Synthesis, Spectroscopic Studies, Crystal Structure and Conformation Analysis of N-(2-Fluoro-3-methoxy)-salicylaldimine

Abstract

The new Schiff base ligand N-(2-fluoro-3-methoxy)-salicylaldimine (C₁₄H₁₂NO₂F) (1) has been synthesised and studied by using, IR, ¹H NMR, ¹³C NMR, UV-visible, GC-MS techniques, X-ray structure analysis and AM1 semi-empirical quantum mechanical methods. Compound 1 crystallises in the orthorhombic space group P2₁2₁2₁ with a =12.5461(1), b =18.0495(1), c =5.2615(1) Å . An intramolecular hydrogen bond connects O1 and N1 [2.575(2)Å], the hydrogen atom being bonded essentially to the oxygen atom. Minimum energy conformations were calculated as a function of two torsion angles θ₁ (C6-C7-C8-N1) and θ₂ (C7-C8-N1-C9), varied every 10 degrees. The optimized geometry of the crystal structure corresponding to the non-planar conformation is the most stable conformation in all calculations. The results strongly indicate that the minimum energy conformation is primarily determined by hydrogen-hydrogen repulsions between the ortho-hydrogen atoms on the aldehyde rings. Complementary IR, ¹H NMR and UV measurements in solution and in the solid state were carried out.