Optical and electrochemical investigation of diaminonaphthalene derivatives

A series of diaminonaphthalene derivatives with naphthalene as a core and butylamino and phenylamino as substituted groups were synthesized and their optical and electrochemical behavior were investigated. Phenylamino substituted naphthalene derivatives exhibit two absorption bands, which are assigned to n → π* electronic transitions that are due to electron transfer from nitrogen lone pairs to the π* orbital of the naphthalene group and the phenyl group, respectively. Comparing with butylamino substitutes, phenylated ones exhibit a red-shift in both absorption and emission for their electron-donating phenyl groups. The fluorescence quantum yields of the molecules were measured in THF. Cyclic voltammetric measurements demonstrated that the diaminonaphthalene derivatives possess two oxidation processes and the solid-state ionization potentials were estimated from the electrochemical potential. The phenylamino-naphthalenes possess higher ionization potentials than those of the alkylated ones. The relative HOMO and LUMO levels for these materials, important parameters for the design of efficient organic light-emitting or photovoltaic devices, were assessed through electrochemical and spectroscopic measurements.