Enhancement of molecular polarizabilities by the push-pull mechanism; a DFT study of substituted benzene, furan, thiophene and related molecules

Abstract

We report Density Functional Theory (DFT) studies of the dipole polarizabilities of benzene, furan and thiophene together with a number of substituted and related systems. All geometries were optimized (and characterized) at the B3LYP/6-311g (2d, 1p) level of theory and polarizabilities then calculated with B3LYP/6-311++ G (2d, 1p). For the R-ring systems we find group polarizabilities in the order R= NO2∼ OCH3∼ CN∼ CHO> NH2> OH> H= 0. For systems R-ring-R,< α> differs little from the additivity model, with small positive and negative increments. For systems D-ring-A (where D and A are deactivating and activating groups) we find a positive enhancement to< α> over and above the value expected on the basis of pure additivity for all pairs A and D studied. This enhancement can be increased greatly by extending the length of the conjugated chain to D-ring-CH= CH-ring-A and D-ring-N= N-ring-A systems …