C O M M U N I C A T I O N S
6nha exhibits strong blue fluorescence in CHCl3 with emission
maximum at 461 nm. The fluorescence quantum yield (ΦF) was
determined to be 0.52 with reference to 9,10-diphenylanthracene.
The first reduction peak potential value was found to be -2.65 V
versus Ag/Ag+. Nevertheless, the discovery of a compound bearing
both high fluorescence efficiency and a high electron-accepting
property is of great interest.
Figure 2. Emissive behaviors and fluorescence spectra of 4jha with various
solvents.
During the course of our investigation on photophysical proper-
ties (UV/vis and fluorescence measurements) of pyrimidine-core
extended π-systems, it was found that the introduction of a p-Me2-
NC6H4 group (h) onto the pyrimidine ring substantially increases
the fluorescence efficiency (Figure 1). For example, while the parent
4aaa exhibits almost no fluorescence in solution, 4aha was found
to emit strong blue light upon irradiation (λmax ) 444 nm, ΦF )
0.63). Although a similar increase of fluorescence efficiency was
also observed with 4aah, the effect was much smaller (ΦF ) 0.05)
than that observed with 4aha, indicating the importance of the
attaching site of π-units on the photophysical properties.
Acknowledgment. This work was partly supported by a Grant-
in-Aid for Scientific Research from the Ministry of Education,
Culture, Sports, Science, and Technology, Japan.
Supporting Information Available: Experimental procedures and
analytical and spectroscopic data of compounds. This material is
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