Achieving Maximal Enhancement of Electron Spin Polarization in Stable Nitroxyl Radicals at Room Temperature

Enhancing the polarization of spin levels at room temperature is one of the active research areas in magnetic resonance. Generation of electron spin hyperpolarization involves a complex interplay of electronic and spin processes. In this work, the optimization of crucial electron spin polarization (ESP) generating parameters and synthesis of a radical-chromophore adduct are described. The ESP of the synthesized adduct is about 550 times the equilibrium polarization at room temperature, which is possibly the maximal value for a chromophore-nitroxyl system. The present work highlights the crucial role of the photophysical quenching process toward the generation of a large ESP. Additionally, a chromophore-diradical adduct is synthesized, and the effects of the additional radical in the ESP generation process are discussed. Enhanced photochemical stability is demonstrated for the diradical adducts, thereby suggesting a potential route toward the generation of photostable radical-chromophore adducts for future studies. The large ESP in these molecules should enable a wide range of applications, such as in DNP, spintronics, and magnetometers.

Automated summary

Enhancing the polarization of spin levels at room temperature through the optimization of parameters and synthesis of specific adducts has been studied. The role of photophysical quenching process in generating large ESP is highlighted, and a potential route for the generation of photostable radical-chromophore adducts is suggested. The synthesized diradical adduct demonstrated enhanced photochemical stability, paving the way for a wide range of applications in DNP, spintronics, and magnetometers.