| In this paper,quantum chemistry first principle and ab initio methed were carried out to systematically investigate the nature of hemi-bondings and non-covalent bondings in the radical cation dimer systems(1)(XPH2: SHY)+(X,Y=H,F,Cl,Br);(2)(XFClP: NH3)+(X=H,Br,OH,CH3)and(HFClP: BH3)+(B=N,P,As);(3)(XFClP: OH2)+(X=H,Br,OH,CH3)and(HFClP: AH2)+(A=O,S,Se).We study theoretically on its structures,binding energies,stabilities and bonding characteristics.The “atoms in molecules”(AIM)theory was performed to analyze the electron density(?BCP),Laplacian(?2?BCP)and total electron energy density H at the bond critical points(BCPs).The Natural Bond Orbital(NBO)theory was applied to obtain the Natural Population Analysis(NPA),and the natural bond orbital properties in the systems.The natural charges(q),Wiberg bond index(WBIs)and the orbital composition were characterized clearly with the natural bond orbital(NBO)theory.The stabilities of the systems were compared,and we have been studied the effect of the substituent on the hemi-bond plus pnicogen bond(P-bond)or chalcogen bond(S-bond)configurations.This paper mainly includes the following contents:1.In this part,we use the ab initio method---the perturbation theory(MP2)and the coupled cluster method(CCSD and CCSD(T)),and the first principle---density functional theory(BLYP),to study the structures,stabilities and bonding nature of the systems.We analyzed the typical cases of(H3P:SH2)+,(FH2P:SH2)+ and(H3P:SHF)+.The results show that(H3P:SH2)+ has two configurations: hemi-bond structure and proton transfer hydrogen bond structure;(FH2P:SH2)+ has two kinds of hemibond structures and a proton transfer hydrogen bond structure;(H3P:SHF)+ has two hemi-bond structure and three non-covalent bond structures.NBO and AIM analysis showed that the interaction energy of these hemi-bond structures was stronger than that of non-covalent structures.2.In this part,the structure,relative stabilities and bonding properties of trisubstituted P systems---(XFClP:NH3)+(X=H,Br,OH,CH3)and(HFClP:BH3)+(B=N,P,As)are systematically studied by MP2 method with aug-cc-pVDZ and aug-cc-pVTZ basis sets.The results show that the systems of P substituted by three different substituents can form three kinds of hemi-bond plus pnicogen bonding structures: F-P???N-1,Cl-P???N-2 and X-P???N-3.For the(BrFClP:NH3)+system,the relative stability order of the three configurations is: F-P???N-1<Cl-P???N-2<X-P???N-3;for(XFClP:NH3)+(X=H,OH,CH3)systems,the relative stability order is: X-P???N-3<F-P???N-1<Cl-P???N-2;for different substituents on the same configuration,The order of stability is: CH3-P???N-3<OH-P???N-3<H-P???N-3<Br-P???N-3.From N to As,the interaction can be gradually weakened.In addition,due to the formation of the pnicogen bonding,the pnicogen bond(F-P/Cl-P/X-P)is red shifted accordingly.3.In this part,the hemi-bond plus pnicogen bond in systems(XFClP:OH2)+(X=H,Br,OH,CH3)and(HFClP:AH2)+(A=O,S,Se)was studied under ab initio MP2/aug-cc-pVDZ and MP2/aug-ccpVTZ level.The AIM and NBO theories are performed to analyze the molecular properties.It shows that there are there types of hemi-bond plus pnicogen bond: F-P???O,Cl-P???O and X-P???O.Also the sequence of the interaction energy((35)Eint)of the heterodimer systems is consistent with the conclusion of the system of(XFClP:NH3)+.The linear correlation between the intermolecular distance(R(P???A))and the WBIs,the electron density(?BCP),Laplacian(?2?BCP),the total electron energy density H at bond critical points(BCPs)are linearly related.Its interactions also can be consistent with the molecular distance parameters{R(P???A)}.From O to Se,the interaction can be enhanced gradually,it is opposite to the N/P/As group.The transfer of charge from the lone pair of the central atoms A {Lp(A)}to the anti-bonding orbital of the P-bond {?*(PX)} has a great effect on the stability order of the systems.The order of second order stabilization energy E[Lp(A)??*(PX)] is consistent with the order of structural stabilities. |
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