Thianthrene-based heavy metal-free oxygen analytes exhibiting room temperature phosphorescence and high sensitivity for low oxygen concentration

Abstract

In this work, we present two very sensitive new heavy metal-free thianthrene-based oxygen analytes. Experimental results in combination with theoretical calculations, confirm that both the compounds display room-temperature phosphorescence, with a significant difference in intensity observed in air and oxygen-free environments. The compounds show long emission lifetimes reaching up to 27.08 ms. This indicates the involvement of oxygen-sensitive triplet emission which occur due to intersystem crossing. The compounds show record-high Stern-Volmer constants, reaching 1.57 × 10⁻² ppm⁻¹. These properties suggest that 2-(pentan-3-yl)-6-(anthracen-1-yl)-1H-benzo[de]isoquinolin-1,3(2 H)-dione and 4-(thianthren-1-yl)benzonitrile are perfect candidates for metal-free oxygen sensors with one of the highest sensitivity detection at low oxygen concentrations reported so far.