The effects of π-spacer on electronic properties, charge transfer, and chemical reactivity in D-A′-π-A configured molecules: Computational approach

In this work, a systematic modification of the π-spacer was carried out to evaluate its influence on molecular geometry, electronic structure, charge transport properties, and global chemical reactivity descriptors in a series of D-A′-π-A organic molecules (M1–M4). Density functional theory was employed to analyze key parameters including dihedral angles, highest occupied molecular orbital–lowest unoccupied molecular orbital energies, natural bond orbital interactions, reorganization energies, ionization potential, electron affinity, chemical hardness, chemical potential, electronegativity, and electrophilicity index. The results reveal that M4 demonstrates the most favorable combination of properties, exhibiting the energy gap, reorganization energy, ionization potential, and chemical hardness of 1.4896, 0.4580, 4.8300, and 0.7127 eV, respectively. M4 also shows the highest chemical potential, electronegativity, and electrophilicity index of −4.1174, 4.1174, and 11.8938 eV, respectively. These results demonstrate the critical role of π-spacer engineering in adjusting the electronic behavior of D-A′-π-A systems and suggest that M4 is a promising candidate for high-performance organic semiconducting and optoelectronic uses.