New salicylaldehyde azine esters: Structural, aggregation induced fluorescence, electrochemical and theoretical studies

The establishment of high-tech products relying on organic optoelectronics is focused towards latest strategies for improving the processability and performance. In the present study, two esters of salicylaldehyde azine SAE-F and SAE-NF were synthesized and their structural characterization were performed using FT-IR, ¹H and ¹³C NMR, UV–visible spectroscopy, mass spectrometry and single crystal-XRD technique. The bathochromic shift observed in luminescence measurements from solution to aggregate/solid state, solvent based fluorescence studies, SEM and DLS measurements confirmed the fluorescence emission from the SAE-F aggregates. The DSC data indicated the phase transitions, and the TGA measurements confirmed the thermal stability of SAE-F to withstand temperatures up to 225 °C. The morphological characterization revealed formation of homogeneous pin-hole free uniform films of SAE[sbnd]F. Cyclic voltammetry was used to estimate the HOMO and LUMO energy levels which were found to be −5.46 eV and −3.05 eV respectively with a band gap of 2.41 eV. The p-type semi-conductivity of SAE-F was established using hot probe technique. The dielectric measurements were carried out to measure dielectric constant and ac conductivity at different frequency ranges. The electronic data obtained based on Density Functional Theory calculations were in conformity with the experimental results. Successful fabrication of a diode and the recorded current-voltage characteristics clearly advocated SAE-F to be an excellent candidate for electro-optical devices.