Solvent free mechanochemical synthesis of Eu3+ complex and its luminescent sensing of trace water and temperature

Abstract

Mechanochemical transduction processes which translate macroscopic forces into chemical reactions are a design method to synthesize new advanced functional materials. Herein we present a simple, facile and solventless method for the formation of a Eu³⁺ coordination complex by simply grinding 4′,4′′′′-(1,4-phenylene)bis(2,2′:6′,2′′-terpyridine) and EuCl₃·6H₂O in a mortar for a short time. The resulting complex exhibits outstanding stimuli-responsive emissions for temperature and trace water in organic solvents. The ratiometric luminescence determination method based on the emission intensity ratio of two independent transitions of Eu³⁺ provides a way to rapidly detect traces of water (0.1–5% v/v) in various organic solvents through the luminescence quenching mechanism. Furthermore, by virtue of the temperature-dependent luminescent behavior, the complex allows for the design of a thermometer with an excellent linear response to temperature over a wide range, from 80 to 420 K with a high relative sensitivity of 0.52% per K at 300 K and an unprecedented high sensitivity of 10.26% per K at 420 K. The dynamically reversible complexation between Eu³⁺ and the ligand facilitates its application as a smart material.