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

Hyperbranched Quasi-1D TiO₂ Nanostructure for Hybrid Organic–Inorganic Solar Cells

The performance of hybrid solar cells is strongly affected by the device morphology. In this work, we demonstrate a poly­(3-hexylthiophene-2,5-diyl)/TiO₂ hybrid solar cell where the TiO₂ photoanode comprises an array of tree-like hyperbranched quasi-1D nanostructures self-assembled from the gas phase. This advanced architecture enables us to increase the power conversion efficiency to over 1%, doubling the efficiency with respect to state of the art devices employing standard mesoporous titania photoanodes. This improvement is attributed to several peculiar features of this array of nanostructures: high interfacial area; increased optical density thanks to the enhanced light scattering; and enhanced crystallization of poly­(3-hexylthiophene-2,5-diyl) inside the quasi-1D nanostructure

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

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

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

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

A Superfluorinated Molecular Probe for Highly Sensitive <i>in Vivo</i>¹⁹F‑MRI

¹⁹F-MRI offers unique opportunities to image diseases and track cells and therapeutic agents <i>in vivo</i>. Herein we report a superfluorinated molecular probe, herein called <b>PERFECTA</b>, possessing excellent cellular compatibility, and whose spectral properties, relaxation times, and sensitivity are promising for <i>in vivo</i>¹⁹F-MRI applications. The molecule, which bears 36 equivalent ¹⁹F atoms and shows a single intense resonance peak, is easily synthesized via a simple one-step reaction and is formulated in water with high stability using trivial reagents and methods