Applications of Solvatochromism

Solvatochromic shifts have important implications for the applications of coloured compounds in a variety of outlets, especially where changes in the polarity of the medium are part of the process. 

For decades solvatochromism was a phenomenon without any great technical importance in commercial applications, being used largely to characterise solvents or to understand the excitation behaviour of chromogenic solutes, e.g. commercial azo dyes. However, in the last two decades of the 20th century there was a rapid growth in the use of optical probes and sensors in a range of outlets, and this led to a renewed interest in solvatochromism. 

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Application of Solvatochromic Probes to Supercritical and Mixed Fluid Solvents... 

The final application of solvatochromic solvent strength scales is the correlation of reaction rate and equilibrium constants in SCF solvents. Solvatochromic scales are often quantitative indicators of the solvent effect on rate constants for a variety of reaction mechanismsU) In a SCF, this solvent effect may be achieved conveniently with a single solvent using pressure. Based on solvatochromic data, it was predicted that an activation volume can reach thousands of mL/mol in a SCF(8). This prediction was confirmed for various types of reactionsClSbZl). For example, the solvatochromic parameter Ex for phenol blue... 

The application of solvatochrome dyes for characterizing the strengths (polarities) of solvents was first proposed by Brooker [Br 51]. His solvent scale is based on the shifts in the absorption bands of the following two merocyanine dyes (I and II) ... 

The relative importance of the hafide anion - HO - Cell interactions can be inferred from application of the Taft-Kamlet-Abboud equation to the UV-Vis absorbance data of solvatochromic probes, dissolved in cellulose solutions in different solvent systems, including LiCl/DMAc and LiCl/N-methyl-2-pyrrolidinone [96]. According to this equation, the microscopic polarity measured by the indicator, Ej (indicator), in kcalmol is correlated with the properties of the solvents by Eq. 1 ... 

Rettig W. (1982) Application of Simplified Microstructural Solvent Interaction Model to the Solvatochromism of Twisted Intramolecular Charge Transfer (TICT) States, /. Mol. Struct. 8, 303-327. 

Application of the solvatochromic comparison method (Kamlet and coworkers80) reveals a competition between intermolecular and intramolecular hydrogen bonding in molecules bearing both donor and acceptor groups81 such as 17. 

The chemistry and applications of the colour change grouping, containing all the well-known isms of chromic phenomena, namely photochromism, thermo-chromism, ionochromism, electrochromism and solvatochromism, as well as the lesser-known ones such as tribochromism and vapochromism, are covered in Chapter 1. These chromic phenomena impinge on our everyday life, e.g. in photo-chromic spectacle lens, thermochromic temperature indicators, fax paper, smart windows and mirrors and in visual displays. 

Solvatochromism can be defined as the phenomenon whereby a compound changes colonr, either by a change in the absorption or emission spectra of the molecnle, when dissolved in different solvents. It is one of the oldest of the chromisms, having been described as long ago as 1878, but nowadays it is usual to extend the concept of the solvent to inclnde solids, micelles and films. A textbook published recently covers in detail the theoretical aspects of solvatochromism. Consequently in this section, the theoretical aspects will be dealt with only briefly before moving onto the practical applications of the topic, which have increased noticeably in the last decade. ... 

Reichardt, C., Pyridinium N-phenoxide betaine dyes and their application to the determination of solvent polarities, part 29— Polarity of ionic liquids determined empirically by means of solvatochromic pyridinium N-phenolate betaine dyes. Green Chem., 7, 339-351, 2005. 

Owing to the original determination from uv—vis spectral solvatochromic shifts, 7T, B, and QLm are called solvatochromic parameters. General rules for estimation of these variables have been proposed (258). Examples of individual parameter investigations are available (260,261). As previously mentioned, individual LFER—LSER studies are performed on related materials. A common method to link these individual studies to group contribution methods, and thereby expand the applicability, is by expansion of solvatochromic parameters to log—linear relationships, such as... 

A sampling of applications of Kamlet-Taft LSERs include the following. (/) The Solvatochromic Parameters for Activity Coefficient Estimation (SPACE) method for infinite dilution activity coefficients where improved predictions over UNIFAC for a database of 1879 critically evaluated experimental data points has been claimed (263). (2) Observation of inverse linear relationship between log 1-octanol—water partition coefficient and liquid... 

This technique has been applied to organic compounds where charge transfer is dominated by one transition this is not often the case for organometallics. The applicability of this technique to organometallics thus far has not been tested there are no reports where solvatochromism has been used to examine the second-order nonlinearities of transition-metal organometallics, and only one report of its application to two organoboron compounds.30... 

It should be mentioned that water and 1-octanol are not completely immiscible. The solubility of water in 1-octanol is = 2.46 mol/L at 25 °C [=mole fraction x(H20) = 0.289], and that of 1-octanol in water is = 3.29 10 mol/L [=x( 1-octanol) = 9.32-10 " ] [148]. In the application of Aio/w values, it is tacitly assumed that the solvent properties of 1-octanol saturated with water are not different from those of neat 1-octanol. In practice, the presence of water in 1-octanol should increase the concentration of polar and H-bonding solutes and decrease the concentration of nonpolar solutes. However, solvatochromic studies by Carr et al. have shown that the water saturation of 1-octanol has only a very small effect on the properties of bulk 1-octanol. The water is almost completely associated with the hydroxy group of 1-octanol and scarcely affects the properties of this medium [148]. 

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