Theoretical Study Of Dihydrogen Bonds Of NH₂BH₂, HBeH And XZnH With Several Small Molecules

In this paper, Ab initio quantum chemistry methed was employed to investigate the dihydrogen bonds B-H…H-X(X=C,F,Cl, Ar, Kr) between (NH2BH2,HBeH,HZnH) as the proton acceptors and small molecules (HArF, HKrF, HF, HCl, CHF3,HCC13, HCOCl and HCOF) as the proton donors. We used the AIM theory to study the topological proporties of electron density of the monomers and complexes, and used the NBO (natural bond orbital) method to study interactions between molecular orbitals of the monomers, and the changes of the atomical orbitals, molecular orbitals and chemical bonds in a monomer upon formation of the dihydrogen bonds. We also used the CHelpG method to simulate the electrostatic field of the proton acceptor, and studied the contribution of the electrostatic interaction to the formation of dihydrogen bonds.1.Ab initio quantum chemistry method was employed to investigate the dihydrogen bonds B-H…H-X(X=C,F,Cl) between NH2BH2 as proton donor and small molecules (HF, HCl, CHF3,HCCl3,HCOCl and HCOF) as proton acceptors. Calculation indicated that in all of the systems the formation of dihydrogen bond leads to red shifts of BH bonds, red shifts of H-F and H-Cl bonds in the compounds of NH2BH2…HF and NH2BH2-HCl, and blue shifts of H-C in the compounds of NH2BH2…CHF3, NH2BH2-HCC13,NH2BH2…HCOF and NH2BH2…HCOC1. There are also tranditional hydrogen bonds N-H…Y(Y=C1, F, O) in these systems. The results of AIM and NBO analysis showed that electrostatic interaction plays an important role in dihydrogen bonds and tranditional hydrogen bonds in all the systems. The red and blue shifts of vibration frequency were caused by intermolecular electron dentisy transfer, and the intramolecules hyperconjugation must be considered.2.Ab initio quantum chemistry methods were applied to investigate the dihydrogen bonds HBeH...HRgF(Rg=Ar,Kr) at the MP2(full)/6-311++G(2d,2p) level. The results show that all the monomers and complexes are linear, and the interaction energies are large.Electrostatic interaction and electron density transfer caused by intermolecular hyperconjugationσ(BeH)→σ*(HRg) weaken the HRg bond of the proton donor and cause its frequency red shift, electrostatic interaction is predominant; the intramolecular hyperconjugation n(F)→σ*(HRg) in the proton donor weakens the affect of charge transfer. Meanwhile, the intermolecular hyperconjugation causes the BeH bond weakening and elongating with concomitant frequency red shift.3.Ab initio quantum chemistry methods were applied to investigate the dihydrogen bonds XZnH...HKrF(X= F,Cl,Br) at the MP2(full)/6-311++G(2d,2p) level. The results show that all the monomers and complexes are linear. the intermolecular hyperconjugationσ(ZnH)→σ*(HRg) causes the ZnH bond weakening and elongating with concomitant frequency red shift. Meanwhile, electron density transfer caused by intermolecular hyperconjugationσ(ZnH)→σ*(HRg) weaken the HRg bond of the proton donor and cause its frequency red shift. the intramolecular hyperconjugation n(F)→σ*(HRg) in the proton donor weakens the affect of charge transfer.