The Interplay between Charge Transport and CO2 Capturing Mechanism in [EMIM][SCN] Ionic Liquid: A Broadband Dielectric Study.

The hoisted increment in the CO2 emission in the atmosphere is a noteworthy environmental problem. Gas-liquid absorption is a well-known strategy that can be used to control CO2 emissions from an increased rate of fossil fuel industrializations. In this work, a combination of broadband dielectric spectroscopy, Fourier infrared (FTIR) spectroscopy, and quantum chemical calculations were used to study the absorption, desorption and kinetic mechanism of a room temperature imidazolium ionic liquid (IL) with cyanide anion, 1-ethyl-3-methylimidazolium thiocyanate ([EMIM][SCN]) on CO2 exposure. Initially, the charge transport and glassy dynamics of [EMIM][SCN] is investigated in a wide frequency and temperature range using broadband dielectric spectroscopy and differential scanning calorimetry. The conductivity relaxation was well fitted with Havriliak-Negami function in the modulus formalism, while the dc conductivity correlated well with the Barton-Nakajima-Namikawa relation. Then, the conductometric approach was taken to monitor the interplay between the ionic conductivity of [EMIM][SCN] and diffusion of captured CO2 in it. The resistance of the IL increases upon CO2 exposure, indicating a chemical change at the molecular level of [EMIM][SCN]. The possible CO2 capturing mechanisms for [EMIM][SCN] were investigated with density functional theory calculations and FTIR spectroscopy. Thus, this work proposes a new strategy to explain the mechanism underlined in chemisorption of CO2 in the [EMIM][SCN]. This can be extended to more promising CO2 capturing materials including ionic liquids especially imidazolium-based ionic liquids with cyanide anions like dicyanimide, tricyanometanide, tetracyanoborate, etc.

DFT and QTAIM based investigation on the structure and antioxidant behavior of lichen substances Atranorin, Evernic acid and Diffractaic acid.

In this study, the structural and antioxidant behavior of the three lichen-derived natural compounds such as atranorin (AT), evernic acid (EV) and diffractaic acid (DF) has been investigated in the gas and water phase using both B3LYP and M06-2X functional level of density functional theory (DFT) with two different basis sets 6-31+G (d, p) and 6-311++G (d, p). The intramolecular H-bonds (IHB) strength, aromaticity and noncovalent interactions (NCI) have been computed with the help of the quantum theory of atoms in molecules (QTAIM). This calculation gives major structural characteristics that indirectly influence the antioxidant behavior of the investigated compounds. The spin density (SD) delocalization of the unpaired electron is found to be the main stabilizing factor of neutral and cationic radical species. The main mechanisms, recommended in the literature, for the antioxidant action of polyphenols as radical scavengers such as hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET), were examined. The result shows that the HAT and SPLET mechanism are the most conceivable one for the antioxidant action of this class of compounds in gas and water phase respectively. Preference of SPLET over HAT in water phase is due to the significantly lower value of proton affinity (PA) compared to the bond dissociation enthalpy (BDE) value. This study reveals that O2-H3, O9-H26 and O4-H45 respectively are the most favored site of AT, EV and DF for homolytic as well as heterolytic OH bond breaking.

DFT studies on global parameters, antioxidant mechanism and molecular docking of amlodipine besylate.

Amlodipine besylate (AMB) is a synthetic dihydropyridine calcium channel blocker with antihypertensive and anti-anginal effects. Quantum computational investigations on AMB were done using DFT/B3LYP/6-311++G (d, p) level of theory, to study the molecular structural properties, nonlinear properties and antioxidant properties of AMB. The electrophilic and nucleophilic sites along with complete NBO analysis helps to locate the intermolecular electronic interactions and their stabilization energies. Complete NBO analysis was additionally done to locate the intermolecular electronic interactions and their stabilization energies. Charge distributions of Mulliken population, NBO and MEP are correlated. Also, the antioxidant properties of AMB were assessed to check whether these antioxidant effects contribute to the effects of antioxidant therapy. Further, the molecular docking studies of these compounds demonstrated a good selectivity profile with Monoamine oxidase B with better binding affinity and confirms AMB is a potent antioxidant.

Novel 4,4'-Fluoresceinoxy Bisphthalonitrile Showing Aggregation-Induced Enhanced Emission and Fluorescence Turn off Behavior to Fe3+ Ions.

A novel 4,4'-fluoresceinoxy bisphthalonitrile FPN is synthesized from fluorescein and 4-nitrophthalonitrile by aromatic nucleophilic ipso nitro substitution reaction. The structure of FPN constitutes phthalonitrile-fluorescein-phthalonitrile, acceptor-donor-acceptor, A-D-A form and the solvatochromic study of newly synthesized compound FPN was done in hexane, cyclohexane, CHCl3, DCM, DMF, acetonitrile, ethanol and in methanol. The aggregation behavior of FPN was investigated in good-poor solvent mixture DMF-water in various proportions and the molecule was found to be exhibiting Aggregation Induced Emission Enhancement AIEE for volume percentage of water beyond 50% with a significant hypsochromic shift of 70 nm in the emission maxima from 458 to 388 nm. This phenomenon is termed as Aggregation Induced Blue Shifted Emission Enhancement AIBSEE and was reported in substituted phthalonitrile for the first time. The chemo sensing activity of FPN with various transition metal ions also has been checked by fluorescence spectroscopy where the new molecule FPN exhibited fluorescence turn OFF behaviour towards Fe3+ ion in acetonitrile-methanol ACN-MeOH solution. The binding stoichiometry of FPN with Fe3+ was verified by Job's plot analysis and Density Functional Theory DFT-B3LYP computational methodology by using Gaussian 09 software. Graphical Abstract A novel 4,4'-fluoresceinoxy bisphthalonitrile FPN was synthesized by base catalyzed coupling reaction of fluorescein with 4 nitrophthalonitrile. The newly synthesized compound has been characterized using UV-vis, FTIR, 1HNMR, fluorescence spectral data and single crystal X-ray diffraction studies. The compound FPN was found to be exhibiting positive solvatochromism in various organic solvents and Aggregation Induced Blue Shifted Emission Enhancement AIBSEE in DMF-aqueous mixture when water volume exceed above 50%. As a metal ion chemo sensor FPN exhibited a selective fluorescence turn OFF behavior towards Fe3+ ion in the stoichiometric ratio 1:2 in acetonitrile-methanol mixture and limit of detection LOD of Fe3+ by FPN was calculated to be 3.665 µM.

A computational exploration into the structure, antioxidant capacity, toxicity and drug-like activity of the anthocyanidin "Petunidin".

A computational investigation on the structure and antioxidant property of a natural food colorant Petunidin (PT) was performed under DFT/B3LYP/6-31+ G (d, p). PT has a drug score of +0.804 which indicates its drug-like nature. The antioxidant property of PT was well explained by HAT mechanism and it has been found that the electron releasing substituents decreases the BDE value. PT has lowest BDE value at C3 position and is confirmed by the lowest pKa value, high atomic charge and lowest bond order. PT easily donates the hydrogen atom and exists in the deprotonated form in blood as the pKa value at C3 is less than the pH value of blood. PT shows no violation to Lipinski's rule of 5 indicating its nature as an orally admissible drug. More over PT has considerable bioactivity against nuclear receptor ligand while it shows only moderate activity towards GPCR and ion channel modulator. Also it shows moderate activity as an enzyme inhibitor and protease inhibitor but shows considerable activity as a kinase inhibitor. PT is non toxic in nature and all these factors favor its use as a potential antioxidant and a drug.

QSAR classification-based virtual screening followed by molecular docking studies for identification of potential inhibitors of 5-lipoxygenase.

Developments of novel inhibitors to prevent the function of 5-lipoxygenase (5-LOX) proteins that are responsible for a variety of inflammatory and allergic disease are a major challenge in the scientific community. In this study, robust QSAR classification models for predicting 5-LOX activity were developed using machine learning algorithms. The Support Vector Machines (SVM), Logistic Regression, k-Nearest Neighbour (NN) and Decision Trees were adopted to improve the prediction ability of the classification models. The most informative molecular descriptors that contribute to the prediction of 5-LOX activity are screened from e-Dragon, Ochem, PowerMV and Combined databases using Filter-based feature selection methods such as Correlation Feature Selection (CFS) and Information Gain (IG). Performances of the models were measured by 5-fold cross-validation and external test sets prediction. Evaluation of performance of feature selection revealed that the CFS method outperforms the IG method for all descriptor databases except for PowerMV database. The best ensemble classification model was obtained with the IG filtered 'PowerMV' descriptor database using kNN (k = 5) algorithm which displayed an overall accuracy of 76.6% for the training set and 77.9% for the test set. Finally, we employed this model as a virtual screening tool for identifying potential 5-LOX inhibitors from the e-Drug3D drug database and found 43 potential hit candidates. This top screened hits containing one known 5-LOX inhibitors zileuton as well as novel scaffolds. These compounds further screened by applying molecular docking simulation and identified four potential hits such as Belinostat, Masoprocol, Mefloquine and Sitagliptin having a comparable binding affinity to zileuton.

Data on the UV filtering and radical scavenging capacity of the bitter masking flavanone Eriodictyol.

A computational analysis of UV filtering and radical scavenging capacity of a flavanone, Eriodictyol has been performed under DFT-B3LYP/6-31+ G (d, p). Eriodictyol is nontoxic and nonirritant bitter masker used in wine and can be used for photo protection due to its potential UV filtering and radical scavenging capacity. The compound has an absorbance in the UV-A and UV-B region of electromagnetic spectrum, it can be used as a potential UV filter in sunscreen lotions and other cosmetic products. Eriodictyol is a potent antioxidant than the most commonly studied Quercetin. The most active site in the compound is 3׳ position and is confirmed by NPA, NBO and pKa value analysis. The BDE values follow the order 3'<4'<7<5. The major transitions in the UV-visible spectrum of Eriodictyol are between HOMO and HOMO-1 with LUMO level and are well explained by NBO-NLMO tool in G09.

Studies on the UV filtering and radical scavenging capacity of the bitter masking flavanone Eriodictyol.

A computational analysis of UV filtering and radical scavenging capacity of a flavanone, Eriodictyol has been performed under DFT-B3LYP/6-31+ G (d, p). Eriodictyol is nontoxic and nonirritant bitter masker commonly used in the wine industry. It has been reported that the flavanones were widely acceptable for photoprotection due to its potential UV filtering and radical scavenging capacity. This study provides theoretical evidence that the eriodictyol has an absorbance in the UV-A and UV-B region of the electromagnetic spectrum and therefore can be used as a potential UV filter in sunscreen lotions and other cosmetic products. The major transitions in the UV-Visible spectrum of Eriodictyol are between HOMO and HOMO-1 with LUMO level and are well explained by NBO-NLMO tool in G09 software. In addition to this, Eriodictyol is a potent antioxidant than that of the most commonly studied Quercetin. The most active site in the compound is 3' position and is confirmed by NPA, NBO and pKa value analysis. The lowest energy conformer of Eriodictyol contains a Hydrogen bond between carbonyl oxygen (O2) and H30. This is confirmed by the highest value of interaction energy between lone pairs of O2 and σ* of O3- H30. Both the two lone pairs of O2 interacts with the σ* of O3-H30. This decreases the bond order of 5 OH and at the same time it restricts the hydrogen transfer from this position to form a radical. Similarly, the lone pair of O5 (3' position) interacts with H33 resulting in the low bond order value and consequently less favorable for radical formation. These results indicate that the BDE values follow the order 3' < 4' < 7 < 5. Thus the title compound can be used for photo protection due to its potential UV filtering and radical scavenging capacity.

A non toxic natural food colorant and antioxidant 'Peonidin' as a pH indicator: A TDDFT analysis.

A computational inestigation on the difference in colors of two plants 'Peony' and 'Morning glory' by the same pigment 'Peonidin' has been performed by means of absorption characteristics. Peonidin imparts purple color to the flowers in Peony and blue to that in Morning glory. TDDFT tool in Gaussian 09 software package has been employed to analyze the UV-vis spectra and has shown that in acidic media Peonidin exists in its flavylium cationic form where as in alkaline media it exists in the quinoidal base form. These two structural forms have colors red and blue respectively. TDDFT results of flavylium ion in acetic acid moves the absorption to higher wavelength and corresponds to purple color and is the color of Peony flower. One of the quinoidal bases in alkaline media gives violet-blue color to flowers in Morning glory. This is true as Peony grows in acidic soil only while Morning glory grows in alkaline soil only. The affinity towards pH values makes Peonidin to act as pH indicator besides its radical scavenging capacity. Further a good food colorant must be non toxic. The toxicological analysis has shown that Peonidin is non-irritant, non-mutagenic, non-carcinogenic and non-tumorigenic. The compound has sufficient solubility to use as a potential drug. Also the compound has a positive drug score. All these results confirm the potential druggability of Peonidin and its non toxicity.

The natural food colorant Peonidin from cranberries as a potential radical scavenger - A DFT based mechanistic analysis.

A theoretical evaluation of the antioxidant property of a natural food colorant Peonidin has been performed. The most suitable mechanism for explaining the radical scavenging capacity of Peonidin is the Hydrogen Atom Transfer and the most active site for radical formation is position 3 and is confirmed through Mulliken charge analysis, pKa value evaluation, Bond Dissociation Energy values, and Natural Bond Orbital analysis. Position 3 and 5 in Peonidin exists in blood as deprotonated as their pKa values are lower than the pH of blood. Peonidin is highly reactive than Quercetin and less stable than flavan-3-ols due to the small band gap. Global descriptor analysis shows that PN prefers to accept electrons than to donate. The effect of number of OH groups and the nature of substituents are well explained through this work.

Experimental and density functional theory studies on benzalkonium ibuprofenate, a double active pharmaceutical ingredient.

Molecular aspects of a double active pharmaceutical ingredient in ionic liquid form, benzalkonium ibuprofenate (BaIb), were studied using density functional theory (DFT/B3LYP/6-31+G (d, p)). A detailed discussion on optimized geometry, energy, heat and the enthalpy of BaIb was carried out. The computed vibrational results agree well with the experimental results. The stability and biological activity were compared to the parent drugs on the basis of global descriptive parameters. The electrophilic and nucleophilic sites were pointed out in the MESP structures well evidently. NBO analysis was also done to predict the relative aromaticity, delocalization effects and the contribution towards stabilization energy of the title compound. The information about non-covalent, non-ionic weak interaction between the cation and anion was obtained from the list of Mulliken charges and NBO analysis.

A DFT based analysis of adsorption of Hg2+ ion on chitosan monomer and its citralidene and salicylidene derivatives: Prior to the removal of Hg toxicity.

A Density functional theory based study of adsorption of the toxic metal Hg (II) ion by chitosan monomer and two of its derivatives; citralidene and salicylidene chitosan, has been performed. The effect of structural features on the stability of studied complexes has been analyzed by using Gaussian03 software package. All the possible conformations of these adsorbents were studied using the global minimum geometries. All the adsorbing sites were studied by placing the metal ion on the centroid of the atoms and the stable conformer of the adsorbent-metal ion complex was identified. Interaction between Hg (II) and the adsorbents is found to be electrostatic. Metal ion binding with nitrogen atom is stronger than that with oxygen atoms in all the cases as the charge density of nitrogen is enhanced on Schiff base formation. The advantage of derivatives over chitosan monomer is their stability in acidic media. ΔE value of the complexes are in the order SC-Hg (II)>chitosan-Hg (II)>CC-Hg (II) which indicates that the stability of complexes increases with increase in energy gap. The study reveals that aromatic Schiff base derivatives of chitosan is better for Hg(II) intake than aliphatic derivatives.

A computational investigation on the structure, global parameters and antioxidant capacity of a polyphenol, Gallic acid.

A computational DFT-B3LYP structural analysis of a poly phenol, Gallic acid (GA) has been performed by using 6-311++ G (df, p) basis set. The GA is a relatively stable molecule with considerable radical scavenging capacity. It is a well known antioxidant. The NBO analysis shows that the aromatic system is delocalized. The results reveal that the most stable radical is formed at O3-atom upon scavenging the free radicals. Global descriptive parameters show that GA acts as an acceptor center in charge transfer complex formation which is supported by ESP and contour diagrams and also by Qmax value. The GA is a good antioxidant and it can be better understood by HAT and TMC mechanisms as it has low BDE, ΔHacidity and ΔGacidity values. The ΔBDE and ΔAIP values also confirm that the antioxidant capacity of GA can be explained through HAT rather than the SET-PT mechanism.