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1. Halogen-bonded co-crystal containing 1,3-diiodoperchlorobenzene and the photoproduct rtct -tetrakis(pyridin-4-yl)cyclobutane resulting in a zigzag topology

   https://doi.org/10.1107/S2056989023001408  

   Bosch, Eric ; Unruh, Daniel K. ; Santana, Carlos L. ; Groeneman, Ryan H. ( March 2023 , Acta Crystallographica Section E Crystallographic Communications)

   The formation and crystal structure of a zigzag network held together by I...N halogen bonds is reported. In particular, the halogen-bond donor is 1,3-diiodoperchlorobenzene ( C 6 I 2 Cl 4 ) while the acceptor is the photoproduct rtct -tetrakis(pyridin-4-yl)cyclobutane ( TPCB ). Curiously, within the resulting co-crystal ( C 6 I 2 Cl 4 )·( TPCB ), the photoproduct accepts only two halogen bonds between neighbouring 4-pyridyl rings and as a result behaves as a bent two-connected node rather than the expected four-connected centre. In addition, the photoproduct, TPCB , is also found to engage in C—H...N hydrogen bonds, forming an extended zigzag chain. 

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2. Halogen-Bond Mediated [2+2] Photodimerizations: À la Carte Access to Unsymmetrical Cyclobutanes in the Solid State

   https://doi.org/10.3390/molecules27031048  

   Quentin, Jay ; Reinheimer, Eric W. ; MacGillivray, Leonard R. ( February 2022 , Molecules)

   The ditopic halogen-bond (X-bond) donors 1,2-, 1,3-, and 1,4-diiodotetrafluorobenzene (1,2-, 1,3-, and 1,4-di-I-tFb, respectively) form binary cocrystals with the unsymmetrical ditopic X-bond acceptor trans-1-(2-pyridyl)-2-(4-pyridyl)ethylene (2,4-bpe). The components of each cocrystal (1,2-di-I-tFb)·(2,4-bpe), (1,3-di-I-tFb)·(2,4-bpe), and (1,4-di-I-tFb)·(2,4-bpe) assemble via N···I X-bonds. For (1,2-di-I-tFb)·(2,4-bpe) and (1,3-di-I-tFb)·(2,4-bpe), the X-bond donor supports the C=C bonds of 2,4-bpe to undergo a topochemical [2+2] photodimerization in the solid state: UV-irradiation of each solid resulted in stereospecific, regiospecific, and quantitative photodimerization of 2,4-bpe to the corresponding head-to-tail (ht) or head-to-head (hh) cyclobutane photoproduct, respectively.

    

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3. 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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4. Exploiting Boron Coordination: B←N Bond Supports a [2+2] Photodimerization in the Solid State and Generation of a Diboron Bis‐Tweezer for Benzene/Thiophene Separation

   https://doi.org/10.1002/ange.201812174  

   Campillo‐Alvarado, Gonzalo ; D'mello, Kyle P. ; Swenson, Dale C. ; Santhana Mariappan, S. V. ; Höpfl, Herbert ; Morales‐Rojas, Hugo ; MacGillivray, Leonard R. ( March 2019 , Angewandte Chemie)

   B←N coordination supports a [2+2] photodimerization in the solid state. The bond is defined by an orthogonal interaction between stilbazole and a phenylboronic ester to enable a stereocontrolled and rapid photoreaction. The cyclobutane photoproduct affords a novel diboron bis‐tweezer adduct that is used to separate a mixture of benzene and thiophene upon crystallization.

    

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5. Exploiting Boron Coordination: B←N Bond Supports a [2+2] Photodimerization in the Solid State and Generation of a Diboron Bis‐Tweezer for Benzene/Thiophene Separation

   https://doi.org/10.1002/anie.201812174  

   Campillo‐Alvarado, Gonzalo ; D'mello, Kyle P. ; Swenson, Dale C. ; Santhana Mariappan, S. V. ; Höpfl, Herbert ; Morales‐Rojas, Hugo ; MacGillivray, Leonard R. ( March 2019 , Angewandte Chemie International Edition)

   B←N coordination supports a [2+2] photodimerization in the solid state. The bond is defined by an orthogonal interaction between stilbazole and a phenylboronic ester to enable a stereocontrolled and rapid photoreaction. The cyclobutane photoproduct affords a novel diboron bis‐tweezer adduct that is used to separate a mixture of benzene and thiophene upon crystallization.

    

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