Synthesis, spectroscopic studies, crystal structure and conformation analysis of N-(2-fluoro-3-methoxy)-salicylaldimine

The new Schiff base ligand N-(2-fluoro-3-methoxy)-salicylaldimine (C14H12NO2F) (1) has been synthesised and studied by using, IR, H-1 NMR, C-13 NMR, UV-visible, GGMS techniques, X-ray structure analysis and AM1 semi-empirical quantum mechanical methods. Compound I crystallises in the orthorhombic space group P2(1)2(1)2(1) with a = 12.5461(1), b = 18.0495(1), c = 5.2615(1) Angstrom. An intramolecular hydrogen bond connects O1 and N1 [2.575(2) Angstrom], the hydrogen atom being bonded essentially to the oxygen atom. Minimum energy conformations were calculated as a function of two torsion angles theta(1) (C6-C7-C8-N1) and theta(2) (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, H-1 NMR and UV measurements in solution and in the solid state were carried out.