Innentitelbild: An Unprecedented [BO₂]‐Based Deep‐Ultraviolet Transparent Nonlinear Optical Crystal by Superhalogen Substitution (Angew. Chem. 28/2024)

A hexagonal prism-shaped crystal known as KBCOB, renowned for its exceptional second-harmonic generation response and high transparency in the deep ultraviolet spectrum, is shown on the cover image. At the center of the image, the crystal's chemical structure is depicted. This structure consists of a tri-layered arrangement of green, multifaceted polyhedral units [B4O5(OH)4]2− representing the borate's boron-oxygen framework. Uniquely, the center of the crystal features a rarely reported superhalogen [BO2]− configuration, as demonstrated by Chi Zhang et al. in their Communication (e202403328).