  The search for new materials is a very intense task in many technological
areas. In 2015, a new variant of graphene was proposed, the pentagraphene,
which was followed by the propose of a pentagonal boron nitride structure
called penta-BN$_2$. Based on these structures, we investigated the electronic,
magnetic, and optical properties of penta-BN$_2$ nanoribbons (p-BNNRs)
considering four different kinds of edges, carefully closing the valence shells
with H atoms to prevent dangling bonds. To achieve this goal, we used
first-principles calculations in a density functional theory framework. Our
findings showed that the p-BNNRs have a rich magneto-electronic behavior,
varying from semiconductor to half-metal. We obtained that they are
ferrimagnetic, having an intrinsic magnetism, which allow potential
applications in spintronic or spinwaves. From an optical absorption point of
view, they mainly absorb at ultraviolet region of the spectrum, especially at
UV-B region, which could indicate a potential application as a UV filter.
