骨架中-H→-NH 取代有利于阳离子识别。这基于静电和 σ O⋯Na 和 HN⋯Na 键的增强。（i）不存在排斥静电铁⋯阳离子相互作用，或（ii）存在具有大电子密度的氧原子，确保羧酸功能化冠醚与阳离子的相互作用比二茂铁化合物更有利。因此，这项工作表明如何通过羧酸或二茂铁功能化冠醚的结构变化来改善阳离子识别，并表明羧酸分子似乎比二茂铁衍生物更适合阳离子识别。
