TY - JOUR
T1 - Crystal design of monometallic single-molecule magnets consisting of cobalt-aminoxyl heterospins
AU - Kanegawa, Shinji
AU - Karasawa, Satoru
AU - Maeyama, Masataka
AU - Nakano, Motohiro
AU - Koga, Noboru
PY - 2008/3/12
Y1 - 2008/3/12
N2 - Five N-aryl-N-pyridylaminoxyls, which have no substituent (PhNOpy), one substituent (MeOPh-NOpy and tert-BuPhNOpy) at the 4-position, and three substituents (TPPNOpy and TBPNOpy) at the 2, 4, and 6-positions of the phenyl ring, were prepared as new ligands for cobalt-aminoxyl heterospin systems. The 1:4 complexes, [Co(NCS)2(PhNOpy)4] (1), [Co(NCS) 2(MeOPhNOpy)4] (2), [Co(NCS)2(tertBuPhNOpy) 4] (3), [Co(NCS)2(TPPNOpy)4] (4), [Co(NCS) 2(TBPNOpy)4] (5a), and [Co(NCO)2(TBPNOpy) 4] (5b), were obtained as single crystals. The molecular geometry revealed by X-ray crystallography for all complexes except 4 is a compressed octahedron. In the crystal structure of 1, 2, and 3, the organic spin centers have various short contacts within 4 Å with the neighboring molecules to form 3D and 2D spin networks. On the other hand, complexes 5a and 5b have no significant short intermolecular contacts, indicating that they are magnetically isolated. 1 and 2 behaved as a 3D antiferromagnet with a Neel temperature, TN, of 22 K and as a weak 3D antiferromagnet with a TN of 2.9 K and a spin-flop field at 1.9 K, Hsp(1.9), of 0.7 kOe, respectively. 3 was a canted 2D antiferromagnet (a weak ferromagnet) with T N = 4.8 K and showed a hysteresis loop with a coercive force, H c, of 1.3 kOe at 1.9 K. On the other hand, the trisubstituted complexes 4, 5a, and 5b functioned as single-molecule magnets (SMMs). 5b had an effective activation barrier, Ueff, value of 28 K in a microcrystalline state and 48 K in a frozen solution.
AB - Five N-aryl-N-pyridylaminoxyls, which have no substituent (PhNOpy), one substituent (MeOPh-NOpy and tert-BuPhNOpy) at the 4-position, and three substituents (TPPNOpy and TBPNOpy) at the 2, 4, and 6-positions of the phenyl ring, were prepared as new ligands for cobalt-aminoxyl heterospin systems. The 1:4 complexes, [Co(NCS)2(PhNOpy)4] (1), [Co(NCS) 2(MeOPhNOpy)4] (2), [Co(NCS)2(tertBuPhNOpy) 4] (3), [Co(NCS)2(TPPNOpy)4] (4), [Co(NCS) 2(TBPNOpy)4] (5a), and [Co(NCO)2(TBPNOpy) 4] (5b), were obtained as single crystals. The molecular geometry revealed by X-ray crystallography for all complexes except 4 is a compressed octahedron. In the crystal structure of 1, 2, and 3, the organic spin centers have various short contacts within 4 Å with the neighboring molecules to form 3D and 2D spin networks. On the other hand, complexes 5a and 5b have no significant short intermolecular contacts, indicating that they are magnetically isolated. 1 and 2 behaved as a 3D antiferromagnet with a Neel temperature, TN, of 22 K and as a weak 3D antiferromagnet with a TN of 2.9 K and a spin-flop field at 1.9 K, Hsp(1.9), of 0.7 kOe, respectively. 3 was a canted 2D antiferromagnet (a weak ferromagnet) with T N = 4.8 K and showed a hysteresis loop with a coercive force, H c, of 1.3 kOe at 1.9 K. On the other hand, the trisubstituted complexes 4, 5a, and 5b functioned as single-molecule magnets (SMMs). 5b had an effective activation barrier, Ueff, value of 28 K in a microcrystalline state and 48 K in a frozen solution.
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U2 - 10.1021/ja0767579
DO - 10.1021/ja0767579
M3 - Article
C2 - 18275188
AN - SCOPUS:41449097756
SN - 0002-7863
VL - 130
SP - 3079
EP - 3094
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 10
ER -