Structure, magnetic properties and fluorescence selectivity of 1D chain complexes based on the pyrazolyl nitronyl nitroxide radical

Abstract

The reaction of the pyrazole azoxyl radical NIT-4-OMe-3PyzPh (3-methoxy-4-(1H-pyrazol-1-yl)-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide) with Ln(hfac)₃ and Cu(hfac)₂ results in the formation of three 2p–3d–4f chain compounds [LnCu(hfac)₅(NIT-4-OMe-3PyzPh)₂]_n (Ln = Gd (1), Tb (2), and Dy (3)). In these compounds, each pyrazolyl-functionalized radical ligand coordinates with Ln(hfac)₃ and Cu(hfac)₂ units via NO groups and the N atom of the pyrazole ring, respectively. Variable-temperature magnetisation shows ferromagnetic coupling in the Gd-NIT of complex 1 and antiferromagnetic interactions between NIT and NIT. AC measurements reveal a temperature-dependent behaviour in the imaginary component of complex 2 at 3 kOe, suggesting slow magnetic relaxation. Furthermore, the fluorescence properties of complex 2 were investigated. The Cr₂O₇²⁻ and Fe³⁺ ions significantly quench its fluorescence, hence it can be used as an effective and selective fluorescent probe for Cr₂O₇²⁻ anions.