Synthesis and derivatization of an isomer of an N-heterotriangulene bearing five-, six- and seven-membered rings around the central nitrogen atom†

The functionalization of N-heterotriangulenes has been extensively investigated for their potential as optoelectronic materials. However, the study on the influence of molecular geometry on the properties of N-heterotriangulenes is still rare. Here we present the synthesis of an isomer of an N-heterotriangulene containing five-, six- and seven-membered rings around the central nitrogen atom. The isomer can be further derivatized by condensing with ortho-diamine compounds to extend the molecular conjugation. The photophysical and electrochemical properties of related compounds were characterized. The isomer bearing three carbonyl groups demonstrates room temperature phosphorescence, which is absent in the corresponding tert-butylated carbonyl-bridged N-heterotriangulene. Furthermore, the chemical oxidation of one of the isomers of the N-heterotriangulene to generate a cationic radical was also studied.