Tuning quantum tunnelling of magnetization through 3d-4f magnetic interactions: an alternative approach for manipulating single-molecule magnetism

The magnetic relaxation and magnetization blocking barriers of butterfly complexes, [Dy2Zn2(L)(4)(NO3)(2)( CH3OH)(2)] (1), [Dy2Mn2(L)(4)(NO3)(2)(DMF)(2)] (2) and [Dy2Co2(L)(4)(NO3)(2)(DMF)(2)]center dot 2DMF (3) (H2L = (E)-2-ethoxy-6-(((2-hydroxyphenyl)imino)methyl)phenol), were systematically investigated. The change of SMM behavior originating from the purposeful replacement of two Zn-II sites in 1 with Mn-II and Co-II was elucidated by a combined experimental and theoretical study. The quantum tunnelling of magnetization (QTM) was observed in 1. Contrarily, it was quenched in 2 and 3 by spin-spin exchange. A detailed comparative study on these closely-related model complexes reveals the remarkable changes of the ligand field splitting, anisotropy of the Dy-coordinated moiety and the total exchange spectrum due to the replacement of Zn-II with Co-II and Mn-II.