- 作者: 儲三陽
- 作者服務機構: Department of Chemistry, National Tsing Hua University, Hsinchu 30043, Taiwan, R.O.C.
- 中文摘要: The protonated water dimer has a symmetric structure 2 in contrast to the asymmetric structure of the protonated ammonia dimer 1. To make a general understanding of factors affecting structural symmetry in these protonated dimer systems, we carried out a systematic theoretical study using the B3LYP/6-31+G** method on several D-A-D systems with D as the electron-pair donors NH3, H2O, and CO and A as the electron-pair acceptors H+ and Li+. We found the magnitude of the first bonding energy for the monomer (BE(1)) is decisive for the symmetry of the D-A-D system. A larger BE(1) leads to a smaller BE(2), the bonding energy of D-A with the second donor. This gives rise to a stronger tendency towards asymmetry. The magnitude of BE(1) correlates well with the difference in ionization potential (DIP) of the orbitals involved in the D-A interaction. The donor-donor distance (RD-D) also plays an important role for the asymmetry, since it is also capable of modifying the ratio of BE(2)/BE(1). The parameter c, correlated to system asymmetry, defined as RD-D/RD-A is a useful parameter insensitive to the type of the system studied, with RD-A referring to the bond distance in the monomer.
- 英文摘要: --
- 中文關鍵字: Proton affinity; Ionization potential; Structural asymmetry; Hydrogen bond; Resonance.
- 英文關鍵字: --