Thermo‐Chromium: A Contactless Optical Molecular Thermometer

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 region. The temperature dependence of this dual emission allows the use of [1] 3+ as an unprecedented molecular ratiometric thermometer in the 210–373 K temperature range in organic and in aqueous media. Incorporation of [1] 3+ in biocompatible nanocarriers, such as 100 nm‐sized polystyrene nanoparticles and solutol micelles, provides nanodimensional thermometers operating under physiological conditions.