N-Alkylimidazol-5-yl-substituted Nitronyl Nitroxides and Their Mononuclear Cu(II) Complexes: Synthesis, Structure and Magnetic Properties

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 center dot-N-C=N -> O and the imidazole ring in Ln-Pr. This work reports a selective method for the synthesis of N-alkylimidazol-5-yl-substituted nitronyl nitroxides in high yields. And also, a new family of molecular heterospin complexes was obtained by the reaction of new nitroxides and Cu(hfac)2.image