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The Three Possible 2-(Pyrenylethynyl) Adenosines: Rotameric Energy Barriers Govern the Photodynamics of These
Andreas J Reuss1, Christian Grünewald2, Markus Braun1
1Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue-Str. 7, 60438, Frankfurt, Germany.
Abstract:
This article presents a comprehensive study of the photophysics of 2-(2-pyrenylethynyl) adenosine and 2-(4-pyrenylethynyl) adenosine, which are structural isomers of the well-established fluorescent RNA label 2-(1-pyrenylethynyl) adenosine. We performed steady-state and ultrafast transient absorption spectroscopy studies along with time-resolved fluorescence emission experiments in different solvents to work out the interplay of locally excited and charge-transfer states. We found the ultrafast photodynamics to be crucial for the fluorescence decay behavior, which extends up to tens of nanoseconds and is partially multi-exponential. These features in the ultrafast dynamics are indicative of the rotational energy barriers in the first excited state.
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