Localized singlet diradicals have attracted much attention, not only in the field of bond-homolysis chemistry, but also in nonlinear optical materials. In this study, an extremely long lived localized singlet diradical was obtained by using a new molecular design strategy in which it is kinetically stabilized by means of a macrocycle that increases the molecular strain of the corresponding σ-bonded compound. Notably, the lifetime of this diradical (14 μs) is two orders of magnitude longer than that of a standard singlet diradical without a macrocyclic structure (≈0.2 μs) at 293 K. The species is persistent below a temperature of 100 K. In addition to the kinetic stabilization of the singlet diradical, the spontaneous oxidation of its corresponding ring-closed compound at 298 K produced oxygenated products under atmospheric conditions. Apparently, the “stretch effect” induced by the macrocyclic structure plays a crucial role in extending the lifetime of localized singlet diradicals and increasing the reactivity of their corresponding σ-bonded compounds.
@article{harada2018extremely,title={Extremely Long Lived Localized Singlet Diradicals in a Macrocyclic Structure: A Case Study on the Stretch Effect},author={Harada, Y. and Wang, Z. and Kumashiro, S. and Hatano, S. and Abe, M.},journal={Chem. Eur. J.},volume={24},issue={55},pages={14808--14815},year={2018},month=jul,publisher={wiley},doi={10.1002/chem.201803076},url={https://doi.org/10.1002/chem.201803076},dimensions={true},tab={paper}}
