Pyrrole- and Naphthobipyrrole-Strapped Calix[4]pyrroles as Azide Anion Receptors

Journal Article · Wed Feb 14 00:00:00 EST 2018 · Journal of Organic Chemistry

DOI:https://doi.org/10.1021/acs.joc.7b03135· OSTI ID:1480249

Kim, Seung Hyeon ^[1]; Lee, Juhoon ^[2]; Vargas-Zúñiga, Gabriela I. ^[2]; Lynch, Vincent M. ^[2]; Hay, Benjamin P. ^[3]; Sessler, Jonathan L.  ^[2]; Kim, Sung Kuk  ^[1]

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1. Gyeongsang National Univ., Jinju (Korea)
2. Univ. of Texas, Austin, TX (United States)
3. Supramolecular Design Inst., Oak Ridge, TN (United States)

Here, the binding interactions between the azide anion (N₃^–) and the strapped calix[4]pyrroles 2 and 3 bearing auxiliary hydrogen bonding donors on the bridging moieties, as well as of normal calix[4]pyrrole 1, were investigated via ¹H NMR spectroscopic and isothermal titration calorimetry analyses. The resulting data revealed that receptors 2 and 3 have significantly higher affinities for the azide anion in organic media as compared with the unfunctionalized calix[4]pyrrole 1 and other azide receptors reported to date. Single crystal X-ray diffraction analyses and calculations using density functional theory revealed that receptor 2 binds CsN₃ in two distinct structural forms. As judged from the metric parameters, in the resulting complexes one limiting azide anion resonance contributor is favored over the other, with the specifics depending on the binding mode. In contrast to what is seen for 2, receptor 3 forms a CsN₃ complex in 20% CD₃OD in CDCl₃, wherein the azide anion is bound only vertically to the NH protons of the calix[4]pyrrole and the cesium cation is complexed within the cone shaped-calix[4]pyrrole bowl. The bound cesium cation is also in close proximity to a naphthobipyrrole subunit present in a different molecule, forming an apparent cation-π complex.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
• Sponsoring Organization: USDOE Office of Science (SC); National Research Foundation of Korea (NRF); National Institutes of Health (NIH); Robert A. Welch Foundation
• Grant/Contract Number: AC02-05CH11231; 2015R1C1A1A02037578; 2017R1A4A1014595; GM103790A; F-1018
• OSTI ID: 1480249
• Journal Information: Journal of Organic Chemistry, Vol. 83, Issue 5; ISSN 0022-3263
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Binding modes
Azides
Anions
Crystal structure
Receptors