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Combined Monte Carlo and quantum mechanics study of the solvatochromism of phenol in water. The origin of the blue shift of the lowest π–π* transition

“…In agreement, phenol in liquid ethanol presents a small red shift of B370 cm À1 . However, phenol in liquid water shifts to the blue side 12 by nearly the same amount (460 cm À1 ). The different sign of these two shifts is unexpected on the basis that water and ethanol normally lead to the same sign for the shift with the magnitude larger for water than for ethanol.…”

“…This information used for the liquid situation suggests that bulk water has a very important role to play in deciding what is the net solvatochromic shift in protic solvents. In fact in the recent experiment 12 the spectral shift of the S 0 -S 1 transition (lowest p-p*) of phenol in water and in ethanol have different signs. The usual rule states that p-p* transitions in polar solvents shift to the red side of the spectrum.…”

“…The ultraviolet-visible (UV-Vis) spectra of phenol in different solvents have attracted experimental interest for decades. [1][2][3][4][5][6][7][8][9][10][11][12][13] The long wavelength region of the electronic absorption spectrum of phenol is characterized by a strong and broad transition in the region of 270 nm. The spectral maximum of this absorption shifts on different solvents and this solvatochromism is related to the intermolecular interaction between phenol and the solvent molecules.…”

Characterization and spectroscopic analysis of phenol–ethanol hydrogen bonded clusters

“…In fact, in water the p ? p* transition shifts towards the blue, opposite to what is seen in ethanol, where a small red shift of $370 cm À1 is obtained [18]. The situation in water seems well understood in terms of partial contributions of the hydrogen bonded water molecules [12].…”

“…Understanding the origin and the nature of these two contributions is important to rationalize the observed spectral shift in different specific cases. For instance, compared to gas phase when phenol is solvated by water leads to a spectral shift that is surprisingly opposite to that when it is solvated by ethanol [12,18]. The origin of the resultant blue shift has been analyzed recently [12] and the separate role of phenol as hydrogen donor or hydrogen acceptor is one important aspect both in the liquid phase as in hydrogen bonded phenol-water cluster.…”