Research On Of Dendrimer The Theory

Dendrimers are highly ordered hyperbranched macromolecules,which are prepared by either convergent or divergent method.This class of molecules has attracted considerable attention because of their potential application. Silicon-based dendrimers are dendrimers with Si atoms used as branch point between two generations.There are three important type of Silicon-based dendrimers that are siloxane dendrimers,carbosilane dendrimers and silane dendrimers.The silicon-based dendrimers can be connected with organometallic compounds which are located at either the surface of the dendrimer or the core of the dendrimer.This paper presents a theoretical study of dendritic dendrimers by density functional calculation and molecular mechanic method.Some important and valuable results are summarizes as follows.1.A theoretical approach to the prediction of relative catalytic power of structurally related core-functionalized dendritic catalysts is developed.From the beginning catalysis has been recognized as one of the main potential applications of dendritic molecules.Using density functional method,we have studied two palladium complexes integrating dendronized alkylsilyl chains linked to the para-carbon atoms of the phenyl groups of the arylphosphine ligands with the purpose of developing a theoretical approach to the prediction of relative catalytic power of structurally related core-functionalized dendritic catalysts. which will be helpful for the design of molecular structures of catalysts2.Molecular dynamics(MD)simulations have been employed to study maximum generation issue.Molecular dynamics(MD)simulations have been employed to search the minimum energy configurations of eight types of structurally related polysilane dendrimers of various generations.Calculations reveal that for the studied dendrimers, the innermost Si-Si bonds adjoining the silicon atom at the center of the core structure are extended for steric relief with the amount of extension increasing with the number of generations due to the rise of the spatial hindrance inside these molecules.To determine at which generation the growth of additional layers would terminate,we have carried out a series of fully atomistic simulation on different generations of polysilane dendrimers.The new findings in the paper are as follows.1.In this paper,we have developed a new method combining density functional calculation with the hard-sphere collision theory to predict the catalytic power of dendritic catalysts.Using this approach,we have studied two palladium complexes integrating dendronized alkylsilyl chains linked to the para-carbon atoms of the phenyl groups of the arylphosphine ligands, which are of general formula[PdCl₂(L)₂]and named with 3a and 3b respectively(L=[P(C₆H₅)_n((C₆H₄CH₂CH₂Si(CH₂CH₂CH₂SiEtMe₂)₃)_3-n)],n equals 2 for 3a and 1 for 3b,respectively).The computational results rationalize the experimental finding.Our work could motivate the development in the design of dendritic catalysts.2.The search of reasonable conformations of dendritic polysilanes has been carried out by theoretical modeling and molecular level simulation.The correlation between the density of methyl groups located at the surface of molecule and the molecular stability is studied.In order to confirm the reliability of molecular simulation,we compare our results with the experimental data.The maximum generation of silane dendrimers is predicted first time.