Angelina Flores-Parra

This research provides how chiral imidazolium salts {1,3-bis[1'-chloro-1'-phenylpropan-2'-yl]-imidazolium} (1a) and enantiopure {1,3-bis[(R)-1-chlorobutan-2-yl]-imidazolium} [1b] can be utilized in diverse synthetic pathways to obtain new carbene-borane adducts (2a-2d): {1,3-bis[1'-chloro-1'-phenylpropan-2'-yl]-imidazolyl-2-ylidene-borane} (2a), {1,3-bis[(Z)-1'-phenylpropen-2'-yl]-imidazolyl-2-ylidene-borane} (2b), {1,3-bis[(R)-1-chlorobutan-2-yl]-imidazolyl-2-ylidene-borane} (2c), and {1,3-bis[but-1-en-2-yl]-imidazolyl-2-ylidene-borane} (2d). The carbene-borane adducts were synthesized and characterized by ¹³C, ¹H, and ¹¹B nuclear magnetic resonance spectroscopy and time-of-flight mass spectrometry. The X-ray crystal analyses of compounds 2a and 2b were performed, and to understand the structure and interactions of 2a, a computational study was carried out. The effect of N-substituents in the NHC-borane adducts was clearly observed in the C-B bond lengths obtained by single-crystal X-ray diffraction, where the C-B bond is longer for adducts with N-(R)-chloroethyl substituents than for vinyl substituents. The analysis of the reduced density gradient and the bond critical point calculations of 2a showed intramolecular proton-hydride and Cl···N interactions. These chiral imidazolium salts could have applicability in the development of new materials and possibly in pharmaceutical research.

Formaldehyde is a simple chemical compound that is used as a building block in obtaining a wide range of products. The versatility of formaldehyde in chemical synthesis becomes evident when it is reacted with N-alkylethylenediamines. Therefore, this paper reports the structure and reactivity of a series of compounds derived from easily accessible molecules, such as formaldehyde, sodium hydrosulphide, and N-alkylethylenediamines. The 1,3,5-triazines (1a-1d) and bis(3-alkyl-imidazolidin-1-yl)methanes (2a-2d) were obtained by simple reaction conditions. Additionally, different proportions of sodium hydrosulphide and formaldehyde were used with N-benzylamine to obtain N-benzyltriazinane (3), N-benzylthiadiazinane (4) and N-benzyldithiazinane (5). All these compounds were characterized by analytical, spectroscopic, and spectrometric techniques, such as melting point, solubility, one-dimensional and two-dimensional nuclear magnetic resonance (¹³C, ¹H, ¹⁵N, COSY, HETCOR, NOESY, COLOC), elemental analysis, high- and low-resolution mass spectrometry, among others. The structures of compounds 4 and 5 were obtained by single-crystal X-ray diffraction. The results show that small variations in the stoichiometry and the reaction conditions significantly influence the products obtained.

In the title hydrated molecular salt, 2C₇H₈N₃ ⁺·SO₄ ²⁻·H₂O, the components are linked by numerous N—H...O and O—H...O hydrogen bonds.

The fluorescence properties of some imidazolium derivatives are relevant in photosensing and therefore, the structural analysis of them is a key point for its rational design, which would be useful to prepare new systems with novel applications. Herein we report a multidisciplinary study of the fluorescence and voltammetric properties of three imidazolium compounds {1,3‐bis[(R,R)‐1′‐chloro‐1′‐phenylpropan‐2′‐yl]‐imidazolium chloride (1), 1,3‐bis[(Z)‐1′‐phenylprop‐1′‐en‐2′‐yl]imidazolium chloride (2) 1,3‐bis[(R)‐1′‐chlorobutan‐2′‐yl]‐imidazolium chloride (3)}. Electronic structure calculations and Bader analyses were used to correlate both fluorescence and the capability of the molecules to be reduced through a heterogeneous electron transfer process. Both properties are strongly dependent on the proton in position two of the imidazolium ring, where the electron transfer as well as the excitation of the electrons are carried out. The reactivity in this position is controlled by the N‐substituents on the imidazolium ring and is due to single contacts H⋅⋅⋅Cl⁻, tricentric contacts Cl⋅⋅⋅Cl⁻⋅⋅⋅Cl, π‐electronic delocalization and π‐stacking interactions.

Reactions of 1,4-bis[(S) methylbenzyl]-1,4-diazabutadiene (1), 1,4-bis[(R) 1′-chlorobutan-2′-yl]-1,4-diazabutadiene (2), 1,4-bis[(S,S) 1′-chloro-1′-phenyl-propan-2′-yl]-1,4-diazabutadiene (3), and 1,4-di-tert-butyl-1,4-diazabutadiene (4) with aluminum and indium halides were performed. Reaction of 1,4-diazabutadienes 1–4 with two equivalents of aluminum halides in toluene afforded ionic aluminum coordination compounds (5–10) which in THF solution are transformed into 1,3-dialkyl-2-methaneiminealkyl imidazolium heterocycles (11–14) by condensation of two 1,4-diazabutadienes and elimination of amine hydrochloride. Equimolar reactions of 1–4 with InCl3 in dry acetonitrile at −78 °C afforded the neutral and diamagnetic InCl3 coordination compounds (15–18), which are stable in the solid state under dry conditions, but in THF solution are slowly transformed into the corresponding 1,3-dialkyl-imidazolium heterocycles 19–22. The X-ray diffraction analyses of compounds 2, 3, 10, 11, 14 and 17 are described. Quantum mechanical calculations were performed in order to find the minimum energy conformers of 1,4-diazabutadienes, 1,3-dialkyl-2-methaneiminealkyl imidazolium and 1,3-dialkyl-imidazolium derivatives as well as the aluminum and indium coordination compounds.