Abstract
The synthesis of 1,3,5 / 2,4,6 differentially functionalized hexaethynylbenzene derivatives is described. Interesting solvatochromic behavior was observed for 9b in the absorption and emission spectre. A twisted intramolecular charge transfer (TICT) state in polar solvents appears to be involved.
Original language | English |
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Pages (from-to) | 3499-3502 |
Number of pages | 4 |
Journal | Tetrahedron Letters |
Volume | 38 |
Issue number | 20 |
DOIs | |
State | Published - May 19 1997 |
Bibliographical note
Funding Information:All of the hexaethynylbenzene derivatives reported here, except for 8d and 9a, are highly fluorescent. However, the optical properties of the dimethylamino derivative 9b are particularly intriguing. The UV-vis absorption spectrum of 9b shows strong solvatochromic behavior - the spectrum in cyclohexane is markedly different from spectra taken in more polar solvents such as CH2C12 (Figure 3), and the maximum absorption proceeds to longer wavelengths as solvent polarity is increased up to 2-methyltetrahydrofuran (MTHF) and acetonitrile (not shown). This solvatochromism is carried over into the fluorescence spectra - the emission band is much more resolved and comes at a lower wavelength in nonpolar solvents. This suggests that an intramolecular charge-transfer interaction occurs between the electron-rich dimethylaminophenyl moieties situated on the perimeter of the molecule and the electron-accepting hexaethynylbenzene core of 9b. 14 Furthermore, the fluorescence occurs at higher energy in a MTHF glass at 77 K than in the solution state at ambient temperature. This is a strong indication that a twisted intramolecular charge transfer (TICT) state is involved in more polar solvents. 15 Acknowledgment. This work was supported by the Office of Naval Research, and by Beckman and NSF Young Investigator Awards to Y.R.
ASJC Scopus subject areas
- Biochemistry
- Drug Discovery
- Organic Chemistry