Molecular Design And DFT Investigation Of Organic Conductor Based Upon The Pyrazine Group

In this paper, several conjugated compounds with the pyrazine group are studied by Density Functional Theory (DFT) methods, the electronic properties of monomers and oligomers are also computed and analyzed. We have elaborated the impact of the substituted pyrazine group on the conductive polymer, and the electronic properties of the donor-acceptor alternating polymers, the intrinsic relationship between the electronic properties of their monomers, oligomers and polymer are also explicated.In chapter 1, we introduced briefly the development of the organic conducting polymer and some conjugated polymers. The conjugated polymer with special structure has been the focus of the design of conductive polymer, and been widely used in the photonic materials. In addition, the work we do and its significance are summarized.In chapter 2, we introduced the computation methods-Density Function Theory, including basis principles and some common methods in this paper. In addition, we also introduced some important theoretical analytical tools and methods, including Nucleus-independent chemical shifts (NICS), nature bond orbital (NBO) and atoms in molecular (AIM) theory, and so on.In chapter 3, the conductivity and electronic structures of 1H-pyrrole and 6H-pyrrole [3,4-b] pyazine, as well as their oligomers and polymers are calculated by theoretical method. The electronic structure studies show that the conjugation degree of the central bond is increased with the increasing of the polymeric number. In summary, the p-Pyz (polymer of Pyz) can improve the conductivity apparently. This polymer has the narrow band gap (0.37 eV), the large HOMO and LUBO bandwidths and the small effective masses of electron, all of these can suggest that this polymer p-Pyz have potential application in transparent conductor.In chapter 4, the structures and electronic properties of oligomers and polymers involvin g 6H-Pyrrolo[3,4-b]pyrazine(PPZ), Thieno[3,4-b]pyrazine(TPZ), Furo[3,4-b]pyrazine(FPZ), co-6 H-Pyrrolo[3,4-b]pyrazine-thieno[3,4-b]pyrazine(PPZ-TPZ), co-6H-Pyrrolo[3,4-b]pyrazine-fruo[3,4-b]pyrazine(PPZ-FPZ) and co-Thieno[3,4-b]pyrazine-furo[3,4-b]pyrazine(TPZ-FPZ) are studied b y DFT method. The changes of bondlength, electron density at BCPs, NICS and WBIs are employed to examine the conjugation degree, and the results show that these values are clos ely related to conjugation degree. The band gaps of homopolymers (PPZ, TPZ and FPZ) ind icate substituent is the most important factor in reducing the band gaps. The pyrazine substit uent also can reduce the reorganizationλvalue of molecules. For co-polymer (PPZ-TPZ, P PZ-FPZ and TPZ-FPZ), intramolecular interactions of a noncovalent nature are posed to be r esponsible for the coplanarity obtained in the oligomers and the lowered band gaps of the p olymers.In chapter 5, the donor-acceptor compounds are calculated and theoretical analyzed, we use the Thieno[3,4-b]pyrazinetpz(TPZ) and Furo[3,4-b]pyrazine(FPZ) as the acceptor part resp ectively, the pyrrole(Pyr), thiophene(Thio),4H-Thieno[3,2-b]pyrrole(Tp) and 4H-Dithieno[3,2-b; 2',3'-d]pyrrole(Dtp) are used for the donor part respectively. The analysis of the HOMO-LUM O energy of monomer shows that the HOMO energy of donor part and the LUMO energy of acceptor part which we select should be close, when designing this donor-acceptor condu cting polymer, it will reduce the band gap of these donor-acceptor altering copolymers. The electronic structure studies show that with the increase of polymerization degree, the intermo lecular conjugation and electron delocalization are enhanced. The NICS analysis shows that t he charge is flowing from the donor part to the acceptor part in the molecules, and the con jugation in central section is stronger than that in the outer section. The band structure anal ysis shows that the four copolymers all have small band gap, they can be good conductive polymers.