Regulating Magnetic Relaxations of Cyano-Bridged {DyIII MoV } Systems by Tuning the N-Sites in β-Diketone Ligands.

Abstract

Cyano-bridged 4d-4f molecular nanomagnets have re-called increasing research interests in molecular magnetism since they offer more possibilities in achieving novel nanomagnets with versatile structures and magnetic interactions. In this work, four β-diketone ligands bearing different substitution N-sites were designed and synthesized, namely 1-(2-pyridyl)-3-(3-pyridyl)-1,3-propanedione (HL1 ), 1,3-Bis (3-pyridyl)-1,3-propanedione (HL2 ), 1-(4-pyridyl)-3-(3-pyridyl)-1,3-propanedione (HL3 ), and 1,3-Bis (4-pyridyl)-1,3-propanedione (HL4 ), to tune the magnetic relaxation behaviors of cyano-bridged {DyIII MoV } systems. By reacting with DyCl3 ⋅ 6H2 O and K4 Mo(CN)8 ⋅ 2H2 O, four cyano-bridged complexes, namely {[Dy[MoV (CN)8 ](HL1 )2 (H2 O)3 ]} ⋅ 6H2 O (1), {[Dy[MoV (CN)8 ](HL2 )(H2 O)3 (CH3 OH)]}2 ⋅ 2CH3 OH ⋅ 3H2 O (2), {[Dy[MoV (CN)8 ](HL3 )(H2 O)2 (CH3 OH)] ⋅ H2 O}n (3), and {[Dy[MoV (CN)8 ](HL4 )2 (H2 O)3 ]} ⋅ 2H2 O⋅CH3 OH (4) were obtained. Structural analyses revealed that 1 and 4 are binuclear complexes, 2 has a tetragonal structure, and 3 exhibits a stair-like polymer chain structure. The DyIII ions in all complexes have eight-coordinated configurations with the coordination spheres DyO7 N1 for 1 and 4, DyO6 N2 for 2, and DyO5 N3 for 3. Magnetic measurements indicate that 1 is a zero-field single-molecule magnet (SMM) and complexes 2-4 are field-induced SMMs, with complex 4 featuring a two-step relaxation process. The magnetic characterizations and ab initio calculations revealed that changing the N-sites in the β-diketone ligands can effectively alter the structures and magnetic properties of cyano-bridged 4d-4f nanomagnets by adjusting the coordination environments of the DyIII centers.