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Cyclic Single‐Molecule Magnets: From Even‐Numbered Hexanuclear to Odd‐Numbered Heptanuclear Dysprosium Clusters
Author(s) -
Tian Haiquan,
Bao SongSong,
Zheng LiMin
Publication year - 2016
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201600392
Subject(s) - chemistry , dysprosium , crystallography , pyrazine , hydrazone , carboxylate , ligand (biochemistry) , molecule , stereochemistry , inorganic chemistry , organic chemistry , receptor , biochemistry
An ingenious self‐assembly method has been employed to achieve noncentered cyclic metal cages by integrating single and double pyrazinyl hydrazone ligands in the presence of an organo phosphonic acid. An even‐numbered hexanuclear and an odd‐numbered heptanuclear dysprosium(III) cluster, namely [Dy 6 (spch) 6 (O 3 PC 10 H 7 ) 2 (pyra) 2 (MeOH)(H 2 O)] · 8.5H 2 O [ 1 , H 2 spch = ( E )‐ N′ ‐(2‐hydroxybenzylidene)pyrazine‐2‐carbohydrazide, pyra = pyrazine‐2‐carboxylate] and [Dy 7 (eddc) 2 (spch) 2 (O 3 PC 10 H 7 ) 4 (OAc) 5 (MeOH) 4 ] · 4MeOH [ 2 , H 2 eddc = ( E , E )‐ N′ , N′′ ‐(ethane‐1,2‐diylidene)bis(pyrazine‐2‐carbohydrazide)] have been synthesized successfully. Single‐crystal X‐ray diffraction analysis revealed that compound 1 is composed of six identical [Dy 2 (spch)] 4+ building blocks containing a single pyrazinyl hydrazone ligand of spch 2– welded to each other to form a hexanuclear ring, whereas compound 2 possesses an enlarged skeleton with a heptanuclear ring made up of two [Dy 3 (eddc)] 7+ and two [Dy 2 (spch)] 4+ building blocks by virtue of the inclusion in the synthesis of double pyrazinyl hydrazone ligand eddc 2– . Compounds 1 and 2 exhibit drastically distinct dynamic magnetic properties. Compound 1 shows a complex slow relaxation of the magnetization with two types of temperature dependence with energy barriers ( U eff ) of 4.7 and 20.3 K and pre‐exponential factors ( τ 0 ) of 9.1 × 10 –5 and 2.6 × 10 –6 s for the low‐ and high‐temperature regimes, respectively, whereas compound 2 exhibits a two‐step relaxation process ( U eff (1) : 45.1 K, τ 0 (1) : 4.4 × 10 –7 s; U eff (2) : 48.7, τ 0 (2) : 2.7 × 10 –8 s) in the out‐of‐phase alternating current signals.