C,C′-Bis(benzodiazaborolyl)dicarba-closo-dodecaboranes: Synthesis, structures, photophysics and electrochemistry
作者:Lothar Weber、Jan Kahlert、Regina Brockhinke、Lena Böhling、Johannes Halama、Andreas Brockhinke、Hans-Georg Stammler、Beate Neumann、Carlo Nervi、Rachel A. Harder、Mark A. Fox
DOI:10.1039/c3dt51125a
日期:——
Six new C,Câ²-bis(benzodiazaborolyl)dicarba-closo-dodecaboranes, 1,A-R2-1,A-C2B10H10, where R represents the group 2-(1,3-Et2-1,3,2-N2BC6H4) or 2-(1,3-Ph2-1,3,2-N2BC6H4) and A is 2, 7 or 12, were synthesized from o-, m-, and p-dicarbadodecaboranes (carboranes) by lithiation and subsequent treatment with the respective 2-bromo-1,3,2-benzodiazaboroles. UV-visible and fluorescence spectra of all carboranes display low energy charge transfer emissions. While such emissions with Stokes shifts between 17â330 and 21â290 cmâ1 are typical for C,Câ²-bis(aryl)-ortho-carboranes, the observed low-energy emissions with Stokes shifts between 8320 and 15â170 cmâ1 for the meta- and para-isomers are unusual as high-energy emissions are typical for meta- and para-dicarbadodecaboranes. Fluorescence quantum yields (ÏF) for the novel 1,7- and 1,12-bis(benzodiazaborolyl)-carboranes depend on the substituents at the nitrogen atoms of the heterocycle. Thus, the para-carborane with N-ethyl substituents 1,12-(1â²,3â²-Et2-1â²,3â²,2â²-N2BC6H4)2-1,12-C2B10H10 has a ÏF value of 41% in cyclohexane solution and only of 9% in the solid state, whereas the analogous 1,12-(1â²,3â²-Ph2-1â²,3â²,2â²-N2BC6H4)2-1,12-C2B10H10 shows quantum yields of 3% in cyclohexane solution and 72% in the solid state. X-ray crystallographic, computational and cyclic voltammetry studies for these carboranes are also presented.
六种新的 C,Câ²-双(
苯并二
氮硼酰基)二卡巴-
氯代十二
硼烷 1,A-R2-1,A-C2B10H10,其中 R 代表 2-(1,3-Et2-1,3,2-N2BC6H4)或 2-(1,3-Ph2-1,3,2-N2BC6H4)基团,A 为 2、7或12,通过石化作用从邻、间和对二
碳十二
硼烷(
碳硼烷)合成,然后用相应的 2-
溴-1,3,2-
苯并二
氮硼烷处理。所有
碳硼烷的紫外可见光谱和荧光光谱都显示出低能电荷转移发射。对于 C,C²-双(芳基)正
硼烷来说,这种斯托克斯位移介于 17â330 和 21â290 cmâ1 之间的发射是典型的,而对于元异构体和对位异构体来说,观察到的斯托克斯位移介于 8320 和 15â170 cmâ1 之间的低能发射是不寻常的,因为元和对位二
碳酸二
硼烷具有典型的高能发射。新型 1,7- 和 1,12- 双(
苯并二
氮硼烷基)
硼烷的荧光量子产率(ÏF)取决于杂环
氮原子上的取代基。因此,带有
N-乙基取代基 1,12-(1â²,3â²-Et2-1â²,3â²,2â²-N2BC6H4)2-1,12-C2B10H10 的对位
硼烷在
环己烷溶液中的 ÏF 值为 41%,而在固态中仅为 9%、而类似的 1,12-(1â²,3â²-Ph2-1â²,3â²,2â²-N2BC6H4)2-1,12-C2B10H10 在
环己烷溶液中的量子产率为 3%,在固态中为 72%。此外,还介绍了这些
碳硼烷的 X 射线晶体学、计算和循环伏安法研究。