Ferromagnetic nanoscale electron correlation promoted by organic spin-dependent delocalization.
Ferromagnetic nanoscale electron correlation promoted by organic spin-dependent delocalization.
复制标题
DOI：
10.1021/ja904648r
复制
发表时间：
2009-12-30
影响因子：
15
通讯作者：
Lee, Junghyun
中科院分区：
文献类型：
--
作者：
Kirk, Martin L.;Shultz, David A.;Schmidt, Robert D.;Habel-Rodriguez, Diana;Lee, Hyoyoung;Lee, Junghyun
本文报道了两个新的金属配合物NN-SQ-CoIII（py）2Cat-NN（1）和NN-Ph-SQ-CoIII（py）2Cat-Ph-NN（2）（NN =硝基氮氧自由基，Ph = 1，4-亚苯基，SQ = S = 1/2半醌自由基，Cat = S = 0邻苯二酚，py =吡啶）的电子结构和铁磁交换耦合的起源. 1和2的近红外电子吸收光谱揭示了一个低能光学带，该带已被指定为涉及离域二氧戊环（SQ/Cat）价前线分子轨道的成键和反键线性组合的π u → π g跃迁。1中的铁磁交换相互作用是如此之强，以至于在高达300 K的温度下，只有高自旋四重态（ST = 3/2）才被热填充。2的温度依赖性的磁化率数据表明，激发态自旋二重态（ST = 1/2）是在较高的温度下填充，表明亚苯基间隔调制的磁交换的大小。二氧戊环二分体2内的价离域导致两个局部NN自由基的铁磁排列，其间隔超过22 π。铁磁交换1和2的结果从一个自旋依赖的离域（双交换型）的过程和这种强电子相关的起源已被理解的价键组态相互作用（VBCI）模型。我们发现，有机混合价促进的铁磁耦合提供了敏锐的洞察力的能力，单分子在纳米尺度的距离上通信自旋信息。此外，巡回dioxolene电子和本地化NN电子自旋之间的强相互作用影响我们的能力，以了解在技术上重要的稀磁半导体材料中的离域电子和钉扎磁性杂质之间的交换相互作用。介导这种耦合的巡游电子的长相关长度（22 π）表明，高自旋π-离域有机分子可以作为纳米级自旋极化电子注入器和分子导线找到应用。
We describe the electronic structure and the origin of ferromagnetic exchange coupling in two new metal complexes, NN-SQ-CoIII(py)2Cat-NN (1) and NN-Ph-SQ-CoIII(py)2Cat-Ph-NN (2) (NN = nitronylnitroxide radical, Ph = 1,4-phenylene, SQ = S = 1/2 semiquinone radical, Cat = S = 0 catecholate, and py = pyridine). Near-IR electronic absorption spectroscopy for 1 and 2 reveals a low energy optical band that has been assigned as a Ψu → Ψg transition involving bonding and antibonding linear combinations of delocalized dioxolene (SQ/Cat) valence frontier molecular orbitals. The ferromagnetic exchange interaction in 1 is so strong that only the high-spin quartet state (ST = 3/2) is thermally populated at temperatures up to 300 K. The temperature-dependent magnetic susceptibility data for 2 reveals that an excited state spin doublet (ST = 1/2) is populated at higher temperatures, indicating that the phenylene spacer modulates the magnitude of the magnetic exchange. The valence delocalization within the dioxolene dyad of 2 results in ferromagnetic alignment of two localized NN radicals separated by over 22 Å. The ferromagnetic exchange in 1 and 2 results from a spin-dependent delocalization (double exchange type) process and the origin of this strong electron correlation has been understood in terms of a valence bond configuration interaction (VBCI) model. We show that ferromagnetic coupling promoted by organic mixed-valency provides keen insight into the ability of single molecules to communicate spin information over nanoscale distances. Furthermore, the strong interaction between the itinerant dioxolene electron and localized NN electron spins impacts our ability to understand the exchange interaction between delocalized electrons and pinned magnetic impurities in technologically important dilute magnetic semiconductor materials. The long correlation length (22 Å) of the itinerant electron that mediates this coupling indicates that high-spin π-delocalized organic molecules could find applications as nanoscale spin-polarized electron injectors and molecular wires.
登录
查看更多内容
影响因子：
4.6
作者：
Gamelin, DR;Bominaar, EL;Solomon, EI
通讯作者：
Solomon, EI
影响因子：
4.4
作者：
GIRERD, JJ
通讯作者：
GIRERD, JJ
影响因子：
41.2
作者：
Kittilstved, KR;Liu, WK;Gamelin, DR
通讯作者：
Gamelin, DR
影响因子：
15
作者：
LYNCH, MW;HENDRICKSON, DN;PIERPONT, CG
通讯作者：
PIERPONT, CG
影响因子：
2.6
作者：
Kirk, ML;Shultz, DA;Depperman, EC
通讯作者：
Depperman, EC