  Magnetic graphene nanoribbons (GNRs) have become promising candidates for
future applications, including quantum technologies. Here, we characterize
magnetic states hosted by chiral graphene nanoribbons (chGNRs). The
substitution of a hydrogen atom at the chGNR edge by a ketone group effectively
adds one p_z electron to the {\pi}-electron network, thus producing an unpaired
{\pi} radical. A closely related scenario occurs for regular
ketone-functionalized chGNRs in which one oxygen atom is missing. Two such
radical states can interact via exchange coupling and we study those
interactions as a function of their relative position, which includes a
remarkable dependence on the chirality, as well as on the nature of the
surrounding GNR, i.e., with or without ketone functionalization. In addition,
we determine the parameters whereby this type of systems with oxygen
heteroatoms can be adequately described within the widely used mean-field
Hubbard model. Altogether, we provide new insights to both theoretically model
and devise GNR-based nanostructures with tunable magnetic properties.
