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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

Orientation and magnitude of the absolute shielding (σij) for C1, C2, and C3 before and after the inclusion of AgI.
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fig02: Orientation and magnitude of the absolute shielding (σij) for C1, C2, and C3 before and after the inclusion of AgI.

Mentions: Because of the C3 symmetry point group of [Ag([2.2.2]pCp)]+, six chemically different aromatic carbon types are advised from theoretical 13C NMR calculations, as depicted in Figure S1 and Table S1 (Supporting Information), given by C(1)=137.9, C(4)=137.8, C(2)=119.7, C(3)=118.6, C(5)=133.5, and C(6)=130.0 ppm, obtained as δij=σTMS−σij22 (σTMS=193.10 ppm). To take into account the dynamic scenario resulting from the solution-state NMR experiment,15 the related nuclei were averaged into three main chemically different groups of aromatic carbon atoms, namely C1, C2, and C3 (Figure 2). Such groups are composed of C(1)–C(4), C(2)–C(3), and C(5)–C(6), depicting para-, upper-meta, and lower-meta carbons, respectively (Figure 2). Hence, the 13C NMR shifts amount to 137.8 ppm for C1, 119.1 ppm for C2, and 131.8 ppm for C3 (Table 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)

Orientation and magnitude of the absolute shielding (σij) for C1, C2, and C3 before and after the inclusion of AgI.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig02: Orientation and magnitude of the absolute shielding (σij) for C1, C2, and C3 before and after the inclusion of AgI.
Mentions: Because of the C3 symmetry point group of [Ag([2.2.2]pCp)]+, six chemically different aromatic carbon types are advised from theoretical 13C NMR calculations, as depicted in Figure S1 and Table S1 (Supporting Information), given by C(1)=137.9, C(4)=137.8, C(2)=119.7, C(3)=118.6, C(5)=133.5, and C(6)=130.0 ppm, obtained as δij=σTMS−σij22 (σTMS=193.10 ppm). To take into account the dynamic scenario resulting from the solution-state NMR experiment,15 the related nuclei were averaged into three main chemically different groups of aromatic carbon atoms, namely C1, C2, and C3 (Figure 2). Such groups are composed of C(1)–C(4), C(2)–C(3), and C(5)–C(6), depicting para-, upper-meta, and lower-meta carbons, respectively (Figure 2). Hence, the 13C NMR shifts amount to 137.8 ppm for C1, 119.1 ppm for C2, and 131.8 ppm for C3 (Table 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