Design of oxygen sensors based on quenching of luminescent metal complexes : effect of ligand size on heterogeneity

A detailed study of the oxygen quenching for luminescent ReL(CO) 3 CNR + (L=α-diimine and R =alkyl) in silicone polymers shows a high degree of heterogeneity, which depends on the size of L but not of R. All quenching is dynamic with little or no static quenching. Microheterogeneity is important in the nonlinear quenching responses. Quenching data are well described by a two-site model, although detailed lifetime measurements suggest a more complex underlying system. The appearance of two dominant sites indicates that the complex can bind in sites that are either readily or poorly quenched by oxygen. The variations of this ratio with the size of L suggests that there is a distribution of binding site sizes and that binding of L in these sites is necessary to protect the complex from quenching