Tetraphenylsilane-based oligo(azomethine)s containing 3,4-ethylenedioxythiophene units along their backbone: Optical, electronic, thermal properties and computational simulations

A series of three new oligo-poly(azomethine)s (o-PAzMs) were successfully synthesized, incorporating tetraphenylsilane (TPS) and 3,4-ethylenedioxythiophene (EDOT) moieties with M_n and M_w between 3.9 and 5.4 kDa and 8.3–11.6 kDa, respectively. The silylated o-PAzMs were highly soluble in low-boiling point solvents such as CHCl₃, THF, and CH₂Cl₂. All three materials are highly thermally stable, with onset temperatures of degradation of at least 250 °C and with TDT_10% between 340 and 460 °C. The glass transition temperature values agree with the flexibility of the repetitive units and showed values between 125 and 155 °C. The absorption and emission of the o-PAzMs were observed in the blue-violet UV–vis region (350–550 nm) with moderate Stokes shifts (48–71 nm). The oligomers are π-conjugated wide-band gap materials (2.83–2.73 eV), where the high electronic transitions would be associated with disruption of π-conjugation, which is promoted by the TPS core and (d-p)π orbital interactions. This disruption controls the effect from the EDOT unit rich donor on HOMO (−5.79 eV to −5.71 eV) and LUMO (−2.98 eV to −2.89 eV) energy values. Furthermore, DFT and TDDFT calculations were performed to theoretically characterize the observed UV–Vis transitions and frontier molecular orbitals (MOs) energies.