The relation of solvatochromism and thermochromism to the solvent dielectric constant: The basis of the E_T and E'_T polarity scales

Abstract

We have measured the thermochromism of pyridinium‐N‐phenoxide betaine and its penta‐tert‐butyl substituted derivative dissolved in MTHF together with the solvent dielectric properties in order to relate polarity scales to the dielectric constants of the solvent. Both thermochromic and solvatochromic shifts of the absorption band of the dyes can be rationalized on the basis of the MSA theory for relating the solvation free energy to the static dielectric constant. Deviations between theory and experiment in the regime of higher viscosities can be attributed to changes in the offset between absorption maximum and electronic transition energy.

The Complexity of the Pr to Pfr Phototransformation Kinetics Is an Intrinsic Property of Native Phytochrome

“…For the calculation of the two P, spectra, we neglected a possible solvent-determined thermochromism (37)(38)(39) that should also contribute to the observed temperature effect.…”

“…Because the 65 kDa recombinant chromoprotein is monomeric, the observed thermochromism cannot be due to the presence of phytochrome as a dimer. An alternative explanation could be a solvent-determined thermochromism, as found for simpler systems (38,40). It is difficult to assess at present the weight of this effect, as several molecular parameters needed for the calculation (37) are not known for phytochrome.…”

Motional narrowing of broadband absorption of solvatochromic indicator Betaine 30

“…Substantial color change has also been noticed on temperature rise above the ambient [2][3][4][5]. On cooling down to glass temperature the solvatothermochromism is even stronger ($10, 1 kcal/mol, 1 kcal/mol ¼ 350 ¼ 350 cm À1 ), and nearly independent of the nature of liquid [6][7][8]. In contrast to extensively studied peak maxima, the bandwidths have rarely been considered, and theoretical models of electron-phonon coupling (EPC) applied [9,10].…”

Effect of reaction solvent on hydroxyapatite synthesis in sol–gel process

“…Solvents with high dielectric constants favour complete dissociation of electrolytes, while solvents with low dielectric constant cause ion pairing. Dielectric constant of solvent mixture can be calculated as a simple additive function of weighted average of the dielectric constants of the components [ 44 , 45 ]. Calculated dielectric constant values for all three reaction schemes are given in table 2 .…”