Lanthanide radii controlled one-dimensional polymer and dinuclear complexes and their fluorescent properties

Abstract

A bi-phosphonate ligand tetraethyl-(2,3,5,6-tetramethyl-1,4-phenylene) bis(methylene)diphosphonate has been designed and synthesized. The bi-phosphonate as a bridging ligand reacts with lanthanide nitrates forming four different types of 1D coordination complexes: ribbon polymer (type I), semi-ribbon polymer (type II), zigzag polymer (type III), and dinuclear-triligand short chain (type IV), which changed according to the decrease of the radius of the lanthanide. They have been characterized by IR spectroscopy, elemental analysis, and X-ray diffraction spectroscopy. The photophysical properties of Sm³⁺, Eu³⁺, Tb³⁺ and Dy³⁺ complexes at room temperature were also investigated. They exhibit strong fluorescence by excitation of the Ln³⁺ ion absorption bands and the quantum yield values of Eu³⁺ and Tb³⁺ complexes are no less than 20%.