A thiophene-based bisazomethine and its inclusion complex with permethylated β-cyclodextrin: Exploring structural characteristics and computational chemistry models

The condensation reaction of 5-bromo-2-thiophenecarboxaldehyde (1) with p-phenylene diamine (2) in 2:1 M ratio yielded the thiophene-based bisazomethine with bromine ends (3). The threading of 3 into the permethylated β-cyclodextrin (TMe-βCD) cavity allowed the formation of a new 3∙TMe-βCD inclusion complex. Spectral techniques like NMR, FTIR, XRD and ESI-MS were involved to assess the structural characteristics of 3 and 3∙TMe-βCD. The X-ray diffraction, DFT computations and molecular docking simulations were used to support the experimental findings. The surface morphology as well the ability to form stable monolayers at the air-water interface was further explored in detail. According to the molecular docking simulation, the 3∙TMe-βCD inclusion complex was stabilized through hydrophobic contacts and exhibited better surface parameters and thermal properties. With regard to the optical behavior, the 3∙TMe-βCD exhibited a higher green fluorescence with two decay times of 0.48 ns (87.40 %) and 3.48 ns (12.60 %). The surface pressure isotherms revealed the tendency of 3∙TMe-βCD to form highly organized monolayers from dilute DCM solution at the air-water interface. The Brewster angle microscopy (BAM) investigations also demonstrated a better homogeneity of the 3∙TMe-βCD layers than those of the reference 3. The comparative investigation of the photophysical and electrochemical properties highlighted the superiority of the encapsulated 3∙TMe-βCD compound that are of fundamental importance in organic electronics.