Electrostatic Interactions Are Key to C═O n-π* Shifts: An Experimental Proof
| Autor: | Sayan Bagchi, Tapas Haldar |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Quantitative Biology::Biomolecules
010304 chemical physics Hydrogen bond Chemistry 010402 general chemistry Electrostatics 01 natural sciences Molecular physics 0104 chemical sciences Blueshift Dipole Computational chemistry Excited state 0103 physical sciences Polar General Materials Science Physical and Theoretical Chemistry Ground state Excitation |
| Zdroj: | The journal of physical chemistry letters. 7(12) |
| ISSN: | 1948-7185 |
| Popis: | Carbonyl n-π* transitions are known to undergo blue shift in polar and hydrogen-bonding solvents. Using semiempirical expressions, previous studies hypothesized several factors like change in dipole moment and hydrogen-bond strength upon excitation to cause the blue shift. Theoretically, ground-state electrostatics has been predicted to be the key to the observed shifts, however, an experimental proof has been lacking. Our experimental results demonstrate a consistent linear correlation between IR (ground-state phenomenon) and n-π* frequency shifts (involves both ground and excited electronic-states) of carbonyls in hydrogen-bonded and non-hydrogen-bonded environments. The carbonyl hydrogen-bonding status is experimentally verified from deviation in n-π*/fluorescence correlation. The IR/n-π* correlation validates the key role of electrostatic stabilization of the ground state toward n-π* shifts and demonstrates the electrostatic nature of carbonyl hydrogen bonds. n-π* shifts show linear sensitivity to calculated electrostatic fields on carbonyls. Our results portray the potential for n-π* absorption to estimate local polarity in biomolecules and to probe chemical reactions involving carbonyl activation/stabilization. |
| Databáze: | OpenAIRE |
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