Charge transfer in hydrogen bonding

THE PROTONIC CHARGE TRANSFER IN HYDROGEN BONDED SYSTEMS ... 

The next important question which may be raised concerns the nature of the electron displacements accompanying hydrogen bond formation. This has been discussed abundantly in the past, particularly in connection with the possible role of charge transfer in hydrogen bonding, but the incompleteness of the models utilized did not permit definitive conclusions. 

One possible alternative to the complex modular scheme has been proposed by Meyer and co-workers, and is based upon the integration of excitation, electron, and proton transfer in one single concerted step. Instead of conventional PCET, where light excitation precedes a proton and electron transfer event, the authors propose a mechanism based on photo-EPT. This as a concept has been tested for intramolecular charge transfer in hydrogen bonded dyes, but further development is needed before it can be applied to light driven water splitting devices. 

J. M. Cullen, Int. J. Quantum Chem., Quantum Chem. Symp., 25, 193 (1991). An Examination of the Effects of Basis Set and Charge Transfer in Hydrogen-Bonded Dimers with a Constrained Hartree-Fock Method. 

The interaction of the template with monomer and/or the propagating radical may involve solely Van der Waals forces or it may involve charge transfer complexation, hydrogen bonding, or ionic forces (Section 8.3.5.1). In other cases, the monomer is attached to the template through formal covalent bonds (Section 8.3.5.2). 

M. Montejo, A. Navarro, G. J. Kearley, J. Vazquez, J. J. Lopez-Gonzalez. Intermolecular charge transfer and hydrogen bonding in solid furan. J. Am. Chem. Soc. 126, 15087-15095... 

Due to the involvement of nonbonded and lone electron pairs in n —> n intramolecular charge-transfer transitions, hydrogen-bonding effects play a major role in the appearances of these spectra. Dipolar effects are most pronounced in intramolecular charge-transfer spectra because of the large dipole-moment changes accompanying the associated transitions. 

Ionizable compounds such as basic compounds (triazines and pyridinones) and acidic compounds (carboxylic acids and phenols) can sorb by ionic mechanisms when they are ionized. Weakly basic compounds may sorb by cation exchange weakly acidic compounds may sorb by anion exchange. For these chemicals ion exchange is not the sole sorption mechanism. For instance, sorption of bipyridylium cations, ie, diquat and paraquat, is primarily the result of cation exchange. Other physicochemical forces, such as charge-transfer interactions, hydrogen bonding, and van der Waals forces, can also be involved in the sorption process. 

The electrostatic templating principle would not be limited to anions capable of only electrostatic interactions. Intermolecular interactions between anions may predispose the anions to form extended networks. For example, anion networks may form as a consequence of charge transfer or hydrogen bonding, which both tend to be anisotropic. In these circumstances, the electrostatic... 

In addition to charge transfer and hydrogen-bonding, other interactions which may be found between molecules in the solid state include those between pairs of N-O- bonds and between pairs of C=0 bonds. Thus the structure of 9-azabicycloI3,3,l]nonan-3-one-9-oxyF consists of centro-... 

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