Correlations between experimental and DFT(B3LYP)/6-31++G** H-bonding parameters for closed X center dot center dot center dot H-O center dot center dot center dot H-N (X = N, O or S) H-bonded complexes
Correlations between experimental and DFT(B3LYP)/6-31++G** calculated parameters for a series of closed H-bonded complexes of type X...H-O...H-N between a water molecule and a purine or pyrimidine base are investigated. Regular relationships are observed between: (1) the calculated H-bond distance and the H-bond angle; (2) the frequency shift, -Deltanu(OH)(b) (experimental and theoretical) and the X...H distance/the elongation of the O-H bond; (3) the experimental relative frequency shift, Deltanu (N-H...)/nudegrees(N-H) and the calculated interaction energy; and (4) the experimental and the calculated frequency shift, -Deltanu(OH)(b). All the X...H-O...H-O complexes used in this work correlate similarly in all relationships, although the nature of the different H-bond-acceptor groups, i.e. X = N, O or S, is clearly expressed in some of the correlations. (C) 2003 Elsevier B.V. All rights reserved.