Magnetic properties and theoretical calculations of mononuclear lanthanide complexes with a Schiff base coordinated to Ln(III) ion in a monodentate coordination mode

Abstract

Three new mononuclear rare earth (RE) complexes [RE(HL)2(NO3)3(CH3OH)] (HL = 1-[N-(4-bromophenyl)]aminomethylidene-2(1H)naphthalenone; RE = Y (1), Dy (2), Er (3)) have been synthesized. The structures of complexes 1–3 were determined by single-crystal X-ray diffraction analyses. Each complex contains two HL ligands which bind to the RE(III) ion in a monodentate coordination mode, three NO3– and one coordinated methanol ligands, exhibiting a distorted tricapped trigonal prism (D3h) configuration. Slow relaxation of the magnetization under 1 kOe can be observed for complex 2. Further ab initio calculations show that the orientation of the ground magnetic easy axis is parallel with the line of O(HL)-O(HL) with the deviation angle being 4.29°. In addition, the ground gz value of complex 2 is 19.6858, which approximates the limit value of 20. However, the gz value of the low-lying ground state of complex 3 deviates severely from the limit value of 18, indicating weak axial anisotropy. Further measurements of ac susceptibilities confirmed the weak magnetic behavior in complex 3.