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Influence of Ag(+) on the Magnetic Response of [2.2.2]Paracyclophane: NMR Properties of a Prototypical Organic Host for Cation Binding Based on DFT Calculations.

MacLeod Carey D, Gomez T, Morales-Verdejo C, Muñoz-Castro A - ChemistryOpen (2015)

Bottom Line: Through this study we sought a deeper understanding of the effects the metal center has on the NMR spectroscopic properties of the prototypical organic host, generating theoretical reasons for the observed experimental results with an aim to determine the role of the cation-π interaction in a host-guest scenario.From an analysis of certain components of the induced magnetic field and the (13)C NMR shielding tensor under its own principal axis system (PAS), the local and overall magnetic behavior can be clearly described.This proposed approach can be useful to gain further insight into the local and overall variation of NMR shifts for host-guest pairs involving both inorganic and organic hosts.

View Article: PubMed Central - PubMed

Affiliation: Facultad de Ingeniería, Universidad Autonoma de Chile Llano Subercaceaux 2801, San Miguel, Santiago, 780-0026, Chile.

ABSTRACT
The complexation of metal cations into a host-guest situation is particularly well exemplified by [2.2.2]paracyclophane and Ag(I), which leads to a strong cation-π interaction with a specific face of the host molecule. Through this study we sought a deeper understanding of the effects the metal center has on the NMR spectroscopic properties of the prototypical organic host, generating theoretical reasons for the observed experimental results with an aim to determine the role of the cation-π interaction in a host-guest scenario. From an analysis of certain components of the induced magnetic field and the (13)C NMR shielding tensor under its own principal axis system (PAS), the local and overall magnetic behavior can be clearly described. Interestingly, the magnetic response of such a complex exhibits a large axis-dependent behavior, which leads to an overall shielding effect for the coordinating carbon atoms and a deshielding effect for the respective uncoordinated counterparts, evidence that complements previous experimental results. This proposed approach can be useful to gain further insight into the local and overall variation of NMR shifts for host-guest pairs involving both inorganic and organic hosts.

No MeSH data available.


Related in: MedlinePlus

Magnitude in variation of the principal components for C1, C2, and C3 (isovalue ±5 ppm), denoting shielding for positive values in blue, and deshielding for negative values in red.
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fig03: Magnitude in variation of the principal components for C1, C2, and C3 (isovalue ±5 ppm), denoting shielding for positive values in blue, and deshielding for negative values in red.

Mentions: For C1, σ33 is shifted by ∼2.25 ppm toward the upfield region, whereas σ11 and σ22 are shifted downfield. In such a nucleus, the main difference leading to the chemical shift variations is taken into account by the σ22 component (Table 1). The shift of the σ33 PAS component located at C2 amounts to 5.28 ppm upfield; however, despite the orientation of such a component toward the Ag+ center, it is not the more influenced term of the respective shielding tensor. For C2, the σ11 component, which is oriented through the C−H bond, is largely upfield shifted by ∼12.03 ppm, followed by the σ22 component by ∼7.53 ppm. In contrast, C3 exhibits a lesser σ33 shift, denoting a larger downfield shift for σ22 of about −10.29 ppm, and of −5.23 ppm for σ11. From Figure 3, the differences between each principal component before and after the inclusion of the Ag+ center are described, where it can be clearly seen that the σ11 and σ22 components are the more influenced terms in the nuclear shielding of the representative carbon atoms. As result, the atoms in the aromatic ring located in the face below are deshielded, whereas those in the upper face are shielded, and hence the through-space effect due to inclusion of the Ag+ ion is of a shielding nature.


Influence of Ag(+) on the Magnetic Response of [2.2.2]Paracyclophane: NMR Properties of a Prototypical Organic Host for Cation Binding Based on DFT Calculations.

MacLeod Carey D, Gomez T, Morales-Verdejo C, Muñoz-Castro A - ChemistryOpen (2015)

Magnitude in variation of the principal components for C1, C2, and C3 (isovalue ±5 ppm), denoting shielding for positive values in blue, and deshielding for negative values in red.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4608534&req=5

fig03: Magnitude in variation of the principal components for C1, C2, and C3 (isovalue ±5 ppm), denoting shielding for positive values in blue, and deshielding for negative values in red.
Mentions: For C1, σ33 is shifted by ∼2.25 ppm toward the upfield region, whereas σ11 and σ22 are shifted downfield. In such a nucleus, the main difference leading to the chemical shift variations is taken into account by the σ22 component (Table 1). The shift of the σ33 PAS component located at C2 amounts to 5.28 ppm upfield; however, despite the orientation of such a component toward the Ag+ center, it is not the more influenced term of the respective shielding tensor. For C2, the σ11 component, which is oriented through the C−H bond, is largely upfield shifted by ∼12.03 ppm, followed by the σ22 component by ∼7.53 ppm. In contrast, C3 exhibits a lesser σ33 shift, denoting a larger downfield shift for σ22 of about −10.29 ppm, and of −5.23 ppm for σ11. From Figure 3, the differences between each principal component before and after the inclusion of the Ag+ center are described, where it can be clearly seen that the σ11 and σ22 components are the more influenced terms in the nuclear shielding of the representative carbon atoms. As result, the atoms in the aromatic ring located in the face below are deshielded, whereas those in the upper face are shielded, and hence the through-space effect due to inclusion of the Ag+ ion is of a shielding nature.

Bottom Line: Through this study we sought a deeper understanding of the effects the metal center has on the NMR spectroscopic properties of the prototypical organic host, generating theoretical reasons for the observed experimental results with an aim to determine the role of the cation-π interaction in a host-guest scenario.From an analysis of certain components of the induced magnetic field and the (13)C NMR shielding tensor under its own principal axis system (PAS), the local and overall magnetic behavior can be clearly described.This proposed approach can be useful to gain further insight into the local and overall variation of NMR shifts for host-guest pairs involving both inorganic and organic hosts.

View Article: PubMed Central - PubMed

Affiliation: Facultad de Ingeniería, Universidad Autonoma de Chile Llano Subercaceaux 2801, San Miguel, Santiago, 780-0026, Chile.

ABSTRACT
The complexation of metal cations into a host-guest situation is particularly well exemplified by [2.2.2]paracyclophane and Ag(I), which leads to a strong cation-π interaction with a specific face of the host molecule. Through this study we sought a deeper understanding of the effects the metal center has on the NMR spectroscopic properties of the prototypical organic host, generating theoretical reasons for the observed experimental results with an aim to determine the role of the cation-π interaction in a host-guest scenario. From an analysis of certain components of the induced magnetic field and the (13)C NMR shielding tensor under its own principal axis system (PAS), the local and overall magnetic behavior can be clearly described. Interestingly, the magnetic response of such a complex exhibits a large axis-dependent behavior, which leads to an overall shielding effect for the coordinating carbon atoms and a deshielding effect for the respective uncoordinated counterparts, evidence that complements previous experimental results. This proposed approach can be useful to gain further insight into the local and overall variation of NMR shifts for host-guest pairs involving both inorganic and organic hosts.

No MeSH data available.


Related in: MedlinePlus