Affiliation:
1. Empa – Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
2. Center for Advancing Electronics Dresden (cfaed) & Faculty of Chemistry and Food Chemistry, Technische Universität Dresden, Mommsenstrasse 4, 01062 Dresden, Germany
Abstract
The synthesis of circumazulene, a nonalternant isomer of circumnaphthalene, and its π-expanded derivatives poses a considerable challenge due to the lack of a suitable synthetic strategy. In this work, we present our efforts toward achieving tetrabenzo-fused circumazulene (1) through both solution and on-surface syntheses. In the case of in-solution synthesis, we obtained a product (P) with the desired target mass, but the structural verification proved to be challenging owing to the presence of various structural isomers. In the on-surface synthesis approach, a series of unexpected azulene-embedded nanographenes were obtained, including a molecule with an additional pentagonal ring (U1) based on the backbone of 1. Furthermore, theoretical calculations were conducted to shed light on these unexpected structures and to investigate their aromaticity. This work opens a new avenue for the design and synthesis of novel nonalternant graphene nanostructures incorporating circumarene.