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A Cobalt Pyrenylnitronylnitroxide Single‐Chain Magnet with High Coercivity and Record Blocking Temperature
Author(s) -
Vaz Maria G. F.,
Cassaro Rafael A. Allão,
Akpinar Handan,
Schlueter John A.,
Lahti Paul M.,
Novak Miguel A.
Publication year - 2014
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.201304852
Subject(s) - coercivity , antiferromagnetism , magnet , moiety , condensed matter physics , cobalt , materials science , hysteresis , relaxation (psychology) , magnetic field , chemistry , crystallography , stereochemistry , physics , metallurgy , psychology , social psychology , quantum mechanics
Coordination of a [Co(hfac) 2 ] moiety (hfac=hexafluoroacetylacetonate) with a nitronylnitroxide radical linked to bulky, rigid pyrene (PyrNN) gives a helical 1:1 chain complex, in which both oxygen atoms of the radical NO . groups are bonded to Co II ions with strong antiferromagnetic exchange. The complex shows single‐chain magnet (SCM) behavior with frequency‐dependent magnetic susceptibility, field‐cooled and zero‐field‐cooled susceptibility divergence with a high blocking temperature of around 14 K (a record among SCMs), and hysteresis with a very large coercivity of 32 kOe at 8 K. The magnetic behavior is partly related to good chain isolation induced by the large pyrene units. Two magnetic relaxation processes have been observed, a slower one attributable to longer, and a faster one attributable to short chains. No evidence of magnetic ordering has been found.