The role of different nonspecific interactions and halogen contacts in the crystal structure organization of 5‐chloroisatoic anhydride

The crystal structure of 6‐chloro‐2,4‐dihydro‐1H‐3,1‐benzoxazine‐2,4‐dione (5‐chloroisatoic anhydride), C₈H₄ClNO₃, has been determined and analysed in terms of connectivity and packing patterns. The compound crystallizes in the noncentrosymmetric space group Pna2₁ with one molecule in the asymmetric unit. The role of different weak interactions is discussed with respect to three‐dimensional network organization. Molecules are extended into one‐dimensional helical arrangements, making use of N—H…O hydrogen bonds and π–π interactions. The helices are further organized into monolayers via weak C—H…O and lone pair–π interactions, and the monolayers are packed into a noncentrosymmetric three‐dimensional architecture by C—Cl…π interactions and C—H…Cl and Cl…Cl contacts. A Hirshfeld surface (HS) analysis was carried out and two‐dimensional (2D) fingerprint plots were generated to visualize the intermolecular interactions and to provide quantitative data for their relative contributions. In addition, tests of the antimicrobial activity and in vitro cytotoxity effects against fitoblast L929 were performed and are discussed.