Hydrogen bonding interactions can decrease clar sextet character in acridone pigments

Computed nucleus-independent chemical shifts (NICS), contour plots of isotropic magnetic shielding (IMS), and gauge-including magnetically induced current (GIMIC) plots suggest that polarization of the π-system of acridones may perturb the numbers and positions of Clar sextet rings. Decreasing numbers of Clar sextets are connected to experimental observations of a narrowing HOMO–LUMO gap and increased charge mobility in solid-state assemblies of quinacridone and epindolidione.