Tetraphenylsilane-containing oligo(azomethines)s based on asymmetric biaryl dialdehydes. Computational calculations and properties

A new aromatic diamine containing tetraphenylsilane core was synthesized and subsequently reacted with asymmetric biaryl dialdehydes to yield a series of oligo (azomethine)s (o-PAZs) with a degree of polymerization of three and a molecular weight (M_w) ranging from 3.6 to 3.8 kDa. The samples showed high solubility in chloroform, tetrahydrofuran and in DMF after heating, results which were correlated with minimum energy conformations via DFT calculations on the respective trimeric structures. Due to the high aromatic content, o-PAZs exhibited exceptional thermal stability, with T_5% values surpassing 320 °C. Furthermore, the materials exhibited T_g values ranging from 78 to 92 °C, which was attributed to the alkoxy chains, present in both the diamine and the dialdehydes. These oligomers exhibited similar UV–visible absorption behavior, with λ_max^abs occurring between 348 and 375 nm. Slight variations in the emission were observed due to the distinct emissive units. Their optical bandgap energies ranged from 2.99 eV to 2.76 eV, classifying o-PAZs as wide-bandgap materials. The samples exhibited relatively high energy levels for HOMO (−5.74 to −5.61 eV) and LUMO (−3.24 to −2.85 eV). These electronic properties can be attributed to the electron-donating effect of the alkoxy side chains, which modulate electronic charge delocalization along the oligomer backbone.