Influence of specific and non-specific solvent effects on frontal MO of DMABI system

Abstract

Derivatives of 2-(4'-dimethylaminobenzylidene)-1,3-indandione (DMABI) are classical push-pull chromophores containing carbonyl groups like numerous other non-linear chromophores for electro-optical devices. The energy of the intramolecular charge transfer exciton of DMABI is determined by the difference of HOMO-LUMO energies and can be varied in width range by chemical modifications of the DMABI structure or by the nonspecific and specific solvent effects if the chromophore is incorporated into condensed environment. The condensed medium in a thin film (polymer or molecular glass) exhibits a solid state solvation effect similar to the effect of the organic solvents in a solution. The value of the medium effect depends on specific and non-specific interactions between the chromophore and medium. The main purpose of this work is to evaluate the specific effects. The chromophores often contain few centres for specific interaction, and thus we have synthesised and investigated UV-Vis spectra of three derivatives of DMABI and also three derivatives of 4-aza-DMABI in solutions with strong H-bond donor properties. The experimentally obtained results show that the strong H-bond with carbonyl group lowers the intramolecular charge-transfer energy by 900 cm−1, the strong H-bond with carbonyl group and heterocyclic nitrogen in 4-aza-DMABI by 1500 cm−1 and the protonation of heterocyclic nitrogen in 4-aza-DMABI by 3250 cm−1 respectivelly.