Long-range pi-type hydrogen bond in dimers CH2O-HF, CH2O-H2O, and CH2O-NH3

摘要

Using four basis bets, (6-311G(d,p), 6-31+G(d,p), 6-31++G(2d,2p), and 6-311++G(3df,3pd), the optimized structures with all real frequencies were obtained at the MP2 level for the dimers CH2O-HF, CH2O-H2O, CH2O-NH3, and CH2O-CH4. The structures of CH2O-HF, CH(2)0-H2O, and CH2O-NH3 are cycle-shaped, which result from the larger bend of sigma-type hydrogen bonds. The bend of sigma-type H-bond O...H-Y (Y=F, O, N) is illustrated and interpreted by an attractive interaction. of a chemically intuitive pi-type hydrogen bond. The pi-type hydrogen bond is the interaction between one of the H atoms of CH2O and lone pair(s) on the F atom ill HF, the O atom in H2O or the N atom in NH3. In contrast with the above three dimers, for CH2O-CH4, because there is not a pi-type hydrogen bond to bend its linear hydrogen bond, the structure of CH2O-CH, is noncyclic shaped. The interaction energy of hydrogen bonds and the pi-type H-bond are calculated and discussed at the CCSD (T)/6-311++G(3df,3pd) level. (c) 2005 Wiley Periodicals, Inc.