Organic Fluorescent Thermometers Based on Borylated Arylisoquinoline Dyes. Issue 25 (23rd May 2014)

• Record Type: Journal Article
• Authors: Pais, Vânia F.; Lassaletta, José M.; Fernández, Rosario; El‐Sheshtawy, Hamdy S.; Ros, Abel; Pischel, Uwe
• Is Part Of: Chemistry. Volume 20:Issue 25(2014)
• Page Start: 7638
• Page End: 7645
• Publication Date: 2014-05-23
• Subjects: boron -- charge transfer -- fluorescence -- molecular devices -- Lewis pairs; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201402027
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Borylated arylisoquinolines with redshifted internal charge‐transfer (ICT) emission were prepared and characterized. Upon heating, significant fluorescence quenching was observed, which forms the basis for a molecular thermometer. In the investigated temperature range (283–323 K) an average sensitivity of −1.2 to −1.8 % K −1 was found for the variations in fluorescence quantum yield and lifetime. In the physiological temperature window (298–318 K) the average sensitivity even reaches values of up to −2.4 % K −1 . The thermometer function is interpreted as the interplay between excited ICT states of different geometry. In addition, the formation of an intramolecular Lewis pair can be followed by 11 B NMR spectroscopy. This provides a handle to monitor temperature‐dependent ground‐state geometry changes of the dyes. The role of steric hindrance is addressed by the inclusion of a derivative that lacks the Lewis pair formation. Abstract : Getting warmer : A series of molecular fluorescent thermometers with good to very good sensitivity is reported. Borylated arylisoquinolines show pronounced fluorescence quenching upon heating (see figure), which can be reverted by cooling. The analysis of kinetic parameters revealed the involvement of a thermally activated nonradiative excited‐state decay channel.