Colour/luminescence changes of transition metal complexes induced by gaseous small molecules for monitoring reaction progress and environmental changes

Abstract

Transition metal complexes act as monitoring devices for reaction progress and environmental changes through their color/luminescence changes. In this paper, we focus on colour/luminescence changes induced by gaseous small molecules in the environment. The gradual decrease in O₂ content in solution can be monitored by the luminescence enhancement of an Ir(III) complex in dimethyl sulfoxide during photoirradiation. CO₂ in air can be captured by a Pt(II) complex in basic aqueous solution, resulting in a colour change from yellow to red to blue-green due to higher degree aggregate formation. Moisture in air induces colour/luminescence changes in Ru(II) and Ir(III) complex salts due to the sorption of H₂O into hydrophilic channels in the crystal. Volatile organic compound vapours such as CHCl₃ and CH₂Cl₂ change the purple colour of Pt(II) complex crystals to red and blue, respectively. The purple crystal can adsorb two CHCl₃ molecules under ambient conditions but only one CH₂Cl₂ molecule.