Seung Hyeon Kim1, Juhoon Lee2, Gabriela I Vargas-Zúñiga2, Vincent M Lynch2, Benjamin P Hay3, Jonathan L Sessler2, Sung Kuk Kim1. 1. Department of Chemistry and Research Institute of Natural Science, Gyeongsang National University , Jinju 660-701, Korea. 2. Department of Chemistry, The University of Texas at Austin , 105 E. 24th, Street-Stop A5300, Austin, Texas 78712-1224, United States. 3. Supramolecular Design Institute , 127 Chestnut Hill Road, Oak Ridge, Tennessee 37830-7185, United States.
Abstract
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.
The binding interactions between the azide anion (N3-) and the strapped n class="Chemical">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.
Authors: Dae-Wi Yoon; Dustin E Gross; Vincent M Lynch; Jonathan L Sessler; Benjamin P Hay; Chang-Hee Lee Journal: Angew Chem Int Ed Engl Date: 2008 Impact factor: 15.336
Authors: Sung Kuk Kim; Juhoon Lee; Neil J Williams; Vincent M Lynch; Benjamin P Hay; Bruce A Moyer; Jonathan L Sessler Journal: J Am Chem Soc Date: 2014-10-08 Impact factor: 15.419