Alkyl chain length influence of the functionalized diethanolamine ligand on the slow relaxation of the magnetization in {Co^III₃ Dy^III₃} complexes

We report the synthesis, structural characterization and magnetic properties of a series of Co(III)/Dy(III) complexes built up from an N-alkyl derivatized amino-alcohol ligand diethanolamine, functionalized with CnH2n+1 alkyl chains (n = 3, 4, 6, 8 and 10). While n = 3 afforded a butterfly {(Co2Dy2III)-Dy-III} core, the other alkyl chains (n = 4, 6, 8) afforded hexanuclear triangle-in-triangle {(Co3Dy3III)-Dy-III} complexes as shown by single-crystal X-ray determinations. Infrared spectroscopy allows us to characterize the C-10 derivative complex, which did not crystallize. Magnetic ac susceptibility data collected below 10 K at driving frequencies up to 10 kHz under zero-dc field and up to 1 T provide insight into the SMM behaviour of the studied complexes. The characteristic time of the magnetization dynamics can be understood in terms of the competing Raman, Direct and Orbach-like mechanisms. A relationship between the magnetization dynamics within the family of complexes and the increasing alkyl chain length is discussed.