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1. Mechanochemical Mediated Coexistence of B←N Coordination and Hydrogen Bonding

   https://doi.org/10.1002/anie.202308350  

   Guadalupe_Vasquez‐Ríos, María; Campillo‐Alvarado, Gonzalo; MacGillivray, Leonard R (August 2023, Angewandte Chemie International Edition)

   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. 

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2. Structural flexibility of halogen bonds showed in a single-crystal-to-single-crystal [2+2] photodimerization

   https://doi.org/10.1107/S2052252518007583  

   Sinnwell, Michael A.; Blad, Jared N.; Thomas, Logan R.; MacGillivray, Leonard R. (July 2018, IUCrJ)

   Halogen bonds have emerged as noncovalent forces that govern the assembly of molecules in organic solids with a degree of reliability akin to hydrogen bonds. Although the structure-directing roles of halogen bonds are often compared to hydrogen bonds, general knowledge concerning the fundamental structural behavior of halogen bonds has had limited opportunity to develop. Following an investigation of solid-state reactions involving organic syntheses and the development of photoresponsive materials, this work demonstrates the ability of the components of intermolecular N...I halogen bonding – a `workhorse' interaction for the crystal engineer – to support a single-crystal-to-single-crystal [2+2] photodimerization. A comparison is provided of the geometric changes experienced by the halogen-bonded components in the single-crystal reaction to the current crystal landscape of N...I halogen bonds, as derived from the Cambridge Structural Database. Specifically, a linear-to-bent type of deformation of the halogen-bonded components was observed, which is expected to support the development of functional halogen-bonded materials containing molecules that can undergo movements in close-packed crystal environments. 

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3. Comparison of the Ability of N‐Bases to Engage in Noncovalent Bonds

   https://doi.org/10.1002/cphc.202300326  

   Amonov, Akhtam; Scheiner, Steve (August 2023, ChemPhysChem)

   Abstract The lone pair of the N atom is a common electron donor in noncovalent bonds. Quantum calculations examine how various aspects of the base on which the N is located affect the strength and other properties of complexes formed with Lewis acids FH, FBr, F₂Se, and F₃As that respectively encompass hydrogen, halogen, chalcogen, and pnicogen bonds. In most cases the halogen bond is the strongest, followed in order by chalcogen, hydrogen, and pnicogen. The noncovalent bond strength increases in the sp²³order of hybridization of N. Replacement of H substituents on the base by a methyl group or substituting N by C atom to which the base N is attached, strengthens the bond. The strongest bonds occur for trimethylamine and the weakest for N₂. 

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4. Crystal structure of 4-methyl- N -(4-methylbenzyl)benzenesulfonamide

   https://doi.org/10.1107/S2056989020000535  

   Stenfors, Brock A.; Staples, Richard J.; Biros, Shannon M.; Ngassa, Felix N. (February 2020, Acta Crystallographica Section E Crystallographic Communications)

   null (Ed.)

   The title compound, C 15 H 17 NO 2 S, was synthesized via a substitution reaction between 4-methylbenzylamine and p -toluenesulfonyl chloride. In the crystal, N—H...O hydrogen bonds link the molecules, forming ribbons running along the b -axis direction. One of the aromatic rings hosts two intermolecular C—H...π interactions that link these hydrogen-bonded ribbons into a three-dimensional network. 

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5. Supramolecular chemistry under mechanochemical conditions: a small molecule template generated and integrated into a molecular-to-supramolecular and back-to-molecular cascade reaction

   https://doi.org/10.1039/C9SC05823K  

   Yelgaonkar, Shweta P.; Swenson, Dale C.; MacGillivray, Leonard R. (April 2020, Chemical Science)

   null (Ed.)

   We describe the integration of a small-molecule hydrogen-bond-donor template into a cascade reaction that is comprised of a combination of molecular and supramolecular events. The cascade is performed mechanochemically and in the presence of μL amounts of water. The small-molecule template is generated (molecular) using water-assisted vortex grinding and is then used to assemble an alkene (supramolecular) to undergo an intermolecular [2 + 2] photodimerization reaction (molecular). The chemical cascade results in a cyclobutane photoproduct that we show serves as a building block of a hydrogen-bonded network with a topology that conforms to T-silica. Remarkably, the molecular–supramolecular–molecular chemical cascade occurs stepwise and entirely regioselectively within the continuous mechanochemical conditions employed. 

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