Single-component solid state white-light emission and photoluminescence color tuning of a Cd() complex and its application as a luminescence thermometer

A single-component solid white-light emitter, the Cd( ii ) complex Cd 2 (Sal) 4 (PyNH 2 ) 2 ( 1 ) (where Sal = 2-formylphenolato, PyNH 2 = 4-aminopyridine), was synthesized in a simple procedure. Crystals of 1 display almost pure white-light emission upon excitation in a wide range from 300 to 400 nm. The white-light emission of 1 is composed of complementary blue and yellow components in an appropriate ratio, which belong to the ligand to metal (PyNH 2 to Cd( ii )) charge transfer (LMCT) and the π-π* transition of Sal, respectively. Grinding crystals of 1 led to the transformation into the amorphous state along with the white-cyan-green emission color change and a color change from orange to yellow. The color of amorphous 1 could return to orange when heated. The emission color of amorphous 1 undergoes a gradual change from green to yellow when heated to 180 °C without a change in the molecular structure, and the corresponding color temperature exhibits a linear relationship with the heating temperature in a wide range (323-453 K), which makes amorphous 1 a reliable luminescence thermometer based on the photoemission energy. A single-component white-light emitting Cd( ii ) complex exhibits tunable photoluminescence and acts as a novel luminescence thermometer based on the correlation between temperature and color temperature.