%0 Journal Article %A Haldar, Tapas %A Bagchi, Sayan %D 2016 %T Electrostatic Interactions Are Key to CO n‑π* Shifts: An Experimental Proof %U https://acs.figshare.com/articles/journal_contribution/Electrostatic_Interactions_Are_Key_to_C_O_n_Shifts_An_Experimental_Proof/3413047 %R 10.1021/acs.jpclett.6b01052.s001 %2 https://acs.figshare.com/ndownloader/files/5334397 %K ground state %K IR %K probe chemical reactions %K correlation %K Electrostatic Interactions %K carbonyl hydrogen bonds %K shift %X 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. %I ACS Publications