Influence of diamagnetic chelating ligand (L) on spin exchange coupling in heterospin chain complexes, [Cu(L)2NOpy2

Abstract

The mixtures of dipyridine aminoxyl, NOpy2, and chelated copper complexes, Cu(L)2; L=trifluoroacetylacetonato (tfac), hexafluoroacetylacetonato (hfac), and decafluoroheptanedionato (dfhd), in 1:1 ratios gave polymeric complexes, formulated as [Cu(L)2(NOpy2)]n; L=tfac (1), hfac (2), and dfhd (3). X-ray crystallography for 1, 2, and 3 revealed that the magnetic coupler NOpy2 coordinated with the copper ions in trans configurations to form one-dimensional chain structures. Noticeably, complex 2 showed a unique crystal structure that was analyzed as a static disorder of cis and trans configuration of the pyridine ring. The bond lengths of Cu–Npy for 1, 2, and 3, were 2.40, 2.14, and 2.02Å, respectively and became shorter with increasing the number of fluorine substituents. In the complexes, the aminoxyl centers ferromagnetically interacted with the copper ion. The spin exchange coupling constants, JCu–NO/kB, for 1, 2, and 3, depended on the diamagnetic chelating ligands and were estimated to be 5.7, 32, and 55K, respectively.