An extending evidence of molecular conformation on spectroscopic properties of symmetrical bis-Schiff bases

• Extending evidence was provided to clarify the conformation effect upon the spectra.
• UV spectrum is dependent on the substituents and the dihedral angle τ.
• Dihedral angle τ has a limited effect on the δC(CN) of symmetrical bis-Schiff bases.

The relationship between the molecular conformation and spectroscopic properties of symmetrical bis-Schiff bases, was explored experimentally. The synthesis, crystal structures, and spectroscopic behaviors of symmetrical bis-Schiff bases derived from 1,4-Phthalaldehyde, p-YC6H4NCHC6H4CHNC6H4p-Y (Y = OMe, Me, H, Cl, or F) were reported. The results show when the effect of distance between X or Y and the imine carbon was considered, a good correlation between the υmax or δC(CN) of symmetrical bis-Schiff bases and the substituent parameters was obtained. The correlation results indicate that for both symmetrical bis-Schiff bases derived from 1,4-Phenylenediamine and 1,4-Phthalaldehyde, the UV absorption spectrum is dependent on the substituent at the aniline ring and the dihedral angle τ, and the term sin(τ) is suitable to modify the substituent effects on the υmax. However, experimental investigations indicate that the dihedral angle τ has a limited effect on the values of δC(CN). This study provides an extending evidence of molecular conformation effects on spectroscopic properties of symmetrical bis-Schiff bases.

Dihedral angle τ displays important effects on their υmax, and sin(τ) is suitable to modify the effects.Figure optionsDownload as PowerPoint slide