Optical Window to Polarity of Electrolyte Solutions

Abstract

Medium polarity plays a crucial role in charge-transfer processes and electrochemistry. The added supporting electrolyte in electrochemical setups, essential for attaining the needed electrical conductivity, sets challenges for estimating medium polarity. Herein, we resort to Lippert–Mataga–Ooshika (LMO) formalism for estimating the Onsager polarity of electrolyte organic solutions pertinent to electrochemical analysis. An amine derivative of 1,8-naphthalimide proves to be an appropriate photoprobe for LMO analysis. An increase in electrolyte concentration enhances the polarity of the solutions. This effect becomes especially pronounced for low-polarity solvents. Adding 100 mM tetrabutylammonium hexafluorophosphate to chloroform results in solution polarity exceeding that of neat dichloromethane and 1,2-dichloroethane. Conversely, the observed polarity enhancement that emerges upon the same electrolyte addition to solvents such as acetonitrile and N,N-dimethylformamide is hardly as dramatic. Measured refractive indices provide a means for converting Onsager to Born polarity, which is essential for analyzing medium effects on electrochemical trends. This study demonstrates a robust optical means, encompassing steady-state spectroscopy and refractometry, for characterizing solution properties important for charge-transfer science and electrochemistry.

How Permanent Are the Permanent Macrodipoles of Anthranilamide Bioinspired Molecular Electrets?

“…, where ε is the relative static dielectric constant and n 2 , i.e., the square of the refractive index, represents the dynamic dielectric constant at optical frequencies. 34 and electronic polarizations, respectively. Entropic randomization of the solvent balances the electrofreeze from prevailing as the distance from the solvation cavity increases.…”

“…(b) Calculated average dipole moments of Aaa-Box3-Aaa as a function of Onsager solvent polarity ( f 0 ): 33 f 0 ( x ) = 2( x – 1)(2 x + 1) −1 and f 0 = f 0 (ε) – f 0 ( n 2 ), where ε is the relative static dielectric constant and n 2 , i.e., the square of the refractive index, represents the dynamic dielectric constant at optical frequencies. 34 (c) Estimated intramolecular HB energy, E HB , per residue. Representative HB interactions between the electret molecule and solvent molecules for (d) MeCN, (e) DCM, and (f) MeOH.…”

Poly(dimethylsiloxane) as a room-temperature solid solvent for photophysics and photochemistry

“…The nature of the samples also affects their loading distribution. Using this DCM-soaking method for introducing non-charged dyes, such as N -phenyl-4-dimethylamino-1,8-naphthalimide (Ph-ANI), 96,97 yields improved homogeneity of the sample distribution in the PDMS blocks (Fig. 1(h), leftmost block).…”