Host−guest interactions in the C$_{59}$N$^•$$\subset$[10]CPP supramolecular radical

Tanuma, Yuri (author), Anézo, Bastien (author), Knaflič, Tilen (author), Volkmann, Jannis (author), Wegner, Hermann A. (author), Sideri, Ioanna K. (author), Tagmatarchis, Nikos (author), Ewels, Christopher Paul (author), Arčon, Denis (author)

A remarkable stability of a supramolecular radical comprising an azafullerene (C$_{59}$N$^•$) radical sterically protected by a [10]cycloparaphenylene ([10]CPP) nanoring, C$_{59}$N$^•$$\subset$[10]CPP, has recently been observed by various experimental probes. In order to investigate the host−guest interaction in these supramolecular complexes, we carried out electron paramagnetic resonance (EPR) measurements, theoretically supported by density functional theory (DFT) calculations. The continuous wave (CW) EPR spectrum shows the presence of two active spin components: C$_{59}$N$^•$$\subset$[10]CPP monomers that can in certain cases polymerize into oligomeric radicals. Two- and three-pulse electron spin echo envelope modulation (ESEEM) measurements allow for determination of experimental hyperfine coupling constants for $^{13}$C and $^1$H atoms and also show the strong coupling to the $^{14}$N atom adjacent to the radical C of the azafullerene. These experimental hyperfine coupling constants reasonably agree with those calculated for the DFT optimized supramolecular structures. The results are consistent with a small spin delocalization from the guest (C$_{59}$N$^•$) to the host ([10]CPP), thereby explaining weak but non-negligible interaction between them. Our study demonstrates that ESEEM experiments in alliance with DFT computations can offer valuable insights into the radical host−guest structures.

• Language: English
• Keywords: physical chemistry, carbon, chemical structure, electron paramagnetic resonance spectroscopy, energy levels, quantum mechanics
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FMF - Faculty of Mathematics and Physics
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: Str. 9057-9065
• Numbering: Vol. 129, iss. 19
• PID: 20.500.12556/RUL-169266
• UDC: 544
• ISSN on article: 1932-7447
• DOI: 10.1021/acs.jpcc.4c07474
• COBISS.SI-ID: 236551683
• Publication date in RUL: 21.05.2025

Record is a part of a journal

• Title: The journal of physical chemistry. C
• Publisher: American Chemical Society
• ISSN: 1932-7447
• COBISS.SI-ID: 28455429

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: fizikalna kemija