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 (HL ¹), 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 (HL ¹-HL³), we were studied electrochemical properties of the ligands at the different pH and scan rates.