Diketopyrrolopyrroles disubstituted with alkylated thiophenes: effect of the donor unit size and solubilizing substituents on their redox, photo- and electroluminescence properties

摘要: Systematic studies of redox, spectroscopic and electroluminescent properties donor–acceptor–donor (DAD) electroactive compounds consisting a diketopyrrolopyrrole central accepting unit symmetrically disubstituted with mono-, bi- or terthiophenes (T1, T2 T3 series) are presented. The potential the reduction is influenced neither by type alkyl substituent at pyrrole nitrogen atoms, nor position substituents in thiophene rings D segment. Being range −1.66 to −1.67 V vs. Fc/Fc+ T1 series it is, however, raised 100–120 mV for compounds. oxidation studied even more strongly affected segment, decreasing from 0.51–0.52 0.25–0.26 ones. It also dependent on solubilizing ring, being ca. 40 changing 5 3. electrochemical data perfect agreement results, as judged close similarity optically- electrochemically-determined band gaps. trends observed experimentally reproduced DFT calculations. calculated values ionization potentials electron affinities very experimental highest photoluminescence quantum yields, approaching 80%, were measured compounds, whereas ones this value dropped below 20%. Time resolved consistently showed shorter emission lifetimes larger non-radiative rate constants lower yields. Guest/host-type single layer light emitting diodes fabricated most luminescent (T1 series), molecularly dispersed (1 wt%) matrix 70 wt% poly(N-vinylcarbazole) 30 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole. Appropriate alignment components energy levels those resulted effective electroluminescence guest molecules. luminance exceeding 2600 cd m−2 luminous efficiency 0.7 A−1.