Unlocking pedal motion of the azo group: three- and unexpected eight-component hydrogen-bonded assemblies in co-crystals based on isosteric resorcinols

Kristin M. HutchinsDepartment of Chemistry, University of Iowa, Iowa City, IA, USA

http://orcid.org/0000-0001-8792-2830

Shweta P. YelgaonkarDepartment of Chemistry, University of Iowa, Iowa City, IA, USA

Brittany L. Harris-ConwayDepartment of Biological Sciences, Webster University, St. Louis, MO, USA

Eric W. ReinheimerDepartment of Chemistry and the W.M. Keck Foundation Center for Molecular Structure, California State University, San Marcos, CA, USA

Leonard R. MacGillivrayDepartment of Chemistry, University of Iowa, Iowa City, IA, USACorrespondence[email protected]

http://orcid.org/0000-0003-0875-677X

Ryan H. GroenemanDepartment of Biological Sciences, Webster University, St. Louis, MO, USACorrespondence[email protected]

http://orcid.org/0000-0002-4602-6287

Abstract

Co-crystallization of 3-phenylazopyridine (3PAzP) with dihalogenated resorcinols (res) 4,6-diX res (where: X = Cl, Br, and I) yields co-crystals that support molecular pedal motion in the crystalline state. The co-crystals are sustained by hydrogen-bonded assemblies, with the pattern of hydrogen-bonding drastically different based on the res. For 4,6-diCl res, an unexpected eight-component hydrogen-bonded assembly is realized, while three-component hydrogen-bonded assemblies are observed for 4,6-diBr res and 4,6-diI res. We show the co-crystallization approach to afford pedal motion in the azo core, while no such motion is present in the absence of a res. Pure 3PAzP packs to form a noncentrosymmetric herringbone structure.

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Acknowledgements

R.H.G. gratefully acknowledges financial support from Webster University in the form of Faculty Research Grants. L.R.M. gratefully acknowledges the National Science Foundation (DMR-1708673).

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