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Spontaneous solvent-controlled solid-state transformations were observed for a series of polymeric chain solvates [Cu(hfac)2LPr]·0.5Solv (Solv = (CH3)2CO, THF, CH2Cl2, CH2Br2, CHCl3) with 2-(1-propyl-1H-imidazol-5-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (LPr) under ambient conditions. The conversion of powdered polymeric chain [Cu(hfac)2LPr]·0.5THF and [Cu(hfac)2LPr]·0.5(CH3)2CO complexes, accompanied by the loss of solvent molecules, occurs completely to binuclear [Cu(hfac)2LPr]2 within a day. On the other hand, in the case of [Cu(hfac)2LPr]·0.5Solv (Solv = CH2Cl2, CH2Br2, CHCl3), the partial transformation into a desolvated 1D polymer [Cu(hfac)2LPr] or its mixture with [Cu(hfac)2LPr]2 takes much longer time. The magnetic behavior of the isostructural solvates is highly sensitive to the included solvent molecules. The complexes with THF, CH2Cl2, CH2Br2, and CHCl3 undergo a transition to a magnetically ordered state below 4 K, a phenomenon reported for the first time for the polymeric chain Cu(II) complexes with a "head-to-tail" motif. [Cu(hfac)2LPr]·0.5THF and [Cu(hfac)2LPr]·0.5(CH3)2CO undergo a spin transition at 190 K, which is induced by the transformation of the Cu atom environment. In the case of the THF solvate, the increase in the distances between the Cu and oxygen atoms leads to enhanced ferromagnetic exchange interactions, while in the acetone solvate, the nitroxide coordination type changes from axial to equatorial at certain coordination sites, resulting in the emergence of strong antiferromagnetic exchange. [ABSTRACT FROM AUTHOR]

A novel synthetic approach has been employed to synthesize a series of new nitronyl nitroxides: 2‐(1‐propyl‐1H‐imidazol‐5‐yl)‐ (Ln−Pr), 2‐(1‐isopropyl‐1H‐imidazol‐5‐yl)‐ (Li−Pr) and 2‐(1‐butyl‐1H‐imidazol‐5‐yl)‐4,4,5,5‐tetramethyl‐4,5‐dihydro‐1H‐imidazole‐3‐oxide‐1‐oxyl (Ln−Bu). The reaction of Cu(hfac)2 with LR in a 1 : 2 ratio yields mononuclear heterospin complexes [Cu(hfac)2(LR)2] (LR=Ln‐Pr, Li‐Pr, Ln‐Bu), which have a similar crystal structure to the "jumping" crystals [Cu(hfac)2(LMe)2] that exhibit chemomechanical activity. It was shown that an increase in the alkyl substituent R leads to changes in the crystal packing of the molecules and the absence of chemomechanical activity. Furthermore, it was found that two polymorph modifications of the heterospin complex [Cu(hfac)2(Ln−Pr)2] can be obtained, and magnetic properties of [Cu(hfac)2(Ln−Pr)2] strongly depend on the angle between the planes of the paramagnetic fragment O•–N‐C=N→O and the imidazole ring in Ln−Pr. [ABSTRACT FROM AUTHOR]

The first compound of a new type, [Cu[(SQ).sub.2]NIT-mPy].[C.sub.6][H.sub.6], and a series of model complexes of Cu[(SQ).sub.2] with diamagnetic Py and DABCO (where Cu[(SQ).sub.2] is bis(3,6-di-tert-butyl-o-benzosemiquinonato)copper(II)) are isolated and their structures are characterized. It is shown that the energy of the antiferromagnetic exchange interaction between the odd electrons of the SQ ligands in the Cu[(SQ).sub2.] bischelate is sensitive to both the nature of the extra ligand and structural distortions of the coordination unit.

Spontaneous solvent-controlled solid-state transformations were observed for a series of polymeric chain solvates [Cu(hfac) 2 L Pr ]·0.5Solv (Solv = (CH 3 ) 2 CO, THF, CH 2 Cl 2 , CH 2 Br 2 , CHCl 3 ) with 2-(1-propyl-1 H -imidazol-5-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1 H -imidazole-3-oxide-1-oxyl (L Pr ) under ambient conditions. The conversion of powdered polymeric chain [Cu(hfac) 2 L Pr ]·0.5THF and [Cu(hfac) 2 L Pr ]·0.5(CH 3 ) 2 CO complexes, accompanied by the loss of solvent molecules, occurs completely to binuclear [Cu(hfac) 2 L Pr ] 2 within a day. On the other hand, in the case of [Cu(hfac) 2 L Pr ]·0.5Solv (Solv = CH 2 Cl 2 , CH 2 Br 2 , CHCl 3 ), the partial transformation into a desolvated 1D polymer [Cu(hfac) 2 L Pr ] or its mixture with [Cu(hfac) 2 L Pr ] 2 takes much longer time. The magnetic behavior of the isostructural solvates is highly sensitive to the included solvent molecules. The complexes with THF, CH 2 Cl 2 , CH 2 Br 2 , and CHCl 3 undergo a transition to a magnetically ordered state below 4 K, a phenomenon reported for the first time for the polymeric chain Cu(II) complexes with a "head-to-tail" motif. [Cu(hfac) 2 L Pr ]·0.5THF and [Cu(hfac) 2 L Pr ]·0.5(CH 3 ) 2 CO undergo a spin transition at 190 K, which is induced by the transformation of the Cu atom environment. In the case of the THF solvate, the increase in the distances between the Cu and oxygen atoms leads to enhanced ferromagnetic exchange interactions, while in the acetone solvate, the nitroxide coordination type changes from axial to equatorial at certain coordination sites, resulting in the emergence of strong antiferromagnetic exchange.

A novel synthetic approach has been employed to synthesize a series of new nitronyl nitroxides: 2-(1-propyl-1H-imidazol-5-yl)- (L n-Pr ), 2-(1-isopropyl-1H-imidazol-5-yl)- (L i-Pr ) and 2-(1-butyl-1H-imidazol-5-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (L n-Bu ). The reaction of Cu(hfac) 2 with L R in a 1 : 2 ratio yields mononuclear heterospin complexes [Cu(hfac) 2 (L R ) 2 ] (L R =L n-Pr , L i-Pr , L n-Bu ), which have a similar crystal structure to the "jumping" crystals [Cu(hfac) 2 (L Me ) 2 ] that exhibit chemomechanical activity. It was shown that an increase in the alkyl substituent R leads to changes in the crystal packing of the molecules and the absence of chemomechanical activity. Furthermore, it was found that two polymorph modifications of the heterospin complex [Cu(hfac) 2 (L n-Pr ) 2 ] can be obtained, and magnetic properties of [Cu(hfac) 2 (L n-Pr ) 2 ] strongly depend on the angle between the planes of the paramagnetic fragment O•-N-C=N→O and the imidazole ring in L n-Pr ., (© 2023 Wiley-VCH GmbH.)