Tunable electron and spin transfer from ionized polythiophene oligomers encapsulated in cycling hydrocarbons: A combined DFT and EPR approach

The structural, electronic, and magnetic properties of thiophene oligomer ions, which possess polarons excited on their main axis and are encapsulated within polyaromatic cyclic hydrocarbons, were investigated using density functional theory and electron paramagnetic resonance methods. Charge and spin densities, analyzed using Mulliken and Löwdin population analyses, reveal how cyclic rings locally affect the effective parameters of the dual organic π-systems. The energy gap of these composites depends on their structure and the reorientation of the polaron spin in a magnetic field and was identified as a key feature to tune electronic and magnetic properties. The appearance of equidistant peaks in population and energy dependencies was explained in terms of the concept of magic numbers, which are linked to symmetrical and conjugated clusters. Anisotropic hyperfine coupling and g-factor eigenvalues were shown to depend on the ionic charge and spin orientation in a magnetic field, as well as on the structural properties of the surrounding cyclic belt. Separate intermolecular transfer of electronic and spin clouds to the surrounding subsystem could potentially be used for independent control of the corresponding processes in all-organic molecular devices. This could provide a foundation for designing electronic and spintronic components with independently controlled charge and spin parameters.