Probing Charge-Transfer Processes in a Covalently Linked [Ge9]-Cluster Imine Dyad.
Probing Charge-Transfer Processes in a Covalently Linked [Ge9]-Cluster Imine Dyad.
复制标题
探测共价连接的 [Ge9]-簇亚胺二元体中的电荷转移过程。
作者：
C. Wallach;Yasmin Selic;F. S. Geitner;Ajeet Kumar;Erling Thyrhaug;J. Hauer;A. Karttunen;T. Fässler
C60 供体二元组（其中碳笼与供电子单元共价连接）已被讨论为电子转移系统的一种可能性，并且已表明球形 [Ge9] 簇阴离子在电子结构方面与富勒烯表现出密切的关系。然而，这些簇和官能化簇衍生物的光学性质几乎是未知的。我们现在报告了与扩展 π 电子系统相连的深红色 [Ge9] 簇的合成。 [Ge9{Si(TMS)3}2{CH3C=N}-DAB(II)Dipp]- (1-) 是由 [Ge9{Si(TMS)3}2]2- 与溴代重氮杂硼烷 DAB(II)Dipp-Br 在 CH3CN 中反应形成（TMS = 三甲基硅基；DAB(II) = 具有不饱和主链的 1,3,2-二氮硼杂环；Dipp = 2,6-二异丙基苯基）。 1- 中亚胺实体的可逆质子化产生深绿色两性离子簇 [Ge9{Si(TMS)3}2{CH3C=N(H)}-DAB(II)Dipp] (1-H)，反之亦然。光谱与时间相关的密度泛函理论相结合表明，团簇和亚胺部分的反键 π* 轨道之间的电荷转移激发是强烈着色的原因。电磁波谱红色区域的 1-H 吸收最大值以及相应的最低能量激发态（λ = 669 nm）使该化合物成为针对光活性簇化合物设计的进一步研究的有趣起点。
C60 donor dyads in which the carbon cage is covalently linked to an electron-donating unit have been discussed as one possibility for an electron-transfer system, and it has been shown that spherical [Ge9] cluster anions show a close relation to fullerenes with respect to their electronic structure. However, the optical properties of these clusters and of functionalized cluster derivatives are almost unknown. We now report on the synthesis of the intensely red [Ge9] cluster linked to an extended π-electron system. [Ge9{Si(TMS)3}2{CH3C=N}-DAB(II)Dipp]- (1-)is formed upon the reaction of [Ge9{Si(TMS)3}2]2- with bromo-diazaborole DAB(II)Dipp-Br in CH3CN (TMS = trimethylsilyl; DAB(II) = 1,3,2-diazaborole with an unsaturated backbone; Dipp = 2,6-di-iso-propylphenyl). Reversible protonation of the imine entity in 1- yields the deep green, zwitterionic cluster [Ge9{Si(TMS)3}2{CH3C=N(H)}-DAB(II)Dipp] (1-H) and vice versa. Optical spectroscopy combined with time-dependent density functional theory suggests a charge-transfer excitation between the cluster and the antibonding π* orbital of the imine moiety as the cause of the intense coloration. An absorption maximum of 1-H in the red region of the electromagnetic spectrum and the corresponding lowest-energy excited state at λ = 669 nm make the compound an interesting starting point for further investigations targeting the design of photo-active cluster compounds.