Synthesis, Crystal structure and Fluorescence properties of a Binuclear Terbium(Iii) complex of N-(2-Pyridinyl)Ketoacetamide

Abstract

A binuclear terbium(III) complex of N-(2-pyridinyl)ketoacetamide (HL) was synthesized and its crystal structure determined. Each terbium(III) binds to one N,O-bidentate HL, one O,O-bidentate L and two N,μ-O,O-tridentate bridging L ligands; the coordination polyhedron is a distorted square antiprism. The pyridine N and keto O atoms of the binucleating ligand are coordinated to each Tb with the amide O acting as a bridging atom. The adjacent [Tb₂(HL)₂L₄]²⁺ units are bridged by double C(R)NH…ONO₂…HN(R)C hydrogen bonds to form an infinite 1-D chain, and a 2-D layer structure results from a rare near face-to-face π,π-stacking interaction between the pyridine rings of the adjacent chains. The crystal structure analysis reveals that the ligands completely shield the Ln(III) ions. Excited by the absorption band at 370 nm, the Tb(III) complex displays characteristic metal-centered fluorescence while the ligand fluorescence is completely quenched, showing that efficient ligand-to-metal energy transfer (antenna effect) occurs.

Keywords:

• Binuclear terbium(III) complex
• N-(2-Pyridinyl)ketoacetamide
• Crystal structure
• Fluorescence
• π,π-Stacking interactions