Effect of ionic liquids on the conformation of a porphyrin-based viscometer

Abstract

Structure of the cationic and anionic counterparts of ionic liquids has a significant impact on the conformational bias of the porphyrin rotor; an apparent correlation between the conformation and the viscosity of ionic liquids was noted, albeit it was found to be distinct and more complex from that found in molecular solvents.

A homodimeric BODIPY rotor as a fluorescent viscosity sensor for membrane-mimicking and cellular environments

“…It appeared that changing the viscosity of the media (by using ethanol–glycerol mixtures 25 ) did not significantly affect the shape and peak emission wavelength (Figure 2A). A small shift of the emission maximum (~7 nm) was observed when viscosity changed from that of ethanol to that of glycerol and this could be ascribed to slight changes of the media polarity.…”

Mechanothermally induced conformational switch of a porphyrin dimer in a polymer film

“…This observation was not surprising because PD was shown to adopt the twisted conformation in highly viscous media. 9b,10b Importantly, progressive stretching of the PVA film (from 5 to 20 mm; Figures 3A, 3B, and S5) at 70 °C ‡ resulted in a significant shift from the twisted to planar conformation, as judged by the increase of the 780/710 nm ratio (Figure 3). Specifically, the amount of the planar conformation increased from below ca.…”

“…The distinct photophysical properties of the two conformers allow for the facile assessment of PD ’s conformation in a variety of different media including organic solvents, ionic liquids, micellar, and cellular environments. 9b,10 In all aforementioned examples, the conformation of PD was not locked, and dynamic equilibrium was established between the planar and twisted conformations depending on the nature of the media. Fluorescence spectroscopy was found to be particularly useful in accessing the conformer ratio as a function of the media’s viscosity.…”

Conformational preference of a porphyrin rotor in confined environments

“…In single component molecular solvents and mixtures of molecular solvents the conformational preference of PD depends solely on the viscosity of the media, whereas the twisted conformation dominates in more viscous media such as glycerol or methanol-glycerol mixtures, for example, and the planar conformer exists in less viscous media such as neat methanol or ethanol. 7,15 In the case of ILs on the other hand, the structure of IL was found to play an important role in the conformational bias of PD. 7 Specically, in all ILs with a common cation, a similar conformation of PD was present, regardless of viscosity.…”

“…7,15 In the case of ILs on the other hand, the structure of IL was found to play an important role in the conformational bias of PD. 7 Specically, in all ILs with a common cation, a similar conformation of PD was present, regardless of viscosity. Furthermore, an order of magnitude larger viscosity was required to promote a similar amount of the twisted conformation as compared to that found in the molecular solvents.…”