Fluorination Modulates Solid-State Reactivity and Guest Confinement in Organoboronic Ester Adducts

Fluorination of organoboronic ester adducts via B ← N coordination enables the formation of photoactive solids capable of [2 + 2]-photodimerization, or confinement of a hydrocarbon guest (i.e., benzene). Specifically, self-assembly of organoboronic acids with varying levels and patterns of fluorination with catechol and 4-stilbazole resulted in T-shaped B ← N adducts, that organize into either photoactive dimeric assemblies (2,4- and 3,5-difluorophenlboronic acids) or photostable architectures that encapsulate benzene (2,4,6-trifluorophenylboronic and 2,3,5,6-tetrafluorophenylboronic acids). Combined crystallographic analysis, molecular modeling, and Hirshfeld surface analysis revealed the formation of photoactive adducts with up to two fluorine atoms to be driven by enhanced face-to-face [π…π] stacking aided by [CH…π] contacts, while [CH…F], [CH…O], and [CH…π] contacts in adducts with higher fluorination level sustained the inclusion of benzene molecules in the lattice. These findings support fluorination of organoboron systems as an effective strategy for property engineering in molecular materials.