title: Magnetic properties of 1:2 mixed cobalt(II) salicylaldehyde Schiff-base complexes with pyridine ligands carrying high-spin carbenes (Scar = 2/2, 4/2, 6/2, and 8/2) in dilute frozen solutions: role of organic spin in heterospin single-molecule magnets.
abstract: The 1:2 mixtures of Co(p-tolsal)2, p-tolsal = N-p-tolylsalicylideniminato, and diazo-pyridine ligands, DXpy; X = 1, 2, 3l, 3b, and 4, in MTHF solutions were irradiated at cryogenic temperature to form the corresponding 1:2 cobalt-carbene complexes Co(p-tolsal)2(CXpy)2, with Stotal = 5/2, 9/2, 13/2, 13/2, and 17/2, respectively. The resulting Co(p-tolsal)2(CXpy)2, X = 1, 2, 3l, 3b, and 4, showed magnetic behaviors characteristic of heterospin single-molecule magnets with effective activation barriers, Ueff/kB, of 40, 65, 73, 72, and 74 K, for reorientation of the magnetic moment and temperature-dependent hysteresis loops with a coercive force, Hc, of ∼0, 6.2, 10, 6.5, and 9.0 kOe at 1.9 K, respectively. The relaxation times, τQ, due to a quantum tunneling of magnetization (QTM) were estimated to be 1.6 s for Co(p-tolsal)2(C1py)2, ∼2.0 × 10(3) s for Co(p-tolsal)2(C2py)2, and >10(5) s for Co(p-tolsal)2(CXpy)2; X = 3b, 3l, and 4. In heterospin complexes, organic spins, carbenes interacted with the cobalt ion to suppress the QTM pathway, and the τQ value increased with increasing the Stotal values.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyushu University , 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582 Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Karasawa
authors.forename: Kimihiro
authors.initials: K
authors.lastname: Nakano
authors.forename: Daisuke
authors.initials: D
authors.lastname: Yoshihara
authors.forename: Noriko
authors.initials: N
authors.lastname: Yamamoto
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Tanokashira
authors.forename: Takahito
authors.initials: T
authors.lastname: Yoshizaki
authors.forename: Yuji
authors.initials: Y
authors.lastname: Inagaki
authors.forename: Noboru
authors.initials: N
authors.lastname: Koga
mesh_terms: D003035:Cobalt / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D008024:Ligands; D008697:Methane / Q000031:analogs & derivatives / Q000737:chemistry; D015394:Molecular Structure; D011725:Pyridines / Q000737:chemistry*; D012545:Schiff Bases / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D008024:Ligands; D011725:Pyridines; D012545:Schiff Bases; C030011:carbene; D003035:Cobalt; C023666:pyridine; D008697:Methane