1,3-Diynes as Precursors for the Synthesis of Triazene- and Diethylaniline-Bearing Push-Pull NLOphores

Within the scope of this study, a total of eight new NLOphores of the D-pi-A-pi-D type have been synthesized. This was achieved by applying click-type [2+2] cycloaddition-retroelectrocyclization reactions of unsymmetrical 1,3-diynes with well-known electron-deficient alkenes, TCNE, and TCNQ. Furthermore, essential insights into the optical properties of the synthesized NLOphores were obtained from comparisons with four model compounds synthesized separately within this study. The thermal stability of the NLOphores was assessed through thermal gravimetric analysis (TGA). NLOphores synthesized using two distinct electron-deficient alkenes exhibit low energy absorption bands covering most of the visible region with lambda max values ranging from 466 nm to 723 nm. Theoretical studies, including time-dependent density functional theory (TD-DFT) investigations, frontier orbital visualizations, and electrostatic potential maps, have been utilized to further investigate the intramolecular charge transfer properties of chromophores. The NLO responses of the chromophores were determined through DFT calculations. It is worth noting that the average polarizability and first hyperpolarizability values (alpha(tot)=106.392-159.709x10-24 esu; beta(tot)=387.552-417.359x10-30 esu) obtained from these calculations show significant promise compared to literature data. Two distinct families of D-pi-A-pi-D-type NLOphores were synthesized via [2+2] cycloaddition-retroelectrocyclization reactions. These compounds, featuring low-energy ICT bands (lambda max: 466-723 nm) exhibit significant potential for optical applications. Computational studies revealed valuable insights, showing good average polarizability (154.377-159.709x10-24 esu) and first hyperpolarizability (387.552-417.359x10-30 esu) values. image