- Orientational and Vibrational Relaxation Dynamics of Perylene and 1-Methylperylene in n-Alcohols: Probing the Balance between van der Waals and Hydrogen-Bonding Interactions
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We report on the rotational diffusion and vibrational population relaxation dynamics of perylene and 1-methylperylene in the primary normal alcohols methanol through n-decanol. The rotational diffusion dynamics of the two chromophores are the same to within the experimental uncertainty for n-propanol through n-decanol. We observe a double exponential decay of the induced orientational anisotropy for 1-methylperylene in all of the alcohols and for perylene in n-propanol through n-decanol. These data are consistent with previous literature reports on perylene in high-viscosity solvents and on 1-methylperylene in n-alkanes longer than n-octane. These data also reveal a substantial difference in the behavior of perylene in n-alkanes and n-alkanols. Both chromophores reorient as oblate rotors in the n-alkanols, with the aspect ratio of the oblate ellipsoid describing their motion depending on the solvent aliphatic chain length. The vibrational population relaxation dynamics of the two probe molecules differ significantly, not only because of the difference in the nature of the solvent-solute coupling but also because of subtle differences in the organization of the solvent around the two chromophores. These data reflect the importance of solvent self-association in determining the local environments of these two chromophores.
- Goldie,Blanchard
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- A methylation platform of unconventional inert aryl electrophiles: Trimethylboroxine as a universal methylating reagent
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Methylation is one of the most fundamental conversions in medicinal and material chemistry. Extension of substrate types from aromatic halides to other unconventional aromatic electrophiles is a highly important yet challenging task in catalytic methylation. Disclosed herein is a series of transition metal-catalyzed methylations of unconventional inert aryl electrophiles using trimethylboroxine (TMB) as the methylating reagent. This transformation features a broad substrate type, including nitroarenes, benzoic amides, benzoic esters, aryl cyanides, phenol ethers, aryl pivalates and aryl fluorides. Another important merit of this work is that these widespread "inert"functionalities are capable of serving as directing or activating groups for selective functionalization of aromatic rings before methylation, which greatly expands the connotation of methylation chemistry.
- Feng, Boya,Yang, Yudong,You, Jingsong
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p. 6031 - 6035
(2020/07/10)
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