Interplay of Intrinsic, Environmental, and Dynamic Effects in Tuning the EPR Parameters of Nitroxides: Further Insights from an Integrated Computational Approach

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• 作者：Michele Pavone ; Paola Cimino ; Orlando Crescenzi ; Atte Sillanpä ; ä ; Vincenzo Barone
• 刊名：Journal of Physical Chemistry B
• 出版年：2007
• 出版时间：August 2, 2007
• 年：2007
• 卷：111
• 期：30
• 页码：8928 - 8939
• 全文大小：250K
• 年卷期：v.111,no.30(August 2, 2007)
• ISSN：1520-5207

文摘

The role of stereoelectronic, environmental, and short-time dynamic effects in tuning the hyperfine andgyromagnetic tensors of a prototypical nitroxide spin probe has been investigated by an integrated computationalapproach based on extended Lagrangian molecular dynamics and discrete-continuum solvent models.Trajectories were generated in two protic solvents as well as in the gas phase for reference; structural analysisof the dynamics, and comparison with optimized solute-solvent clusters, allowed for the identification ofthe prevailing solute-solvent hydrogen-bonding patterns and helped to define the strategy for the computationof magnetic parameters. This was performed in a separate step, on a large number of frames, by a high-levelDFT approach coupling the PBE0 hybrid functional with a tailored basis set and with proper account ofspecific and bulk solvent effects. Remarkable changes in solvation networks are found on going from aqueousto methanol solution, thus providing a rationalization of indirect experimentally available evidence. Thecomputed magnetic parameters are in satisfactory agreement with the available measured values and allowfor an unbiased evaluation of the role of different effects in tuning the overall EPR observables. Apart fromtheir intrinsic interest, our results pave the route toward the development of tunable detection protocols basedon specific spectroscopic signatures.