A convergent strategy for the synthesis of three generations of dendrons comprised of carbazole moieties is described. The procedure to build the dendrons involves an iterative palladium catalysed amination–debenzylation sequence using N-benzyl-3,6-dibromocarbazole. The three carbazolyl focussed dendrons are then attached to a reactive fac-tris[2-phenylpyridyl]iridium(III) core by a palladium catalysed amination to give the dendrimers. The three generations of dendrons have one, three, and seven carbazole units leading to dendrimers with fac-tris[2-phenylpyridyl]iridium(III) cores and three, nine and twenty one carbazole units. The use of 9,9′-dialkylfluorenyl surface groups gave the dendrimers excellent solubility. The attachment of the carbazolyl-based dendrons did not change the emission colour significantly with the dendrimers emitting green phosphorescence. The dendrimers were highly luminescent with solution photoluminescence quantum yields of the order of 70%. Ground state molecular orbital calculations showed that while the “LUMO” was concentrated on the core iridium(III) complex the “HOMO” was delocalised across the core and each of the dendrons. This was reflected in the oxidation properties of the dendrimers whereby the increased carbazolyl character of the “HOMO” resulted in the first oxidation being moved to more positive potentials.
本文描述了由
咔唑部分组成的三个世代树枝状分子的合成方法。构建树枝状分子的过程包括使用N-苄基-
3,6-二溴咔唑进行
钯催化胺化-脱苯基化反应。然后,通过
钯催化胺化将三个以
咔唑为焦点的树枝状分子连接到反应性三[
2-苯基吡啶]
铱(III)核上,得到树枝状分子。三个世代的树枝状分子分别具有一个、三个和七个
咔唑单元,从而得到具有三[
2-苯基吡啶]
铱(III)核和三个、九个和二十一个
咔唑单元的树枝状分子。使用9,9′-二烷基
芴表面基团使树枝状分子具有优异的溶解性。以
咔唑为基础的树枝状分子的连接不会显著改变其发射颜色,树枝状分子发射绿色
磷光。树枝状分子具有高发光性,溶液光致发光量子产率约为70%。基态分子轨道计算表明,虽然“LUMO”集中在
铱(III)核络合物上,但“HOMO”却跨核和每个树枝状分子分布。这反映在树枝状分子的氧化特性上,即“HOMO”中
咔唑基特性的增加导致第一次氧化移动到更正的势。