The electronic spectrum of N-methylacetamide in aqueous solution: a sequential Monte Carlo/quantum mechanical study

Sequential Monte Carlo/quantum mechanical (S-MC/QM) calculations are perfor med to study the solvent effects on the electronic transitions of N-methyla cetamide (NMA) in aqueous solution. Full quantum mechanical INDO/CIS calcul ations are performed in the super-molecular clusters generated by Monte Car lo (MC) simulation. The largest calculation involves the ensemble average o f 75 quantum mechanical results obtained with the NMA solute surrounded by 150 water solvent molecules. After extrapolation to the bulk limit we find that the n --> pi* transition suffers a blue shift of 1755 cm(-1) upon solv ation and the pi --> pi* transition undergoes a red shift of 1180 cm(-1), i n good agreement with the experimental findings. (C) 2001 Published by Else vier Science B.V.