Ferrocene conjugated donor-π-acceptor malononitrile dimer: Synthesis, theoretical calculations, electrochemical, optical and nonlinear optical studies

Abstract

Abstract The donor-π-acceptor ferrocene conjugated malononitrile dimer [C5H5–Fe–C5H4–C(H) C(CN)–C(NH2) = C(CN)2] (1) has been synthesized and characterized with the aid of analytical and spectroscopic techniques [FT-IR, GC-Mass, 1H and 13C NMR]. The thermal stability of the compound 1 was investigated using thermogravimetric analysis (TGA) and differential thermal analysis (DTA), exhibit the compound is stable up to 180 °C. The photophysical properties were performed by UV–visible and fluorescence spectroscopic methods and the compound 1 exhibited weak fluorescence emission. In addition, the optical band gap (Eg) was calculated using diffused reflectance spectroscopic technique which shows the band gap value of Eg = 3.6 eV. The redox wave of the compound 1 was determined by cyclic voltammetry, revealed that one electron transfer ability of the ferrocene to ferrocenium ion. The experimentally observed HOMO and LUMO values are good agreement with the theoretical calculation by DFT-M06 method using 6–31 + G** as basis set. The solvatochromic studies of compound 1 shows negative solvatochromism due to the high ground state polarizability in presence of cyano acceptors. Further, the nonlinear optical properties were investigated by Q-switched Nd-YAG laser and second harmonic generation efficiency (SHG) using para-nitroaniline (p-NA) as a standard and the results of SHG efficiency is 0.35 times comparable with p-NA.