Direct Observation of the Solvent Effects on the Low-Lying ne and pi pi* Excited Triplet States of Acetophenone Derivatives in Thermal Equilibrium

Sudhakar Narra, Shinsuke Shigeto

研究成果: Article同行評審

5 引文 斯高帕斯(Scopus)

摘要

Low-lying excited triplet states of aromatic carbonyl compounds exhibit diverse photophysical and photochemical properties of fundamental importance. Despite tremendous effort in studying those triplet states, the effects of substituents and solvents on the energetics of the triplet manifold and on photoreactivity remain to be fully understood. We have recently studied the ordering of the low-lying n pi* and pi pi* excited triplet states and its substituent dependence in acetophenone derivatives using nanosecond time-resolved near-IR (NIR) spectroscopy. Here we address the other important issue, the solvent effects, by directly observing the electronic bands in the NIR that originate from the lowest n pi* and pi pi* states of acetophenone derivatives in four solvents of different polarity (n-heptane, benzene, acetonitrile, and methanol). The two transient NIR bands decay synchronously in all the solvents, indicating that the lowest n pi* and pi pi* states are in thermal equilibrium irrespective of the solvent polarity studied here. We found that the pi pi* band increases in intensity relative to the n pi* band as solvent polarity increases. These results are compared with the photoreduction rate constant for the acetophenone derivatives in the solvents to which 2-propanol was added as a hydrogen-atom donor. Based on the present findings, we present a comprehensive, solvent- and substituent-dependent energy level diagram of the low-lying n pi* and pi pi* excited triplet states.
原文English
頁(從 - 到)3808-3814
頁數7
期刊Journal of Physical Chemistry B
119
發行號9
DOIs
出版狀態Published - 5 三月 2015

指紋 深入研究「Direct Observation of the Solvent Effects on the Low-Lying ne and pi pi* Excited Triplet States of Acetophenone Derivatives in Thermal Equilibrium」主題。共同形成了獨特的指紋。

引用此