Highly blue luminescent triazine-amine conjugated oligomers.
[Reaction: see text]. The novel synthetic strategy and optical properties of highly fluorescent, triazine-amine conjugated oligomers are described herein. Under basic conditions, aromatic dinitrile compounds, NC-C6H4-X-C6H4-CN (X = NMe, O, CH2), underwent cyclic trimerization of the cyano groups at both ends to give a series of triazine-containing oligomers. The oligomers can be expressed as (2n + 1) mer, where n represents the number of triazine rings in the oligomer. The absorption maximum of an amine-conjugated trimer (X = NMe, n = 1) was outstandingly red-shifted as compared with those of the other trimers (X = CH2, O). In acidic media, the amine-conjugated trimer showed two-step bathochromic shifts caused by protonation. The absorption maxima of the amine-conjugated (2n + 1) mers (X = NMe, n = 1-4) did not depend on n; instead, shoulder peaks appeared in the long-wavelength region when n 2. The oligomers involving alternate conjugation of triazines and NMe groups through phenylene groups showed strong fluorescence in chloroform. In particular, the pentamer was the most efficient blue emitter (PhiF = 0.82). The other triazine-containing oligomers (X = CH2, O) did not show fluorescence at all. Therefore, it is concluded that the emission properties are due to the strong electron-donating and accepting abilities of the NMe and triazine moieties, respectively.
Murase
Takashi
T
Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
Fujita
Makoto
M