Effects of Solvent Dielectric Constant and Viscosity on Two Rotational Relaxation Paths of Excited 9-(Dicyanovinyl) Julolidine

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• 作者：Songqiu Yang ; Keli Han
• 刊名：Journal of Physical Chemistry A
• 出版年：2016
• 出版时间：July 14, 2016
• 年：2016
• 卷：120
• 期：27
• 页码：4961-4965
• 全文大小：344K
• 年卷期：0
• ISSN：1520-5215

文摘

The understanding of the interplay between microenvironment and molecular rotors is helpful for designing and developing of molecular sensors of local physical properties. We present a study on the two rotational relaxation paths of excited 9-(dicyanovinyl) julolidine in several solvents. One rotational path (C–C single-bond rotation, τ_b) quickly leads to the formation of a twisted state. The other path (C═C double-bond rotation, τ_c) shows that the populations go back to the ground state directly via a conical intersection between the S₁ and ground state. The increase in the solvent dielectric constant shows little effect on the τ_b lifetime for its small energy barrier (<0.01 eV), but τ_c lifetime is increased in larger dielectric constant solvents due to the larger energy gap at conical intersection. Both τ_b and τ_c are increased greatly with the increased solvent viscosity. τ_b is more sensitive to viscosity than τ_c may be due to its larger rotational moiety.