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An efficient solvent-free procedure for the synthesis of pillar[6]arenes has been developed. The procedure involves the solid-state condensation of finely milled 1,4-dialkoxybenzene and paraformaldehyde by grinding in the presence of a catalytic amount of H2SO4. The use of organic solvents for the extraction of products has also been avoided. Operational simplicity, compatibility with various 1,4-dialkoxybenzenes, non-chromatographic purification technique, high yields and mild reaction conditions are the notable advantages of this procedure. A large scale reaction demonstrated the practical applicability of this methodology. [ABSTRACT FROM AUTHOR]

Temporal variations of the ambient mixing ratio of greenhouse gas (CH4 and N2O) in a riparian rice-based agro-ecosystem of tropical region were studied during 2005–2006 in coastal Odisha. The endeavour was made with the hypothesis that the ambient mixing ratio of CH4 and N2O depends on the changes in the flux of CH4 and N2O from the rice fields in the riparian rice ecosystems. A higher ambient mixing ratio of CH4 was recorded during the tillering to grain filling stages of the rice crop, during both dry and wet seasons. The higher ambient mixing ratio of CH4 during the wet season may attribute to the higher CH4 emission from the rice field. The average mixing ratio of CH4 was recorded as 1.84 ± 0.05 ppmv and 1.85 ± 0.06 ppmv during 2005 and 2006, respectively. The ambient CH4 mixing ratio was recorded negatively correlated with the average ambient temperature. The N2O mixing ratio ranged from 261.57 to 399.44 ppbv with an average of 330.57 ppbv during 2005. However, the average mixing ratio of N2O was recorded as 318.83 ± 20.00 ppbv during 2006. The N2O mixing ratio was recorded to be negatively correlated with rainfall and average ambient temperature. Significant negative correlation (r = −0.209) of N2O with sunshine hours may attribute to the photochemical break down of N2O. The temporal variation of N2O flux from the rice field does not affect the ambient mixing ratio of N2O in the same way as in the case of the ambient mixing ratio of CH4. However, the higher mixing ratio of N2O during the fallow period of the post monsoon period may attribute to the N2O flux from soil. Results indicate that intensively cultivated coastal ecosystems can be a major source of ambient greenhouse gas. [ABSTRACT FROM AUTHOR]

Ultrasmall nanoparticles on nanocarbons enhance the electrocatalytic nitrogen reduction (NRR) efficiency. Herein, we demonstrate a novel method for depositing MoO 3 nanoparticles on defective graphene, achieving a high faradaic efficiency (FE) of 43.1% at -0.2 V vs. RHE.

Herein, we report that triplet vinylnitrenes with 1,3-biradical character can directly participate in photocycloaddition reactions with olefins to produce single diastereomers of the corresponding 1-pyrrolines under 420 nm LEDs in acetonitrile solvent. Moreover, a one-pot method has been developed to produce pyrroles directly through photocycloaddition and oxidation sequences. The excited state of the substrate olefin can sensitize vinyl azide via energy transfer, eliminating the need for an external photocatalyst or sensitizer.

Supramolecular assemblies of stimuli-responsive amphiphilic molecules have been of utmost interest in targeted drug delivery applications, owing to their capability of sequestering drug molecules in one set of conditions and releasing them in another. To minimize undesired disassembly and stabilize noncovalently encapsulated drug molecules, the strategy of core or shell cross-linking has become a fascinating approach to constructing cross-linked polymeric or small molecule-based nanoassemblies. In this article, we discuss the design and synthetic strategies for cross-linked nanoassemblies from small molecule-based amphiphiles, with robust stability and enhanced drug encapsulation capability. We highlight their potential biomedical applications, particularly in drug or gene delivery, and cell imaging. This feature article offers a comprehensive overview of the recent developments in the application of small molecule-based covalently cross-linked nanocarriers for materials and biomedical applications, which may inspire the use of these materials as a potential drug delivery system for future chemotherapeutic applications.

The excited state processes of a bacteriophytochrome are studied using high-level multireference methods. The various non-radiative channels of deactivation are identified for the chromophore. The effects of the protein environment and substituents are elucidated for these excited state processes. It is observed that while the excited states are completely delocalized in the Franck-Condon (FC) region, they acquire significant charge transfer character near the conical intersections. Earlier studies have emphasized the delocalized nature of the excited states in the FC region, which leads to absorption spectra with minimal Stokes shift [Rumyantsev et al. , Sci. Rep. , 2015, 5 , 18348]. The effect of the protein environment on the vertical excitation energies was minimal, while that on the conical intersection (CI) energetics was significant. This may lead one to believe that it is charge transfer driven. However, energy decomposition analysis shows that it is the effect of the dispersion of nearby residues and the steric effect on the rings and substituents that lead to the large effect of proteins on the energetics of the CIs.

A β-thioester and tertiary amine based covalently cross-linked nanoassembly coined as a nanonetwork (NN) endowed with dual pH responsive features (tumor acidity induced surface charge modulation and endosomal pH triggered controlled degradation) has been designed and synthesized for stable sequestration and sustained release of drug molecules in response to endosomal pH. An amphiphile integrated with tertiary amine and acrylate (ATA) functionalities was synthesized to fabricate the nanonetwork. This amphiphile showed entropically driven self-assembly and micellar nanostructures (nanoassemblies), which can sequester hydrophobic drug molecules at neutral pH. To further stabilize the nanoassemblies and the sequestered drug molecules even below its critical aggregation concentration (CAC), the micellar core was cross-linked via the thiol-acrylate Michael addition click reaction to generate multiple copies of acid labile β-thioester functionalities in the core, which undergo slow hydrolysis at endosomal pH (∼5.0), thus enabling sustained release of the anti-cancer drug doxorubicin at endosomal pH. The nanonetworks showed a significant decrease in drug leakage compared to the nanoassemblies (NAs), which was also justified by a low leakage coefficient calculated from the fluorescence resonance energy transfer experiment. The NN also exhibited dilution insensitivity and high serum stability, whereas the NA disassembled upon dilution and during serum treatment. The biological evaluation revealed tumor extracellular matrix pH (∼6.4-6.8) induced surface charge modulation and cancer cell (HeLa) selective activated cellular uptake of the doxorubicin loaded nanonetwork (NN-DOX). In contrast, the benign nature of NN-DOX towards normal cells (H9c2) suggests excellent cell specificity. Thus, we believe that the ease of synthesis, nanonetwork fabrication reproducibility, robust stability, smart nature of tumor microenvironment sensitive surface charge modulation, boosted tumoral-cell uptake, and triggered drug release will make this system a potential nanomedicine for chemotherapeutic treatments.

Flexible, free-standing polyvinyl alcohol (PVA)-zirconia (mean particle size ∼24 nm) nanocomposite films have been synthesized and their performance as a potential next-generation resistive switching device material has been assessed in this report. The nanocomposite films switch from a high resistive state (HRS) to a low resistive state (LRS) at the SET potential and from LRS to HRS at the RESET potential within the voltage window of 5 V. The origination of trap-assisted SET/RESET potentials has been experimentally validated by analyzing the experimental data and invoking various theoretical models. The impregnation of zirconium dioxide (ZrO 2 ) nanoparticles considerably enhances the interfacial charges facilitated by the formation of dangling bonds. The current ( I )-voltage ( V ) characteristics elucidate how the alteration of free volumetric space in the nanocomposites can modify the SET-RESET potential. This leads to tunable SET/RESET potential, good resistance ratio (∼80), and extensive cycling ability of these PVA-ZrO 2 organic flexible nanocomposite films. Herein, we have also investigated the effect of applying external bias voltage (equal to the RESET potential) for possible energy bandgap modification and polymer chain orientation. The impedance spectra differ considerably when the sample is subjected to SET, RESET, and zero voltage bias. The observations have been correlated with the UV-vis absorption spectra and electrical studies. The adopted analysis method and obtained results can open up new avenues for designing and analyzing resistive switching-based random-access memory devices.

1-Butane sulfonic acid-3-methylimidazolium tosylate, [BSMIM]OTs, is a remarkable catalyst for the cascade synthesis of coumarin-functionalized indole derivatives via a tandem cyclization reaction of aniline and phenylglyoxal monohydrate. This reaction possibly proceeds through imine formation/nucleophilic addition/cyclization. In addition, this method shows lower E -factors. A clean reaction, easily accessible reactants, metal-free and environmentally friendly reaction conditions, and reusability of the catalyst are the notable advantages of this procedure. In addition, molecular docking studies show the theoretical possibility of binding these types of synthesized compounds to key proteins in tumorigenesis.

A plethora of 6-(hetero)aryl C-C and C-N bonded tacrine analogues has been made accessible by employing palladium mediated (Suzuki-Miyaura, Heck, Sonogashira, Stille and Buchwald) cross-coupling reactions, starting from either halogenated or borylated residues. The successful use of Pd(dppf)Cl 2 ·CH 2 Cl 2 as a common catalytic system in realizing all these otherwise challenging transformations is the highlight of our optimized protocols. The analogues thus synthesized allow the available chemical space around the C-6 of this biologically relevant tacrine core to be explored. The in silico docking studies of the synthesized compounds were carried out against the acetylcholinesterase (AChE) enzyme. The hepatotoxicity studies of these compounds were done against complexes of CYP1A2 and CYP3A4 proteins with known inhibitors like 7,8-benzoflavone and ketoconazole, respectively., Competing Interests: The authors declare no conflicts of interest., (This journal is © The Royal Society of Chemistry.)

2,7-Diazapyrenes are promising azaaromatic scaffolds with a unique structural geometry and supramolecular properties. This core moiety and its derivatives with some N -methyl cations like N -methyl-2,7,-diazapyrenium, and N , N '-dimethyl-2,7-diazapyrenium attract special attention due to their challenging photophysical properties, especially in the context of interactions with DNA and some of its mononucleotides. This review focuses on the analysis of the main synthetic approaches to 2,7-diazapyrene and its functional derivatives employing various strategies under different reaction conditions. The opportunities of applications of 2,7-diazapyrenes, including their remarkable photophysical and supramolecular properties, DNA-bindings, in sensors, molecular electronics, supramolecular systems, and related areas are also highlighted., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Fragments of 1,2,4-triazolo[5,1- c ][1,2,4]triazin-7-one are found in many compounds with various types of biological activities, including the antiviral drug Riamilovir (Triazavirin®), which shows activity against SARS-CoV-2 (COVID-19). Therefore, the development of convenient methods for the synthesis of new derivatives of 1,2,4-triazolo[5,1- c ][1,2,4]triazin-7-one is always in demand. This review systematizes the information on the most common synthetic methods for constructing the 1,2,4-triazolo[5,1- c ][1,2,4]triazin-7-one heterocyclic system.

Computer vision (CV) algorithms are widely utilized in imaging processing for medical and personal electronics applications. In sensorics CV can provide a great potential to quantitate chemosensors' signals. Here we wish to describe a method for the CV-assisted spectrofluorometer-free detection of common nitro-explosive components, e.g. 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT), by using polyaromatic hydrocarbon (PAH, PAH = 1-pyrenyl or 9-anthracenyl) - based bola -type chemosensors. The PAH components of these chemical bolas are able to form stable, bright emissive in a visual wavelength region excimers, which allows their use as extended matrices of the RGB colors after imaging and digital processing. In non-polar solvents, the excimers have poor chemosensing properties, while in aqueous solutions, due to the possible micellar formation, these excimers provide "turn-off" fluorescence detection of DNT and TNT in the sub-nanomolar concentrations. A combination of these PAH-based fluorescent chemosensors with the proposed CV-assisted algorithm offers a fast and convenient approach for on-site, real-time, multi-thread analyte detection without the use of fluorometers. Although we focus on the analysis of nitro-explosives, the presented method is a conceptual work describing a general use of CV for quantitative fluorescence detection of various analytes as a simpler alternative to spectrofluorometer-assisted methods., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

We have observed that a reagent combination of NaIO 4 and NH 2 OH·HCl reacts with α,β-unsaturated ketones followed by the nucleophile ethylene glycol allowing the synthesis of 2,3-disubstituted 1,4-dioxanes using cesium carbonate as a base under Williamson ether synthesis. This reaction is useful for the synthesis of functionalized 1,4-dioxane having a carbonyl functionality. A variety of 2,3-disubstituted 1,4-dioxanes have been synthesized using these reaction conditions. A probable reaction mechanism has also been proposed.

The development of bacterial tolerance against pesticides poses a serious threat to the sustainability of food production. Widespread use of copper (Cu)-based products for plant disease management has led to the emergence of copper-tolerant pathogens such as Xanthomonas perforans ( X. perforans ) strains in Florida, which is very destructive to the tomato ( Solanum lycopersicum ) industry. In this study, we report a hybrid nanoparticle (NP)-based system, coined Locally Systemic Pesticide (LSP), which has been designed for improved efficacy compared to conventional Cu-based bactericides against Cu-tolerant X. perforans . The silica core-shell structure of LSP particles makes it possible to host ultra-small Cu NPs (<10 nm) and quaternary ammonium (Quat) molecules on the shell. The morphology, release of Cu and Quat, and subsequent in vitro antimicrobial properties were characterized for LSP NPs with core diameters from 50 to 600 nm. A concentration of 4 μg mL -1 (Cu): 1 μg mL -1 (Quat) was found to be sufficient to inhibit the growth of Cu-tolerant X. perforans compared to 100 μg mL -1 (metallic Cu) required with standard Kocide 3000. Wetting properties of LSP exhibited contact angles below 60°, which constitutes a significant improvement from the 90° and 85° observed with water and Kocide 3000, respectively. The design was also found to provide slow Cu release to the leaves upon water washes, and to mitigate the phytotoxicity of water-soluble Cu and Quat agents. With Cu and Quat bound to the LSP silica core-shell structure, no sign of phytotoxicity was observed even at 1000 μg mL -1 (Cu). In greenhouse and field experiments, LSP formulations significantly reduced the severity of bacterial spot disease compared to the water control. Overall, the study highlights the potential of using LSP particles as a candidate for managing tomato bacterial spot disease and beyond., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

In this study, a new hyperbranched polyester copolymer was designed using a proprietary monomer and diethylene glycol or triethylene glycol as monomers. The synthesis was carried out using standard melt polymerization technique and catalyzed by p-tolulenesulfonic acid. The progress of the reaction was monitored with respect to time and negative pressure, with samples being subjected to standard characterization protocols. The resulting polymers were purified using the solvent precipitation method and characterized using various chromatographic and spectroscopic methods including GPC, MALDI-TOF, and NMR. We have observed polymers with a molecular weight of 29 643 Da and 33 996 Da, which is ideal to be used as a drug delivery system. Thus, these polymers were chosen for further modification into folate-functionalized polymeric nanoparticles for the targeted treatment of cancer, in this case we have chosen prostate cancer cells as a model. We hypothesized that due to the 3D structure of the A2B monomer, we expect a pseudo-branched polymer that is globular in shape which will be ideal for drug carrying and delivery. We used a solvent diffusion method for the one-pot formulation of water-dispersable polymeric nanoparticles as well as theraputic drug (doxorubicin) encapsulation. The efficacy of this delivery system was gauged by treating LNCaP cells with the drug-loaded nanoparticles and assessing the results of the treatment. The results were analyzed by cytotoxicity (MTT) assays, drug release studies, and fluorescence microscopy. The experimental results collectively show a nanoparticle that was biocompatible, target-specific, and successfully initiated apoptosis in an in vitro prostate cancer model.

An efficient and new approach has been developed to synthesize bis(β,β'-dialkoxy carbonyl) derivatives through the reaction between N-tosylaziridines and malonate esters under ambient air using tBuOK in DMSO solvent. A plausible reaction pathway has been predicted. Control experiments suggested that the reactions proceed through the formation of α-aminoketones. This reaction offers a broad substrate scope, metal-free synthesis, excellent regioselectivity, easily accessible reactants, and simple operation. A gram-scale synthesis demonstrates the potential applications of the present method.

A library of substituted quinolines has been synthesized by the reaction of aldehydes, anilines and nitroalkanes using a catalytic amount of Fe(iii) chloride. The reaction is a simple, efficient, one-pot, three-component domino strategy in ambient air which afforded the products in high yields. A probable pathway of the reaction is a sequential aza-Henry reaction/cyclization/denitration. The use of commercially available chemicals as starting materials, an inexpensive metal catalyst, aerobic reaction conditions, tolerance of a wide range of functional groups, and operational simplicity are the notable advantages of this present protocol.

A bolaamphiphilic cross-linked nanoassembly endowed with pH responsive degradation features has been designed and fabricated for stable noncovalent guest encapsulation and controlled release. The self-assembled bolaamphiphile is utilized to prepare cross-linked nanoassemblies to further stabilize the noncovalent guest encapsulation at a concentration below its critical aggregation concentration (CAC) in a large volume of water or serum for drug delivery applications. Thus, this system can simultaneously address premature drug release and safety issues. The nanoassemblies integrated with a β-thioester linker, which can be hydrolyzed selectively under mildly acidic conditions (pH ∼ 5.3) at a slow rate, thus enable controlled release of guest molecules. Biological evaluation revealed that doxorubicin loaded cross-linked nanoassemblies (CNs-DOX) are nontoxic to normal cells such as HEK-293 or PBMC, but in contrast, showed a robust apoptotic effect on colon cancer cells, HCT-116, indicating excellent specificity. Thus, the fabrication reproducibility, robust stability, triggered drug release and cell selective toxicity behavior make this small molecular system very promising in the field of chemotherapeutic applications., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The interactions between substituted 5-R-3-(pyridyl-2)-1,2,4-triazines with in situ generated substituted aryne intermediates have been studied. The reaction afforded either inverse demand (ID) aza-Diels-Alder products or 1,2,4-triazine ring rearrangement (domino) products as major ones depending on the nature of both the substituents at the C5 position of the 1,2,4-triazine core or in the aryne moiety. The structures of the key products were confirmed based on X-ray data. Based on the density functional theoretical (DFT) studies of the Diels-Alder transition state geometries, the influence of the nature of arynes on the direction of the 1,2,4-triazine transformation has been proposed.

Highly diastereo- and enantioselective 1,6-addition of 1,3-ketoamides to p -quinone methides ( p -QMs) using chiral NHCs as Brønsted base catalysts is developed. The reaction is based on the utilization of a 1,3-ketoamide having acidic N-H that forms a chiral ion-pair consisting of the enolate and the azolium ion. Different β-ketoamides and functionalized p -QMs are applicable to the reaction. Synthetic application of the method is demonstrated via the preparation of highly enantioenriched β and γ-lactam derivatives.

A small number of key-residues in a protein sequence play vital roles in the function, stability, and folding of the protein. The nonuniform conformational disorder of a small protein Chymotrypsin Inhibitor 2 (CI2) and its secondary segments has been quantified in the ethanol governed temperature induced unfolding process by estimating its change in configurational entropy in several water-ethanol mixed solutions. Such calculations further assist us in identifying the key-residues, from where the unfolding of the protein was initiated. Our findings match well with the reported experimental results. We then make an attempt to explore the properties of the solvent water and ethanol around the key-residues of the protein in its folded and unfolded forms at ambient temperature to identify the individual role of ethanol and water in the protein unfolding. We find that the key-residues of the unfolded protein are in good contact with both water and ethanol as compared to those of the folded protein. In the presence of ethanol, water molecules are noticed to form a rigid structurally bound solvation layer around the key-residues of the protein, irrespective of its conformational state. The restricted translational motion and prominent caging effect of the water and ethanol molecules present around the key-residues of the unfolded protein are a signature of the existence of a rigid mixed water-ethanol layer as compared to that around the folded protein. Furthermore, comparable restricted structural relaxation of the key-residue-water and key-residue-ethanol hydrogen bonds in the unfolded protein as compared to that in the folded one implies that the formation of a strong long-lived hydrogen bonding environment nourishes the unfolding process. We believe that our findings will shed light to several co-solvent governed unfolding processes of a protein in general.

Herein, a bis-amido tris-amine macrocycle and five bipyridine-based bidentate chelating ligands were investigated towards various divalent transition metal ion (Ni II , Co II , Cu II , and Zn II )-templated syntheses of metallo [2]pseudorotaxanes. The formation of these ternary complexes was elucidated via different spectroscopic techniques such as ESI-MS, absorption spectroscopy, EPR spectroscopy, and single-crystal X-ray diffraction studies wherever possible. Azide-terminated Ni II , Co II , Cu II , Zn II -templated [2]pseudorotaxanes were explored to generate [2]rotaxane, ROT, via reaction with an alkyne-terminated triphenylene unit as a stopper under the mild reaction condition of the Cu I -catalyzed azide-alkyne cycloaddition reaction. Ni II -templated [2]pseudorotaxane was found to be the best precursor towards the high-yield synthesis of ROT. The interpenetrative nature of the center piece in metal-free rotaxane was also established through various spectroscopic techniques such as ESI-MS and 1D and 2D (COSY, NOESY, ROESY, and DOSY) NMR spectroscopy. Furthermore, ROT was functionalized via tri-acetylation as AcROT to incorporate three tertiary amides at the tris-amine centers; this AcROT exhibited rotamer-induced molecular motions in an interpenetrated system via the formation of multiple conformers/co-conformers. Additionally, the existence of multiple rotamers was established via variable-temperature NMR spectroscopic studies. Li + and 12-crown-4 were found to be suitable for the reversible conformation/co-conformation fixation of tri-acetylated bis-amido tris-amine macrocyclic wheel-based rotaxane.

The threading of 'U' shaped bent axles having diverse functionalities (Axle1-Axle10) is investigated by using a heteroditopic amido-amine macrocyclic (MC) wheel via Ni II or Cu II metal ion templation. These bent shaped axles are the derivatives of 4,4'-substituted 2,2'-bipyridine, which are composed of various terminal groups like alkene, alkyne, bromide, hydroxyl and azide. Such metallo [2]pseudorotaxanes are well characterised by ESI-MS, EPR and FT-IR spectroscopic studies, UV-Vis absorption studies, elemental analysis and single-crystal X-ray diffraction studies wherever possible. Experimental evidence supports 1 : 1 : 1 ternary complexation between MC, the metal ion and axle. The single crystal X-ray structures of three Cu II templated ternary complexes (PR1', PR3' and PR7') show the penta-coordination arrangement around the templating metal ion. Interestingly, judicious selection of chemical functionalities in the complementary wheel and axle components enables to show the existence of various covalent and non-covalent interactions.

Positively charged functionalized carbon nanodots (CNDs) with a variety of different effective surface areas (ESAs) are synthesized via a cheap and time effective microwave method and applied for the generation of hydrogen via hydrolysis of sodium borohydride. To the best of our knowledge, this is the first report of metal-free controlled hydrogen generation. Our observation is that a positively charged functional group is essential for the hydrolysis for hydrogen production, but the overall activity is found to be enhanced with the ESA. A maximum value of 1066 ml g -1 min -1 as the turnover frequency is obtained which is moderate in comparison to other catalysts. However, the optimum activation energy is found to be 22.01 kJ mol -1 which is comparable to well-known high cost materials like Pt and Ru. All of the samples showed good reusability and 100% conversion even after the 10th cycle. The effect of H + and OH - is also studied to control the on-board and on-demand hydrogen production ("on-off switching"). It is observed that H 2 production decreases inversely with NaOH concentration and ceases completely when 10 -1 M NaOH is added. With the addition of HCl, H 2 production can be initiated again, which confirms the on/off control over production.

A new oxy(ether)tris(amine) macrocycle, MC has been synthesized for CuII complex formation within the cavity of the macrocyclic wheel in endotopic fashion. This complex is further reacted with the bidentate chelating ligands, 1,10-phenanthroline (L1), 2,2′-bipyridyl (L2), 4,4′-dimethyl-2,2′-bipyridyl (L3) and 5,5′-dimethyl-2,2′-bipyridyl (L4) to achieve the pseudorotaxanes PRT1–PRT4, respectively. These bis-heteroleptic complexes were characterized by the electrospray ionization mass spectrometry (ESI-MS), UV/Vis, EPR spectroscopy and Single-crystal X-ray structural analysis. Binding constants of the heteroleptic complexes were found in the range of 1.16 × 10(2) to 1.55 × 103 M(-1) in acetonitrile. Further, the double level selectivity studies of MC using different metal ions [CoII, NiII, CuII, ZnII] and a number of simple bidentate chelating ligands shows the selective formation of PRT1 that justifies the self-sorting nature of the system. Further, substitution of axles from pseudorotaxanes PRT2–PRT4 could also be achieved by L1 with nearly 100% efficiency. To corroborate the experimental studies (comparison with the crystal geometry, importance of the π–π stacking, etc.) the geometries of the pseudorotaxanes were optimized using DFT (B3LYP) in the gas phase.

Imidazopyridine is one of the important fused bicyclic 5-6 heterocycles and it is recognized as a "drug prejudice" scaffold due to its wide range of applications in medicinal chemistry. This moiety is also useful in material science because of its structural character. Synthesis of this moiety from the easily available chemicals is desirable due to its tremendous use in the various branches of chemistry. Here we report a review on the synthesis of this scaffold employing different strategies such as condensation, multicomponent reactions, oxidative coupling, tandem reactions, aminooxygenation, and hydroamination reactions.

Pd NP concentration guided the self-assembly of core-shell Pd@SiO2 nanoparticles (NPs) into microcubes. The Pd NPs were stacked by molten dodecyltrimethylammonium bromide (DTAB) to create the SiO2 envelope. The microcubes demonstrated improved leaching resistance in heterogeneous catalysis over a conventional porous support.

Palladium complexes bearing abnormal N-heterocyclic carbene were used as catalysts in Suzuki-Miyaura cross coupling of aryl chlorides at 25 °C. The catalyst remained active for 10 successive catalytic runs and can activate 4-chlorotoluene at 25 °C with 0.01 mol% catalyst loading resulting in a TON of 9500 within 6 h., (This journal is © The Royal Society of Chemistry 2012)

Temporal variations of the ambient mixing ratio of greenhouse gas (CH(4) and N(2)O) in a riparian rice-based agro-ecosystem of tropical region were studied during 2005-2006 in coastal Odisha. The endeavour was made with the hypothesis that the ambient mixing ratio of CH(4) and N(2)O depends on the changes in the flux of CH(4) and N(2)O from the rice fields in the riparian rice ecosystems. A higher ambient mixing ratio of CH(4) was recorded during the tillering to grain filling stages of the rice crop, during both dry and wet seasons. The higher ambient mixing ratio of CH(4) during the wet season may attribute to the higher CH(4) emission from the rice field. The average mixing ratio of CH(4) was recorded as 1.84 ± 0.05 ppmv and 1.85 ± 0.06 ppmv during 2005 and 2006, respectively. The ambient CH(4) mixing ratio was recorded negatively correlated with the average ambient temperature. The N(2)O mixing ratio ranged from 261.57 to 399.44 ppbv with an average of 330.57 ppbv during 2005. However, the average mixing ratio of N(2)O was recorded as 318.83 ± 20.00 ppbv during 2006. The N(2)O mixing ratio was recorded to be negatively correlated with rainfall and average ambient temperature. Significant negative correlation (r = -0.209) of N(2)O with sunshine hours may attribute to the photochemical break down of N(2)O. The temporal variation of N(2)O flux from the rice field does not affect the ambient mixing ratio of N(2)O in the same way as in the case of the ambient mixing ratio of CH(4). However, the higher mixing ratio of N(2)O during the fallow period of the post monsoon period may attribute to the N(2)O flux from soil. Results indicate that intensively cultivated coastal ecosystems can be a major source of ambient greenhouse gas.

Possible precursor complexes for the aerobic oxidation of benzene to phenol in CuHY zeolites were studied by QM/MM calculations. Structures limited to just one copper center were determined, in which both, benzene and dioxygen are adsorbed to and activated by the same transition metal cation. Frequency analyses reveal that these complexes can be identified by the frequency shift of the O(2) stretching mode.

The adsorption of dioxygen to copper in CuHY zeolites has been studied by means of FTIR spectroscopy and model calculations at the quantum mechanical/molecular mechanics (QM/MM) level. Different Si/Al ratios, substitution patterns and adsorption sites within the cavities of the zeolite lead to a large number of different isomers to be studied. In addition, these parameters control the end-on vs. side-on adsorption of dioxygen. High-level multireference benchmark calculations for the singlet and triplet states of such adsorption complexes corroborate the use of density functional theory for the investigation of these systems. Comparison of the experimental and computed data allows for the identification of a preferred adsorption site and a small number of isomers which appear to be most relevant for the adsorption process. Redshifts of >250 cm(-1) are obtained for the vibrational frequencies of adsorbed O(2).

A robust water-in-oil microemulsion method of making water-dispersible ultra-small (<30 nm) size fluorescent chitosan nanoparticles is reported for the first time and specific targeting of these FCNPs to human leukemia cells via aptamer recognition is demonstrated.

Here we report a simple strategy for selective detection of cadmium ions by manipulating the electron transfer pathways of surface-engineered quantum dots.

TAT (a cell penetrating peptide)-conjugated CdSratioMn/ZnS quantum dots (Qdots), intra-arterially delivered to a rat brain, rapidly (within a few minutes) labeled the brain tissue without manipulating the blood-brain-barrier (BBB). Qdot loading was sufficiently high that it allowed a gross fluorescent visualization of the whole rat brain using a low power hand-held UV lamp. Histological data clearly showed that TAT-conjugated Qdots migrated beyond the endothelial cell line and reached the brain parenchyma. Qdots without TAT did not label the brain tissue confirming the fact that TAT peptide was necessary to overcome the BBB. The present study clearly demonstrated the possibility of delivering a large amount of Qdot-based imaging agents to the brain tissue.

Water-in-oil (w/o) microemulsion synthesis of 70 nm size monodisperse TAT (a cell penetrating peptide, CPP) conjugated, FITC (fluorescein isothiocyanate) doped silica nanoparticles (TAT-FSNPs) is reported; human lung adenocarcinoma (A549) cells (in vitro) and rat brain tissue (in vivo) were successfully labeled using TAT-FSNPs.

Synthesis of diethyl malonate based wholly aliphatic hyperbranched polyesters having suitable polar matrix for irreversible molecular encapsulation is carried out for the first time., (Copyright 2004 The Royal Society of Chemistry)

In this report, we demonstrate the biochemical modification of silica based nanoparticles. Both pure and dye-doped silica nanoparticles were prepared, and their surfaces were modified with enzymes and biocompatible chemical reagents that allow them to function as biosensors and biomarkers. The nanoparticles produced in this work are uniform in size with a 1.6% relative standard deviation. They have a pure silica surface and can thus be modified easily with many biomolecules for added biochemical functionality. Specifically, we have modified the nanoparticle surfaces with enzyme molecules (glutamate dehydrogenase (GDH) and lactate dehydrogenase (LDH)) and a biocompatible reagent for cell membrane staining. Experimental results show that the silica nanoparticles are a good biocompatible solid support for enzyme immobilization. The immobilized enzyme molecules on the nanoparticle surface have shown excellent enzymatic activity in their respective enzymatic reactions. The nanoparticle surface biochemical functionalization demonstrates the feasibility of using nanoparticles for biosensing and biomarking applications.