Department of Material Science, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan.
Chemistry. 2009 Oct 26;15(42):11210-20. doi: 10.1002/chem.200900350.
AnOV is a pi-conjugated radical built from an anthracene (An) unit linked by a p-phenylene to an oxoverdazyl (OV) moiety. The mono-oxidized (cationic) form of AnOV was generated both electrochemically and photochemically (in the presence of an electron acceptor). The triplet nature (S=1) of the electronic ground state of AnOV(+) was demonstrated by combining spectroelectrochemistry, electron-spin resonance (ESR) experiments, and ab initio molecular orbital (MO) calculations. The intramolecular spin alignment (ISA) within AnOV(+) results from the ferromagnetic coupling (J(electrochem)>0) of the two unpaired electrons located on the oxidized electron donor (An(+)) and on the pendant OV radical. The spin-density distribution pattern of AnOV(+) is akin to that of AnOV when photopromoted (AnOV*) to its high-spin (HS) lowest excited quartet (S=3/2) state. This high-spin state results from the ferromagnetic coupling (J(photophys)>0) of the triplet locally excited state of An ((3)An*) with the doublet ground state of OV. As a shared salient feature, AnOV(+) and AnOV* (HS) show a spin delocalization within the domain of activated An in either An(+) or (3)An* (nexus states) forms. The present study essentially contributes to establish and clarify relationships between electrochemical, photophysical, and photochemical pathways to achieve ISA processes within AnOV. In particular, we discuss the impact of the spin polarization of the unpaired electron of OV on electronic features of the An electron-donating subunit. Close analysis of this polarizing interplay allows one to derive a novel functional paradigm to manipulate electron spins at the intramolecular level with light and under an external magnetic field. Indeed, two original functional elements are identified: light-triggered donors of spin-polarized electrons and spin-selective electron acceptors, which are of potential interest for molecular spintronics.
一个OV 是由蒽（An）单元通过亚苯基连接到氧代重氮（OV）部分构建的π共轭自由基。AnOV 的单氧化（阳离子）形式是通过电化学和光化学（在电子受体存在下）产生的。AnOV(+) 的电子基态的三重态性质（S=1）通过结合光谱电化学、电子自旋共振（ESR）实验和从头算分子轨道（MO）计算来证明。AnOV(+) 内的分子内自旋排列（ISA）是由两个不成对电子在氧化的电子给体（An(+))和侧挂的 OV 自由基上的铁磁耦合（J(electrochem)>0) 引起的。AnOV(+) 的自旋密度分布模式类似于光促进（AnOV*）到其高自旋（HS）最低激发四重态（S=3/2) 态的 AnOV。这种高自旋状态是由蒽的三重态局域激发态（(3)An*）与 OV 的二重态基态的铁磁耦合（J(photophys)>0) 引起的。作为一个共同的显著特征，AnOV(+) 和 AnOV*（HS）在 An(+) 或 (3)An*（联络态）形式的活化 An 域内显示出自旋离域。本研究主要有助于建立和阐明电化学、光物理和光化学途径之间的关系，以实现 AnOV 内的 ISA 过程。特别是，我们讨论了 OV 未成对电子的自旋极化对 An 电子给体亚基电子特性的影响。对这种极化相互作用的仔细分析可以得出一种新的功能范例，即用光和外加磁场在分子内水平上操纵电子自旋。事实上，确定了两个原始功能元素：光触发的自旋极化电子供体和自旋选择性电子受体，它们对分子自旋电子学具有潜在的兴趣。
