Solvent spectroscopic properties

The discriminatory emission properties between two-coordinate d ° gold(I) complexes and their respective three-coordinate counterparts have been demonstrated in the literature [6, 10-13]. As discussed in the later sections, Che and coworkers have rationalized that the extraordinarily large Stokes shift of the visible emission of [Au2(diphosphine)2] from the [5da 6pa] transition is due to the exciplex formation ofthe excited state with solvent or counterions [6]. Fackler [14—16] reported the photophysical properties of monomeric [AUL3] complexes, which show visible luminescence with large Stokes shifts (typically lOOOOcm ), suggesting significant excited-state distortion. Gray et al. [10] examined the spectroscopic properties of... 

The spectroscopic properties of the solute-solvent system accounting fluctuations of solution structures can be analyzed using a simple model that includes a fluorescent solute and its immediate surrounding contributing to full potential of... 

Although continuum solvation models do appear to reproduce the structural and spectroscopic properties of many molecules in solution, parameterization remains an issue in studies involving solvents other than water. In addition, the extension of these approaches to study proteins embedded in anisotropic environments, such as cell membranes, is clearly a difficult undertaking96. As a result, several theoretical studies have been undertaken to develop semi-empirical methods that can calculate the electronic properties of very large systems, such as proteins28,97 98. The principal problem in describing systems comprised of many basis functions is the method for solving the semi-empirical SCF equations ... 

During studies on the effect of solvent on spectroscopic properties, photobleaching of (20) was observed.412 In addition to true photobleaching, a photoproduct which fluoresces at 625 nm was produced in ethyl acetate solution. 

Some years ago, Kamlet and Taft embarked upon a study of how solvents influence the properties of solutes, focusing initially upon the effects of hydrogen bonding upon electronic transitions.184185 This led eventually to an empirical relationship between a spectroscopic property X of a given solute, e.g., the position or intensity of a peak, and certain solvent parameters, a, p and it 186... 

Rurack K, RadegliaR (2000) Transition metal ion complexes of 2,2 -bipyridyl-3,3 -diol and 2,2 -bipyridyl-3-ol spectroscopic properties and solvent-dependent binding modes. Eur J Inorg Chem 2271-2282... 

In 1948, Grunwald and Winstein2 4 attempted to define the ionizing power of a solvent by the Y parameter, based on the comparison of the rate for the solvolysis of t-butyl chloride. In 1956, Kosower5 made an attempt to define the polarity of a medium (solvent) by introducing the Z parameter based on the spectroscopic properties (in various solvents)... 

In 1963, Dimroth6 introduced the Et parameter based on the spectroscopic properties of an intramolecular charge transfer of the pyridinium phenoxide betaine dyes 2, to define the solvent polarity for interpreting solvent effects on the reactivities. 

The formation of charge transfer complexes between N,N-dimethylaniline or N,N-diethylaniline and Cspectroscopic studies, also in view of their potential optical and electronic applications. Even if the spectroscopic properties of Cgo, C70 are complicated by the presence of aggregates in room temperature solutions, the emissions from the excited state charge transfer complexes between fullerenes and iVjV-dialkylani lines are strongly solvent-dependent exciplet emissions are observed in hexane, but in toluene they are absent145. 

Recent attempts to unify the polarity scales of solvents (for non-specific interactions) are of great interest in rationalizing the medium effects166. Generally, the spectroscopic properties of appropriate substances are used to check the solvating ability of solvents. 4-Nitroaniline is a useful indicator for estimating solvent polarity because it is an electron acceptor molecule which presents incomplete complexation with weak donor solvents167. 

Taft and Topsom151 have fairly recently written an extensive review of the electronic effects of substituents in the gas phase. This article includes a tabulation of substituent inductive and resonance parameters. The inductive parameters (designated Op) are based on measured spectroscopic properties in either the gas phase or in hydrocarbon or similar solvents. The resonance parameters were arrived at through the treatment of 38 gas-phase reactivity series by iterative multiple regression, using the cr values of Bromilow and coworkers155 as the starting point. The of value for NO2 was found to be 0.65 (quoted... 

The block copolymer was complexed with Cu(II) ion in methanol, then the methanol was evaporated to dryness. The Cu complexed block copolymer was soluble in water. Its spectroscopic property showed that the structure and stability of the Cu complex were similar to those of the complex in a benzene solvent. But the reactivity of the Cu complex in the block copolymer could not be examined. The Cu complex was occuluded so tightly in the... 

In 1976, Kamlet and Taft introduced their solvatochromic comparison method [25, 26], The hydrogen-bond donor acidity a and basicity /3 together with the solvent polarity and polarizability jv were employed to correlate the solvent effects on reaction rates, equilibria, and spectroscopic properties XYZ according to equations of the form... 

When a solute particle is introduced into a liquid, it interacts with the solvent particles in its environment. The totality of these interactions is called the solvation of the solute in the particular solvent. When the solvent happens to be water, the term used is hydration. The solvation process has certain consequences pertaining to the energy, the volume, the fluidity, the electrical conductivity, and the spectroscopic properties of the solute-solvent system. The apparent molar properties of the solute ascribe to the solute itself the entire change in the properties of the system that occur when 1 mol of solute is added to an infinite amount of solution of specified composition. The solvent is treated in the calculation of the apparent molar quantities of the solute as if it had the properties of the pure solvent, present at its nominal amount in the solution. The magnirndes of quantities, such as the apparent molar volume or heat content, do convey some information on the system. However, it must be realized that both the solute and the solvent are affected by the solvation process, and more useful information is gained when the changes occurring in both are taken into account. 

The particular case of the solubilities of organic solutes in water can be dealt with by rather simple equations, based on a general equation for solvent-dependent properties, apphed to solubilities, distribution ratios, rate constants, chromatographic retention indices, spectroscopic quantities, or heats of association [4] [see Eq. (2.12) for an example of its application]. For the molar solubilities of (liquid) aliphatic solutes B in water at 25°C the equation... 

The presence of a folded state was evaluated by studying the spectroscopic properties of 1-9 in both chloroform and acetonitrile, which are good and bad solvents, respectively [23,25,26]. The molar absorptivity of 1-9 in chloroform increased in a linear fashion with respect to oligomer length (Fig. 2). However, when UV spectra were taken in acetonitrile two linear trends were identified. Oligomers 1-5 displayed a slope similar to that observed in chloroform, while 4-9 displayed a much smaller slope. The decrease in slope is... 

Tables 3-2 and 3-3 summarize the infrared and proton-NMR (nuclear magnetic resonance) spectroscopic properties of alcohols and ethers. In the proton NMR, the oxygen atom is deshielding. Phenols and alcohols rapidly exchange protons so their NMR spectra are solvent dependant. The alcohol and ether groups don t have any characteristics absorptions in UV-vis spectra.

The formation and the spectroscopic properties of the [Ru(CO) I ] species can be easily studied in different solvents by reacting RuCCO) directly with the iodide promoters (HI, Nal etc,). Thus the hydrido species HRu(00)313, which up to now was not well characterized has been obtained in concentrated solutions in different solvents at room temperature from Ru(CO) I and gaseous or aqueous HI. ( Mass spectrum M/e 567 (M+) 539 (M -CO) 511 (M+-2C0) 483 (M+-3C0)). 

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