| Abstract
| - Quantum chemical calculations are performed on the complex formed by silicane and ammonium in order toinvestigate the binding characteristics and nature of the dihydrogen bond. The calculation results using B3LYPand MP2 methods with the basis sets from 6-31G* to 6-311++G(2df,2pd) reveal that the dihydrogen-bondangle is ∼180.0° and that the bond length is ∼1.60 Å. The calculated enthalpies of formation of this complexusing B3LYP/6-311++G(2df,2pd) and MP2/6-311++G(d,p) methods, corrected by basis-set superpositionerror (BSSE) and thermal energy, are −5.595 and −4.465 kcal/mol, respectively. Taking into account ourCCSD(T)/6-311++G(2df,2p) and G2 results, we suggest that the binding strength between SiH4 and NH4+is ∼5.0 ± 0.5 kcal/mol. The BSSE released from the B3LYP method seems to converge at the basis set6-311++G(d,p). In addition, charge distribution, electrostatic interaction energy, and the molecular-orbitalcoefficient analysis on all molecular orbitals of this complex show that s−s orbital interaction plays a keyrole in their bindings. Three intrinsic vibrational bands of this complex are identified by the normal-modeanalysis on the calculated vibration spectra. The thermodynamic parameters of the possible reaction betweenSiH4 and NH4+ are also calculated, which show that the equilibrium constants of this reaction are about 4.34× 106 and 1.78 × 107 for the B3LYP/6-311++G(2df,2pd) and MP2/6-311++G(d,p) methods, respectively.All of these results are helpful for us to better understand the nature and the characteristics of the dihydrogenbond and exploit its application.
|
