Halogen bonding is rapidly emerging as a reliable primary interaction at the disposal of the supramolecular chemist. With the σ-hole of the halogen atom guiding the strength and directionality of these interactions, current research focuses on tuning the electrostatic potential of the σ-hole via molecular design. We have designed and synthesized 1,3,5triiodo-2,4,6-trinitrobenzene (TITNB), a compound which, to the best of our knowledge, exhibits the largest σ-hole among organic halogenated compounds. The strength of halogen bonding through this enhancement of the σ-hole is demonstrated here and probed through eight novel cocrystals containing TITNB. These cocrystals exhibit notably short halogen bonds. For instance, the I•••S interaction in TITNBthiourea and I•••O¯contact in TITNB-4-picoline-N-oxide are the shortest known in their respective categories. Moreover, the primary interactions in all these cocrystals exhibit hierarchical pairing based on Lewis basicity of the donor, highlighting a predictable chemical recognition with potential for use in crystal engineering. Further, interaction energy calculations on TITNB and other triiodoarene derivatives computed using ammonia as halogen bond acceptor show that TITNB-NH 3 exhibits the most stable interaction among halogen bond acceptors.

Disease management is critical to ensuring healthy crop yields and is often targeted at flowers because of their susceptibility to pathogens and direct link to reproduction. Many disease management strategies are unsustainable however because of the potential for pathogens to evolve resistance, or nontarget effects on beneficial insects. Manipulating the floral microbiome holds some promise as a sustainable alternative to chemical means of disease control. In this perspective, we discuss the current state of research concerning floral microbiome assembly and management in agroecosystems as well as future directions aimed at improving the sustainability of disease control and insect-mediated ecosystem services.