Regulating Magnetic Relaxations of Cyano‐Bridged {DyIIIMoV} 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 (HL 1 ), 1,3‐Bis (3‐pyridyl)‐1,3‐propanedione (HL 2 ), 1‐(4‐pyridyl)‐3‐(3‐pyridyl)‐1,3‐propanedione (HL 3 ), and 1,3‐Bis (4‐pyridyl)‐1,3‐propanedione (HL 4 ), to tune the magnetic relaxation behaviors of cyano‐bridged {Dy III Mo V } systems. By reacting with DyCl 3 ⋅ 6H 2 O and K 4 Mo(CN) 8 ⋅ 2H 2 O, four cyano‐bridged complexes, namely {[Dy[Mo V (CN) 8 ](HL 1 ) 2 (H 2 O) 3 ]} ⋅ 6H 2 O ( 1 ), {[Dy[Mo V (CN) 8 ](HL 2 )(H 2 O) 3 (CH 3 OH)]} 2 ⋅ 2CH 3 OH ⋅ 3H 2 O ( 2 ), {[Dy[Mo V (CN) 8 ](HL 3 )(H 2 O) 2 (CH 3 OH)] ⋅ H 2 O} n ( 3 ), and {[Dy[Mo V (CN) 8 ](HL 4 ) 2 (H 2 O) 3 ]} ⋅ 2H 2 O⋅CH 3 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 Dy III ions in all complexes have eight‐coordinated configurations with the coordination spheres DyO 7 N 1 for 1 and 4 , DyO 6 N 2 for 2 , and DyO 5 N 3 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 Dy III centers.