Charge transfer from solvent

Fig. 5. Single-ion charge-transfer from solvent data. Correlation of AG (Table VIII) with l/r(A), where r(A) is the crystal radius of the reduced form of the ion. The dashed line is drawn with the slope predicted from Eq. (75).

Mehnert R, Brede O, Naumarm W. (1982) Charge transfer from solvent radical cations to solutes in pulse-irradiated liquid -butylchloride. Ber Bunsen es Phys Chem 86 525-529. 

Fig. 20 The proposed mechanism of ESPT incorporating a solvent-polarity-induced barrier in protic solvents following optical charge transfer and solvent relaxation. See full name of each compound in text (reprint from ref. [141], Copyright 2008 Wiley-VCH)...

An ideal polarity probe based on photoinduced charge transfer and solvent relaxation should (i) undergo a large change in dipole moment upon excitation but without change in direction, (ii) bear no permanent charge in order to avoid contributions from ionic interactions, (iii) be soluble in solvents of various polarity, from the apolar solvents to the most polar ones. 

Figure 5.2. Grabowski s model of TICT formation in DMABN the locally excited (LE) state with near-planar conformation is a precursor for the TICT state with near perpendicular geometry. The reaction coordinate involves charge transfer from donor D to acceptor A. intramolecular twisting between these subunits, and solvent relaxation around the newly created strong dipole. Decay kinetics of LE and rise kinetics of the TICT state can be followed separately by observing the two bands of the dual fluorescence. For medium polar solvents, well-behaved first-order kinetics are observed, with the rise-time of the product equal to the decay time of the precursor, but for the more complex alcohol solvents, kinetics can strongly deviate from exponentiality, interpretable by time-dependent rate constants. 52 ...

Similar interface to that used for ESI. In APCI, a corona discharge is used to ionize the analyte in the atmospheric pressure region. Ions are formed by charge transfer from the solvent as the solution passes through a heated nebulizer into the APCI source... 

The photodynamics of electronically excited indole in water is investigated by UV-visible pump-probe spectroscopy with 80 fs time resolution and compared to the behavior in other solvents. In cyclohexane population transfer from the optically excited La to the Lb state happens within 7 ps. In ethanol ultrafast state reversal is observed, followed by population transfer from the Lb to the La state within 6 ps. In water ultrafast branching occurs between the fluorescing state and the charge-transfer-to-solvent state. Presolvated electrons, formed together with indole radicals within our time resolution, solvate on a timescale of 350 fs. 

From the steady state fluorescence spectrum of indole in water a fluorescence quantum yield of about 0.09 is determined. Since the cation appears in less than 80 fs a branching of the excited state population has to occur immediately after photo excitation. We propose the model shown in Fig. 3a). A fraction of 45 % experiences photoionization, whereas the rest of the population relaxes to a fluorescing state, which can not ionize any more. A charge transfer to solvent state (CITS), that was also introduced by other authors [4,7], is created within 80 fs. The presolvated electrons, also known as wet or hot electrons, form solvated electrons with a time constant of 350 fs. Afterwards the solvated electrons show no recombination within the next 160 ps contrary to solvated electrons in pure water as is shown in Fig. 3b). 

When a solution containing a small amount of monomer is irradiated, the cation radicals and electrons are formed primarily from solvent molecules. In this case, cationic intermediates are formed from monomer through positive charge transfer or proton transfer from solvent to solute monomer. Anionic intermediates of monomer are formed by the combination between electrons and monomer molecules. If the solvent has the nature to stabilize the electrons and inhibit succeeding anionic reactions, ionic reactions involving monomer are limited to cationic ones. The situation is the reverse, if the solvent is able to stabilize the cationic intermediates primarily formed. Therefore, the ionic reactions involving monomer may be simple enough in some suitable solvents to be studied. 

The solvent is characterized by a dielectric constant and a donicity D (see Reference 84). Clncluding estimated correlation corrections of 30 ppm (see Reference 83a for details). Solvation without any charge transfer from S to RjSi- ". 

From a chemical point of view, however, it is reasonable that the measured dipole moment increases with solvent polarity, simply because in these conjugated systems the intramolecular charge transfer from the electron donor to the electron acceptor is... 

Photooxidation of the central atom Os(II) in hexacoordinated porphyrin complexes is supposed to start with the ejection of an electron from an charge-transfer to solvent excited state, CTTS, of the complexes. A complicated set of elimination, addition and redox steps involving radicals terminates in the formation of the complexes OsIV(Por)Cl2. Solvent molecules (CC14, CHC13, CH2C12) served as a source of chlorine atoms [92, 192]. 

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