Lippert-Mataga equations

The first point to be addressed is the increase in dipole moment, Apt, on excitation of PRODAN (Formula in Figure 7.4). The determinations of A/x reported in the literature, apart from one, are based on solvatochromic shifts analyzed with the Lippert-Mataga equation. In the original paper by Weber and Farris Apt was estimated to be 20 D, but this value was later recognized to be overestimated and recalculation led to a value of 8 Da) b). Another study yielded a consistent value of 7 Dc) d). A completely different method based on transient dielectric loss measurement provided a somewhat lower value 4.4-5.0 Dd. From all these results, it can be concluded that the increase in dipole moment on excitation is not responsible for the high sensitivity of PRODAN to solvent polarity. 

There are a number of empirical tests for the near ideality of potential probes. Ideal probes should exhibit a solvent dependence of the fluorescence Stokes-shift (hvabs - hvn) that is in account with the Lippert-Mataga equation [9,10]. 

Light-harvesting antenna chromophore, 236 Liposomes, 260 Lippert-Mataga equation, 14 Lumi-F intermediate in Pfr - Pr transformation, 268 Lumi-R intermediate in Pr — Pfr transformation, 250... 

The expression most commonly used in fluorescence spectroscopy is, however, the somewhat simphfied Eq. (6-5b), first developed by Lippert [47, 488] and Mataga [14, 489]. It is based on Onsager s reaction-field theory, which assumes that the fluorophore is a point dipole residing in the center of a spherical cavity with radius a in a homogeneous and isotropic dielectric with relative permittivity e,. The so-called Lippert-Mataga equation is as follows ... 

For CS and CR processes, an alternative is provided by the Onsager model [46] of a point dipole in a sphere (of mean radius rD/A). In the limiting case of CS (CR), the initial (final) state dipole moment (/z) is zero, and the shift in dipole (Ap,) is given by the final (initial) p value. This leads to the Lippert-Mataga (LM) dipolar analog of Equation (3.93) [47]... 

The same expression was also deduced by Lippert [57] and Mataga [58], which neglected by a change of the angle y however, the function / (To. no) has another form than in (19) as the effect of polarizability of solvent molecules was not accounted. Mac Ray also accounted the solute polarization and obtained [59] the same equation as (20) with similar function/(fio, oj as in (19). 

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