ISSN:
0894-3230
Keywords:
Organic Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The radical cation of N,N′-bis-(4-dimethylaminophenyl)pyridazine (3·+) has a near-IR band with a transition energy of 29·7 ± 0·5 kcal mol-1 (1 kcal = 4·184 kJ) in acetonitrile. This band is assigned to a Hush-type charge-transfer band, and the transition energy to the Marcus λ value for electron transfer. Such a large λ is inconsistent with previous estimates of λ for intermolecular electron transfer between mono-p-phenylenediamines and their radical cations. It agrees well with estimates of λ based on AM1 semi-empirical MO calculations, which gives the enthalpy contribution to λin at about 21 kcal mol-1 for 3·+. It is suggested that the traditional method of estimating λin by summing bond displacements weighted by force constants produces values which are significantly too low for systems such as phenylenediamines, where pyramidalization changes are important. The results suggest that λ for tetramethyl-p-phenylenediamine self-electron transfer (10/·+) has been significantly underestimated, and that this prototype organic electron transfer reaction is not as strongly diabatic as was previously concluded.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/poc.610070202
