Enhancement of molecular polarizabilities by the push–pull mechanism: A DFT study of substituted hexatriene

The static polarizabilities α for a series of substituted hexatriene molecules of the NO2–(CHCH)3-D and NO2–(CHCH)3-A types (D, A = N(Me)2, Br, OCH3,CH3, NH2, Cl, OH, F, COCN, C2H, COF, NO, CHO, CN, CF3) have been computed using DFT method at B3LYP/6-311 G(d,p) level of theory. Our results allowed to sort out the considered Π-donor and Π-acceptor substituents by decreasing static isotropic α value. An excellent agreement between the DFT and PM6 results, they give a correlation coefficient of 0.97. Miller QSAR-quality polarizability calculations give a correlation coefficient of 0.99 when compared with B3LYP/6-311G(d,p) values. Empirical models based on molecular volumes give unrealistic values for <α> but these values correlate well 0.97 with B3LYP/6-311G(d,p) results.