Etude electrochimique du cation argent en presence de |2.2.2| paracyclophane (π-prismand) et de molecules apparentees

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

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.

[2.2.2]Paracyclophane, preference for η6 or η18 coordination mode including Ag(i) and Sn(ii): a survey into the cation–π interaction nature through relativistic DFT calculations

[2.2.2]Paracyclophane is a versatile π-cryptating structure, which can exhibit η²:η²:η² and η⁶:η⁶:η⁶ coordination with metal ions, involving two or six carbon atoms in each aromatic ring.

Role of the cation formal charge in cation–π interaction. A survey involving the [2.2.2]paracyclophane host from relativistic DFT calculations

Of charge and cations. Isoelectronic cation–π complexes unravel the nature of variation of the interaction.

Preparation of a Polymer-Supported Fluorene-Based Receptor for Quantitative and Efficient Binding of Silver Cations

We have designed and synthesized a polymer-supported material in which a versatile fluorene-p-xylene-based receptor is woven onto the backbone of polystyrene. This polymer-supported receptor adopts a pi-prismand-like conformation through a simple C--C bond rotation that results in the quantitative binding of a single silver cation per receptor site with a remarkable efficiency that exceeds the binding abilities of the well-known tris[2.2.2]-p-cyclophane (or pi prismand) by at least a factor of 100. More importantly, the binding event can be readily monitored by 1H NMR spectroscopy, as well as by a more sensitive emission spectroscopic technique in which the quenching of fluorescence of the receptor moiety is quantitatively related to the binding of silver cations.

Convergent Synthesis of Alternating Fluorene-p-xylene Oligomers and Delineation of the (Silver) Cation-Induced Folding

Convergent synthetic routes for the preparation of hitherto unknown fluorene-p-xylene oligomers (containing up to 10 fluorene moieties) from readily available starting materials are described. The conformationally adaptable monomeric receptor (which is made of a pair of fluorene and one p-xylene ring, i.e., Z1) undergoes a simple C-C bond rotation in the presence of silver cations to produce a pi-prismand-like receptor which binds a single silver cation with remarkable efficiency (i.e., K approximately 15,000 M(-1)). The data on 1H NMR spectroscopic titrations with Ag+ together with the density functional theory and AM1 calculations allows us to establish that various oligomers of Z1 (i.e., Z2-Z9) also undergo ready folding into the structures that contain multiple pi-prismand-like receptor sites in the presence of silver cations. The multiple cavities in Z3-Z9 accommodate a single silver cation per cavity with efficiency similar to that of Z1.