Solvent effects on the absorption and emission of [Re(R₂bpy)(CO)₃X] complexes and their sensitivity to CO₂ in solution

The solvatochromic properties of a series of rhenium(I) organometallic compounds have been studied. For this goal, their absorption and emission spectra have been undertaken in a wide range of solvents with different polarity. Kamlet-Taft multiparametric equation and DFT calculations have been used to explain the solvent effect in the MLCT transition of the [Re(R₂bpy)(CO)₃X] (R = H, t-Bu; X = Cl^-, OTf^-, C{triple bond, long}CpyRe(R₂bpy)(CO)₃) complexes. Polarity/polarizability is observed to play an important role in the solvatochromism of the compounds. In spite of this, in general, the splitting of the solvent contributions shows that this effect is not the solely responsible for the observed variations in the energy of this transition and solvent coordination also affects the observed solvatochromism. Compounds with a labile position in the coordination sphere of the metal atom have also been explored in sensorial applications for CO₂ detection in solution by means of reversible changes in the recorded emission spectra intensity. The solvent effect on the sensing process is discussed.