| Research Abstract |
Ortho-substitution of the amino amino group was found to produce efficiently fluorescent 2, 2' : 6', 2"-terpyridines (tpy), whose fluorescence were observed around 380 nm. Among them 6-amino tpy showed considerably large fluorescence quantum yield (Φ=0.70). On the other hand, that of 4'-amino tpy was very small (<0.01). We successfully developed the highly fluorescent tpys, and presented that introduction of the amino group (s) at appropriate position (s) is important.
4'-phenyltpy (ptp) also exhibited an efficient fluorescence. Substitution at para-position of the phenyl group of ptp showed that amino- and dimethylamino- ptp exhibited a largely red-shifted fluorescence. Solvent dependence of the spectra and MO calculation suggested that introduction of strongly electron donating group elevated the energy level of HOMO-1 over that of HOMO.There have been no reports on tuning the fluorescence property by controlling the energy level of the molecular orbital, and this result would open the way on novel strategy for designing the fluorescence propeties.
As a new designing concept of the fluorescent bpy, 7-aminodipyrido [3, 2-a : 2', 3'-c] phenazine (dppz-NH_2), which has condensed structure of the known fluorophore, 2-aminophenazine, and bpy, was synthesized. The result showed an efficient fluorescence of dppz-NH_2 and the usefulness of the new method of the molecular design. Dppz-NH_2 displayed selective chelate formation with divalent cations, and concomitant fluorescence response. Moreover, Ru-dppz-NH_2 complex was found to be an efficient photo-sensitizing unit, and easy to bind with acceptor molecules using the amino group. The ability of dppz-NH_2 as a photo-functional molecule was confirmed.
In conclusion, we developed some novel fluorescent polypyridyl compounds. In addition, we showed their characteristic photo-functions and their potentials as novel photo-functional materials.
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