Four-, five- and six-coordinated transition metal complexes based on naphthalimide Schiff base ligands: Synthesis, crystal structure and properties

摘要

Two bidentate Schiff base ligands (HL1=N-n-butyl-4-[(E)-2-(((2-aminoethyl)imino)methyl)phenol]-1,8-naphthalimide; and HL2=N-n-butyl-4-[(E)-2-(((2-aminoethyl)imino)methyl)-6-methoxyphenol]-1,8-naphthalimide) with their metal complexes [Cu(L-1)(2)] (1), [Zn(L-1)(2)(Py)](2)H2O (2) and [Ni(L-2)(2)(DMF)(2)] (3) have been synthesized and characterized. Single-crystal X-ray structure analysis reveals that complex 1 has a four-coordinated square geometry, while complex 2 is a five-coordinated square pyramidal structure and complex 3 is a distorted six-coordinated octahedral structure. Cyclic voltammograms of 1 indicate an irreversible Cu2+/Cu+ couple. In vitro antioxidant activity assay demonstrates that the ligands and the two complexes 1 and 3 display high scavenging activity against hydroxyl (HO center dot) and superoxide (O-2(-center dot)) radicals. Moreover, the fluorescence properties of the ligands and complexes 1-3 were studied in the solid state. Metal-mediated enhancement is observed in 2, whereas metal-mediated fluorescence quenching occurs with 1 and 3.