(dominant isomer). The anisotropy barrier Ueff determined by AC magnetic susceptibility measurements is Ueff/kB = 17.0 K in 1, 16.6 K in 2, 15.6 K in 3.Et2O, 5.95 K in 4, and 3.5 K in 5. Both |D| and U(eff) are found to increase with increasing helical pitch of the Fe(O2Fe)3 core. The fourth-order longitudinal anisotropy parameter B4(0), which affects the shape of the anisotropy barrier, concomitantly changes
具有类似螺旋桨结构的四
铁 (III) 单分子磁
铁 (
SMM) 在高度和形状上都表现出可调节的磁各向异性势垒。簇 [Fe4(L1)2(dpm)6] (1), [Fe4(
L2)2(dpm)6] (2), [Fe4(L3)2(dpm)6].Et2O (3.Et2O) , 和 [Fe4(OEt)3(L4)(dpm)6] (4) 是通过 [Fe4(OMe)6(dpm)6] (5) 与三足
配体 RC(CH2OH)3 (H3L1, R = Me;H3
L2,R =
CH2Br;H3L3,R = Ph;H3L4,R = tBu;Hdpm = 二戊酰
甲烷)。
铁 (III) 离子呈现中心三角形拓扑结构,并由六个烷氧桥连接,这些桥会传播反
铁磁相互作用,导致 S = 5 基自旋态。4 的单晶可重复地包含至少两种几何异构体。从高频 EPR 研究中,轴向零场分裂参数 (D) 始终为负,如 5 (D = -0.21 cm(-1))