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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.


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Optimized structures of [2.2.2]paracyclophane and [2.2.2]paracyclophane–AgI, depicting the decrease in symmetry upon inclusion of AgI from a D3 {C3;3C2′} to a C3 {C3} point group.
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fig01: Optimized structures of [2.2.2]paracyclophane and [2.2.2]paracyclophane–AgI, depicting the decrease in symmetry upon inclusion of AgI from a D3 {C3;3C2′} to a C3 {C3} point group.

Mentions: [2.2.2]Paracyclophane can display several conformations given by the relative orientation of the −(CH2)2− bridges35 ranging from a D3 to a C2 structure. The early characterization of [Ag([2.2.2]pCp)]+ by NMR solution experiments was later corroborated structurally, denoting a coordination of the Ag+ center above the center of the π-prismane ligand.15,18 Such a coordination mode can be ascribed to a η2:η2:η2 hapticity, in which two aromatic carbon atoms of each six-membered ring are involved in the interaction.19 The characterized structure of [Ag([2.2.2]pCp)]+ depicts slight variations from the C3 point group (RMSD: 0.134 Å), which can be attributed to crystal packing and counter-ion effects. Such a structure results from [2.2.2]pCp in a D3 conformation, in which the inclusion of Ag+ breaks the perpendicular C2 rotation axis, leading to the consequent symmetry depicting three equivalent aromatic rings (Figure 1).


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)

Optimized structures of [2.2.2]paracyclophane and [2.2.2]paracyclophane–AgI, depicting the decrease in symmetry upon inclusion of AgI from a D3 {C3;3C2′} to a C3 {C3} point group.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig01: Optimized structures of [2.2.2]paracyclophane and [2.2.2]paracyclophane–AgI, depicting the decrease in symmetry upon inclusion of AgI from a D3 {C3;3C2′} to a C3 {C3} point group.
Mentions: [2.2.2]Paracyclophane can display several conformations given by the relative orientation of the −(CH2)2− bridges35 ranging from a D3 to a C2 structure. The early characterization of [Ag([2.2.2]pCp)]+ by NMR solution experiments was later corroborated structurally, denoting a coordination of the Ag+ center above the center of the π-prismane ligand.15,18 Such a coordination mode can be ascribed to a η2:η2:η2 hapticity, in which two aromatic carbon atoms of each six-membered ring are involved in the interaction.19 The characterized structure of [Ag([2.2.2]pCp)]+ depicts slight variations from the C3 point group (RMSD: 0.134 Å), which can be attributed to crystal packing and counter-ion effects. Such a structure results from [2.2.2]pCp in a D3 conformation, in which the inclusion of Ag+ breaks the perpendicular C2 rotation axis, leading to the consequent symmetry depicting three equivalent aromatic rings (Figure 1).

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