Investigating the effect of acene-fusion and trifluoroacetyl substitution on the electronic and charge transport properties by density functional theory

We designed novel derivatives of 4,6-di(thiophen-2-yl)pyrimidine (DTP). Two benchmark strategies including mesomerically deactivating group, as well as the extension of π-conjugation bridge (acene-fusion) have been employed to enhance the electrical and charge transport properties. The density functional theory (DFT) and time dependent DFT methods have been used to get optimized geometries in ground and first excited state, respectively. The structural properties (geometric parameters), electronic properties (frontier molecular orbitals; highest occupied and lowest unoccupied molecular orbitals), photophysical properties (absorption, fluorescence and phosphorescence), and important charge transport properties are discussed to establish a molecular level structure–property relationship among these derivatives. Our calculated electronic spectra i.e., absorption, fluorescence and phosphorescence have been found in good semi-quantitative agreement with available experimental data. All the newly designed derivatives displayed significantly improved electron injection ability than those of the parent molecule. The values of reorganization energy and transfer integral elucidate that DTP is a potential hole transport material. Based on our present investigation, it is expected that the naphtho and anthra derivatives of DTP are better hole transporters than those of some well-known charge transporter materials like naphthalene, anthracene, tetracene and pentacene.