Synthesis and Photophysical Properties of Aza[n]helicenes

Synthesis and study of aza[7]­helicene and aza[9]­helicene is presented in this paper. Photo-dehydrocyclization of the 3,6-bis-styryl derivative of carbazole leading to sterically less demanding aza[7]­helicene resulted in smooth reaction, and only the desired angular–angular product was detected. However, in the case of aza[9]­helicene, along with the expected angular–angular cyclization, three other products involving linear mode of cyclization were also isolated and characterized. In this case, the helical compound aza[9]­helicene was predominantly formed at lower concentration while the other isomers were obtained at higher concentration. All of the compounds formed by angular–angular, angular–linear, and linear–linear modes of cyclization were fully characterized, and their photophysical properties were investigated.

本文报道了氮杂[7]螺烯（aza[7]helicene）与氮杂[9]螺烯（aza[9]helicene）的合成与研究工作。以空间位阻更小的氮杂[7]螺合成为目标，对咔唑的3,6-二苯乙烯基衍生物进行光脱氢环化反应，反应进程顺利，仅检测到目标角-角型产物。然而在氮杂[9]螺烯的合成中，除了预期的角-角型环化产物外，还分离得到了另外三种涉及线性环化模式的产物并完成结构表征。在此体系中，当反应浓度较低时，主要生成螺旋状化合物氮杂[9]螺烯；而当反应浓度较高时，则得到其他同分异构体。所有通过角-角型、角-线型以及线-线型环化模式生成的化合物均得到了完整的结构表征，并对其光物理性能展开了研究。