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We designed six 4,6-di(pentacenothiophene-2-yl)pyrimidine molecules with excellent charge transport properties. The optimization of ground-state geometries with B3LYP/6-31G** level is adopted with the help of first-principle investigations. The bridge elongation strategy was employed to strengthen intra-molecular charge transfer. The time-dependent density functional theory (TDDFT) was employed for the measurement of absorption spectra (λabs). The λabs, energy gaps (Egaps), frontier molecular orbitals (FMOs) energies, electron injection, ionization energy (IE), electron affinity (EA) along with reorganization energy (λ) values were computed. The substitution of long-chain polyacene cores as well as thiophene enhanced the EA, reduces hole/electron λ along with their IE. The λ(h), and λ(e), were compared with hole and electron transfer within mostly used compounds, like pentacene and tris(8-hydroxyquinolinato)aluminum (mer-Alq3), respectively. It is anticipated that novel designed compounds may be better to be used for hole transfer (as pentacene) and electron transfer (as mer-Alq3) compounds. These derivatives would act as productive materials that can be employed as p- and n-type semiconductors. The elongation of oligothiophene and acene cores act as excellent hole transfer materials that may be better than frequently used p-type reference compounds. These designed derivative also showed lower λ (e) values exhibited that these may be best/comparable with commonly used n-type mer-Alq3. [ABSTRACT FROM AUTHOR]

Charge transport and electronic character of fluorophore chalcogenides 4,4-Difluoro-8-(-XC4H3)-4-bora-3a,4a-diaza-s-indacene (X = O, S, Se) (BODIPY) derivatives were examined at the molecular level. The effect of chalcogenides was investigated on the transfer integrals, electron affinity (EA), frontier molecular orbitals (FMO), ionisation energy (IE), intrinsic mobility along with reorganisation energies. The ring dissimilarities within 4,4-difluoro-8-(-XC4H3)-4-bora-3a,4a-diaza-s-indacene (X = O, 2-/3-furyl (Comp1/Comp4)); (X = S, 2-/3-thienyl (Comp2/Comp4)) and (X = Se, 2-/3-selenenyl (Comp3/Comp6)) were compared systematically. Among BODIPY chalcogenides derivatives, 2-furyl substitution is more beneficial compared with 2-thienyl, 2-selenenyl and 3-furyl as the prior moiety significantly increases intrinsic hole mobility. The –S or –Se substitution at 2- or 3- position in place of –O at equivalent position reduces the structural polarisation from neutral to cation resulting in reduced hole reorganisation energies. The doping of –S or –Se at 2-position decreases the hole transfer integral in comparison to 2-furyl-substituted derivative. The effect of chalcogen atoms on 2- or 3- position is not so significant on the HOMO/LUMO energy levels. It is expected that –O doping at 2-position in furyl is supporting p-type charge transport channel. These results demonstrated that the studied BODIPY derivatives would be efficient hole transfer materials to be used in organic semiconductor devices. [ABSTRACT FROM AUTHOR]