Crystal, spectroscopic and quantum mechanics studies of Schiff bases derived from 4-nitrocinnamaldehyde

Two Schiff bases, (E)-1-(4-methoxyphenyl)-N-((E)-3-(4-nitrophenyl)allylidene)methanamine (compound 1) and (E)-N-((E)-3-(4-nitrophenyl)allylidene)-2-phenylethanamine (compound 2) have been synthesized and characterized using spectroscopic methods; time of flight MS, H-1 and C-13 NMR, FT-IR, UV-VIS, photoluminescence and crystallographic methods. The structural and electronic properties of compounds 1 and 2 in the ground state were also examined using the DFT/B3LYP functional and 6-31+G(d,p) basis set, while the electronic transitions for excited state calculations were carried out using the TD-DFT/6-31+G(d,p) method. The Schiff base compounds, 1 and 2 crystallized in a monoclinic crystal system and the P2(1)/c space group. The emission spectra of the compounds are attributed to conjugated pi -bond interaction while the influence of the intra-ligand charge transfer resulted in a broad shoulder for 1 and a double emission peak for 2. The calculated transitions at 450 and 369 nm for 1 and 2 respectively are in reasonable agreement with the experimental results. The higher values of dipole moment, linear polarizability and first hyperpolarizability of 1, suggest a better optical property and better candidate for the development of nonlinear optical (NLO) materials.

Automated summary

Two Schiff base compounds were synthesized and characterized using spectroscopic methods, with compound 1 showing better optical properties and being a better candidate for the development of nonlinear optical materials. The structural and electronic properties of the compounds were examined using computational methods, and the calculated transitions were found to be in reasonable agreement with experimental results.