title: Theoretical investigation on the effect of protonation on the absorption and emission spectra of two amine-group-bearing, red "push-pull" emitters, 4-dimethylamino-4'-nitrostilbene and 4-(dicyanomethylene)-2-methyl-6-p-(dimethylamino) styryl-4H-pyran, by DFT and TDDFT calculations.
abstract: A theoretical investigation on the electronic structure of 4-dimethylamino-4'-nitrostilbene (DANS), 4-(dicyanomethylene)-2-methyl-6-p-(dimethylamino) styryl-4H-pyran (DCM), and their protonated forms is presented in an effort to rationalize recent experimental results on the tuning of the emitted color of organic light-emitting diodes through photochemically induced protonation. Density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations have been carried out on the neutral and protonated forms of DANS and DCM, employing both the B3LYP and the CAM-B3LYP functionals. It was found that the CAM-B3LYP functional leads to better agreement than the B3LYP of the calculated with the experimental absorption lambda(max) for DANS, whereas B3LYP is more appropriate than CAM-B3LYP for DCM. The results of the calculations aid in a rationalization of the observed differences of the spectra of DANS and DCM upon protonation, and in particular those differences that make DANS a more attractive system for absorbance and emission tuning.
authors.affiliation: Theoretical and Physical Chemistry Institute, The National Hellenic Research Foundation, 48 Vassileos Constantinou Avenue, 116 35 Athens, Greece.
authors.forename: I D
authors.initials: ID
authors.lastname: Petsalakis
authors.forename: D G
authors.initials: DG
authors.lastname: Georgiadou
authors.forename: M
authors.initials: M
authors.lastname: Vasilopoulou
authors.forename: G
authors.initials: G
authors.lastname: Pistolis
authors.forename: D
authors.initials: D
authors.lastname: Dimotikali
authors.forename: P
authors.initials: P
authors.lastname: Argitis
authors.forename: G
authors.initials: G
authors.lastname: Theodorakopoulos