Ratiometric and Colorimetric Optical Thermometers Using Emissive Dimeric and Trimeric {[Au(SCN)2]−}n Moieties Generated in d–f Heterometallic Assemblies

Abstract

AbstractGold complexes can generate excimers ([Au2]→[Au2]*) and exciplexes ([Au3]→[Au3]*) with light excitation. Four GdIII and YIII complexes were assembled with dimeric {[Au(SCN)2]−}2 and trimeric {[Au(SCN)2]−}3 bis(thiocyanato)gold(I) counterions. The vibrational signature associated with the Au⋅⋅⋅Au vibrational mode was probed with ultralow frequency (ULF) Raman spectroscopy as a function of temperature. Emission spectroscopy was used to explore photophysical properties. Two broad features in the high‐ and low‐energy regions were associated with the fluorescence and phosphorescence of the gold entities, respectively. Temperature‐dependent luminescence measurements showed that the emission color can be tuned from blue to green via cyan and white. Hence, these complexes can act as colorimetric thermometers. Additionally, a ratiometric thermal sensing ability was incorporated with high sensitivity up to 5 % K−1 in the cryogenic temperature range.