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Three series of oligomers containing functionalized imide and thiophene rings, namely the acceptor type bisthiazole imide oligomer with different length (PBTzIn , n = 1–8), the donor-acceptor type derivatives by introducing three electron donating thiophene rings into BTzI (PBTzI3Tm , m = 1–4), and derivatives by substituting the two hydrogen of center thiophene in PBTzI3Tm with fluorine (PBTzI3T-2Fm , m = 1–4), were designed based on some experimentally synthesized oligomers to clarify the roles of oligomer length, thiophene donor, and fluorine-substitution on the charge transfer properties. The charge transfer properties of these imide-functionalized thiazole-based oligomers were systematically studied using density functional theory and traditional Marcus theory in term of geometric structures, frontier molecular orbitals, ionization potentials (IP), electron affinities (EA), reorganization energies, charge transfer integrals, crystal packing models, and charge transfer mobilities. The IP/EA decreased/increased with increasing oligomer length in PBTzIn , rendering long PBTzIn oligomers showing both p- and n-type characteristic of organic semiconductors. The orbital energy level and mobility show saturation characteristics for n = 6. PBTzI8 shows high and balanced hole/electron mobility of 1.089/0.249 cm2 V−1s−1 and thus is good ambipolar semiconductor. The introduced three thiophene rings in PBTzI3Tm (m = 1–4) enhances the backbone conjugate property and reduces the hole injection barrier. Substituting thiophene H atoms with F further enhances the interaction between the non-covalent bond N...S and S...F and thus increases the molecular planarity, rendering PBTzI3T-2Fm (m = 1–4) being better semiconductor. PBTzI3T3 is ambipolar organic semiconductor with hole/electron mobility of 11.760/1.396 cm2V−1s−1, while PBTzI3T-2F3 and PBTzI3T-2F4 show better ambipolar organic semiconductor performance with much larger hole/electron mobility of 16.325/3.674 cm2V−1s−1 and 60.019/5.086 cm2V−1s−1. • Three series of oligomers containing functionalized imide and thiophen rings were designed. • Roles of oligomer length, thiophen donor, and fluorine-substitution on the charge transfer properties were clarified. • Geometric structures, frontier molecular orbitals, ionizationpotentials (IP), electron affinities (EA) were studied. • Reorganization energies, charge transfer integrals, crystal packing models, and charge transfer mobilities were predicted. • New types of n- and ambipolar semiconductors with very high mobilities were designed. [ABSTRACT FROM AUTHOR]

• Different electronic donating/accepting groups (Na, MP, MB, BN) were introduced onto the C8 position of 5-phenyl-5H-benzo[ b ]phosphindole 5-oxide(PhBPO). • Substitution effect on the structure and spectral properties was revealed according to density functional theory (DFT) calculation. • ground state geometries, orbital energy gaps, infrared (IR) spectra, UV–vis spectra, and fluorescence spectra of these PhBPO derivatives were described systematically. • These compounds possess easy-to-modify sites and are good candidates as potential functional building block. • These compounds are good fluorescence materials and substitution helps increase the fluorescence strength. The properties of phosphole-based π-conjugated compounds could be well tuned via simple chemical modification. Four π-conjugated groups with different electronic nature including naphthalen-2-yl, 4-methoxyphenyl, 4-Methyl benzoate, and 4-benzonitrile were introduced to the C8 position of 5-phenylbenzo[ b ]phosphindole 5-oxide (PhBPO) to reveal the relationship between structures and properties. Density functional theory (DFT) calculations were carried out to comparatively study the ground state geometries, orbital energy gaps, infrared (IR) spectra, UV–vis spectra, and fluorescence (FL) spectra of the five PhBPO derivatives. Good correspondences between the simulated and experimental IR and UV–vis spectral properties were found, proving the feasibility of the DFT method. The IR and Uv-vis spectra were assigned and explained in detail on the basis of the calculation results and the substituional effect of different substituents on the structure and spectral properties was revealed. The large FL oscillator strengths indicate these PhBPO derivatives are good candidates for fluorescent materials. PhBPO derivatives possess easy-to-modify sites and thus can be further utilized as functional materials. Image, graphical abstract [ABSTRACT FROM AUTHOR]