Benzo[1,2‐<i>h</i>:4,3‐<i>h</i>′]diquinoline (“1,14‐Diaza[5]helicene”): Synthesis, Structure, and Properties

Abstract

Despite almost equal N ⃛N distances in 1 and 2 (272.8 and 270.5 pm) the basicity constant of 2 is almost two powers of ten smaller than that of 1. The reason for this could be the helical structure of 2, which almost removes the destabilizing “lone-pair” interaction of the N atoms in the case of the free base and hinders an N ⃛H ⃛N bridge along the preferred directions of the “lone pairs” of the N atoms in the case of 2a.