3d–4f heterometallic trinuclear complexes derived from amine-phenol tripodal ligands exhibiting magnetic and luminescent properties

Abstract

A new family of 3d–4f heterometallic trinuclear complexes, namely [M₂LnL₂]·2ClO₄·H₂O (H₃L = tris(((2-hydroxy-3-methoxybenzy1)amino)ethyl)amine, where M = Ni, Ln = Gd (1), Dy (2), and M = Zn, Ln = Gd (3), Dy (4)) were synthesized via the reaction of H₃L and Ln(NO₃)₃·6H₂O and Ni(ClO₄)₂·6H₂O or Zn(ClO₄)₂·6H₂O in a 2 : 1 : 2 ratio in the solution. Complexes 1–4 consisted of three metal ions arranged in an isosceles triangle manner. Magnetic properties investigations showed that complexes 1 and 2 exhibited weak ferromagnetic coupling between the Ni(II) and Ln(III) ions, whereas complex 4 displayed lanthanide single-ion magnetic properties. The alternating current (ac) magnetic susceptibilities of 4 revealed that both the in-phase (χ′) and out-of-phase (χ′′) signals are frequency- and temperature-dependent, which are typical features of the field-induced slow relaxation of the magnetization with U_eff = 124.5 K. Complex 4 also exhibited an obvious butterfly-shaped hysteresis loop at 2 K, indicating that it is a single-ion magnet. Moreover, complex 4 showed stronger fluorescent emissions, which were typical narrow emission bands of lanthanide ions. Therefore, complex 4 can be considered as a molecular magnetic and luminescent material. Comparably, complex 2 showed very weak Dy^III-based emissions because the paramagnetic Ni^II ions quench the fluorescence and thereby lower the population of the triplet state.