1,1-Dicyano-2,2-diphenyl-1,2-dihydronaphthalene: Photochromism and Evidence for Photochemically Induced CCN Bond Cleavage
作者:Helmut Görner、Thomas Mrozek、Jörg Daub
DOI:10.1002/1521-3765(20020902)8:17<4008::aid-chem4008>3.0.co;2-o
日期:2002.9.2
ten-electron electrocyclisation. The distinct differences between the photochromism of DHN and that of dihydroazulene (DHA) stem mainly from stereoelectronic effects. This study, however, has also revealed that photochemically induced bond heterolysis and photochemical/thermal electrocyclisation, representing two basic processes of photochromism, may occur in one molecular unit.
1,1-二氰基-2,2-二苯基-1,2-二氢萘(DHN-1)的光反应已通过光化学技术在室温下各种条件下进行了研究。瞬态物质T(C)在紫外可见光谱中的最大波长为545 nm,在极性非质子溶剂中检出的收率较低,在三氟乙醇(TFE)和六氟丙烷-2-醇(HFP)中的收率较高,被指定为碳阳离子(1-氰基-2,2-二苯基萘),它是通过消除CN(-)进行光化学生成的。发现T(C)的衰减是HFP的一阶过程,其中观察到最长寿命为0.4 s。在TFE中,碳阳离子在ms时标上衰减,而乙醇中的最短寿命为1微米。将水加到醇或乙腈中后,T(C)的产率会大大提高,并在存在大量水(1-20 M)的情况下保持稳定。在TFE或HFP中加水后,碳正离子的寿命会大大缩短。这是由于CN(-)的碳正离子化和释放引起的脉冲感应电荷形成所支持;在选定条件下,电导率衰减与碳正离子的寿命有关。另外,在低极性和高极性的溶剂中通过光谱观察到主要