Emission Switching of 4,6-Diphenylpyrimidones: Solvent and Solid State Effects

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• 作者：Edward Adjaye-Mensah ; Walter G. Gonzalez ; David R. Buss茅 ; Burjor Captain ; Jaroslava Miksovska ; James N. Wilson
• 刊名：The Journal of Physical Chemistry A
• 出版年：2012
• 出版时间：August 30, 2012
• 年：2012
• 卷：116
• 期：34
• 页码：8671-8677
• 全文大小：369K
• 年卷期：v.116,no.34(August 30, 2012)
• ISSN：1520-5215

文摘

The photophysics of 1-ethyl-4,6-bis(4-methoxyphenyl)-2(1H)-pyrimidone (1) and 1-ethyl-4,6-bis(4-(dimethylamino)phenyl)-2(1H)-pyrimidone (2) were investigated to determine the mechanisms of emission switching in response to protonation. UV鈥搗is and steady state emission spectroscopy of the protonated and unprotonated forms across a range of solvents reveal the polarity dependence of the vertical excitation energies. Emission lifetimes and quantum yields show the solvent dependency of the excited states. Emission enhancements were observed in polyethylene glycol solutions and in the solid state (both thin film and single crystal), demonstrating the role of intramolecular rotation in thermal relaxation of the excited states. TD-DFT calculations provide insights into the excited state geometries and the role of intramolecular charge transfer. The collected data show that emission of diphenylpyrimidones can be modulated by four factors, including the identity of the electron-donating auxochrome, protonation state, solvent polarity, and viscosity.