Investigation of a C(sp2)-coupled nitronyl nitroxide diradical by electron paramagnetic resonance

Samsonenko, A. A.; Толстиков, С. Е.; Овчаренко, В. И.; Fedin, Matvey V.; Veber, Sergey L.

doi:10.1007/s11172-021-3355-4

Cited by 2 publications

(1 citation statement)

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“…Considering their individual properties, CW EPR spectra of a nitroxide radical in magnetically concentrated solids usually feature a single line with a width of ca. 1 mT, and the width of this line remains almost constant in the temperature range of 5–300 K. CW EPR spectra of Cu(II) ions depend on the crystal field symmetry, and their EPR signal is commonly broader than those of nitroxide radicals due to g tensor anisotropy and hyperfine splittings. , Typically, a Cu(II) EPR signal retains its shape in a temperature range of 5–300 K without significant broadening upon heating. ,,− …”

Section: Resultsmentioning

confidence: 99%

Five-Spin Copper(II) Nitroxide Complex with Apparently Compressed Octahedral Geometry: Design, Synthesis, and Magnetostructural Studies

Veber

Tumanov

Fokin

et al. 2023

Crystal Growth & Design

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Multispin Cu(II)-nitroxide compounds have attracted significant interest in the field of molecular magnetism; however, complexes involving more than three spins in a single molecule have rarely been reported. In this work we describe the synthesis and detailed physicochemical study of the solvated sixcoordinated five-spin complex [CuL 2 ] (L = 2,2′-(1H-pyrrole-2,5diyl)bis(4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1oxyl)). This complex features a tridentate meridional coordination of the biradical L, resulting in an exchange-coupled cluster of four radical and one Cu(II) spin. The structural and magnetic properties of [CuL 2 ] have been thoroughly investigated using single-crystal X-ray diffraction (XRD), SQUID magnetometry, electron paramagnetic resonance (EPR), Fourier-transform infrared (FTIR) spectroscopy, and quantum chemical calculations (QCC). An apparently compressed octahedral coordination geometry has been found by XRD, which, however, stems from the superposition of two isomeric structures of elongated octahedral CuN 2 O 4 units. Neither X-ray nor FTIR has revealed any structural transitions in [CuL 2 ] at 8−300 K, whereas the magnetic behavior studied by magnetometry and QCC is governed by temperature-dependent populations of high-spin multiplets. EPR spectroscopy revealed a drastic temperature dependence of the line width in [CuL 2 ], which changes by almost 2 orders of magnitude within 4−300 K. A comparison with EPR and QCC data for close-structure four-and three-spin analogues has revealed an interplay of the temperaturedependent population of high-spin multiplets and intermolecular exchange interactions, which govern the line width in such systems.

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