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Theoretical Study Of Dihydrogen Bonds Of NH3BH3,NH3AlH3 And NH3GaH3 With Several Small Molecules

Posted on:2010-09-26Degree:MasterType:Thesis
Country:ChinaCandidate:L F XuFull Text:PDF
GTID:2121360275452666Subject:Physical chemistry
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In present paper,ab initio quantum mechanics method is employed to investigate the origin of red-shifting and blue-shifting dihydrogen bonds between NH3BH3,NH3AlH3,NH3GaH3 and several small molecules.The main contents are the following:1.The bifurcated dihydrogen bonds B-H2…H-X(X=C,N) of NH3BH3 with CHF3,H2CO, HCOOH,HCOCl and HNO have been theoretically stduied.The results show that the dihydrogen H-bond leads to red shift of the B-H bond and blue shift of the X-H bond.The blue shift of the X-H bond is caused by decrease of the intramolecular hyperconjugation,positive repolarization and positive rehybridization of the X-H bond,and the bent configuration of the bifurcated dihydrogen bond;the red shift of the B-H bond are caused mainly by negative replorization and negative rehybridization of the B-H bond.2.The dihydrogen bonds B-H…H-X(X=F,Cl,Br,C,O,N) in the dimer(NH3BH3)2 and the complexes of NH3BH3 with HF,HCl,HBr,H2O and CH3OH have been theoretically studied.The results show that formation of the dihydrogen bond leads to elongation and stretch frequency red shift of the B-H and X-H bonds.For(NH3BH3)2 and the complexes of the halogenides,red shifts of the X-H bonds are caused by the intermolecular hyperconjugationσ(B-H)'σ*(X-H);in the other two systems,the red shift of O-H bond is a secondary effect of the stronger traditional red-shifted H-bonds N-H…O.In all these systems,red shifts of the B-H bonds are caused by the two factors: negative reploarization and negative rehybridization of the B-H bond,and decrease of occupancy onσ(B-H) caused by the intermolecular hyperconjugationσ(B-H)'σ*(X-H).3.The dihydrogen bonds Al-H…H-X(X=F,Cl,Br,C,O) of NH3AlH3 with HF,HCl,HBr,H2O, CH3OH,H2CO and HNO,have been theoretically stduied.The results show that the dihydrogen H-bond leads to red shifts of Al-H and X-H bonds(in the H2CO and HNO system,C-H and N-H bonds blue shift).For(NH3AlH3)2 and the complexes of the halogenides,the red shifts of X-H bonds are caused by the intermolecular hyperconjugationσ(Al-H)'σ*(X-H);for the systems of H2CO and HNO,the blue shift of C-H is caused by decrease of the intramolecular hyperconjugation n(O)'σ*(C-H,N-H);in the other systems,the red shift of X-H bond is a secondoary result of the stronger traditional red-shifted H-bonds N-H…X.In all these systems,the red shifts of Al-H bonds are caused by the two factors:negative replorization and negative rehybridization,and decrease of occupancy onσ(Al-H) caused by the intermolecular hyperconjugationσ(Al-H)'σ*(X-H).4.The dihydrogen bonds Ga-H…H-X(X=F,Cl,Br) of NH3GaH3 with HF,HCl and HBr have been theoretically studied.The results show that the dihydrogen H-bond leads to red shifts of Ga-H and X-H bonds.The red shifts of X-H bonds are caused by the intermolecular hyperconjugationσ(Ga-H)'σ*(X-H);the red shifts of Ga-H bonds are caused by the two factors:negative replorization and negative rehybridization,and decrease of occupancy onα(Ga-H) caused by the intermolecular hyperconjugationα(Ga-H)'σ*(X-H).
Keywords/Search Tags:bifurcated dihydrogen bond, red shift, blue shift, hyperconjugation, negative repolarization and negative rehybridization
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