title: Synthesis and electronic and photophysical properties of [2.2]- and [3.3]paracyclophane-based donor-donor'-acceptor triads.
abstract: Three types of the donor(D)-donor'(D')-acceptor(A) triads 1-6 with different D-A combinations, carbazole (Cz, D)-[n.n]PCP(D')-1,8-naphthalimide (NI, A) (1-3), 10H-phenothiazine (PTZ, D)-[n.n]PCP(D')-NI(A) (4, 5), and 10-methyl-10H-phenothiazine (Me-PTZ, D)-[2.2]PCP-2,1,3-benzothiadiazole (BTD, A) 6, were synthesized for the elucidation of their photophysical properties. The absorption spectra and electrochemical properties indicated that the chromophores (D, D', and A) do not interact with each other in the ground state. Cz-(CH2)3-[2.2]PCP-(CH2)3-NI 1 and Cz-(CH2)3-[3.3]PCP-(CH2)3-NI 2 show an exciplex emission between the PCP and NI moieties in cyclohexane and the intensity of the band is much higher in 2 than in 1, whereas Cz-(CH2)2-[2.2]PCP-(CH2)2-NI 3 does not show any exciplex emission in cyclohexane. These results indicated that the combination of [3.3]PCP and a trimethylene chain is preferable for the exciplex formation. PTZ-(CH2)3-[2.2]PCP-(CH2)3-NI 4 shows a broad band at 519 nm in cyclohexane, which is associated with the formation of the exterplex band among the NI, [2.2]PCP, and PTZ moieties, while PTZ-(CH2)3-[3.3]PCP-(CH2)3-NI 5 does not show the band. Me-PTZ-(CH2)2-[2.2]PCP-(CH2)2-BTD 6 shows a broad fluorescence band due to both the BTD and PTZ moieties in cyclohexane. In CH3CN, the fluorescence spectra of 1-6 suggest the presence of a photoinduced charge separation process. The study of the photoinduced charge separation process will be soon reported elsewhere.
authors.affiliation: Institute for Materials Chemistry and Engineering (IMCE), ‡Department of Chemistry, Graduate School of Sciences, Kyushu University , Hakozaki 6-10-1, Fukuoka 812-8581, Japan.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Miyazaki
authors.forename: Masahiko
authors.initials: M
authors.lastname: Shibahara
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Fujishige
authors.forename: Motonori
authors.initials: M
authors.lastname: Watanabe
authors.forename: Kenta
authors.initials: K
authors.lastname: Goto
authors.forename: Teruo
authors.initials: T
authors.lastname: Shinmyozu