Synthesis, structure, photo-responsive properties of 4-(2-fluorobenzylideneamino)antipyrine: a combined experimental and theoretical study.

In this work, 4-(2-fluorobenzylideneamino)antipyrine (FBIAAP) was synthesized and characterized by elemental analysis, XRD, FT-IR, FT-Raman and UV-Vis techniques as well as density functional calculations. The studied molecule adopts a trans configuration about the imine CN bond, and adjacent molecules are linked through two kinds of weak hydrogen bonds to form supramolecular layered structures along the ab plane. Vibrational spectral analyses show that the benzene moiety directly attached to the central pyrazoline shows good vibrational isolation from the other moiety of pyrazole-imino-benzene presenting good vibrational resonances. UV-vis absorption bands mainly belong to n→π and π→π according to the electron transfer orbital assignments for the electron absorption spectrum of FBIAAP. The first-order hyperpolarizability of FBIAAP is 44.9 times that of urea theoretically. In addition, the thermodynamic properties were also obtained theoretically from the harmonic frequencies of the optimized structure.