Three lanthanide-nitronyl nitroxide complexes: Syntheses, crystal structures, magnetic properties and fluorescence of selective sensing of Fe (III) ions

Three new lanthanide-nitronyl nitroxide radical complexes [Ln(hfac)(3)(NIT-biPh)(2)](Ln = Gd 1, Tb 2, Dy 3) (hfac = hexafluoroacetylacetonate; NIT-biPh = 2-([1,1'-biphenyl]-4-yl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) have been successfully synthesized and characterized. The X-ray crystal structure analysis revealed that three complexes are isomorphous, which exhibiting a mononuclear tri-spin structure. The central Ln (III) ion is eight-coordinated by six oxygen atoms from three hfac ligands and two oxygen atoms from the NO groups of two NIT-biPh ligands. The variable-temperature magnetic susceptibility indicated that ferromagnetic exchange interactions between the coordinated NO groups of radicals and Gd(III) ions, while antiferromagnetic exchange couplings between radicals within complex. Ac magnetic susceptibility exhibited no magnetic relaxation behavior at low temperature in compound 2. In addition, the luminescence properties of complex 2 show the characteristic emission peaks of Tb(III) ions and indicate an excellent fluorescent probe of recognizing Fe3+ ion. (C) 2020 Elsevier Ltd. All rights reserved.