Varying Anion Coordination in New Families of Dinuclear NiIILnIII Complexes: Zero Field Slow Relaxation of Magnetization and Theoretical Validations

Abstract

Herein we report the room-temperature synthesis, structural accounts, and magnetic performances of two new families of dinuclear NiII–LnIII complexes, [NiLn(HL)2(NO3)3]·nH2O·CH3CN (1a-1c) (n=1for Ln = Tb and n= 1.5 for Dy, and Ho) and [NiLn(HL)2(OAc)2(H2O)]Cl·5H2O (2a-2c) (Ln = Tb, Dy, and Ho) developed utilizing the ligand H2L (2-methoxy-6-[(E)-2′-hydroxymethyl-phenyliminomethyl]-phenol). Partial deprotonation of H2L in the reaction medium provided HL¯, ideally suited for trapping NiII and selected 4f ions in its two adjacent pockets. X-ray structural characterizations of complexes 1a–2c showed preferential pinning of octahedral NiII center by imine N-donor alongside LnIII centers with coordination number nine in muffin geometry. Both the Dy analogs exhibited clear out-of-phase signals (1b and 2b; Ueff = 20K and 18.7K), in the absence of an external dc field in the ac magnetic susceptibility measurements, whereas slow relaxation of magnetization was apparent under optimally applied fields of 2 and 3 kOe for the Tb analogs (1a and 2a) and Ho analogs (1c and 2c), respectively. Analysis of the static and dynamic magnetic properties were reinforced by thorough CASSCF-based computational scrutiny and density functional theory (DFT) calculations.