Recognition of Polyfluorinated Compounds Through Self-Aggregation in a Cavity

Polyfluorinated aliphatic compounds were encapsulated by a self-assembled M₆L₄ coordination host in aqueous media. NMR titration and X-ray crystallographic analyses clearly revealed that the aggregation of the fluorinated moieties of the guests in the host cavity plays a significant role in the binding. Polyfluorinated aromatics did not show such aggregation in the cavity because of their “<i>nonfluorous</i>” nature

In the Pursuit of Efficient Anion-Binding Organic Ligands Based on Halogen Bonding

The syntheses and the crystal structures of new multitopic anion-binding organic ligands based on a benzenoid scaffold and bearing two or three 2-iodo-imidazolium arms are reported. The quite short C–I···Br¯ contacts observed in the solid state (0.77 times the normalized contacts) demonstrate the excellent halogen bonding donor ability of iodine atoms in 2-iodoimidazolium cations. The geometric features of obtained bromide anion adducts afford valuable structural insights for the design of effective and selective multitopic anion receptors based on halogen bonding

Solution and Solid State Synthesis of the Discrete Polyiodide I₇^3– under Modular Cation Templation

Discrete I₇³¯ polyiodide is obtained in pure form through solution and solid-state processes thanks to templation by a triammonium cation which elicits the selective formation of the size matching supramolecular anion

Halogen Bonding and Pharmaceutical Cocrystals: The Case of a Widely Used Preservative

3-Iodo-2-propynyl-<i>N</i>-butylcarbamate (IPBC) is an iodinated antimicrobial product used globally as a preservative, fungicide, and algaecide. IPBC is difficult to obtain in pure form as well as to handle in industrial products because it tends to be sticky and clumpy. Here, we describe the preparation of four pharmaceutical cocrystals involving IPBC. The obtained cocrystals have been characterized by X-ray diffraction, solution and solid-state NMR, IR, and DSC analyses. In all the described cases the halogen bond (XB) is the key interaction responsible for the self-assembly of the pharmaceutical cocrystals thanks to the involvement of the 1-iodoalkyne moiety of IPBC, which functions as a very reliable XB-donor, with both neutral and anionic XB-acceptors. Most of the obtained cocrystals have improved properties with respect to the source API, in terms, e.g., of thermal stability. The cocrystal involving the GRAS excipient CaCl₂ has superior powder flow characteristics compared to the pure IPBC, representing a promising solution to the handling issues related to the manufacturing of products containing IPBC

Dynamic Characterization of Crystalline Supramolecular Rotors Assembled through Halogen Bonding

A modular molecular kit for the preparation of crystalline molecular rotors was devised from a set of stators and rotators to gain simple access to a large number of structures with different dynamic performance and physical properties. In this work, we have accomplished this with crystalline molecular rotors self-assembled by halogen bonding of diaza­bicyclo­[2.2.2]­octane, acting as a rotator, and a set of five fluorine-substituted iodo­benzenes that take the role of the stator. Using variable-temperature ¹H <i>T</i>₁ spin–lattice relaxation measurements, we have shown that all structures display ultrafast Brownian rotation with activation energies of 2.4–4.9 kcal/mol and pre-exponential factors of the order of (1–9) × 10¹² s^–1. Line shape analysis of quadrupolar echo ²H NMR measurements in selected examples indicated rotational trajectories consistent with the 3-fold or 6-fold symmetric potential of the rotator

KPF₆ 14.2 mM perfusion induced large amplitude depolarization events that propagated through the cortical mantel, from the hippocampus to the entorhinal (EC) and piriform cortex (PC).

<p>These events were interpreted as spreading depolarization phenomena (Somjen 2001). </p

A: Seizure occurrence after perfusion of the <i>in</i><i>vitro</i> isolated guinea pig brain with different K⁺ salt solutions.

<p>The white columns represent the total number of experiments. The light grey, dark grey and black columns mark the effects of the perfusion of K⁺ salts at 8, 14.2m 20 mM, respectively. <b>B</b>: Time at onset (black columns) and duration (white columns) of seizure activity after perfusion with 14.2 KPF₆, 14.2 mM KClO₄ and 20 mM KBF₄. <b>C</b>: Brain parenchyma concentration of two salts (KPF₆ and KBF₄) estimated by ¹⁹F MR spectroscopy on CA1-EC specimens, collected after arterial perfusion with 14.2 mM KPF₆ (n= 4; black column) and 20 mM KBF₄ (n= 3; grey column). </p

Effects of perfusion of K⁺ salts in the <i>in</i><i>vitro</i> isolated guinea pig brain.

<p>A scheme of the position of the recording and stimulating (S1, on the lateral olfactory tract) electrodes is shown in the upper part of the figure. The upper set of traces illustrates the effect of 14.2 mM KPF₆ perfusion (right) compared to control (left); seizure activity was induced by this salt. In the lower part of the figure the effect of perfusion with 14.2 mM KClO₄ is shown. PC: piriform cortex; EC: entorhinal cortex; HIP: CA1 region of the hippocampus.</p

A. Schematic protocol of the experiments. Electrophysiological recordings are performed for the entire experimental period

<p>Each perfusion of salts lasted 15 min. and was followed by 30 min. wash-out. Brain tissue samples were than collected and processed for the ¹⁹F MR spectroscopy. <b>B:</b> Structures of KX salts (X= PF₆^-, BF₄^-, ClO₄^-, Br^-, AcO^- and Cl^-) and electrostatic potential surfaces (B3LYP/6-311+G**) of individuals ions and ion pairs. Blue regions indicate positive potentials and red regions negative ones. Maximum values of the electrostatic potential, at K atom, and minimum values, at O, F, Br and Cl atoms are indicated besides each structure. Molecular volumes are also reported (ų).</p

Interplay between Structural and Dielectric Features of New Low k Hybrid Organic–Organometallic Supramolecular Ribbons

The synthesis and characterization of low k one-dimensional (1D) hybrid organic–organometallic supramolecular ribbons <b>3a</b>,<b>b</b>, through halogen-bond driven co-crystallization of <i>trans</i>-[Pt­(PCy₃)₂(CC-4-py)₂] (<b>1</b>) with 1,4-diiodotetrafluorobenzene (<b>2a</b>) and <i>trans</i>-1,2-bis-(2,3,5,6-tetrafluoro-4-iodophenyl)-ethylene (<b>2b</b>), are reported. The co-crystals <b>3a</b>,<b>b</b> have been obtained by isothermal evaporation of a chloroform solution containing the corresponding starting materials at room temperature. X-ray structure determinations show that noncovalent interactions other than halogen bonds help in the construction of the crystal packing; these interactions are stronger in <b>3b</b>, thus reducing the chain mobility with respect to <b>3a</b>. Accordingly, the broadband dielectric spectroscopic determinations, carried out from 10^–2 to 10⁷ Hz and at a temperature ranging from 25 to 155 °C, showed that both <b>3a</b> and <b>3b</b> materials exhibit a real component of dielectric permittivity (ε′) significantly lower than SiO₂. In particular in the case of <b>3b</b>, the rigidity of the 1D chain explains the observed ε″ and tan δ values. A permittivity value that is significantly lower than that of the silica reference, tan δ values lower than 0.02 in the entire investigated temperature range, and less than 0.004 at <i>T</i> < 100 °C make <b>3b</b> a very promising low k hybrid organic–organometallic material for application as dielectric films in next generation microelectronics