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Exploring the Effect of Metal Ions and Counteranions on the Structure and Magnetic Properties of Five Dodecanuclear Co II and Ni II Clusters
Author(s) -
Zhou YanLing,
Zeng MingHua,
Liu XiaoChun,
Liang Hong,
Kurmoo Mohamedally
Publication year - 2011
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.201101070
Subject(s) - chemistry , isostructural , electrospray ionization , perchlorate , crystallography , metal , magnetic susceptibility , magnetic relaxation , paramagnetism , counterion , ion , crystal structure , stereochemistry , inorganic chemistry , magnetization , organic chemistry , magnetic field , physics , quantum mechanics
We present the synthesis, characterization of the structures, and magnetic properties of five isostructural dodecanuclear coordination clusters of Ni II and Co II : [Co 12 (bm) 12 (NO 3 )‐ (O 2 CMe) 6 (EtOH) 6 ](NO 3 ) 5 ( 1 ), [Ni 12 (bm) 12 (NO 3 )(O 2 CMe) 6 (H 2 O) 3 ‐ (EtOH) 3 ](NO 3 ) 5 ⋅2 H 2 O ( 2 ), mixed‐metal composition (Ni/Co 1:1) [Co 6 Ni 6 (bm) 12 (NO 3 )(O 2 CMe) 6 (EtOH) 6 ](NO 3 ) 5 ( 3 ), and [M 12 (bm) 12 (NO 3 )‐ (O 2 CMe) 6 (EtOH) 6 ](ClO 4 ) 5 (M=Co ( 4 ), Ni ( 5 )), in which Hbm=(1 H ‐benzimidazol‐2‐yl)methanol. They consist of analogous structural cores that are constructed by three cubanes (M 4 O 4 ) that surround the templating nitrate and bridging auxiliary acetate and the directing ligands bm. They have different magnetic behaviors. Whereas there is the absence of the out‐of‐phase ac susceptibility ( χ ′′) for the Ni II ‐based compounds 2 and 5 , the Co II ‐containing compounds 1 , 3 , and 4 have prominent χ ′′ signals that exhibit frequency dependence, which indicates slow magnetic relaxation behavior above 1.8 K. In particular, the larger perchlorate counterions in 4 further change the overall correlation interaction between clusters, thus leading to an enhanced blocking temperature for the less‐symmetrical 4 (pseudo‐ C 3 ) relative to 1 and 3 (true C 3 ). Interestingly, electrospray ionization mass spectrometry (ESI‐MS) indicates that the three dodecanuclear clusters of 1 – 3 retain their compositions in solution. The mixed‐metal cluster cores of 3 are formed based on the nature of the interchangeability between metal centers in solution.