The structure and interaction properties of two task-specific ionic liquids and acetonitrile mixtures: A combined FTIR and DFT study

Optical trapping of nanoclusters formed in a temperature-responsive ionic liquid aqueous solution under focused near-infrared laser irradiation

Confining molecules and ions at a specific position in a solution enables the control of chemical reactions and analysis of tiny amounts of substances. Here, we demonstrate local condensation of a temperature responsive ionic liquid using optical tweezers. Two kinds of microdroplets are prepared through phase separation or nanocluster formation under irradiation of a near-infrared laser beam. The droplet formation mechanism is discussed in view of the evolution of an optical potential well and the local temperature distribution.

Evaluation of chemical reactivity and polarity of imidazolium-based ionic liquids using quantum chemical calculations

CONTEXT

By using the DFT theory, the orbital energies of twenty-five ionic liquids were estimated. To comprehend their molecular stability and chemical reactivity, the orbital energy values, orbital energy gap (HOMO-LUMO energy gap), chemical hardness (η), chemical softness (S), electronegativity (χ), and electrophilicity index (ω) were computed. The interaction energies between all of the cations and anions under study were then computed and examined. Finally, using quantum chemical calculations, the molecular polarity of all 25 ionic liquids was examined using the sigma profile and sigma potential.

METHODS

Using the lowest orbital energy of the molecules, HF/6-31G* level of theory quantum chemical calculation were carried out using the MOLDEN and GAUSSIAN03 software. The B3LYP DFT approach produced a COSMO file that contained the species optimal SCD.

Carboxymethyl cellulose/starch/reduced graphene oxide composite as a pH-sensitive nanocarrier for curcumin drug delivery

Nanocomposites are promising drug carriers to treat terminal cancers with few adverse effects. Herein, nanocomposite hydrogels composed of carboxymethyl cellulose (CMC)/starch/reduced graphene oxide (RGO) were synthesized via a green chemistry approach and then encapsulated in double nanoemulsions to act as pH-responsive delivery systems for curcumin, a potential antitumor drug. A water/oil/water nanoemulsion containing bitter almond oil served as a membrane surrounding the nanocarrier to control drug release. DLS and zeta potential measurements were used to estimate the size and confirm the stability of curcumin-loaded nanocarriers. The intermolecular interactions, crystalline structure and morphology of the nanocarriers were analyzed through FTIR spectroscopy, XRD and FESEM, respectively. The drug loading and entrapment efficiencies were significantly improved compared to previously reported curcumin delivery systems. In vitro release experiments demonstrated the pH-responsiveness of the nanocarriers and the faster curcumin release at a lower pH. The MTT assay revealed the increased toxicity of the nanocomposites against MCF-7 cancer cells compared to CMC, CMC/RGO or free curcumin. Apoptosis was detected in MCF-7 cells via flow cytometry tests. The results obtained herein support that the developed nanocarriers are stable, uniform and effective delivery systems for a sustained and pH-sensitive curcumin release.

Nanoemulsion carriers of porous γ-alumina modified by polyvinylpyrrolidone and carboxymethyl cellulose for pH-sensitive delivery of 5-fluorouracil

5-Fluorouracil (5-FU) is a cytotoxic drug with a low half-life. These features can cause some problems such as burst drug release and numerous side effects. In the present study, a pH-sensitive nanocomposite of polyvinylpyrrolidone (PVP)/carboxymethyl cellulose (CMC)/γ-alumina developed by using water in oil in water (W/O/W) double emulsion method. The fabricated emulsion has been employed as the 5-FU carrier to investigate its effects on drug half-life, side effects, drug loading efficiency (DLE), and drug entrapment efficiency (DEE). Analyzing the FTIR and XRD indicated the successful loading of 5-FU into the nanocarrier and affirmed the synthesized nanocomposite's chemical bonding and crystalline features. Furthermore, by using DLS and Zeta potential assessment, size and undersize distribution, as well as the stability of the drug-loaded nanocomposite were determined, which demonstrated the monodisperse and stable nanoparticles. Moreover, the nanocomposites with spherical shapes and homogeneous surfaces were shown in FE-SEM, which indicated good compatibility for the constituents of the nanocomposites. Moreover, by employing BET analysis the porosity has been investigated. Drug release pattern was studied, which indicated a controlled drug release behavior with above 96 h drug retention. Besides, the loading and entrapment efficiencies were obtained 44 % and 86 %, respectively. Furthermore, the curve fitting technique has been employed and the predominant release mechanism has been determined to evaluate the best-fitted kinetic models. MTT assay and flow cytometry assessment has been carried out to investigate the cytotoxic effects of the fabricated drug-loaded nanocomposite on MCF-7 and normal cells. The results showed enhanced cytotoxicity and late apoptosis for the PVP/CMC/γ-alumina/5-FU. Based on the MTT assay outcomes on normal cell lines (L929), which indicated above 90 % cell viability, the biocompatibility and biosafety of the synthesized nanocarrier have been confirmed. Moreover, due to the porosity of the PVP/CMC/γ-alumina, this nanocarrier can exploit from high specific surface area and be more sensitive to environmental conditions such as pH. These outcomes propose that the novel pH-sensitive PVP/CMC/γ-alumina nanocomposite can be a potential candidate for drug delivery applications, especially for cancer therapy.

Comparative study of the hydrogen bonding interactions between ester-functionalized/non-functionalized imidazolium-based ionic liquids and DMSO

There have been some studies on the microscopic properties of ester-functionalized ionic liquids (ILs), but the microscopic properties of their mixtures with co-solvents have seldom been reported. In practical applications, ILs are usually used together with co-solvents. Therefore, it is very important to study the microstructure of ester-functionalized ILs and co-solvents. In this work, the hydrogen bonding interactions between ester-functionalized IL 1-acetoxyethyl-3-methylimidazolium tetrafluoroborate (AOEMIMBF₄) and DMSO were studied using spectroscopic methods and quantum chemical calculations. Non-functionalized IL 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄) and DMSO were used for comparison. The results indicate that (1) by adding DMSO, the hydrogen bonding interactions of ν(C2-H) were enhanced, and DMSO could form hydrogen bonds with anions and cations simultaneously. (2) The incorporation of an ester group could enhance the hydrogen bonding interactions. (3) Both the stretching vibration of C2-H and CO indicated changes in the microscopic structure: AOEMIMBF₄ ion clusters first interacted with DMSO, then broke into AOEMIMBF₄-DMSO complexes and finally existed as [AOEMIM]⁺/[BF₄]^--DMSO complexes.

Cation-anion interaction effect on the nonlinear optical behavior of pyridinium-based ionic liquids

Influence of the cation-anion interaction (expressed as internal hydrogen bonds) on the nonlinear optical properties (dipole moment, polarizability, anisotropy of polarizability and first-order hyperpolarizability) for the ionic liquids pyridinium hydrogen sulfate (PHS) and pyridinium bis(dihydrogen phosphate) (P2HP) was investigated in this paper. It was achieved analyzing vibrational modes (FT-IR) and electronic transitions (UV-vis) in PHS and P2HP. Molecular geometry of the title compounds was optimized by means of density functional theory calculations at B3LYP/6-311++G(2d,2p) level. Structural analysis exposed stronger internal hydrogen bonds (H⁷···O³ and H¹⁸···O⁴) between cationic and anionic fragments in the pyridinium hydrogen sulfate than these (H²⁶···O⁴ and H²⁵···O¹²) in pyridinium bis(dihydrogen phosphate). These observations are confirmed by FT-IR and UV-vis methods, where: (i) the infrared bands due to H···O and N-C interactions in P2HP appear at lower frequencies than the same ones in the spectrum of PHS and (ii) the n → π* electron transitions in PHS are more pronounced in comparison with these in P2HP. Based on the weaker cation-anion interaction in P2HP with respect to PHS, the former one is characterized with a remarkably higher first-order hyperpolarizability value. Hence, the ionic liquid P2HP was referred as a better nonlinear optical material than PHS.

The synthesis and characterization of targeted delivery curcumin using chitosan-magnetite-reduced graphene oxide as nano-carrier

To achieve targeted treatment with fewer adverse effects against fatal cancer diseases, the use of nanoparticles as therapeutic agents or drug carriers has been proved to be very extensive and remarkable, today. In this study, chitosan-magnetite-reduced graphene oxide (CS-Fe₃O₄-RGO) nanocomposites (NC) were used for the targeted delivery of curcumin (Cur) as anticancer drugs to suppress MCF-7 breast cancer cells and this was accomplished using a facile water-in-oil (W/O) emulsification procedure. FTIR and XRD were used for characterization. The average size distribution of nanoemulsions and their surface charge (zeta potential) were determined by Dynamic light scattering (DLS) analyzer and zeta potential measurement, respectively. SEM Mapping showed the uniform and flat surface for the NC which was confirmed by the EDX diagram. Measurement of VSM exhibited that the Fe₃O₄-RGOs have superparamagnetic properties. According to the MTT assay, the NC has the highest toxicity at 0.1 against MCF-7 cancer cells. The results of flow cytometry indicated apoptosis in MCF-7 cells. By using the dialysis method, it was determined that curcumin was released faster in an acidic medium. It is expected that the results of this study will be effective in the development of targeted drug delivery as well as the development of CS- Fe₃O₄-RGO-based drug carriers against various cancer cells during future research.

Solvation of anions in acetonitrile solutions: FTIR and quantum chemical study for Br-, ClO4-, AsF6-, and CF3SO3. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2020;229:117873. [PMID: 31813727 DOI: 10.1016/j.saa.2019.117873]

Anion solvation in acetonitrile solutions was comparatively studied using FTIR spectroscopy and quantum chemical calculations at the RTF + MP2/6-311G** level of theory with solvation model density (SMD) corrections. Infrared spectra for all stable anionic complexes X^-(CH₃CN)_n (where X^- = Br^- (monatomic halide), ClO₄^- (polyatomic tetrahedral), AsF₆^- (polyatomic octahedral), CF₃SO₃^- (polyatomic ethane-like) and n = 1-8) were calculated and subsequently used in the analysis of the FTIR spectra of (Bu₄N)X and LiX acetonitrile solutions across a wide range of concentrations. Spectroscopic manifestations of solvation were established for all X^- examined. The results for all four anions under investigation were generalized to reveal the regularities of anion solvation by acetonitrile.

Excess spectroscopy and its applications in the study of solution chemistry

Characterization of structural heterogeneity of liquid solutions and the pursuit of its nature have been challenging tasks to solution chemists. In the last decade, an emerging method called excess spectroscopy has found applications in this area. The method, combining the merits of molecular spectroscopy and excess thermodynamic functions, shows the ability to enhance the apparent resolution of spectra, provides abundant information concerning solution structures and intermolecular interactions. In this review, the thinking and mathematics of the method, as well as its developments, are presented first. Then, research progress related to the exploration of the method is thoroughly reviewed. The materials are classified into two parts, small-molecular solutions and ionic liquid solutions. Finally, potential challenges and the perspective for further development of the method are discussed.

The effect of introducing an ether group into an imidazolium-based ionic liquid in binary mixtures with DMSO

Combined DFT and FTIR investigations reveal interesting hydrogen bonding interactions between dimethyl sulfoxide and an ether-functionalized imidazolium-based ionic liquid.

The structure and hydrogen-bond properties of N-alkyl-N-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide and DMSO mixtures

Mixing ionic liquids (ILs) with molecular solvents can extend the practical applications of ILs and overcome the drawbacks of neat ILs. Knowledge on the structure and hydrogen-bond interaction properties of IL-molecular solvent mixtures is essential for chemical applications. In this work, the structure and hydrogen-bond features of N-alkyl-N-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide ([CnMPyr][Tf2N], n = 3, 4, 6 and 8) and DMSO mixtures were studied using Fourier transform infrared spectroscopy (FTIR) and density functional theory (DFT) calculations. Excess infrared absorption spectroscopy and two-dimensional correlation spectroscopy (2D-COS) were employed to extract structural information on the mixtures from the C-D systematic stretching vibrational (νs(C-D)) region of the methyl groups in DMSO-d6. It was found that the mixing process of [CnMPyr][Tf2N] and DMSO is non-ideal and interaction complexes form between [CnMPyr][Tf2N] and DMSO-d6. They are ion cluster-DMSO-d6 complexes and ion pair-DMSO-d6 complexes. In the mixing processes, the species present in pure DMSO gradually decrease from DMSO dimer to DMSO monomer with an increase in ILs. Besides, the ion cluster-DMSO complexes gradually increase, while the ion pair-DMSO complexes decrease due to the strong electrostatic interaction between the cation and anion. In the ion cluster-DMSO complexes and ion pair-DMSO complexes, the ring hydrogen atoms of the methylene group directly attached to the nitrogen atom are the preferred interaction sites of the [CnMPyr]+ cations. All the hydrogen bonds in the identified complexes are closed-shell, electrostatically dominant and weak.