Carbon–carbon σ-single bonds are crucial for constructing molecules like ethane derivatives (R3C–CR3), which are composed of tetrahedral four-coordinate carbons. Molecular functions, such as light absorption or emission, originate from the π-bonds existing in ethylene derivatives (R2C═CR2). In this study, a relatively stable cyclopentane-1,3-diyl species with π-single bonding system (C−π–C) with planar four-coordinate carbons is constructed. This diradicaloid is energetically more stable than the corresponding σ-single bonding system. The π-electron single bonding system provides deeper insights into the chemical bonding and the physical properties derived from the small energy gaps between the bonding and antibonding molecular orbitals.
@article{onishi2023energetically,title={Energetically More Stable Singlet Cyclopentane-1,3-diyl Diradical with π-Single Bonding Character than the Corresponding σ-Single Bonded Compound},author={Liu, Q. and Onishi, K. and Miyazawa, Y. and Wang, Z. and Hatano, S. and Abe, M.},journal={J. Am. Chem. Soc.},volume={145},issue={49},pages={27089--27094},year={2023},month=nov,publisher={acs},doi={10.1021/jacs.3c10971},url={https://doi.org/10.1021/jacs.3c10971},dimensions={true},tab={paper}}
Generation and Characterization of a Tetraradical Embedded in a Curved Cyclic Paraphenylene Unit
Unique spin–spin (magnetic) interactions, ring-size effects on ground-state spin multiplicity, and in-plane aromaticity has been found in localized 1,3-diradicals embedded in curved benzene structures such as cycloparaphenylene (CPP). In this study, we characterized the magnetic interactions in a tetraradical consisting of two localized 1,3-diradical units connected by p-quaterphenyl within a curved CPP skeleton by electron paramagnetic resonance (EPR) spectroscopy and quantum chemical calculations. Persistent triplet species with zero-field splitting parameters similar to those of a triplet 1,3-diphenylcyclopentane-1,3-diyl diradical were observed by continuous wave (CW) or pulsed X-band EPR measurements. The quintet state derived from the ferromagnetic interaction between the two triplet diradical moieties was not detected at 20 K under glassy matrix conditions. At the B3LYP/6-31G(d) level of theory, the singlet state was lower in energy than the triplet and quintet states. These findings will aid in the development of open-shell species for material science application.
@article{miyazawa2023generation,title={Generation and Characterization of a Tetraradical Embedded in a Curved Cyclic Paraphenylene Unit},author={Miyazawa, Y. and Wang, Z. and Hatano, S. and Takagi, R. and Matsuoka, H. and Amamizu, N. and Kitagawa, Y. and Kayahara, E. and Yamago, S. and Abe, M.},journal={Chem. Eur. J.},volume={29},issue={42},pages={e202301009},year={2023},month=may,publisher={wiley},doi={10.1002/chem.202301009},url={https://doi.org/10.1002/chem.202301009},dimensions={true},tab={paper}}
