The effect of donors–acceptors on the charge transfer properties and tuning of emitting color for thiophene, pyrimidine and oligoacene based compounds

Abstract

We have designed 4,6-di(thiophen-2-yl)pyrimidine (DTP) derivatives with the aim to tune the electronic, optical and charge transport properties then predicted their properties of interests by applying the density functional theory and time dependent density functional theory. The anthracene has been substituted at both ends of the DTP with the aim to enhance the properties. The intra-molecular charge transfer (ICT) has been improved by substituting the electron-donating groups (EDGs) at one end while electron-withdrawing groups (EWDGs) at other end. We have conducted theoretical studies on the effect of EDGs (OH and OCH3), EWDGs (F, Cl, COOH, CN, NO2) and π-backbone on electronic, photophysical (absorption and emission), and charge transfer properties (ionization potentials, electron affinities and reorganization energies). The structure–properties relationship has been discussed. The ground (S0) and excited state (S1) state geometries have been optimized using DFT/B3LYP/6-31G** and TD-B3LYP/6-31G** level of theories, respectively. The comprehensible ICT has been observed from highest occupied molecular orbitals to lowest unoccupied molecular orbitals in new designed derivatives. The decreased injection barrier is revealing that new designed derivatives would be better charge transport materials than the parent molecule. Moreover, smaller hole reorganization energies of DTPBA_OH_Cl, and DTPBA_OH_F are revealing that these might be better/comparable to pentacene. The computed electron reorganization energies of new designed materials are smaller than that of well known and commonly used electron transport material (mer-Alq3) illuminating that the electron mobility of all the new designed derivatives might be better/comparable with mer-Alq3.