Theoretical Study On The Interaction In Noble Metal Halides

In the past few decades,the practical application of noble metal halides in catalysts,hologramsand solid materials has attracted many theoretical and experimental researches.The influence of the d orbital electrons and the relativistic effects of noble metal atoms makes theoretical investigations much more complicated,and the nature of the interaction between noble metals and halogen atoms still remains controversial.In this thesis,the geometric structure,stability and interaction of MX_n?M=Au,Ag,Cu;X=F,Cl,Br,I;n=1–5?and M₃X₃?M=Cu,Ag,Au;X=F,Cl,Br,I?have been investigated systematically by ab initio quantum chemistry calculations.Due to the strong relativistic effects of Au atom,the stable structure and interaction are quite different from other noble metal halides,and we divide the MX_n systems into two parts,AuX_n and MX_n?M=Ag,Cu?,for discussion.The main contents are presented as the following:In chapter 1,cluster physics,the significance of the research,and the main contents areintroduced.In chapter 2,we introduce the quantum chemistry ab initio method,electronic correlation andrelativistic effects,and the software.In chapter 3,the stabilities and interactions of AuX_n?X=F,Cl,Br,I;n=1–5?clusters aresystematically studied at MP2 theoretical level with Gaussian 03 and Multiwfn programs.The results are summarized as follows:?1?The stable structure changes from planar to non-planar structure with the addition of the halogen atoms.AuF₃ and AuCl₃ have the T-shaped structure,while L-shaped AuBr₃ and AuI₃ are the minimum energy structures.?2?NBO analysis shows that the interaction of the Au-X is mainly due to the overlap between the Au spd and halogen sp hybrids.?3?There are clear covalent contributions in AuBr₃ and AuI₃ clusters.Relatively obvious covalent character in AuCl₅ and AuBr₅,and weak covalence character in other systems can be found.In chapter 4,the stable structures of AgX_n and CuX_n?X=F,Cl,Br,I;n=1–5?systems and theinteractions are studied by quantum chemistry ab initio methods.The stable structures of AgX_n are different from that of CuX_n,especially for n=5.A maximum of four halogen atoms can be bound directly to Ag atom to form neutral AgX₅.For CuX₅,there are three X atoms can bind directly to Cu atoms and two halogen atom interact weakly with CuX₃.The bond length of these two halogen atoms is almost equally to that of X₂ molecule and tends to form an free X₂ moiety with a strong covalent interaction.Results show that Ag and Cu can bind up to four halogen atoms directly.NBO,AIM,ELF and RDG analysis indicate that there are obvious covalent contributions in AgX₃?X=Cl,Br,I?,AgX₅,and CuX₅?X=F,Cl,Br,I?systems.In chapter 5,the structure and stability of M₃X₃?M=Cu,Ag,Au;X=F-I?are investigated atMP2 theoretical level.Results show that all the structures are planar D_3h rings with the exception of the C_2vv structure of Au₃F₃.The most prominent bonding contribution occurs between noble metal atom spd hybrids and halogen atoms sp hybrids.The bond length,stability,and covalence in the system show a periodic trend.In addition,the results show that-G/V ratio at BCP can be considered as an important indicator of the covalence of interaction.Due to the d-electron contributions of noble metal,it tends to form a linear coordination in the valence state+1.