Intramolecular excimer emission of triply bridged [3.3.N](3,6,9)carbazolophanes.
The photophysical properties of a series of triply bridged [3.3.n](3,6,9)carbazolophanes ([3.3.n]Cz, n = 3, 4, 5, 6) were studied as a model compound for a fully overlapped carbazole excimer. In these [3.3.n]Cz molecules, a plane angle of the two carbazole moieties changed systematically from nearly parallel to oblique, with increases in the length of the methylene chain n bridging at the 9-position of each carbazole ring. Absorption bands of [3.3.n]Cz showed the blue-shift and the splitting for (1)L(a) <-- (1)A and (1)L(b) <-- (1)A transition bands of the reference carbazole monomer, respectively. These spectral changes in [3.3.n]Cz were explained by Kasha's molecular exciton theory with the distance r and dihedral angle theta between the carbazole moieties in the ground state. In both liquid and glass matrixes, [3.3.n]Cz showed intramolecular excimer emission. The emission peak wavelength changed from 409 nm (n = 6) to 480 nm (n = 3) depending on r in the ground state. The dependence of the peak wavelength on r clearly showed that relative configurations of carbazole moieties in the ground state were preserved even in the excimer states. The smaller radiative rate of the excimer emission than the reference monomer was explained by the dimer symmetry of [3.3.n]Cz.
Benten
Hiroaki
H
Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo, Kyoto 615-8510, Japan.
Ohkita
Hideo
H
Ito
Shinzaburo
S
Yamamoto
Masahide
M
Sakumoto
Naoki
N
Hori
Kazushige
K
Tohda
Yasuo
Y
Tani
Keita
K
Nakamura
Yosuke
Y
Nishimura
Jun
J