Acetylenic quinoxalinodehydro[12]- and -[24]annulenes have been prepared from Boc-protected aminobenzodehydroannulenes and diethynyl-1,2-diones. For the smaller annulene, theoretical and spectroscopic studies reveal Ï-delocalisation over the entire aromatic system, including the external acetylenes. In contrast, the larger annulene prevails in a tub-like conformation, which limits Ï-orbital overlap and gives rise to higher-energy absorption and emission maxima.
乙炔基
喹喔啉脱氢[12]-和-[24]琥珀
烯是由 Boc 保护的
氨基
苯脱氢琥珀
烯和二
乙炔基-1,2-二
酮制备的。对于较小的琥珀
烯,理论和光谱研究揭示了整个芳香系统(包括外部
乙炔基)的Ï-异位。与此相反,较大的
茚以管状构象为主,这限制了Ï-轨道重叠,并产生了能量较高的吸收和发射最大值。