Structural characterization and electrochemical properties of novel salicylidene phosphonate derivatives

In this study, three novel salicylidene phosphonate ligands, diethyl (4-{[(1E)-(2-hydroxyphenyl)methylidene]amino}benzyl)phosphonate (HL1), diethyl (4-{[(1E)-(2-hydroxy-3-methoxyphenyl)methylidene]amino}benzyl)phosphonate (HL2) and diethyl (4-{[(1E)-(2,4-dihydroxyphenyl)methylidene]amino}benzyl)phosphonate (HL3) were synthesized and characterized by the analytical and spectroscopic techniques. We obtained their single crystals from the ethanolic solution. There are intramolecular phenol-imine hydrogen bonds in all three compounds between O1 and N1 atoms. The ligand HL3 contains a second phenol group and this is makes an intermolecular hydrogen bond with the phosphine oxide of a neighbouring molecule O2–O3 (under symmetry operation −x, 0.5 + y, 0.5 − z). In order to investigate the redox behaviours of the salicylidene phosphonate ligands (HL1–HL3), we were studied electrochemical properties of the ligands at the different pH and scan rates.