Radical Pairing Interactions and Donor-Acceptor Interactions in Cyclobis(paraquat-p-phenylene) Inclusion Complexes.

Content Provider	Europe PMC
Author	Wang, Wei Wu, Wei Su, Peifeng
Editor	Casella, Girolamo Carlotto, Silvia
Copyright Year	2023
Abstract	Understanding molecular interactions in mechanically interlocked molecules (MIMs) is challenging because they can be either donor-acceptor interactions or radical pairing interactions, depending on the charge states and multiplicities in the different components of the MIMs. In this work, for the first time, the interactions between cyclobis(paraquat-p-phenylene) (abbreviated as CBPQTn+ (n = 0-4)) and a series of recognition units (RUs) were investigated using the energy decomposition analysis approach (EDA). These RUs include bipyridinium radical cation (BIPY•+), naphthalene-1,8:4,5-bis(dicarboximide) radical anion (NDI•-), their oxidized states (BIPY2+ and NDI), neutral electron-rich tetrathiafulvalene (TTF) and neutral bis-dithiazolyl radical (BTA•). The results of generalized Kohn-Sham energy decomposition analysis (GKS-EDA) reveal that for the CBPQTn+···RU interactions, correlation/dispersion terms always have large contributions, while electrostatic and desolvation terms are sensitive to the variation in charge states in CBPQTn+ and RU. For all the CBPQTn+···RU interactions, desolvation terms always tend to overcome the repulsive electrostatic interactions between the CBPQT cation and RU cation. Electrostatic interaction is important when RU has the negative charge. Moreover, the different physical origins of donor-acceptor interactions and radical pairing interactions are compared and discussed. Compared to donor-acceptor interactions, in radical pairing interactions, the polarization term is always small, while the correlation/dispersion term is important. With regard to donor-acceptor interactions, in some cases, polarization terms could be quite large due to the electron transfer between the CBPQT ring and RU, which responds to the large geometrical relaxation of the whole systems.
Journal	Molecules
Volume Number	28
DOI	10.3390/molecules28052057
PubMed Central reference number	PMC10004262
Issue Number	5
PubMed reference number	36903306
e-ISSN	14203049
Language	English
Publisher	Molecular Diversity Preservation International (MDPI)
Publisher Date	2023-02-22
Access Restriction	Open
Subject Keyword	radical pairing interactions donor–acceptor interactions mechanically interlocked molecules energy decomposition analysis
Content Type	Text
Resource Type	Article
Subject	Physical and Theoretical Chemistry Medicine Chemistry Drug Discovery Pharmaceutical Science Analytical Chemistry Molecular Medicine Organic Chemistry