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Solvation oscillations and excited-state dynamics of 2-amino- and 2-hydroxy-7-nitrofluorene and its 2'-deoxyriboside

Item Type:Article
Title:Solvation oscillations and excited-state dynamics of 2-amino- and 2-hydroxy-7-nitrofluorene and its 2'-deoxyriboside
Creators Name:Karunakaran, V., Pfaffe, M., Ioffe, I., Senyushkina, T., Kovalenko, S.A., Mahrwald, R., Fartzdinov, V., Sklenar, H. and Ernsting, N.P.
Abstract:Push-pull substituted fluorenes are considered for use as dynamic solvation probes in polynucleotides. Their fluorescence band is predicted (by simulations) to show weak spectral oscillations on the subpicosecond time scale depending on the nucleotide sequence. The oscillations reflect the local far-infrared spectrum of the environment around the probe molecule. A connection is provided by the continuum theory of polar solvation which, however, neglects molecular aspects. We examine the latter using acetonitrile solution as a test case. A collective librational solvent mode at 100 cm-1 is observed with 2-amino-7-nitrofluorene, 2-dimethylamino-7-nitrofluorene, 2-hydroxy-7-nitrofluorene, and its 2'-deoxyriboside. Different strengths of the oscillation indicate that rotational friction of nearby acetonitrile molecules depends on the solute structure or that H bonding is involved in launching the librational coherence. Polar solvation in methanol is used for comparison. With hydroxynitrofluorenes, the observation window is limited by intersystem crossing for which rates are reported. A prominent excited-state absorption band of nitrofluorenes at 430 nm can be used to monitor polar solvation. Structural and electronic relaxation pathways are discussed with the help of quantum chemical calculations.
Keywords:Absorption, Acetonitriles, Base Sequence, Fluorenes, Fluorescence, Hydrogen Bonding, Methanol, Monte Carlo Method, Oligonucleotides, Ribose, Solvents, Thermodynamics, Time Factors
Source:Journal of Physical Chemistry A
Publisher:American Chemical Society
Page Range:4294-4307
Date:8 May 2008
Official Publication:https://doi.org/10.1021/jp712176m
PubMed:View item in PubMed

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