THE EXCITONIC STRUCTURE AND EXCITED STATES DYNAMICS OF AZULENES

由于其偶极矩较大，因此很容易形成激基缔合物。然而，激基缔合物和二聚体从未报道过。众所周知，奥林类化合物也能发出与Kasha规则相反的反常S_2荧光。我们合成了具有较大偶极矩的甘菊环氰基衍生物。通过对溶液、晶体和超声射流中的荧光光谱的研究，发现在1-氰基甘菊环溶液中首次观察到S_1荧光，而S_2荧光的量子产率仅为甘菊环的十分之一。在晶体中，在420 nm波段观察到了甘菊环、1-氰基甘菊环和2-氰基甘菊环的激基缔合物荧光。然而，我们不能检测到的准分子荧光溶液和超音速射流。结果表明，激基缔合物的形成除了在晶体中外是非常困难的。为了从S_1的角度阐明动力学，我们测量了氰基甘菊环的烧孔光谱。在1-氰基甘菊环和2-氰基甘菊环中，S_1寿命分别为1.8ps和1.0ps。1-氰基甘菊环的后期内转换与S_1发射的发现有关，甲基-和苯基-甘菊环的电子物理性质也在研究中，以阐明给电子基团的影响。

It is expected that azulene forms the excimer easily because of the large dipole moment. However, the excimer and the dimer have never been reported. Azulenes are also well known to emit anomalous S_2 fluorescence contrary to Kasha's rule. We synthesized azulene cyano-derivatives that have larger dipole moment. The fluorescence spectra in solution, crystal and supersonic jet were observed in order to compare with the fluorescence and the relaxation dynamics of azulene.S_1 fluorescence was first observed in 1-cyanoazulene solution, while the quantum yield of S_2 fluorescence decreased to one tenth of azulene. We discussed these results in relation to the energy gap law.In crystal, the excimer fluorescence of azulene, 1-cyanoazulene and 2-cyanoazulene were observed in 420nm region. However, we could not detect the excimer fluorescence in solutions and a supersonic jet. It was suggested that the excimer formation is very difficult except in crystal. These results are characteristic in azulenes in contrast to other aromatic compound.Hole burning spectra of cyanoazulenes were measured in order to elucidate the dynamics from S_1. The S_1 life time was 1.8ps and 1.0ps in 1-cyanoazulene and 2-cyanoazulene, respectively. The later internal conversion in 1-cyanoazulene was related with the finding of S_1 emission.The photophysical properties of methyl- and phenyl-azulene are also investigating to elucidate the effect of electron donating group.