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In this work, tri-octyl phosphine/tri-octyl phosphine oxide (TOPO)-capped cadmium selenide (CdSe) quantum dots (QDs) of varied sizes (5–9 nm), prepared by varying the input Cd:Se precursor ratio using chemical route, were dispersed in conducting polymer matrices viz. poly[2-methoxy, 5-(2-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and poly(3-hexylthiophene) (P3HT). By using a binary solvent mixture (pyridine–chloroform), homogeneous dispersion of CdSe nanocrystals in polymers (MEH-PPV, P3HT) could be realized. The properties of the resulting dispersions could be tailored by the composition and concentration of QDs in polymer. The emission and structural properties of polymer–CdSe nanocomposites are found to be dependent on the crystallite size and morphology of CdSe nanocrystallites. An effective quenching of photoluminescence emission in the polymer nanocomposite was observed for smaller CdSe quantum dots (size ∼6 nm) as compared to larger CdSe quantum dots (size ∼9 nm), thus ensuring efficient charge transfer process across the polymer–CdSe interface in the former case. The incomplete quenching, particularly for MEH-PPV:CdSe nanocomposites, could be as a result of insufficient coverage of polymers on the surface of CdSe nanocrystallites, mainly due to phase segregation for TOPO-stripped CdSe nanocrystallites. The superior morphology and optical properties of polymer nanocomposite (P3HT:CdSe QDs) could play a pivotal role for the realization of effective charge separation and transport in hybrid solar cells. [ABSTRACT FROM AUTHOR]

In this work, polysorbate surfactants with same functional groups but with varying molecular masses (Tween-80, Tween-40 and Tween-20) in different concentrations (0.1% to 20% w/w) were used to study the effect of the length of the surfactant chain on the luminescence of the entrapped TOPO-capped CdSe nanocrystals. Various phospholipids with different functional headgroups such as ethylene glycol (-PEG) and amine (-NH2) were used to improve biocompatibility and provide sites for bioconjugation respectively. It is understood that that the hydrophobic ends of the surfactant binds with the water repelling groups of the cap layer, thus modifying the CdSe cap layer and making it soluble in aqueous media. It was observed that the PL emission intensity of CdSe increases with increase in concentration of Tween-series surfactant unlike in the case of thiol-coated CdSe nanoparticles. However, higher PL intensity was obtained in the case of stoichiometric CdSe with Tween-40 corresponding to 20% w/w. The efficient PL sustainability of water-soluble CdSe QD’s can be attributed to the simpler chain structure of Tween-40 surfactant resulting in better passivation of the micelle. [ABSTRACT FROM AUTHOR]

The reaction mechanism for the thermal Curtius reaction of formyl azide has been investigated using B3LYP/6-311+G(d,p). It is found that, while the synisomer undergoes nitrogen elimination via a concerted mechanism, yielding isocyanic acid directly, the anti-isomer cannot undergo reaction via the concerted mechanism and first eliminates nitrogen, yielding oxazirene, via a transition state which is higher in energy than that for the concerted mechanism. Singlet formyl nitrene does not exist as an independent moiety. Rather, the strong N&bond;O interaction yields the cyclic isomer oxazirene. The isomerization of oxazirene to isocyanic acid goes through a transition state which is even higher in energy than that for nitrogen elimination. It is hence proposed that this reaction should take place via the concerted mechanism only, the anti-isomer undergoing isomerization first to the syn isomer since the activation barrier for this step is very small. The same mechanism is found to prevail for acetyl and benzoyl azide. These findings are in accord with all experimental data. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [ABSTRACT FROM AUTHOR]

Abstract: The preparation of N-(p-ethylphenyl)thiobenzohydroxamic acid and its spectral properties are described in this paper. The preferred conformation of the acid is investigated by both infrared techniques and theoretical calculations at the DFT level. It is found that the acid exists in the cis thione (Z) form, rather than the trans form (E) in the gas phase. Both infrared spectroscopy and theoretical calculations show that this structure is stabilized by intramolecular hydrogen bonding. [Copyright &y& Elsevier]

Abstract: Some metal ion complexes of thioformin have been investigated by the density functional approach in order to understand its coordination chemistry. Due to the presence of the soft sulfur atom in addition to the oxide ion, thiohydroxamates exhibit a different coordination chemistry compared to their hydroxamate counterparts. It is found that the oxide ion forms bonds with metal ions that are predominantly ionic in nature while the sulfur atom is involved in weak covalent bond formation. Most of the complexes are found to be tetrahedrally distorted square planar structures, showing distinct cis and trans isomers. The exception is Zn(II), which forms tetrahedral complexes. The stabilities of the complexes have been linked with their antibiotic activity. [Copyright &y& Elsevier]

Abstract: The partial molar volume and partial molar adiabatic compressibilities at infinite dilution of dl-aminobutanoic acid, dl-norvaline, β-alanine, 4-aminobutanoic acid, 5-aminopentanoic acid, 6-aminohexanoic acid and glycylglycine have been obtained in water and aqueous solutions of (0.5, 1.0 and 1.5)mol·kg−1 sodium sulphate at (288.15, 298.15 and 308.15)K from measurements of density and ultrasonic velocity. A qualitative interpretation of the results has been given using the Kirkwood model and nature of the interactions in solutions. A model, derived from Scaled Particle Theory, has been used for quantitative explanation of partial molar volumes and for the understanding the volumes of interaction. The results distinguish the behaviour of α-amino acids from that of α,ω-amino acids, and of the “less polar” 5-aminopentanoic acid from that of the analogous, but “more polar”, glycylglycine in solution. These findings are in agreement with previous studies in aqueous solutions and they support the water-structure making ability of sodium sulphate. [Copyright &y& Elsevier]

Abstract: First principles density functional calculations are performed on a number of square planar hydroxamate chelates of several divalent metal ions in order to determine their respective affinities for some biologically important ligands. The structures of the complexes are discussed, and the calculated binding mode is in agreement with experimental results. Extensive calculations have shown that, although the interactions are dominated mainly by electrostatic forces, there is a covalent contribution as well that introduces subtle variations in binding affinities of various metal ions. Thus, although a reasonable correlation is found between the complexation energies and reciprocals of the ionic radii of the metal ions, deviations may be attributed to some covalent character of the metal–ligand bonds, which modify a ligand''s affinity for a metal ion and introduce subtle variations that are ultimately responsible for their biological action. A linear relationship between the partial charge on the metal ion and the LUMO energy shows that metal ions with lower lying vacant orbitals are able to form covalent coordination with the ligand. The affinity of the formohydroxamate ion for Ni(II) is satisfactorily explained on this basis. The bonding characteristics of the investigated complexes are discussed, as is the optimum size of the metal binding site. Some other hydroxamic acids are also investigated in this work. The electronic structures of urease from two microorganisms, and their acetohydroxamate complexes are also investigated in order to understand the inhibition mechanism. This study should prove useful not only for the understanding of coordination bonding, but also in the investigation of metalloenzymes and their inhibition. [Copyright &y& Elsevier]

Abstract: The three isomeric aminophenylhydroxamic acids and their copper (II) complexes have been investigated by the density functional theory using different potentials. The GGA-PBE approach is found to be best suited for such studies. A comparison is made of the electronic structures of the acids to understand why they form different types of complexes. 2-Aminophenylhydroxamic acid is found to be the most stable of the three isomers due to extensive hydrogen bonding, but the complex formation energy for square planar complexes is highest for the 4-aminophenyl isomer. The different properties of the three acids and their Cu(II) complexes are satisfactorily explained from these studies. The nature of bonding in these complexes is also investigated. [Copyright &y& Elsevier]

The B3LYP density functional has been used to calculate the reaction paths for the interconversion of the three stable isomers of C3H4, namely, propyne, allene, and cyclopropene, and the results compared with experimental data. It is found that the trans nonplanar isomer of vinylmethylene plays a central role in the interconversions. Other thermochemical parameters, like the entropies of reaction and activation, have also been calculated. The rate constants of the various competing reactions have been calculated using the Rice–Ramsperger–Kassel–Marcus theory. Kinetic isotope effects for the reactions have also been investigated to gain an insight into their mechanisms. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003 [ABSTRACT FROM AUTHOR]

Semiempirical SCF-MO studies of tautomerism in alloxan preclude the possibility of direct proton transfer in the gas phase due to the strain in the four-centred transition state, in which the proton being transferred is forced to come close to the positively charged carbon atom at the opposite corner of the four-membered ring. However, in aqueous solution, the activation barrier reduces appreciably, not only due to reduction in strain, but also due to charge separation in the transition state, which is stabilized due to ionic resonance. The N-H bond is almost broken, while the O-H bond is only partially formed in the transition state. The other stabilizing effect in aqueous solution is due to bulk solvent dielectric effects, which stabilize the transition state to a greater extent due to its higher dipole moment. Although the transition states for proton transfer to the neighbouring oxygen atoms on either side have comparable energies, as the mechanisms of proton transfer leading to the formation of the 2-hydroxy and 4-hydroxy tautomers are similar, bulk solvent effects are larger in the latter due to the higher dipole moment of the transition state. The reason is the almost complete separation of the two entities, i.e. the alloxan anion and the hydronium ion in the latter case, indicating that in this case a dissociative mechanism of the kind encountered in acid-base equilibria is operating. [ABSTRACT FROM AUTHOR]

Polyphenolic compounds are known to exhibit potent antioxidant properties owing to the presence of various phenolic groups. The present study reports the antioxidant potentials of six retrochalcones, namely echinatin, and licochalcone A, B, C, D and E, isolated from the root of the Glycyrrhiza species, toward various reactive oxygen and nitrogen species. Different mechanistic pathways, viz. hydrogen atom transfer (HAT), single electron transfer (SET), single electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET), have been considered. In addition, two other pathways, i.e. sequential double proton loss electron transfer (SdPLET) and sequential proton loss hydrogen atom transfer (SPLHAT), which are significant for the scavenging of reactive species by the mono-deprotonated forms of retrochalcones, have also been considered. All the calculations were performed using density functional theory at the B3LYP/6–311++G** level in the gas phase and in aqueous solution. The results suggest the predominance of the HAT mechanism in the gas phase, while in aqueous solution, the SPLET mechanism is thermodynamically favored. The possibility of SdPLET increases at higher pH. [Display omitted] The antioxidant activity of six retrochalcones has been investigated considering six mechanistic pathways in the gas phase and in aqueous solution. • Antioxidant activity of six retrochalcones has been studied. • Six different mechanisms have been investigated by DFT calculations. • HAT is the dominant pathway in the gas phase. • SPLET and SdPLET are more favorable in aqueous solution. • The feasibility of scavenging of various ROS/RNS has been discussed. [ABSTRACT FROM AUTHOR]

The classic bifunctional mechanism derived from single crystal models shows practicability for directing hydrogen evolution reaction (HER) in alkaline media for noble-metal based hybrid catalysts, however, whether it can be extensively applied to non-noble metal nano-hybrid ones remains unclear, due to lacking of effective means to identify reaction active sites and key intermediates. Here we present a representative MoSe 2 /CoSe heterogeneous hollow spheres (MoSe 2 /CoSe HHSs) as a nano-hybrid catalyst model and demonstrate its atomic-level identification of catalytic active sites toward alkaline HER, by virtue of advanced experimental and theoretical calculating techniques. Real-time electron paramagnetic resonance (EPR) measurements for hydroxyl reveal the promoting effect of the Co species on water dissociation, whereas X-ray absorption spectroscopy (XAS) tests of pre-and post-HER further unravel the formation of high-valence HO-Co sites and MoSe 2 -H interactions after the electrolysis, both of which synergistically confirm that MoSe 2 /CoSe HHSs follow the classic bifunctional mechanism. Moreover, different from the classic bifunctional mechanism in which there is no substantial interaction between the involved two components, the hybridization of MoSe 2 with CoSe also further optimizes hydrogen binding energy (HBE) of MoSe 2 revealed by density functional theory (DFT) calculations, demonstrating that both the bifunctional mechanism and HBE should be considered simultaneously when designing low-cost alternatives to noble metal catalysts. Furthermore, a general two-step Ostwald ripening strategy is also proposed for hybridized metal sulfide hollow spheres toward mechanism-oriented material design. ga1 We designed MoSe 2 /CoSe HHSs as a model catalyst toward molecular understanding of underlying mechanism in alkaline HER. A series of advanced test techniques and DFT calculations revealed that different from the traditional single crystal Pt catalysts, an integration of bifunctional mechanism and H-binding energy theory is responsible for MoSe 2 /CoSe nano-hybrid catalyst. Furthermore, a general two-step Ostwald ripening strategy is also proposed for hybridized metal sulfide hollow spheres, which can guide the mechanism-oriented material design. • We propose a mechanism-oriented general strategy for hollow-structured hybrids. • Real-time EPR and XAS unravel behavior of key intermediates in alkaline HER. • DFT calculations show optimized hydrogen binding energy (HBE) for MoSe 2 hybrids. • Both bifunctional mechanism and HBE theory determine alkaline HER for nanohybrids. [ABSTRACT FROM AUTHOR]

The application of hierarchically porous sodium dodecylbenzene sulfonate (SDBS) modified vaterite microspheres (Hr-SMV) for the selective adsorption of toxic cationic dyes has been explored in this work. Hr-SMV has been synthesized using a facile and low-cost precipitation method. X-Ray diffraction (XRD), Fourier transform infrared (FTIR), Scanning electron microscopy (SEM), Thermogravimetric analysis (TGA) and N 2 adsorption-desorption isotherms have been used to understand the crystal structure, surface area, morphology and surface functionalities of Hr-SMV. As prepared Hr-SMV possesses a surface area of 31.15 m2 g−1 and a hierarchical porous structure. Influence of adsorption parameters on the adsorption of two cationic dyes, Crystal violet (CV) and Methylene blue (MB) has been studied in detail using batch adsorption studies. Maximum adsorption capacities of 68.8 and 316.8 mg g−1 were exhibited by Hr-SMV for MB and CV, respectively. Further, Hr-SMV shows efficient adsorptive removal of other cationic dyes, including Basic fuchsine (BF) and Auramine O (AO). In binary mixtures of cationic dyes, Hr-SMV efficiently removes both cationic dyes, thus highlighting its prospect for practical applications. In binary mixtures of cationic and anionic dyes, Hr-SMV is found to selectively adsorb cationic dyes with high separation factors. Thus, Hr-SMV has been found to be a promising low-cost adsorbent for the efficient adsorption and separation of cationic dyes from effluents. • Hr-SMV has been synthesized using a facile and low cost precipitation method. • Hr-SMV exhibits high adsorption efficiencies for toxic cationic dyes. • Selective removal of cationic dyes is demonstrated with high separation factors. • Mechanism of cationic dyes adsorption on Hr-SMV has been discussed. [ABSTRACT FROM AUTHOR]

The current study reports a detailed investigation of the adsorption behavior of Mo4, Mo3Co, Mo2Co2, and MoCo3 clusters on graphene by studying their binding energy, charge transfer, band gap, electron density difference plots, and density of states (DOS) plots. The magnetic properties of these surfaces have also been reported. Owing to the strong adsorption power of small metal cluster-decorated graphene surfaces, we have further utilized the Mo4-decorated graphene for the adsorption of SO2F2 and SOF2 gases, which are two gases that are released from the decomposition of SF6, a gas used as an insulating medium in gas-insulated switchgear. The use of Mo4-decorated graphene surface resulted in the dissociative adsorption of these gases with high adsorption energy and large charge transfer. In contrast, only physisorption occurred on pristine graphene. Further details of the adsorption were investigated by studying the DOS and partial DOS (PDOS) plots before and after adsorption. The band gap and electron density difference plots have also been reported. Graphical abstract [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) have attracted significant interest because of their tunable bandgaps, which enable numerous applications in fields such as photovoltaics, biomedicine, and materials science. This study explores various core electron treatments in the density functional theory (DFT) analysis of II-VI semiconductor quantum dots and their bulk counterparts. We compared All-electron (AE), Effective Core Potential (ECP), All-Electron Relativistic (AER), and DFT-Semicore pseudopotential (DSPP) treatments. Our findings indicate that the AE treatment aligns closely with the experimental results for smaller QDs, whereas the accuracy of DSPP increases with larger QDs. DSPP provides an optimal balance between computational efficiency and accuracy, making it suitable for studying II-VI QDs. Notably, the bandgap behavior varies, being direct for zinc and cadmium chalcogenides, whereas mercury chalcogenides are zero-gap semiconductors (semimetals). The inner bonds of the QDs exhibit an ionic character, whereas the terminal bonds display a covalent character. This study enhances our understanding of the structural and electronic properties of II-VI quantum QDs, aiding their application in various technologies. [ABSTRACT FROM AUTHOR]

A computational study on the structural and electronic properties of a special class of artificial atoms, known as quantum dots, has been carried out. These are semiconductors with unique optical and electronic properties and have been widely used in various applications, such as bio-sensing, bio-imaging, and so on. We have considered quantum dots belonging to II-VI types of semiconductors, due to their wide band gap, possession of large exciton binding energies and unique optical and electronic properties. We have studied their applications as chemical ion sensors by beginning with the study of the ion sensing ability of (CdSe)n (n = 3, 6, 9 which are in the size range of ~ 0.24, 0.49, 0.74 nm, respectively) quantum dots for cations of the zinc triad, namely Zn2+, Cd2+, Hg2+, and various anions of biological and environmental importance, and studied the effect of increasing number of rings on their ion sensing ability. The various structural, electronic, and optical properties, their interaction energies, and charge transfer on interaction with metal ions and anions have been calculated and reported. Our studies indicate that the CdSe quantum dots can be employed as sensors for both divalent cations and anions, but they can sense cations better than anions. [ABSTRACT FROM AUTHOR]

Echinatin (Ech), a characteristic retrochalcone isolated from liquorice, a widely used herbal medicine, has been investigated in detail in terms of its conformational and electronic properties in different dielectric media using density functional calculations. Natural bond orbital (NBO) analysis suggests an extended conjugation in the molecule, including a keto-ethylenic group (–CO–CH=CH–) connecting both the rings. The aromaticity of Ech has been studied using the nucleus-independent chemical shift (NICS) method. The acidity constants (pKa) have been simulated for both the hydroxyl groups in the molecule. Molecular electrostatic potentials (MEPs) have been computed to predict the reactivity of Ech toward both electrophiles and nucleophiles. Further, the electronic spectra of the neutral and deprotonated states have been computed in different solvents using an implicit solvation model, SMD. The vibrational spectra of both the neutral and anionic forms have also been simulated. Besides these, 1H-NMR and 13C-NMR spectra have been computed and compared with the experimental values. In addition, the frontier molecular orbital (FMO) energies, a number of global reactivity descriptors, viz., chemical hardness (η), chemical potential (μ), global softness (S), global electrophilicity (ω), and nucleophilicity (N) indices and various thermodynamic parameters have also been calculated in order to get a better insight into the molecular properties. [ABSTRACT FROM AUTHOR]

4-Thiazolidinone compounds have been reported to display good antioxidant activity. In the present work, the five-membered ring has been studied extensively at the DFT-B3LYP/6-311(++)G(d,p) level of theory. The geometrical features of the ring have been explored in the gas and solvent phase. Various molecular descriptor characteristics of the antioxidant compound have been calculated and compared with the reference antioxidant, trolox. Three probable antioxidant mechanisms, hydrogen atom transfer (HAT), single electron transfer (SET), and sequential proton loss electron transfer (SPLET), have been explored, both in the gas and solvent phase. It has been found that the ring exerts its antioxidant activity predominantly following the HAT pathway, both in the gas and solvent phase. In order to determine the feasibility of the overall redox reaction, the standard redox potentials have been calculated for the ring and free radicals. Furthermore, the effect of substitution on the antioxidant parameters of the ring has been explored. Results indicate that substitution at the C2 position is advantageous over that at C5 in improving such parameters. Along with this, the effect of substitution at the C2 position on the proton affinity of the C5 position has also been investigated in detail. [ABSTRACT FROM AUTHOR]

• Graphene-based adsorbents for water remediation. • Experimental and theoretical insights. • Interaction mechanism. • Future scope and challenges. Graphene-based materials have emerged as promising candidates as adsorbents for water treatment. The high surface area, low production costs, large porosities and robustness makes them excellent materials for adsorption studies and removal of toxic compounds such as pesticides, dyes, aromatic polar and non-polar compounds, nitro compounds, halogenated compounds, antibiotics, etc. from aqueous solutions. In recent years, there have been many structural modifications in the 2-D graphene sheet for synthesizing superior materials such as graphene-metal composites, metal oxide composites, bio-composites, hydrogels, etc. for improving the structural properties and widen its applications. In this review, we have incorporated the examples from both experimental and density functional theory studies (DFT) for water remediation by removal of toxic organic pollutants using graphene-based materials from the recent literature, and have further outlined the challenges and future perspectives in this direction. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) studies have been performed on the unprecedented adsorption of glyphosate pesticide on modified pyridine-like nitrogen-doped graphene (PNG) for the purpose of water remediation. The interaction of glyphosate on the PNG sheet, as well as on Pt-Cu decorated PNG substrates, is investigated. The Pt4-nCun (n = 0–4) clusters, such as Pt4, Pt3Cu1, Pt2Cu2, Pt1Cu3, and Cu4, have been decorated on the PNG surface to increase the reactivity of the adsorbent toward glyphosate. The adsorption of glyphosate on the PNG surface is physisorption, indicated by the low adsorption energy and negligible charge transfer. The mixed metal (Pt-Cu) clusters play a significant role in enhancing the interactions between the adsorbate and adsorbent, leading to better results for the adsorption of glyphosate. Exothermic chemisorption is shown by all Pt4-nCun clusters decorated PNG substrates, and chemical bond formation takes place between the adsorbate and adsorbent. Various electronic properties, like electron density difference plots, give information about the adsorption behavior of glyphosate, and density of states (DOS) plots reveal that on decorating with the cluster, the substrates start exhibiting magnetic character. [ABSTRACT FROM AUTHOR]

Hydroxamic acids have emerged as the most promising candidates from among the different classes of inhibitors of urease. In order to understand the mechanism of their action, we have studied in detail using quantum mechanics the active site of Helicobacter pylori urease complexed with acetohydroxamic acid. A diverse library of ligands having the hydroxamate moiety has been prepared and docked into the active site of urease using the QM/MM methodology. It is found that hydroxamic acids with hydrophobic groups attached to them are more potent inhibitors of urease because they can easily penetrate the hydrophobic environment surrounding the active site. The –CONHO − moiety of the hydroxamic acid is also found to be absolutely necessary for chelation and inhibition of urease. In order to determine the roles of residues His 221 and Ala 365, which are not part of the active site, but are nevertheless involved in hydrogen bonding with the ligand, we have performed Molecular Dynamics simulations, both on the wild urease and also on its mutated counterpart, with the two residues substituted, respectively, by alanine and glycine. [ABSTRACT FROM AUTHOR]

Three novel isatin‐triazole tethered tetrahydropyridine‐based colorimetric chemosensors were synthesized for selective recognition of Fe3+ ions. Their selectivity and sensitivity were investigated through colorimetric and UV‐Visible studies in a mixed‐aqueous medium (MeOH/H2O (7 : 3, v/v)). The binding stoichiometry of Chemosensor 3‐methyl 1‐phenyl (5S,6R)‐5‐bromo‐6‐(4‐((2,3‐dioxoindolin‐1‐yl)methyl)‐1H‐1,2,3‐triazol‐1‐yl)‐5,6‐dihydropyridine‐1,3(2H)‐dicarboxylate (6 a) was found to be 1 : 1 with the highest binding constant Ka, 8.6×103 M−1. The detection limit of 6 a for Fe3+ ions (0.47 μM) was much lower than the maximum permissible limit of Fe3+ ion according to Environmental Protection Agency (EPA). Moreover, the 6 a‐Fe3+ complex was found to be recyclable upon the addition of EDTA. Furthermore, the reversible colorimetric changes of 6 a on adding Fe3+ ions and EDTA were found to mimic the 'INHIBIT' molecular logic gate. The chemosensor 6 a recognizes Fe3+ ions by binding through oxygen atoms of isatin as confirmed by Density Functional Theory (DFT) studies. [ABSTRACT FROM AUTHOR]

A series of dicationic N, N'‐disubstituted benzimidazolium salts with Br− and PF6− as the counter anions were synthesized in 75–98 % yields. The single crystal X‐ray diffraction studies of one of the benzimidazolium salts confirmed the structure of these dicationic compounds. These salts exhibited a selective "turn‐off" fluorescence response toward Fe3+ ions in aqueous solution over the other competitive metal ions such as Ag+, Al3+, Ba2+, Ca2+, Co2+, Cr3+, Cu2+, Fe2+, K+, Mg2+, Na+, Ni2+, Pb2+, and Zn2+. Upon addition of 5 equivalents Fe3+ ions, emission intensity was quenched by 94–99 % in pure aqueous media. Detection limits for all probes with Fe3+ ions were found in micromolar range. Further, drug combination analysis was conducted by evaluating the combinatorial treatment effects of two benzimidazolium salts with doxorubicin on breast cancer cells using the Chou‐Talalay method and the Highest Single Agent (HSA) model, and it was found that these compounds showed synergism with doxorubicin. Further, molecular docking studies revealed the best docking score (−6.11) for one of the benzimidazolium salts, and explained its binding affinity with checkpoint kinase 2 (chk2) protein. [ABSTRACT FROM AUTHOR]

Abstract: The conformational behavior of the third generation antitumor drug, oxaliplatin, has been explored by GGA-PW91 density functional calculations and FT-IR spectra. The difference in the biological activities of cisplatin and oxaliplatin are attributed to the presence of the DACH ligand in the latter. The trans forms of the ligand are found to be more stable than the cis form, but, of the two equally stable enantiomers, the trans-l (1R,2R) one is found to be more potent biologically. Since very minor differences are observed in the electronic structures of the two enantiomers, their difference in activity is attributed to the chiral recognition of the ligand by DNA. The calculated vibrational frequencies are in good agreement with our experimental FT-IR spectrum. Calculations have also been performed on the cis isomer and its monohydrate. Comparison between the theoretically predicted geometries and the experimental ones yielded good correspondence, validating our methodology. [Copyright &y& Elsevier]

The structural, electronic, and quantum confinement effects observed in II–VI quantum dots have been described using density functional theory. Various properties like binding energy, Fermi energy, charge distribution, and band gap of various clusters have been determined as a function of cluster size in order to find out the most stable of all the clusters considered. The binding energies are found to be a function of the cluster size but converge to a maximum. Cadmium is observed to possess a larger tendency to form clusters with higher coordination numbers compared to zinc and mercury. In mercury sulfide (HgS)n, the clusters with n = 6 and 13 get dissociated into two graphene-like parallel layers. The adsorptions of single gas molecules on the (CdSe)13 quantum dots are exothermic, indicating that most of the gas molecules adsorb spontaneously on the CdSe quantum dots. Among the various gases, O2 and NO2 are the gas molecules that get most strongly chemisorbed. The CdSe quantum dot acts as an electron donor when it interacts with the oxidizing gases, O2, CO, NO2, and SO2 gases. The vibrational analysis of the combined systems indicates that the intensities of the peaks due to CdSe reduce after adsorption. Extra peaks appear at higher frequencies due to the adsorbed gas molecules. The present work shows insights into the gas sensing properties of the quantum dots under study. [ABSTRACT FROM AUTHOR]

In the present work, the adsorption of carbaryl (CBL) on the modified graphene substrates has been studied by density functional theory (DFT) for the purpose of water remediation. Carbaryl is a carbamate pesticide used worldwide and has been reported as a potential carcinogen. It has been found that CBL adsorption on pristine graphene is endothermic and highly unfavorable. Further results show that the introduction of vacancy defects and Pt clusters significantly improves the reactivity of the graphene substrates towards the carbaryl molecule. The electron density difference plots give overview of the adsorption behavior of CBL and partial density of states (PDOS) give insights into the magnetic character exhibited by substrates after decorating with the cluster. This study reveals the suitability of Pt-decorated graphene substrates as adsorbents for the removal of CBL pesticide. [ABSTRACT FROM AUTHOR]

Human carbonic anhydrase IX (hCA IX) is over-expressed in many tumor types and serves as an important target for the discovery of novel anticancer agents. However, development of compounds that can selectively inhibit hCA IX over its widespread cytosolic isoform human carbonic anhydrase II (hCA II) is a major challenge. This work focuses on recognizing the structural features of the hCA IX receptor that could help in achieving its selective inhibition. Tools such as protein structure alignment, rigid as well as flexible docking, QM/MM calculations and molecular dynamics simulations on SLC-0111, a selective hCA IX inhibitor, in complexation with each receptor, have been used to differentiate the receptor-ligand interactions in the two complexes. It is found that the ligand shows better binding to hCA IX due to stronger coordination to the Zn (II) ion. The ligand provides bidentate coordination through its negatively charged nitrogen and an oxygen of the sulfonamide zinc binding group. Binding energy calculations show that the potency of this ligand is due to the hydrophobic contacts, whereas the selectivity is due to the electrostatic interactions. Molecular docking and binding energy calculations for three different series of SLC-0111 analogs have identified a few molecules that show high potency and selectivity toward hCA IX. It is found that both hydrophobic and polar contacts contribute to the potency and selectivity of the ligands. Unlabelled Image • SLC-0111 preferentially bind to hCA IX active site over hCA II. • Potency of SLC-0111 is due to hydrophobic interaction whereas selectivity is governed by the electrostatic interactions. • SLC-0111 and Triazine hybrids are potent and selective hCA IX inhibitors. • Hydrophobic and electrostatic interactions are responsible for selectivity and specificity of SLC-0111 derivatives. [ABSTRACT FROM AUTHOR]

A series of novel 1‐triazolylpyranopyrazole derivatives has been designed and synthesized using microwave irradiation, with the purpose of obtaining repositioned pharmaceutics. The newly synthesized 1‐triazolylpyranopyrazoles (7 a–7 n), along with their precursor alkyne (5), have been screened for their in‐vitro anti‐tumor activity against Hep3B and HEK cell lines. The majority of triazolylpyranopyrazoles elicited outstanding anti‐cancer activity on Hep3B cell lines even at concentrations as low as 25μg/mL. Further, molecular docking of these active compounds against Topoisomerase IIa substantiated a plausible target site for the compounds inhibiting Hep3B cells effectively. The biological assay results for the triazolylpyranopyrazole even surpassed the activity of the reference drug i. e. Doxorubicin, thereby appearing to be potent anticancer agents. [ABSTRACT FROM AUTHOR]

• Mesoporous rGo@ZnO was synthesized and characterized using various techniques. • Adsorption capacity and catalytic activity for water treatment were analyzed. • Complete adsorptive removal of chlorpyrifos pesticide was achieved in 70 min with 75% adsorption capacity up to 5th cycle. • Crystal violet dye was completely catalytically degraded in 30 min. This study describes the facile fabrication, characterization and applications of mesoporous reduced graphene oxide@zinc oxide (rGO@ZnO) composite for the adsorptive removal of the toxic organophosphorus pesticide chlorpyrifos (CPF) and catalytic oxidative degradation of the crystal violet (CV) dye from their respective aqueous solutions. The physical properties of the as-synthesized composite were evaluated by various state of the art techniques like powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectroscopy. The adsorption efficacy of the rGO@ZnO composite was evaluated by conducting adsorption isotherm studies, kinetics studies and thermodynamic studies. The effect of solution pH, adsorbent dosage, solvent polarity, contact time and regeneration ability of the adsorbent on the adsorptive removal efficiency were also studied. Excellent removal efficiency of 95.4% was achieved within 70 min of contact time with the rGO@ZnO composite and more than 75% of the pesticide was adsorbed at the end of the fifth adsorption cycle. Batch adsorption results fitted well with the Freundlich adsorption isotherm with a high coefficient of determination (R 2). The adsorption kinetics was best described by a pseudo-second-order model with an R 2 value of 0.93. Thermodynamic parameters corroborate the physisorption nature of the adsorption owing to the spontaneous and exothermic adsorption process. Pesticide contaminated water was used to determine the field applicability of the rGO@ZnO composite. The catalytic efficiency was evaluated by the oxidative dye degradation performance of rGO@ZnO based on the activation of oxone to produce sulfate radicals which degraded the CV dye within 30 min. Results indicate that mesoporous rGO@ZnO is an excellent candidate and possesses huge potential in water treatment. [ABSTRACT FROM AUTHOR]

Certain DNA minor groove binders, especially bis-benzimdazole containing compounds, such as Hoechst 33258 and its derivatives, act as potent topoisomerase I inhibitors. The mechanism of action of these drugs is complex and involves hindering the breakage/reunion reaction of topoisomerase I. In the present work, molecular modeling studies have been performed to develop a pharmacophore and 3D-quantitative structure–activity relationship (QSAR) model based on bis- and ter-benzimidazoles, in an attempt to recognize the features that must be present in a molecule for it to behave as a topoisomerase I inhibitor. A data set comprising thirty bis-benzimidazoles and ter-benzimidazoles, known for their cytotoxicity against the RPMI-8402 lymphoblastoma cell line, has been chosen for this study. A five-point common pharmacophore hypothesis (CPH), with two acceptors, one donor and two aromatic features, has been derived for pharmacophore-based alignment of the molecules. The QSAR model, hence generated, shows a reasonable predictive Q2 value of 0.465. The CPH and contour map analyses display features that render antiproliferative properties to molecules against tumor cell lines, thereby ceasing cell growth. Further, the pharmacophore model has been utilized to develop lead molecules that can provide stability to the DNA–topoisomerase I cleavable complex, in turn inhibiting the activity of the enzyme. Virtual screening, followed by docking of obtained hits into the minor groove of B-DNA, gave three potent drugs, which are already approved drugs. The drug having the best fitness and binding score was further docked into the DNA–topoisomerase I cleavable complex. The present study opens up a new dimension in development of drugs for topoisomerase I inhibition. [ABSTRACT FROM AUTHOR]

• Curcumin encapsulated Fe-Phen nanoclusters (NCIP) were prepared in micellar medium. • NCIP are mesoporous and release curcumin in a sustained manner. • Released curcumin exhibits anti inflammatory and anti-oxidant property. • NCIP can be a safe & effective reducer of TNF- α, IL-8 and NO cytokine expressions. • NCIP may ameliorate HIV-1 associated neurotoxicity. A new strategy to encapsulating the drug curcumin into the hydrophobic core of the iron-phenanthroline nanocomplex (NIP) and eventually its release is signified. NIP was prepared via coordinate interaction between Fe2+ and the lone pairs present on the N atoms of the bidentate phenanthroline ligand (spherical morphology, diameter 18.8 nm, mesoporous with pore size 2.443 nm, amorphous). Thereafter, curcumin was successfully encapsulated (NCIP) in NIP, resulting in its enhanced stability (spherical morphology, diameter 46.8 nm). The nanocomplex NIP was used for drug delivery applications. We evaluated the anti-HIV effects of NCIP in vitro on cultures of HIV infected human microglia. The treatment of HIV-1 infected microglia with NCIP significantly decreased the expression of HIV-p24 by 41% and pro-inflammatory mediators TNF-α, IL-8 and NO by 61.2%, 41% and 50.2%, respectively, compared to NIP. F low cytometry data also support the decrease in TNF-α and IL-8 expression in case of NCIP. NCIP induced antioxidative effects by increasing the gene expression of catalase (CAT) and simulatenously decreasing hemeoxygenase-1 (HMOX-1) gene expression, thereby maintaining homeostasis which reduces neuroinflammation. These results support our premise that NCIP may be a significant adjuvant when used with traditional anti-retroviral regimens and may ameliorate HIV-1 associated neurotoxicity. [ABSTRACT FROM AUTHOR]

A water-soluble ferric (Fe 3+ ) ion sensor probe has been synthesized using one-pot multicomponent Hantzsch synthesis, followed by Cu (I) catalyzed “Click reaction”. The synthesized probe C1 shows selective binding towards Fe 3+ ion through a turn-off fluorescence response among various metal ions tested in aqueous medium. C1 shows an average fluorescence lifetime of 4.9 × 10 −10 s, and its selectivity towards Fe 3+ ion has also been studied by Stern-Volmer plot, detection limit and binding studies. The probe C1 forms a 1:1 complex with Fe 3+ ion with an association constant of (K a = 2.50 × 10 3 M −1 ), as evident from the Benesi-Hildebrand plot. Density Functional Theory (DFT) studies of the probe reveal a square pyramidal geometry. Both Fe 2+ and Fe 3+ bind strongly to the probe, but the complexation energy with Fe 3+ is almost double that with Fe 2+ , validating the experimental results. The probe C1 has also been tested for its application in biological systems and the results of an anti-proliferation assay of the fluorescent probe C1 in the absence and presence of FeCl 3 on various cell lines normal (L929) and cancerous (MCF-7, MDA-MB 231, A549 and HepG2) shows that the probe C1 would be non-cytotoxic, both in the absence and presence of Fe 3+ ions in the cells. [ABSTRACT FROM AUTHOR]

Metformin is a biguanide class of drug used for the treatment of diabetes mellitus. It is well known that serum protein-ligand binding interaction significantly influence the biodistribution of a drug. Current study was performed to characterize the binding mechanism of metformin with serum albumin. The binding interaction of the metformin with bovine serum albumin (BSA) was examined using UV–Vis absorption spectroscopy, fluorescence, circular dichroism, density functional theory and molecular docking studies. Absorption spectra and fluorescence emission spectra pointed out the weak binding of metformin with BSA as was apparent from the slight change in absorbance and fluorescence intensity of BSA in presence of metformin. Circular dichroism study implied the significant change in the conformation of BSA upon binding with metformin. Density functional theory calculations showed that metformin has non-planar geometry and has two energy states. The docking studies evidently signified that metformin could bind significantly to the three binding sites in BSA via hydrophobic, hydrogen bonding and electrostatic interactions. The data suggested the existence of non-covalent specific binding interaction in the complexation of metformin with BSA. The present study will certainly contribute to the development of metformin as a therapeutic molecule. [ABSTRACT FROM AUTHOR]