Slow magnetic relaxation and selective luminescence sensor of Ln-radical chain involving imidazole-substituted nitronyl nitroxide radical

Abstract

An imidazole-substituted nitronyl nitroxide radical NIT-Ph-3-(1-Im) was coordinated with Ln(hfac)₃·2H₂O to obtain five new one-dimensional lanthanide-nitronyl nitroxide radical complexes [Ln(hfac)₃(NIT-Ph-3-(1-Im))]_n (Ln = Gd 1, Tb 2, Dy 3, Ho 4, Yb 5; hfac = hexafluoroacetylacetonate; NIT-Ph-3-(1-Im) = 2-(3-(1-imidazole))-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide). The functionalized radical ligand NIT-Ph-3-(1-Im) acts as a bridge ligand to link two Ln(III) ions through a “head-to-tail” mode, leading to a one-dimensional chain. Variable temperature magnetization shows that the antiferromagnetic interactions dominate in complex 1. Magnetic studies reveal that slow magnetization relaxations occur in complexes 2 and 3. Furthermore, complex 2 exhibits an excellent application as a luminescence sensor for detecting Fe³⁺ cations and Cr₂O₇²⁻ anions with high sensitivity and selectivity according to luminescence quenching effects.