Is dual emission of copper subgroup d10-metal complexes a necessary and sufficient condition for ratiometric luminescence thermometry?

Transition metal complexes of copper subgroup metals are actively studied objects for temperature sensors. Their luminescence arising from the ³ILCT, ³MLCT or ³CC excited states is characterized by emission in all ranges of visible spectra and high quantum yields. Due to the ability of the complexes to emit in a dual band mode, these complexes are attractive for the temperature sensing in the ratiometric mode. Dual emission of complexes is usually susceptible of the irregular changes in intensity of two emission bands during the temperature changes. This is an important and necessary property for the utilization of phosphors as ratiometric thermometers. The structures and emission properties of gold(i) and copper(i) complexes are considered with the aim to demonstrate the possibility to apply such complexes as ratiometric molecular luminescent thermometers for the remote control of the object’s temperature.