Fig. 1: Schematic chemical structures of the six azanaphthalene molecules considered in this study.

Quinoline and isoquinoline have a single N centre at two distinct positions in the ring, quinazoline and quinoxaline have two N centres at distinct positions in the same ring, and 1,6-naphthyridine and 1,8-naphthyridine have two N centres with one N atom per ring. Position numbering around the ring system is also indicated, which is referenced in parts of the Discussion.