n-π Electron donor–acceptor complexes. III. Aliphatic amines with dicyanobenzenes. Electric and steric effects of the N-substituents on complex formation

Abstract

. 64,1491 (1986).The interaction of several aliphatic amines as n-donors with 1,2-, 1,3-, and 1,4-dicyanobenzenes as n acceptors in n-hexane has been studied. The spectroscopic behaviour of the mixtures leads us to propose that Electron Donor -Acceptor (EDA) complexes are formed. Correlations of the experimental data with the amine structure were performed for the arnine-1,4-dicyanobenzene complexes. By means of free energy related substituents and regression analysis, the electronic and steric effects of three N-substituents were quantitatively separated. Thus, with K representing the stability constants of the complexes, the values of log K are correlated with Taft's polar substituent constants, a*, and Hancock's corrected steric substituent constants, E: . The results allowed the proposal of a probable structure of the complex, at least with respect to the donor orientation.