Cation recognition controlled by protonation or chemical reduction: a computational study

• Published in: Physical chemistry chemical physics : PCCP Vol. 25; no. 22; pp. 15518 - 1553
• Main Authors: Orenha, Renato Pereira, Borges, Alexandre, de Oliveira Andrade, Ana Lívia, Ferreira, Sergio Eduardo, Furtado, Saulo Samuel Pereira, Glitz, Vinícius Acir, Caramori, Giovanni Finoto, Parreira, Renato Luis Tame
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 07.06.2023
• Subjects: Acids; Carboxylic acids; Cations; Chemical reduction; Crown ethers; Electron density; Electrons; Hydrogen atoms; Iron; Nitrogen dioxide; Oxygen atoms; Protonation; Recognition; Sodium; Substitutes
• ISSN: 1463-9076; 1463-9084
• 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 2 ) or acceptor (-NO 2 ) 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 2 substitution in the ferrocene framework favors the cationic recognition. It is based on the strengthening of the electrostatic and σ O Na + and H 2 N 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. Protonation or chemical reduction processes stimulate cation transport supported by non-covalent interactions. Herein, the potential of carboxylic acid and ferrocene crown ether structures for cation recognition has been compared and improved.