Degree of charge transfer

All alkali metal hypersilanides display highly pyramidal central silicon centers with Si-Si-Si angles around 100°. Remarkably, these angles do not differ in the contact or separated ion pairs, further indicating the large degree of charge transfer from the alkali metal cation to the silanide anion. The pyramidalization is also an expression of the increased />-character of the Si-Si bond, and consequent increase in the alkali metal-silicon bond. 

Thermal electron transfer. The high degree of charge-transfer character in [ArH, NO+] complexes is consistent with the fact that a variety of electron-rich aromatic donors undergo reversible electron transfer (in the dark) to form the corresponding cation-radical pair239 (equation 86). 

Fig. 11 Degree of charge transfer in NO+ complexes with the variation in the ionization potential of the arene donors, as evaluated by (34).

The requirement for partial charge transfer raises the question of what are the controlling factors. One explanation (79ACR79) is that the degree of charge transfer is basically controlled... 

The precursor dithiocarbonates were also used to prepare mesomorphic derivatives of TTF (tetrathiafulvalene), a strong electron donor compound used in the formation of highly conductive charge transfer complexes. Attempts to prepare CT complexes between the mesomorphic dithiolenes as acceptors and these mesomorphic TTF donors showed that the electron acceptor strength of this type of dithiolene does not suffice to form strong donor-acceptor complexes mixtures of the two components form mixed crystals without any visible degree of charge transfer.208... 

Donor-acceptor complexes are formed (by ji-ji interaction) between arylhydrazones and trinitrofluorenes190, chloranil and tetracyanoethylene191. ESR investigation of donor-acceptor mixtures in DMSO and in acetonitrile reveals the presence of a small degree of charge transfer. 

In an infinite crystal, all units must be neutral. The small degree of charge transfer observed in the dimer supports the appropriateness of the dimer as a model for the crystal. In the cases where H-bonds to ortho hydrogens are implicated, the charge increases substantially on the ortho hydrogen upon dimer formation. 

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