Experimental Studies of the <sup>13</sup>C NMR of Iodoalkynes in Lewis-Basic Solvents

Webb, Jeffrey A.; Klijn, Jaap E.; Hill, P. Aru; Bennett, Jordan L.; Goroff, Nancy S.

doi:10.1021/jo035584c

Cited by 61 publications

(63 citation statements)

References 29 publications

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“…The data acquired by Kochi et al suggests that the hydrogen bond donor ability of the solvent has a detrimental effect on halogen bonding, whereas environmental polarity possesses a considerably weaker and ambiguous influence. This conclusion is further supported by the observations of Goroff et al [23], who studied the interaction of 1-iodoalkynes with pyridine, quinolone, THF, acetone, benzophenone, and chloroform in a mixture with hexanes. Based on correlations of the 13 C NMR shifts to a variety of empirical models of solvent basicity, Goroff suggested that basicity plays an important role for the interaction strength, but not polarity.…”

Section: Neutral Two-center Halogen Bond Complexessupporting

confidence: 77%

Halogen Bonding in Solution

Carlsson

Veiga

Erdélyi

2014

Topics in Current Chemistry

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Because of its expected applicability for modulation of molecular recognition phenomena in chemistry and biology, halogen bonding has lately attracted rapidly increasing interest. As most of these processes proceed in solution, the understanding of the influence of solvents on the interaction is of utmost importance. In addition, solution studies provide fundamental insights into the nature of halogen bonding, including, for example, the relative importance of charge transfer, dispersion, and electrostatics forces. Herein, a selection of halogen bonding literature is reviewed with the discussion focusing on the solvent effect and the electronic characteristics of halogen bonded complexes. Hence, charged and neutral systems together with two- and three-center bonds are presented in separate sub-sections. Solvent polarity is shown to have a slight stabilizing effect on neutral, two-center halogen bonds while strongly destabilizes charged, two-center complexes. It does not greatly influence the geometry of three-center halogen bonds, even though polar solvents facilitate dissociation of the counter-ion of charged three-center bonds. The charged three-center bonds are strengthened by increased environment polarity. Solvents possessing hydrogen bond donor functionalities efficiently destabilize all types of halogen bonds, primarily because of halogen vs hydrogen bond competition. A purely electrostatic model is insufficient for the description of halogen bonds in polar systems whereas it may give reasonable correlation to experimental data obtained in noninteracting, apolar solvents. Whereas dispersion plays a significant role for neutral, two-center halogen bonds, charged halogen bond complexes possess a significant charge transfer characteristic.

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Section: Neutral Two-center Halogen Bond Complexessupporting

confidence: 77%

Halogen Bonding in Solution

Carlsson

Veiga

Erdélyi

2014

Topics in Current Chemistry

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“…According to these studies, the observed deshielding in MIF-1 would be consistent with coordination of the imidazole moiety to Zn 2 + ions, which, owing to differences in their coordination sphere, are slightly less strong Lewis acids than those in ZIF-8. [33][34][35] It has been pointed out previously that the chemical shifts and peak widths of the different carbon atoms of the surfactant are a sensitive probe of the conformation of the template confined in inorganic hosts and host-guest interfacial interactions. [36,37] The 13 C signals of all MIFs show a downfield shift of the inner-chain methylene and terminal carbon of the surfactant chain (C4-C15 and C16/17, for labeling see the scheme in Figure 4) by about 1-2 ppm with respect to that typically found for CTAB molecules occluded in hexagonal mesostructures, and are consistent with those found for lamellar mesostructures.…”

Section: Synthesis and Characterizationmentioning

confidence: 99%

Towards Mesostructured Zinc Imidazolate Frameworks

Junggeburth¹,

Schwinghammer²,

Virdi³

et al. 2012

Chemistry A European J

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The transfer of supramolecular templating to the realm of metal-organic frameworks opens up new avenues to the design of novel hierarchically structured materials. We demonstrate the first synthesis of mesostructured zinc imidazolates in the presence of the cationic surfactant cetyltrimethylammonium bromide (CTAB), which acts as a template giving rise to ordered lamellar hybrid materials. A high degree of order spanning the atomic and mesoscale was ascertained by powder X-ray diffraction, electron diffraction, as well as solid-state NMR and IR spectroscopy. The metrics of the unit cells obtained for the zinc methylimidazolate and imidazolate species are a=(11.43±0.45), b=(9.55±0.35), c=(27.19±0.34) Å, and a=(10.98±0.90), b=(8.95±0.95), c=(26.33±0.34) Å, respectively, assuming orthorhombic symmetry. The derived structure model is consistent with a mesolamellar structure composed of bromine-terminated zinc (methyl)imidazolate chains interleaved with motionally rigid cationic surfactant molecules in an all-trans conformation. The hybrid materials exhibit unusually high thermal stability up to 300 °C, at which point CTAB is lost and evidence for a thermally induced transformation into poorly crystalline mesostructures with larger feature sizes is obtained. Treatment with ethanol effects the extraction of CTAB from the material, followed by facile transformation into pure microporous ZIF-8 nanoparticles within minutes, thus demonstrating a unique transition from a mesostructure into a microporous zinc imidazolate.

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“…[44] Additional support for this interpretation was obtained from good correlation with various empirical models of solvent basicity, including Gutmanns donor numbers and Taft and Kamlets b values. [45] Furthermore, poor correlation to Reichardts E N T values and Taft and Kamlets p* parameters suggests that solvent polarity does not play a role. [45] Interestingly, the resonance of the I-CA C H T U N G T R E N N U N G (sp 2 ) moiety of iodoarenes in 13 C NMR spectroscopic analysis does not undergo a downfield shift on changing from a noncoordinating to a coordinating solvent, even though complexation occurs.…”

Section: Introductionmentioning

confidence: 99%

“…[45] Furthermore, poor correlation to Reichardts E N T values and Taft and Kamlets p* parameters suggests that solvent polarity does not play a role. [45] Interestingly, the resonance of the I-CA C H T U N G T R E N N U N G (sp 2 ) moiety of iodoarenes in 13 C NMR spectroscopic analysis does not undergo a downfield shift on changing from a noncoordinating to a coordinating solvent, even though complexation occurs. [46] It was proposed that this phenomenon is because the nonrelativistic complexation shifts and the change in the spin-orbit-induced heavy-atom effect of iodine compensate each other.…”

Section: Introductionmentioning

confidence: 99%

Molecular Assemblies from Imidazolyl‐Containing Haloalkenes and Haloalkynes: Competition between Halogen and Hydrogen Bonding

Bouchmella

Boury

Dutremez

et al. 2007

Chemistry A European J

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The structural characterization of molecular assemblies constructed from imidazolyl-containing haloalkenes and haloalkynes is reported. 1-(3-Iodopropargyl)imidazole (2) and 1-(2,3,3-triiodoallyl)imidazole (5) were synthesized from 1-propargylimidazole (1). In the solid state, these wholly organic modules self-assemble through N...I halogen-bonding interactions, thus giving rise to polymeric chains. The N...I interaction observed in 2 (d(N...I)=2.717 A, angle-spherical C(sp)-I...N=175.8 degrees) is quite strong relative to previously reported data. The N...I interaction in 5 (d(N...I)=2.901 A, angle-spherical C(sp2)-I...N=173.6 degrees) is weaker, in accordance with the order C(sp)-X<--base>C(sp2)-X<--base. Compound 5 was found to give a 1:1 cocrystal 4 with morpholinium iodide (6). In the X-ray crystal studies of 4, N...I halogen-bonding interactions similar to those observed in 5 were shown not to be present, as the arrangement of the molecules is governed by two interwoven hydrogen-bonding networks. The first network involves N-H...O interactions between nearby morpholinium cations, and the second network is based on N-H...N hydrogen bonding between morpholinium cations and imidazolyl groups. Both hydrogen-bonding schemes are charge-assisted. Halogen bonding is not completely wiped out, however, as the triiodoalkene fragment forms a halogen bond with an iodide anion in its vicinity (d(I...I)=3.470 A, angle-spherical C(sp2)-I...I=170.7 degrees). X-ray crystal studies of 6 show a completely different arrangement from that observed in 4, namely, N-H...O interactions are not present. In crystalline 6, morpholinium cations are interconnected through C-H...O bridges (d(H...O)=2.521 and 2.676 A), and the NH2+ groups interact with nearby iodide anions (d(H...I)=2.633 and 2.698 A).

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Experimental Studies of the ¹³C NMR of Iodoalkynes in Lewis-Basic Solvents

Cited by 61 publications

References 29 publications

Halogen Bonding in Solution

Halogen Bonding in Solution

Towards Mesostructured Zinc Imidazolate Frameworks

Molecular Assemblies from Imidazolyl‐Containing Haloalkenes and Haloalkynes: Competition between Halogen and Hydrogen Bonding

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Experimental Studies of the 13C NMR of Iodoalkynes in Lewis-Basic Solvents

Cited by 61 publications

References 29 publications

Halogen Bonding in Solution

Halogen Bonding in Solution

Towards Mesostructured Zinc Imidazolate Frameworks

Molecular Assemblies from Imidazolyl‐Containing Haloalkenes and Haloalkynes: Competition between Halogen and Hydrogen Bonding

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Product

Resources

About

Experimental Studies of the ¹³C NMR of Iodoalkynes in Lewis-Basic Solvents