Exploration of key electronic properties and optical nonlinearity of diamine based Schiff bases: Spectroscopic characterization and DFT study

Abstract

The study focuses on the synthesis and theoretical investigation of a series of newly synthesized diamine-based Schiff bases. Structural confirmation of the synthesized Schiff bases was achieved through various spectroscopic techniques. DFT calculations, utilizing the M06/6311G (d, p) functional, were conducted to assess NLO characteristics. The broader absorption spectrum (444.0 nm) and a smaller bandgap (4.4 eV) were observed for compound:1E,1′E)-N,N'-(1,4-phenylene)bis(1-(4-nitrophenyl)methanimine compared to the other synthesized compounds. The NBOs results provided insight into the hyperconjugative phenomenon that contributes to the stability of entitled compounds. Among all the examined compounds, 1E,1′E)-N,N'-(1,4-phenylene)bis(1-(4-nitrophenyl)methanimine exhibited the highest value (3.7 × 10−29esu) for first hyperpolarizability (βtot). Moreover, the calculated first hyperpolarizability for the newly synthesized diamine-based compounds is greater than standard para-nitroaniline. Above findings ascertained the potential of synthesized compounds for advanced applications in high-tech NLO technologies.