Sven Otto, Norman Scholz, Thomas Behnke, Ute Resch-Genger, Katja Heinze

The unparalleled excited state potential energy landscape of the chromium(III)-based dye [1]3+ ([Cr(ddpd)2]3+; ddpd = N,N'-dimethyl-N,N'-dipyridin-2-yl-pyridin-2,6-diamine) enables a strong dual emission in the near infrared. The temperature dependence of this dual emission allows for the use of [1]3+ as an unprecedented molecular ratiometric thermometer in the 210 - 358 K temperature range in organic and in aqueous media. Incorporation of [1]3+ in biocompatible nanocarriers like 100 nm-sized polystyrene nanoparticles and solutol micelles provides nanodimensional thermometers operating under physiological conditions.