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Magnetothermal Studies of a Series of Coordination Clusters Built from Ferromagnetically Coupled {Mn II 4 Mn III 6 } Supertetrahedral Units
Author(s) -
Nayak Sanjit,
Evangelisti Marco,
Powell Annie K.,
Reedijk Jan
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201001988
Subject(s) - octahedron , crystallography , manganese , chemistry , ion , valence (chemistry) , hydroxymethyl , magnetic susceptibility , pyridine , crystal structure , stereochemistry , medicinal chemistry , organic chemistry
Three high‐nuclearity mixed valence manganese II/III coordination clusters, have been synthesised, that is, [Mn III 6 Mn II 4 (μ 3 ‐O) 4 (HL 1 ) 6 (μ 3 ‐N 3 ) 3 (μ 3 ‐Br)(Br)](N 3 ) 0.7 /(Br) 0.3 ⋅ 3 MeCN ⋅ 2 MeOH ( 1 ) (H 3 L 1 =3‐methylpentan‐1,3,5‐triol), [Mn III 11 Mn II 6 (μ 4 ‐O) 8 (μ 3 ‐Cl) 4 (μ,μ 3 ‐O 2 CMe) 2 (μ,μ‐L 2 ) 10 Cl 2.34 (O 2 CMe) 0.66 (py) 3 (MeCN) 2 ] ⋅ 7 MeCN ( 2 ) (H 2 L 2 =2,2‐dimethyl‐1,3‐propanediol and py is pyridine), and [Mn III 12 Mn II 7 (μ 4 ‐O) 8 (μ 3 ‐η 1 N 3 ) 8 (HL 3 ) 12 (MeCN) 6 ]Cl 2 ⋅ 10 MeOH ⋅ MeCN ( 3 ) (H 3 L 3 =2,6‐bis(hydroxymethyl)‐4‐methylphenol) with high ground‐spin states, S =22, 28±1, and 83/2, respectively; their magnetothermal properties have been studied. The three compounds are based on a common supertetrahedral building block as seen in the Mn 10 cluster. This fundamental magnetic unit is made up of a tetrahedron of Mn II ions with six Mn III ions placed midway along each edge giving an inscribed octahedron. Thus, the fundamental building unit as represented by compound 1 can be described as a Mn 10 supertetrahedron. Compounds 2 and 3 correspond to two such units joined by a common edge or vertex, respectively, resulting in Mn 17 and Mn 19 coordination clusters. Magnetothermal studies reveal that all three compounds show interesting long‐range magnetic ordering at low temperature, originating from negligible magnetic anisotropy of the compounds; compound 2 shows the largest magnetocaloric effect among the three compounds. This is as expected and can be attributed to the presence of a small magnetic anisotropy, and low‐lying excited states in compound 2 .