Adsorption of quinonediimines on aluminum(1 0 0): A computational and FT-IR study

Density functional theory (DFT) calculations were performed on a series of symmetrically substituted quinonediimines, both free and adsorbed on a 42 atom aluminum(1 0 0) lattice. Enthalpies of adsorption for quinonediimines in the emeraldine base oxidation state were calculated to vary from −4.07 to −8.47 kcal mol−1, with the emeraldine salt value at −78.00 kcal mol−1. The enthalpy of absorption for the pernigraniline is calculated to be 30 kcal mol−1. Adsorption onto the aluminum surface caused a change in hybridization of the central imine nitrogen from sp2 to sp3, with concomitant formation of a coordinate covalent bond to two electron deficient aluminum atoms of the surface. Experimental IR studies of three quinonediimines show shifts in absorption bands consistent with strong interaction with the aluminum surface, and consistent with frequencies calculations using DFT.