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We describe the formation of a multidrug salt comprising sulbactam (SUL, β-lactamase inhibitor) and amantadine (AMNH, antiviral). Physicochemical investigation of the SUL·AMNH salt revealed enhanced thermal stability compared to pristine starting materials. In vitro studies found that salt formation in SUL·AMNH does not disrupt antibacterial activity against model organisms Escherichia coli and Staphylococcus epidermidis. To our knowledge, we show the first β-lactamase inhibitor-antiviral salt where both components have been approved by the U.S. Food and Drug Administration (FDA), and the first multicomponent solid containing SUL. We envisage our strategy could inspire the design of multicomponent solids for antimicrobial combination therapies. 

Fluorination of azopyridine N-donors regulates the formation of either B ← N coordination adducts or a co-crystal with phenylboronic acid catechol ester. Specifically, the formation of B ← N adducts is promoted by azopyridines with up to four fluorines, while perfluorination affords a co-crystal via phenyl–perfluoropyridyl [π⋯πF] contacts. Electrostatic potential maps showed supramolecular bonding competition outcomes to be primarily determined by modulation of electron-donating capacity and π surfaces of azopyridine N-donors using fluorination. 

Mechanochemistry afforded a photoactive cocrystal via coexisting (B)O−H⋅⋅⋅N hydrogen bonds and B←N coordination. Specifically, solvent‐free mechanochemical ball mill grinding and liquid‐assisted grinding of a boronic acid and an alkene resulted in mixtures of hydrogen‐bonded and coordinated complexes akin to mixtures of noncovalent complexes that can be obtained in solution in equilibria processes. The alkenes of the hydrogen‐bonded assembly undergo an intermolecular [2+2] photodimerization in quantitative conversion, effectively reporting the outcome of the self‐assembly processes. Our results suggest that interplay involving noncovalent bonds subjected to mechanochemical conditions can lead to functional solids where, in the current case, the structure composed of the weaker hydrogen bonding interactions predominates.

 

Mechanochemistry afforded a photoactive cocrystal via coexisting (B)O−H⋅⋅⋅N hydrogen bonds and B←N coordination. Specifically, solvent‐free mechanochemical ball mill grinding and liquid‐assisted grinding of a boronic acid and an alkene resulted in mixtures of hydrogen‐bonded and coordinated complexes akin to mixtures of noncovalent complexes that can be obtained in solution in equilibria processes. The alkenes of the hydrogen‐bonded assembly undergo an intermolecular [2+2] photodimerization in quantitative conversion, effectively reporting the outcome of the self‐assembly processes. Our results suggest that interplay involving noncovalent bonds subjected to mechanochemical conditions can lead to functional solids where, in the current case, the structure composed of the weaker hydrogen bonding interactions predominates.

 

Abstract This Account describes work by our research group that highlights opportunities to utilize organoboron molecules to direct chemical reactivity in the organic solid state. Specifically, we convey a previously unexplored use of hydrogen bonding of boronic acids and boron coordination in boronic esters to achieve [2+2]-photocycloadditions in crystalline solids. Organoboron molecules act as templates or ‘shepherds’ to organize alkenes in a suitable geometry to undergo regio- and stereoselective [2+2]-photocycloadditions in quantitative yields. We also provide a selection of publications that served as an inspiration for our strategies and offer challenges and opportunities for future developments of boron in the field of materials and solid-state chemistry. 1 Introduction 1.1 Template Strategy for [2+2]-Photocycloadditions in the Solid State 2 Boronic Acids as Templates for [2+2]-Photocycloadditions in the Solid State 2.1 Supramolecular Catalysis of [2+2]-Photocycloadditions in the Solid State Using Boronic Acids 3 Boronic Esters as Templates for [2+2]-Photocycloadditions in the Solid State 3.1 Application of Photoproducts: Separation of Thiophene from Benzene through Crystallization 3.2 Crystal Reactivity of B←N-Bonded Adducts: The Case of Styryl­thiophenes 4 Conclusions and Perspectives