Synthesis and study of Cu II  complex with nitroxide, a jumping crystal analog

R. Z. Sagdeev; S. E. Tolstikov; S. V. Fokin; I. V. Obsharova; S. V. Tumanov; S. L. Veber; G. V. Romanenko; A. S. Bogomyakov; M. V. Fedin; E. V. Tretyakov; M. Halcrow; V. I. Ovcharenko

doi:10.1007/s11172-017-1722-y

Synthesis and study of Cu^II complex with nitroxide, a jumping crystal analog

Authors: Sagdeev R.Z.¹^,2, Tolstikov S.E.¹, Fokin S.V.¹, Obsharova I.V.¹, Tumanov S.V.¹^,3, Veber S.L.¹^,3, Romanenko G.V.¹, Bogomyakov A.S.¹, Fedin M.V.¹^,3, Tretyakov E.V.⁴, Halcrow M.⁵, Ovcharenko V.I.¹
Affiliations:
1. International Tomography Center, Siberian Branch of the Russian Academy of Sciences
2. Kazan (Volga Region) Federal University
3. Novosibirsk State University
4. N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences
5. University of Leeds
Issue: Vol 66, No 2 (2017)
Pages: 222-230
Section: Full Articles
URL: https://journals.rcsi.science/1066-5285/article/view/239964
DOI: https://doi.org/10.1007/s11172-017-1722-y
ID: 239964

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Abstract

We synthesized 1-ethylimidazolyl-substituted nitronyl nitroxides, i.e., 2-(1-ethylimidazol-4-yl)- (L^4Et) and 2-(1-ethylimidazol-5-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole 3-oxide-1-oxyl (L^5Et). The stable radical L^5Et is an ethyl analog of 2-(1-methylimidazol-5-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole 3-oxide-1-oxyl (L^5Me) described earlier, the reaction of which with Cu(hfac)₂ (hfac is 1,1,1,5,5,5-hexafluoropentane-2,4-dionate) leads to the formation of the [Cu(hfac)₂(L^5Me)₂] jumping crystals. The reaction of Cu(hfac)₂ with L^5Et with reagent ratios 1: 2 and 1: 1 yields heterospin complexes [Cu(hfac)₂(L^5Et)₂] and [Cu(hfac)₂L^5Et]₂, respectively. X-ray diffraction study of the mononuclear complex [Cu(hfac)₂(L^5Et)₂] determined that the compound has a packing similar to that of jumping crystals studied earlier, with the only difference being that the O...O contacts between neigh- boring nitroxide groups were found to be 0.3—0.5 Å longer than in [Cu(hfac)₂(L^5Me)₂]. As a result of the lengthening of these contacts, [Cu(hfac)₂(L^5Et)₂] crystals lack chemomechanical activi- ty. We found that when cooling crystals of binuclear complex [Cu(hfac)₂L^5Et]₂ below 50 K, the antiferromagnetic exchange between unpaired electrons of the >N—•O groups of neighboring molecules leads to the full spin-pairing of the nitroxides, with only the Cu²⁺ ions contributing to the residual paramagnetism of the compound.

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Synthesis and study of CuII complex with nitroxide, a jumping crystal analog

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Synthesis and study of Cu^II complex with nitroxide, a jumping crystal analog