1. A Triarylboron-Based Fluorescent Thermometer:
Angew. Chem. Int. Ed. 2011, 50, 8072 –8076
DOI: /anie
Literature seminar
A Triarylboron-Based Fluorescent Thermometer:
Sensitive Over a Wide Temperature Range
Jiao Feng, Kaijun Tian, Dehui Hu, Shuangqing Wang, Shayu Li,* Yi Zeng, Yi Li,* and Guoqiang Yang*
Beijing National Laboratory for Molecular Sciences, Key laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences
Yuna Kim

2. Introduction A challenge to traditional thermometers
- in situ large-area or gradient temperature measurements with high spatial resolution
- required in marine research, underground geochemistry, wind tunnels, and automobile and aircraft industries
Luminescence-based temperature sensors
- fast response, high spatial resolution, and safety of remote handling
- luminescent materials based on phosphors, dyes, or metal–ligand complexes; high and stable quantum yield required
temperature-dependant luminescence intensity and/or decay time of these compounds
- intensity ratio of two emissive compounds

3. twisted intramolecular charge transfer (TICT) compounds
- total luminescence intensity; maintenance or even an enhancement from lower temperature to room temperature
- luminescence colorimetric change; shift of the thermal equilibrium between local excited state emission (LE) and the TICT excited state emission.
thermosensitive molecule design
combining the advantages of TICT compounds with two reverse luminescence intensity changes, and arylboron compounds with high luminescence.

4. Materials A luminescent pyrene-containing triarylboron molecule DPTB
1) intramolecular charge-transfer excited state
electron-deficient boron atom / pyrene (Py) group(e- donor)
2) large steric hindrance from compact Py–B–Py structure
3) Substituents; avoiding radiationless decay
facilitating the high luminescence quantum yield
sterically bulky substituent 2,4,6-triisopropylphenyl (tipp) group; stabilizing boron compound

5. Luminescence color and Accuracy
For the thermometer application…
Luminescence color and Accuracy
dynamic equilibrium
the population of the two distinct excited-state conformations.
evaluation of the reversibility
Heating the system
LE state
hypsochromic luminescence.
Cooling the system
The lower-energy TICT excited state
bathochromic shift
isothermal test

6. Results and discussion
λmax T
a) Absorption and b) corrected emission spectra of DPTB recorded between 50 and 100oC (excitation wavelength 410 nm).
Solvent; 2-methoxyethyl ether (MOE)

7. Results and discussion
The normalized emission spectra of DPTB at 20℃ in THF upon the addition of 0–1.0 equiv. of TBAF.
Binding of fluoride ion to the boron center;
CT process interruption-> activating LE emission
The normalized emission spectra of DPTB in liquid and rigid media.
Intramolecular rotation(Py twisting) at TICT
High viscosity low polarity medium hinders TICT state formation
->No notable FL color change!

8. Results and discussion
wavelength shift per degree centigrade ;
0.30 nm
w/ FL spectrometer, Accuracy; <1oC
w/ CCD cam, Accuracy; ~2oC
a) Temperature dependence of maximum emission wavelength of DPTB. b) *CIE chromaticity diagram showing the temperature dependence of the (x, y) color coordinates of DPTB.
*Commission Internationale de LEclairage (CIE) 1931 coordinates.

9. 100°C before and after 3 hours heating
reversibility;
100°C in 30 cycles
The edge roughness of the DPTB–MOE system ;
~ 30–40 µm
isothermal test
a) Photographs of fluorescence at different temperatures (oC) and the gradient fluorescence of DPTB solution in a quartz tube (central). b) The characters A and C were written at low temperature with DPTB solution in a polyvinyl chloride (PVC)/polypropylene (PP) sandwich structure.
100°C before and after 3 hours heating

10. Conclusion
A novel luminescent thermometer has been developed by using a triarylboron compound, which has a high luminescence quantum yield over a wide temperature
range and exhibits temperature-dependant luminescence.
This thermometer can be applied over a temperature range of 50 to +100 oC with high stability and reversibility. By using this thermometer, the luminescence spectra or the luminescence color can be correlated to the temperature values. The accuracy of former is better than 1oC, and the latter can be observed directly by naked eye or camera, thus facilitating in situ large-area or gradient temperature measurements
with the accuracy of 2oC.
The liquid thermometer can be fabricated in various forms and can thus be adapted for use in different research areas.