Santiago Uriel

We present a new family of halogen-bonded pyridinium salts where both ionic partners participate in halogen bonding, leading to self-assembled smectic phases with nanosegregated ionic channels and high ionic conductivity.

We present two hydantoin isomers that self-assemble through hydrogen bonding in solution and in bulk, either in a bowl-shaped or planar rosette, resulting in remarkable liquid crystals and gelation properties.

A study of the solution-phase, solid-state structures of halogen-bonded co-crystals of 1,4-bis(iodoethynyl)benzene (p-BIB) with three salts, namely, decyltrimethylammonium bromide (DTMABr), tetrapropylammonium bromide (TPABr), and tetrabutylammonium bromide (TBABr), has been carried out, along with theoretical calculations. Isothermal titration calorimetry (ITC) showed that the binding constant of bromide with p-BIB in THF is not strongly dependent on the cation, and that the entropic term clearly dominates the enthalpic one in the free energy of binding. In the three crystal structures, the bromide anion acts as a doubly connected node for halogen bonding interactions, which results in linear or angular open chains. The intrachain angles (I⋯Br⁻⋯I) of the 1D supramolecular polymers based on p-BIB depend on the geometry and size of the cation and vary from 180° for DMTABr to 75° for TBABr. Non-covalent interaction (NCI) analysis of selected motifs and optimized crystals demonstrates that the balance between halogen bonds, hydrogen bonds, and van der Waals interactions, especially type-I halogen⋯halogen contacts, determines the crystal structures.

4-Iodo-N-(4-pyridyl)benzamide (INPBA) and four derived coordination complexes were synthesized in order to explore the combination of halogen and hydrogen bonding interactions in coordination chemistry. An electron-withdrawing carbonyl group attached to the aromatic ring bearing an iodine atom has been introduced to increase its halogen bonding ability. Single crystal X-ray diffraction analyses of INPBA, [Ag(INPBA)₂]NO₃ (1), [ZnBr₂(INPBA)₂] (2), [Zn(OCOPh)₂(INPBA)₂] (3) and [HgI₂(INPBA)]_n (4) show the versatility of the INPBA building block yielding a variety of different interesting structures. Iodine atom arrangement plays a key role by reinforcing and extending crystalline structures into diverse 3D supramolecular networks via I⋯O, I⋯N, and I⋯I halogen bonding interactions. Besides this, the overall supramolecular architecture of the coordination complexes is modulated by the N–H⋯O, N–H⋯Br, and C–H⋯O hydrogen bonds formed by the carboxamide group. The combination of both, halogen and hydrogen bonds, allows very different coordination networks to be designed.

A novel approach for the formation of bisindolylmethane derivatives (BIMs) is described as a proof of concept to evaluate the catalytic capacity of iodoalkynes. The use of these derivatives is reported as an example of simple halogen bond-based organocatalyst. This kind of activation has not been used before for the synthesis of bisindolylmethane derivatives 3. Interestingly, the preparation of 3-(1H-indol-3-yl)-1-phenylbutan-1-one (8) has been also achieved for the first time with an iodoalkyne derivative. We prove the efficiency of this family of new catalysts by developing a simple and easy operational methodology, opening the door to the development of alternative catalysts in the area of halogen bond-based organocatalysts.

Racemic 2,8-diiodo-6H,12H-5,11-methanodibenzodiazocine (rac-1) and racemic 2,8-diiodoethynyl-6H,12H-5,11-methano-dibenzodiazocine (rac-2) proved to be self-complementary tectons that are particularly suitable for the formation of porous supramolecular structures by halogen bonding. Crystals structures of clathrate rac-1·CH₂Cl₂ and rac-2 show channels, which represent 20% of the cell volume, and these are stabilized by strong C–I⋯N and C–I⋯π_(Ar) halogen bonds.

Theoretical calculations are proposed to investigate chiral photoinduction in achiral materials in the search for new routes for achieving chiral supramolecular organizations.

Achiral compounds 4‐methoxy‐4‐(p‐methoxyphenyl)cyclohexanoneethylene ketal (2), 4‐hydroxy‐4‐(p‐methoxy phenyl)cyclohexanoneethylene ketal (3), and 3,5‐dimethyl‐4‐nitropyrazole (4) crystallized in chiral structures and the samples showed an enantiomeric excess. We have determined the absolute structures of these compounds by using X‐ray diffraction with copper radiation at low temperatures. Moreover, we have also established the prevalent absolute structures in these samples, by comparing their calculated and solid‐state vibrational circular dichroism (VCD) spectra. The consistency of this method was confirmed by using (R,R)‐2,8‐diiodo‐4,10‐dimethyl‐6 H,12H‐5,11‐methano‐dibenzo[b,f][1,5]diazocine, Tröger′s base, (R,R)‐1, as a chiral compound of known absolute configuration.