Theoretical Study Of Hydrogen Bonds And Dihydrongen Bonds Between π-conjugate Hetero-cyclic Molecules And Some Proton Donors

In the present paper,ab initio quantum mechanics method is employed to investigate the origin of hydrogen bonds and dihydrongen bonds between borazine,pyridine and H_xCF_4-x(x=1～3),HX,HCX₃(X=F,Cl,Br),H₂O,CH₃COOH and CH₃OH.The main contents are the following:1.The dihydrogen Bonds B-H…H-C and traditional H-bonds N-H…F between B₃N₃H₆ and H_xCF_4-x(x=1～3) have been theoretically studied by use of the density functional theory in the level of B3LYP/6-31G(d,p),6-311+G(d,p),6-311++G (d,p),6-311++G(2df,2p),AUG-cc-pVDZ,AUG-cc-pVTZ.We found that upon formation of the dihydrogen Bonds the BH bonds are red-shifted and the CH bonds are blue-shifts,and that the formation of the traditional H-bonds cause the NH bonds red-shifted.The topological properties of the complexes show that these intermolecular interactions are indeed H-bonds.The natural bond orbital analysis shows that these H-bonds can be interpreted by use of the theory of inter- and intra-molecular hyperconjugation and rehybridization.2.The dihydrogen bonds B-H…H-X and traditional H-bonds N-H…X and X-H…X(X=F,Cl,O) between B₃N₃H₆ and HF,HCl and H₂O have been theoretically studied by use of the ab initio quantum mechanics method(MP2).We found that upon formation of the dihydrogen Bonds,the BH bonds and HX bond are red-shifted,and that the formation of the traditional H-bonds causes the NH and HX bonds red-shifted. The topological properties of the complexes show that these intermolecular interactions are indeed H-bonds.The natural bond orbital analysis shows that these H-bonds can be interpreted by use of the theory of hyperconjugation and rehybridization.3.The N…H-X(X=N,O,C) and C-H…O interaction between pyridine and HOCNH₂,CH₃CONH2,HCOOH,CH₃COOH et al.was investigated by means of quantum chemical method of Becke 3-parameter hybrid exchange functionals and Lee-Young-Parr correlation functionals of DFT in the level of 6-311++G(d,p),6-311++G(2df,2p) and AUG-cc-pVDZ.For the N…H-X(X=N,O,C) interaction classical H-bonds are formed with an elongation of C-H and a red shift.However,for the C-H…O interaction blue shifting H-bonds are identified with a contraction of C-H and a blue shift.We found that H-X(X=N,O,C) bonds are stronger than C-H bonds.The NBO analysis show that the competitions of hyperconjugation and rehybridization result in two kinds of H-bonds.