Photophysical Characterization of a Benzo-Fused Analogue of Brooker鈥檚 Merocyanine: Solvent Polarity and pH Effects

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• 作者：Edward Adjaye-Mensah ; Walter G. Gonzalez ; Jaroslava Miksovska ; James N. Wilson
• 刊名：The Journal of Physical Chemistry A
• 出版年：2012
• 出版时间：December 27, 2012
• 年：2012
• 卷：116
• 期：51
• 页码：12470-12475
• 全文大小：337K
• 年卷期：v.116,no.51(December 27, 2012)
• ISSN：1520-5215

文摘

The photophysical properties of 4-[2-(6-hydroxy-2-naphthalenyl)-ethenyl]-1-methyl-pyridinium (HNEP⁺) and its deprotonated form (NEP), a benzofused derivative of Brooker鈥檚 merocyanine (BM), were investigated through a combined spectroscopic and computational approach. Despite their structural similarities and similar pK_a values, HNEP⁺/NEP and BMH⁺/BM differ in the extent of charge delocalization in the ground and excited states. NEP exhibits the spectral characteristics of a charge transfer species in solvents in which BM exists in a charge-delocalized quinoid; however, quantum chemical calculations show that the CT absorption of NEP is not necessarily a consequence of the zwitterionic character. HNEP⁺ displays larger Stokes shifts than BMH⁺, and NEP demonstrates enhanced solvatochromism relative to BM as a consequence of benzofusion.