Studies On The Electronic Structures And Behavior Of Several Models Correlated With Polysilane Assembly

Polysilanes and its derivatives are the potential and significant semiconductor materials.However,their applications are limited due to the defect of classical synthesis.Accordingly,it is a challenge and exciting topic to improve their structure and performance through the self-assembled technique.The research objective is to purposefully tune polysilanes' photoelectric properties based on the basic ideas and principles of the supramolecular self-assembly.With the aid of the quantum chemical methods,present study involves the exploration from the microscopic property and mechanism to the macroscopic structure and performance.This paper has accomplished primary theoretical investigation of the correlated models with polysilane self-assembly using coordination bonds,which discusses in detail the bonding properties of thienylsilanes complexes with transition metals by using the density functional theory(DFT) method,aiming to effectively guide the future experimental design in the coordinate self-assembly of the thiophene-functionalized polysilanes.Several correlated models with the polysilanes were investigated in this paper.The reasearch was based on the detailed analysis of the performance of the currently available density functionals in the reproduction of a large variety of chemical properties,including bond lengths and angles,barrier heights,atomization energies, binding energies,ionization potentials,electron affinities,heats of formation,and several types of nonbonded interactions(hydrogen bonding,charge transfer,dipole interactions,weak interactions,π-πinteractions).Three kinds of theoretical chemical methods were selected to explore the models of the polysilanes,which are B3LYP, BB95 and MPB1K.In order to test the reliability of the theoretical methods performed in this paper and their applicability to the thienylsilane models,we purposefully synthesis several thienylsilanes.These compounds have well-defined structures measured by the experiment,so they can be used to test and evaluate the performance of theoretical calculation,which is important to carry out the next study.The interactions between the several correlated models with polysilane assembly and the transition metals were investigated in this paper.The coordination of thiophene,thienylsilanes to the transition metals(Fe,Co and Ni) were analysed in detail,including the geometrical structures,bonding properties,stability,vibrational and excitated stated spectral properties of complexes that are difficult to be get through experiment.In thiophene/ thienylsilanes complexes with the transition metals(Fe,Co and Ni),there exists two interaction,M-πinteraction and M-S interaction.The thiophene can coordinate to single metal centers through the sulfur (η~1),two carbons(η~2),four carbons(η~4),and five atoms(η~5) of the thiophene ring, respectively.Theη~2-,η-~4 andη~5-bonding interactions are belong to the M-πinteraction,and theη~1-bonding interaction is belong to the M-S interaction.The calculated results show thatη~1-coordination is weaker than other coordinate modes. Theoretical study predictes the vibrational spectra and electronic absorption spectra of complexes,which provides the reliable and referenable information for the future work.The effects of the type and positions of substituents on the electronic structures of polysilane are also studied in this paper.A theoretical calculation is performed for the geometric and electronic structures of a series of asymmetrically substituted functional oligosilanes bearing carbosilyl side chains.This study presents the changes of geometries and spectral properties induced by varying the size and species of the substituting groups.The substituent effects on the conformation and behavior of oligosilanes were investigated in order to purposefully tune the spectrum of polysilane and design the self-assembled aggregates of the asymmetrical chiral polysilanes with optical activity.