Solid, Solution and Gas Phase Interactions of an Imidazolium-Based Task-Specific Ionic Liquid Derived from Natural Kojic Acid

Abstract

Um líquido iônico imidazólio de função específica derivado do ácido kójico natural teve suas interações supramoleculares investigadas no estado sólido, em solução e em fase gasosa. Diferentes técnicas como difração de raios X de monocristal, espectroscopia de ressonância magnética nuclear (NMR), espectrofotometria UV-Vis, medidas de condutividade, espalhamento de raios X em baixo ângulo (SAXS), espectrometria de massas (tandem) com ionização por electrospray (ESI-MS(/MS)) e cálculos teóricos permitiram uma investigação estrutural aprofundada desse líquido iônico de função específica e suas interações supramoleculares. An imidazolium-based task-specific ionic liquid derived from the natural kojic acid had its supramolecular interactions investigated in solid, solution and gas phase. The use of a set of techniques formed by single-crystal X-ray diffraction, nuclear magnetic resonance (NMR) spectroscopy, UV-Vis spectrophotometry, conductivity measurements, small angle X-ray scattering (SAXS), electrospray (tandem) mass spectrometry (ESI-MS(/MS)), and theoretical calculations allowed a deep investigation of the structural organization of the task-specific ionic liquid and its supramolecular interactions.Keywords: ionic liquids, imidazolium, task-specific ionic liquids, supramolecular interactions, organization, X-ray, SAXS, UV-Vis, NMR, ESI-MS IntroductionIonic liquids (ILs) and task-specific ionic liquids (TSILs), especially those based on the imidazolium cation, are part of a class of attractive compounds of widespread use in many scientific and technological areas.1-3 These organic salts have already been successfully used in the chemical industry for many years. 4 Their prominence is exemplified by many review articles recently published regarding several features of these unique chemical species. 5-21The possibility of tuning the physical and chemical properties of ILs and TSILs associated with their attractive physicochemical properties, such as very low vapor pressure, large electrochemical window, good thermal and chemical stabilities, have also opened a wealth of other applications for these ionic materials. Despite all progress already reached by ILs, fine details about their supramolecular organization, the importance of H-bonds and a deep understanding on the directionality of imidazolium-based derivatives are only now emerging. Each IL/TSIL has unique physicochemical properties and it has been estimated that ca. 10 6 combinations of known Neto et al. 2281 Vol. 25, No. 12, 2014 cations and anions may afford a new type of such ionic compounds. 22 The effort towards a better comprehension on the physicochemical properties of such materials is therefore very challenging; and each new structure demands specific efforts and a set of characterizations to depict its unique structural features and properties. Despite the diversity, some general trends have been established, and it is, for instance, known that the physicochemical properties of ILs/TSILs are intimately associated with their ionic structures, 23...

Explicit Aqueous Solvation Treatment of Epinephrine from Car–Parrinello Molecular Dynamics: Effect of Hydrogen Bonding on the Electronic Absorption Spectrum

“…The Laplacian of the electron density, ∇ 2 ρ­( r ), provides a measure of either charge concentration (∇ 2 ρ­( r ) < 0) or depletion (∇ 2 ρ­( r ) > 0) of the electron density distribution, the latter being characteristic of closed-shell interactions such as H-bonding when ρ­( r ) is relatively small . ∇ 2 ρ­( r ) values at the BCP ranging from 0.024 to 0.139 (atomic units), ellipticity values ε < 0.1, and ρ­( r ) in the range of 0.002–0.040 (au) are commonly associated with HB-type interactions. − Looking at Table , the ellipticity criterion is retained for all HB BCPs, whereas for the ∇ 2 ρ­( r ) and ρ­( r ), values were not strictly within the literature classification . Nonetheless, the aforementioned classification was established by Koch and Popelier for C–H–O HBs, whereas in the present work, we focus only on conventional HBs.…”

Bond Ellipticity Alternation: An Accurate Descriptor of the Nonlinear Optical Properties of π-Conjugated Chromophores

“…Within QTAIM, the ellipticity of the electron density has been employed to characterize electrocyclic reactions, owing to its ability to capture the changes in the anisotropy of the electron density at the BCP, or to clarify the nature of intermolecular interactions. , The bond ellipticity (ε) is defined in terms of the cylindricity of the electron density at the BCP, accounting for its principal curvatures (eigenvalues of the Hessian matrix, λ 1 , λ 2 , and λ 3 , such that λ 1 and λ 2 are the negative eigenvalues) and is written as ε = λ 1 /λ 2 – 1. The negative eigenvalues of the Hessian of the electron density (∇ 2 ρ­( r )) at the BCP are degenerate when the axes associated with the respective curvatures are symmetrically equivalent, as in the single CC bond of ethane (i.e., λ 1 = λ 2 and ε = 0) (Figure ).…”

A Flow Cytometry Evaluation of Poly (1‐vinyl‐3‐alkyl imidazolium) Based Ionic Liquid's In Vitro Effect on Various Cellular Components of Blood

“…The UV-Vis analysis indicates the presence of π conjugated systems in the imidazolium ring and can be utilized to confirm the structure of imidazolium-based PILs. [19] The UV-vis spectra of the synthesized poly ((1-vinyl-3 alkyl imidazolium) bromide) have been recorded in the 200-400 nm range (Figure 3). The effect of alkyl chain length on the UV absorption of 1-alkyl-3methylimidazole tetrafluoroborate [Cnmim][BF 4 ] where n = 2, 4 and 8 have been reported.…”