83 charge-transfer transition chloranil

Fig. 2 Mulliken correlation of the ionization potentials (IP) of various enol silyl ethers with the charge-transfer transition energies (/jvct) of their EDA complexes with chloranil. Reproduced with permission from Ref. 36.

Solutions of a mixture of an electron donor D, such as hexamethylbenzene (40), and an electron acceptor A, such as chloranil (41), often exhibit an absorption band that is not present in solutions of the pure components. This band has been assigned to an electron transfer from the donor to the acceptor and is therefore referred to as a donor-acceptor or a CT (charge transfer) transition. Mulliken (1952) has developed a theory of CT transitions which can be summarized as follows If the ground configuration and the polar configuration produced by electron transfer are described by wave functions and ,, i, respectively, the interaction of these two configurations... 

Pal et al. [89] have reported on substituted ferrocenyl compounds, where one of the cyclopentadienyl rings is linked to an aromatic Schiff base, that were synthesized and analyzed for their second-order nonlinearity ((3). Their results indicate that the metal to ligand charge transfer (MLCT) transition dominates their second-order response. These compounds form charge transfer (CT) complexes with acceptors such as Ij, p-chloranil (CA), 2,3-dichloro-5,6-dicyano-l,4-bcnzoquinonc (DDQ), tetracyanoethylene (TCNE), and 7,7,8,8-tetracyanoquinodimethane (TCNQ). The CT complexes exhibit much higher second-order response. Bisferrocenyl complexes where two ferrocene moieties are linked through the same aromatic Schiff base... 

Use of nonaqueously prepared DEAE celluloses as Lewis bases offers potential for formation of metal ion complexes between transition metal ions such as Cu and Ni 2j formation of charge-transfer complexes with electron acceptor compounds such as ortho-and para-chloranils or bromanils and with other Lewis acid compounds such as BI3. 

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