Theoretical Investigation Of Structures And Electronic Spectra Of Dithienothiophene And Its Derivatives

β-oligothiophenes are one of organic materials used to model the conjugatedπ-electron systems,which have been widely applied as active components in the electronic or optical devices.The relevant examples include the increase of critical temperatures in organic superconductors,as well as improvement of mobility in organic field effect transistors(OFETs).In recent years,dithieno[2,3-b:3',2'-d]thiophene(s-DTT) has attracted much attention,as the building block for higher homologues of helicenes.Also,its derivatives are attractive as models of the conjugatedπ-systems.Recently,our group synthesized a series of s-DTT derivatives.To interpret the relationship between structure and properties,we performed extensively theoretical investigations on s-DTT and its derivatives.See below in detail:In the first chapter,we introduced the theoretical methods,research background.In the second and third chapters,we carried out density functional theory(DFT) studies on s-DTT and a set of its derivatives.The equilibrium geometries and frontier orbitals energies of these species were illuminated.The studies indicate that the involvement of the substitutional groups in the annelated trimer will increase the conjugated properties of the delocalizedπ-electron systems and give rise to the red-shift of the absorption wavelengths.In addition,the selected vertical excitation energies calculated by the time-dependent density functional theory(TD-DFT) approach are in good agreement with the available experimental results.