1,1-Dimethyl-2,3,4,5-tetraphenylsilole as a Molecular Rotor Probe to Investigate the Microviscosity of Imidazolium Ionic Liquids

Aggregation-Induced Emission: Together We Shine, United We Soar!

“…(B) Bar chart illustrating the difference between the measured bulk kinematic viscosities of the four ILs studied and their corresponding microviscosities. Adapted with permission from ref . Copyright 2013 Springer Science+Business Media New York.…”

“…The ultrahigh sensitivity to the polarity and viscosity of the systems in which they are dispersed as well as the marked AIE effect make AIEgens promising probes for the microenvironments present in ILs. 1,1-Dimethyl-2,3,4,5-tetraphenylsilole (DMTPS), for example, was employed as a molecular probe for the investigation on the microviscosities of three imidazolium ILs: butylmethylimidazolium tetrafluoroborate ([BMIM]­[BF 4 ]), butylmethylimidazolium hexafluorophosphate ([BMIM]­[PF 6 ]), and octylmethylimidazolium tetrafluoroborate ([QMIM]­[BF 4 ]) . Since ILs are viscous and composed of ions, the Φ F values for DMTPS in these ILs were measured and compared with those recorded for the same probe in nonpolar (hexane/mineral oil) and polar viscous (glycerol/ethanol) solvent systems (Figure A).…”

“…1,1-Dimethyl-2,3,4,5-tetraphenylsilole (DMTPS), for example, was employed as a molecular probe for the investigation on the microviscosities of three imidazolium ILs: butylmethylimidazolium tetrafluoroborate ([BMIM][BF 4 ]), butylmethylimidazolium hexafluorophos-phate ([BMIM][PF 6 ]), and octylmethylimidazolium tetrafluoroborate ([QMIM][BF 4 ]). 839 Since ILs are viscous and composed of ions, the Φ F values for DMTPS in these ILs were measured and compared with those recorded for the same probe in nonpolar (hexane/mineral oil) and polar viscous (glycerol/ ethanol) solvent systems (Figure 150A). The microviscosities were calculated using the Forster−Hoffmann equation.…”

The effect of structural heterogeneity upon the microviscosity of ionic liquids

“…A number of molecular rotors have been applied to the measurement of the microviscosities of ionic liquids. 13 – 16 When the microviscosities, determined by reference to calibrations conducted in molecular solutions, were compared to the bulk viscosities of the ionic liquids determined by rheometry, complex relationships were observed.…”

“…Measurements of the photoluminescence quantum yields of the molecular rotor 1,1-dimethyl-2,3,4,5-tetraphenylsilole in [C 4 C 1 im][BF 4 ], [C 4 C 1 im][PF 6 ] or [C 8 C 1 im][BF 4 ] predicted lower viscosities than directly measured by viscometry using common calibrations. 13 For Thioflavin-T in [C 2 C 1 im][FAP] or [(HO) 2 C 2 C 1 im][FAP] (FAP = tris(pentafluoroethyl)trifluorophosphate) 14 and for 9-(dicyanovinyl)julolidine in [C 2 C 1 im][NTf 2 ], [C 4 C 1 im][NTf 2 ], [(OH) 2 C 2 C 1 im][NTf 2 ], [C 2 C 1 im][EtSO 4 ], [C 4 C 1 im][BF 4 ] or [(OH) 2 C 2 C 1 im][BF 4 ] the fluorescence measurements predicted higher viscosities than rheometric measurements (although in this study this was reversed for [C 2 C 1 im][PF 6 ]). 15 Other reports also describe the relationship between fluorescence spectra of molecular rotors and the viscosity measured by rheometry as complex.…”