Can. J. Chem. 66, 2532. Charge-transfer complexation of N,N-dimethyl-p-toluidine (DMT) with each of the following N-methyl cations has been investigated in acetonitrile solution at 25OC: acridinium; phenanthridinium; 3-X-quinolinium and 4-X-isoquinolinium (X = H, Br, CONH2, CN); 5-nitroisoquinolinium; 3-X-pyridinium (X = CONH2, CN) (also the N-benzyl pyridinium cations); N,N1-dimethyl-4,4'-dipyridylium dication. Charge-transfer absorption maxima are reported, and extinction coefficients ( E , , , ) at these maxima and association constants (K) for 1:l complex formation have been evaluated from the dependence of absorbance upon [DMT]. In general, the longest wavelength absorption maximum increases with increasing association constant. There is a strictly linear relationship between E, , , and 1/K. These observations are considered in the context of theories of charge-transfer spectra. Such charge-transfer species are considered as models for the association complexes that are believed to exist upon the reaction pathway for hydride transfer between heteroaromatic cations. Although some significant qualitative relationships are apparent, variations in susceptibility of heteroaromatic cations to charge-transfer complexation are much smaller than variations in the reactivity of these cations towards hydride donor species. i. ces maxima ainsi que les constantes d'association (K) pour la formation des complexes 1 :l. I1 existe une relation strictement lintaire entre le E , , , et 1 /K. On considkre ces observations dans le contexte des thCories des spectres de transfert de charge. On considkre que de telles esp6ces de transfert de charge sont de bons modkles pour les complexes d'association qui existeraient lors du cheminement rtactionnel des hydrures au cours de leur transfert entre des cations hCtCroaromatiques. MCme s'il semble exister des relations qualitatives importantes, les variations dans la susceptibilitk des cations hCtCroaromatiques i. la complexation de transfert de charge sont beaucoup plus faibles que les variations observkes dans la rCactivitC de ces cations vis-a-vis des espkces donneurs d'hydrure.[Traduit par la revue]