Structural and magnetic properties of lanthanide–tetraphenol–cyclen complexes: slow magnetic relaxation of the Nd(iii) complex

Abstract

Reactions of the macrocycle 1,4,7,10-tetrakis(2,4-dimethyl-1-hydroxy-6-methyl-benzyl)-1,4,7,10-tetraazacyclododecane (H₄L^Me,Me) with LnCl₃·6H₂O afforded the complexes [Ln(HL^Me,Me)]·MeOH (Nd: 1, Gd: 2, Tb: 3, Ho: 4) and the corresponding analogous ligand 1,4,7,10-tetrakis(2-chloro-4-dimethyl-1-hydroxy-6-methyl-benzyl)-1,4,7,10-tetraazacyclodo decane (H₄L^Me,Cl) with HoCl₃·6H₂O yielded [Ho(HL^Me,Cl)]·2MeOH (5). All complexes were spectroscopically and structurally characterized, and their magnetic properties were investigated over a temperature range of 2–300 K. They display similar geometrical structural features with coordination number seven around the central Ln(III) ion. The Nd(III) complex, [Nd(HL^Me,Me)]·MeOH (1), revealed a single-magnet behavior with magnetic relaxation occurring through a combination of Orbach and Raman processes. Both static (dc) and dynamic (ac) magnetic properties were rationalized using ab initio calculations. Complex 1 represents one of the rare Nd(III) single-ion magnets exhibiting slow relaxation dynamics.