A series of solution-processable tetraalkoxy-substituted dinaphtho[2,3-a:2′,3′-h]phenazines were synthesized by reductive functionalization of indanthrone (6,15-dihydrodinaphtho-[2,3-a:2′,3′-h]phenazine-5,9,14,18-tetraone), an old intractable dye. The melting point of these new compounds was found to decrease from 204 °C to 98 °C upon extension of the number of carbons from 4 to 12 in the alkoxy substituent. All derivatives show a strong tendency to self-organize in 2D as evidenced by STM investigations of monolayers deposited on HOPG. The 2D structure is less dense and shows different alkoxy group interdigitation pattern as compared to the 3D structure determined from the X-ray diffraction data obtained for the corresponding single crystals. Electrochemical, absorption, and emission properties of tetraalkoxy-substituted dinaphtho[2,3-a:2′,3′-h]phenazines, studied in solution, are essentially independent of the length of the alkoxy substituents. All derivatives exhibit high photoluminescence quantum yield, approaching 60%. When molecularly dispersed in a solid matrix consisting of poly(9-vinylcarbazole) (PVK) (60 wt %) and (2tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole) (PBD) (40 wt %) (so-called "guest/host configuration"), they show green electroluminescence due to an effective energy transfer from the matrix to the luminophore. The best light-emitting diodes were obtained for the butoxy derivative showing a luminance approaching 1500 cd/m 2 and a luminous efficiency over 0.8 cd/A.
A detailed experimental characterization and theoretical evaluation of optical as well as other relevant physicochemical properties of a series of 9,10-dihydro-9,10-diboraanthracene bis(8-oxyquinolinates) and a few other related systems is reported. The obtained compounds exhibit green luminescence with quantum yields of emission up to 63% in CH 2 Cl 2 . Single crystal X-ray diffraction studies indicate that 9,10-dihydro-9,10-diboraanthracene complexes exist either as bent conformers (stabilized by a weak intramolecular CH…O interaction bringing two 8-oxyquinolinato ligands closer to each other) or symmetrical ones (bearing both ligands related by the centre of symmetry and separated one from the other). Theoretical calculations revealed that the LUMO levels are lower for the bent conformers than for the symmetrical ones. This suggests that the luminescent properties of the studied compounds are affected by their specific structural properties. The obtained compounds were used as emitters for the construction of organic light emitting diodes (OLEDs). The highest luminance of ca. 2,000 cd·m −2 was recorded for the device containing only 2.0 wt% of 1,6-difluoro-9,10-dihydro-9,10-diboraanthracene core in the poly(Nvinylcarbazole/2-t-butylphenyl-5-biphenyl-1,3,4-oxadiazole (PVK:PBD) matrix. The fabricated OLEDs exhibit current efficiency in the range from 0.5 to 1.1 cd·A −1 .
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