Tuning Anisotropy Barriers in a Family of Tetrairon(III) Single-Molecule Magnets with an <i>S</i> = 5 Ground State
作者:Stefania Accorsi、Anne-Laure Barra、Andrea Caneschi、Guillaume Chastanet、Andrea Cornia、Antonio C. Fabretti、Dante Gatteschi、Cecilia Mortalò、Emiliano Olivieri、Francesca Parenti、Patrick Rosa、Roberta Sessoli、Lorenzo Sorace、Wolfgang Wernsdorfer、Laura Zobbi
DOI:10.1021/ja0576381
日期:2006.4.1
(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;H3L2,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))