Solvatochromic shifts of the pi-pi* and n-pi* transitions for the pyridinium-N-phenoxide [2-(pyridinium-1-yl)phenolate] betaine changing from vacuum to water, have been investigated using Monte Carlo simulations and time-dependent density functional theory schemes using standard and long-range corrected functionals. The classical Boltzmann distribution of the interring twist angle obtained from the calculated free energy agrees with a Car-Parrinello distribution. For the calculated spectral shifts BHandHLYP/6-311+G(2d,p) performs better than the CAM-B3LYP/6-311+G(2d,p) or LC-omega PBE/6-311+G(2d,p) model but the experimental shift is very well reproduced only after the inclusion of solute polarization and proper consideration of the twist geometry relaxation associated with the intramolecular charge transfer. (C) 2011 Elsevier B.V. All rights reserved.