The Ground State of Multispin Systems Based on Verdazyl and Nitrene Radicals: An EPR and Quantum-Chemical Study.

In this study, low-temperature EPR spectroscopy and quantum-chemical techniques were employed to investigate multispin systems─1,5-diphenyl-3-(3-nitrenophenyl)-6-oxoverdazyl and 1,5-diphenyl-3-(4-nitrenophenyl)-6-oxoverdazyl─that contain a nitrene center at either a - or -position, respectively. Ground states and magnetic zero-field splitting (ZFS) parameters of these multispin systems were determined by experimental and computational methods. The results indicated that the high-spin quartet state is a ground state, and the quartet-doublet energy gap is close to 10 kcal/mol for the -position of the nitrene group, with ZFS parameters = 0.

The study of the photochemical behavior of 5-aryl-2,3-dihydropyrazine 1,4-dioxides.

For the first time, the photochemical behavior of aryl-substituted 2,3-dihydropyrazine 1,4-dioxides was investigated. A common feature of all observed photoprocesses is the conversion of nitrone moieties into an oxaziridine ring to give substituted bi- or polycyclic systems. It was shown that the direction of the reaction depends on the irradiation wavelength and the employed solvent.

A Spin-Labeled Derivative of Gossypol.

Gossypol and its derivatives arouse interest due to their broad spectrum of biological activities. Despite its wide potential application, there is no reported example of gossypol derivatives bearing stable radical functional groups. The first gossypol nitroxide hybrid compound was prepared here via formation of a Schiff base.

Toward New Horizons in Verdazyl-Nitroxide High-Spin Systems: Thermally Robust Tetraradical with Quintet Ground State.

High-spin organic tetraradicals with significant intramolecular exchange interactions have high potential for advanced technological applications and fundamental research, but examples reported to date exhibit limited stability and processability. In this work, we designed the first tetraradical based on an oxoverdazyl core and nitronyl nitroxide radicals and successfully synthesized it using a palladium-catalyzed cross-coupling reaction of an oxoverdazyl radical bearing three iodo-phenylene moieties with a gold(I) nitronyl nitroxide-2-ide complex in the presence of a recently developed efficient catalytic system. The molecular and crystal structures of the tetraradical were confirmed by single crystal X-ray diffraction analysis.

Synthesis and photoinduced behavior of DPP-anchored nitronyl nitroxides: a multifaceted approach.

Understanding and controlling spin dynamics in organic dyes is of significant scientific and technological interest. The investigation of 2,5-dihydropyrrolo[4,3-]pyrrolo-1,4-dione derivatives (DPPs), one of the most widely used dyes in many fields, has so far been limited to closed-shell molecules. We present a comprehensive joint experimental and computational study of DPP derivatives covalently linked to two nitronyl nitroxide radicals (DPP-NN).