Mechanochemical Mediated Coexistence of B←N Coordination and Hydrogen Bonding

Abstract

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.

Solid‐State Synthesis of B←N Adducts by the Amine‐Facilitated Trimerization of the Phenylboronic Acid

“…The aromatic amine 4,4’‐bipyridine (bpy) is commonly used to build larger molecular assemblies due to its directional and versatile bonding modes. It is structurally similar to the amine bpe used in the experiments of the MacGillivray group [14] …”

“…It is structurally similar to the amine bpe used in the experiments of the MacGillivray group. [14] The DFT results (Tables 3, S2 and S3) indicated that in case of bpy, the H-bonded structures are close in stability to the B ! N adducts.…”

“…This structural change has been exploited in many areas, from the design of MIDA boronates (stable boronate esters of N-methyliminodiacetic acid) [12] to the construction of macromolecular assemblies. [13] Recently, the MacGillivray group [14] showed that the boroxine-amine adduct A61-bpe obtained from phenylboronic acid (PBA) and trans-1,2-bis(4-pyridyl)ethylene (bpe) coexists under mechanochemical conditions [15] with a hydrogen-bonded boronic acid-amine assembly H22*-bpe (Scheme 1). No further details about boroxines or boronic acid behavior in the presence of amines under mechanochemical conditions are available.…”

“…Recently, the MacGillivray group [14] showed that the boroxine‐amine adduct A61‐bpe obtained from phenylboronic acid (PBA) and trans ‐1,2‐bis(4‐pyridyl)ethylene (bpe) coexists under mechanochemical conditions [15] with a hydrogen‐bonded boronic acid‐amine assembly H22*‐bpe (Scheme 1). No further details about boroxines or boronic acid behavior in the presence of amines under mechanochemical conditions are available.…”

Synthesis, Structural Characterization, and Photochemical [2 + 2] Cycloaddition of a Coordination Polymer: Multiweek Inorganic–Organic Chemistry Experiments

“…Because of the regular arrangement of alkene molecules in the crystals, the solid-state [2 + 2] photocycloaddition reactions of olefins usually exhibit high regioselectivity and stereoselectivity. Therefore, the photochemical [2 + 2] cycloadditions within crystalline solids can be applied to synthesize cyclobutene derivatives with specific configurations that cannot be obtained in solution. − The template-directed photoreactions based on the supramolecular interactions including hydrogen bonding and electrostatic interactions as well as coordination interactions have been developed to promote the directional synthesis of stereoselective products in the photocycloaddition reactions. − …”