The understanding and development of molecular electronics depends on the discovery and exploitation of new pextended organic materials. [1] One area of interest is the design of small molecules that are suitable as the fluorescent component in blue organic light-emitting diodes (OLEDs). OLEDs based on small organic molecules or conjugated polymers have been explored for applications in full-colour flat-panel displays, since the seminal work by the group at Kodak. [2] Some classes of low-mass blue-emitting materials have been exploited, such as spirobifluorenes, [3] oligofluorenes, [4] siloles [5] and distyrylarylenes, [6] but the introduction of completely new structural motifs remain scarce. To this end, we report the acid-mediated condensation of a 2,3-di-A C H T U N G T R E N N U N G alkyl-1,4-benzoquinone with 1,4-naphthoquinone to produce a series of highly soluble p-extended tetraoxa[8]circulenes (Figure 1) as well as the application of these materials in blue OLEDs.
Tetraoxa[8]circulene (4 B) is a planar heteroaromatic compound formed in trace amounts by treating 1,4-benzoquinone with strong acids. [7] The structure of the tetraoxa[8]circulene framework was deduced by means of mass spectrometry of the all-naphthalene tetraoxa[8]circulene (4 N) by Erdtman and Hçgberg, and was later confirmed by single-crystal X-ray crystallography. [8][9][10][11] It became clear that when one side of the 1,4-benzoquinone was substituted, either by using 1,4-naphthoquinone or a 2,3-disubstituted-1,4-benzoquinone, the tetraoxa[8]circulene was a major [a] Dr.