Slow magnetic relaxation in 8-coordinate Mn() compounds

• Published in: Dalton transactions : an international journal of inorganic chemistry 2023-10, Vol.52 (41), p.14797-1486
• Main Authors: Wang, Li-Xin, Wu, Xiao-Fan, Jin, Xin-Xin, Li, Jia-Yi, Wang, Bing-Wu, Liu, Ji-Yan, Xiang, Jing, Gao, Song
• Format: Article
• Language: English
• Subjects: Coordination compounds; Coordination numbers; Crystallography; Direct current; Iron; Magnetic induction; Magnetic properties; Magnetic relaxation; Magnets; Transition metal compounds
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/d3dt02307a

The design and synthesis of high-spin Mn( ii )-based single-molecule magnets (SMMs) have not been well developed to a great extent, as compared with a large number of SMMs based on the other first row transition metal complexes. In light of our success in designing Fe( ii ), Co( ii ) and Fe( iii )-based SMMs with a high coordination number of 8, it is of great interest to design Mn( ii ) analogues with such a strategy. In this contribution, four Mn( ii ) compounds, [Mn II ( L n ) 2 ](ClO 4 ) 2 ( 1-4 ) were obtained from reactions of neutral tetradentate ligands, L 1 -L 4 , with hydrated Mn II (ClO 4 ) 2 ( L 1 = 2,9-bis(carbomethoxy)-1,10-phenanthroline, L 2 = 2,9-bis(carbomethoxy)-2,2′-dipyridine, L 3 = N 2 , N 9 -dibutyl-1,10-phenanthroline-2,9-dicarboxamide, L 4 = 6,6′-bis(2-(tert-butyl)-2 H -tetrazol-5-yl)-2,2′-bipyridine). Their crystal structures have been determined by X-ray crystallography and it clearly shows that the Mn( ii ) centers in these compounds have an oversaturated coordination number of 8. Their magnetic properties have been investigated in detail; to our surprise, all of these Mn( ii ) compounds show interesting slow magnetic relaxation behaviors under an applied direct current field, although they have very small negative D values. Four mononuclear 8-coordinate Mn( ii ) compounds have been obtained and all the compounds show field-induced slow magnetic relaxation (SMR) behaviors.