Showing papers in "Journal of Chemical Sciences in 2015"

Recent developments in solar H 2 generation from water splitting

Abstract: Hydrogen production from water and sunlight through photocatalysis could become one of the channels, in the not-so-distant future, to meet a part of ever growing energy demands. However, accomplishing solar water splitting through semiconductor particulate photocatalysis seems to be the ‘Holy Grail’ problem of science. In the present mini-review, some of the critical strategies of semiconductor photocatalysis are focused with the aim of enumerating underlying critical factors such as visible light harvesting, charge carrier separation, conduction and their utilization that determine the quantum efficiency. We attempted to bring out the essential requirements expected in a material for facile water splitting by explaining important and new designs contributed in the last decade. The newly emerged designs in semiconductor architecture employing nanoscience towards meeting the critical factors of facile photocatalysis are elucidated. The importance of band gap engineering is emphasized to utilize potential wide band gap semiconductors. Assistance of metal nanostructures and quantum dots to semiconductors attains vital importance as they are exuberant visible light harvesters and charge carrier amplifiers. Benevolent use of quantum dots in solar water splitting and photoelectrochemical water splitting provides scope to revolutionize the quantum efficiency by its multiple exciton generation features. A list of drawbacks and issues that hamper the much needed breakthrough in photocatalysis of water splitting is provided to invite attention to address them and move towards sustainable water splitting.

Structural and optical properties of zinc titanates synthesized by precipitation method

Abstract: Synthesis of zinc titanates was carried out using a simple precipitation method followed by calcination at different temperatures to obtain different phases of the material. The phase transition characteristics, presence of functional groups, structural aspects and optical bandgaps with respect to calcination temperature were studied by thermal analysis, EDAX, FT-IR, powder XRD, Raman and UV-Vis spectroscopy respectively. The compound on heat treatment at 100∘C for 24 h showed broadened peaks in XRD. With increasing temperature of calcination, the compound appeared to turn to crystalline phase and cubic ZnTiO3 phase was observed at 600∘C. Partial phase transformation of cubic phase ZnTiO3 into hexagonal ilmenite type ZnTiO3 was observed in the temperature range 700∘C to 900∘C. At 1000∘C both cubic and hexagonal ilmenite phases decomposed into cubic phase Zn2TiO 4 and rutile TiO2. FT-IR showed M-O bonds in the range of 400 cm −1 to 700 cm −1. Raman spectra of cubic defect spinel ZnTiO3 and cubic inverse spinel Zn2TiO4 were found to be similar. The optical bandgap calculated using diffuse reflectance spectra was found to be in the range of 3.59 to 3.84 eV depending on calcination temperature.

Adsorption of small gas molecules on B 36 nanocluster

Abstract: Adsorption of CO, N2, H2O, O2, H2 and NO molecules on B36 cluster was studied using density functional theory (DFT) with B3LYP functional and 6-311 + G(d,p) basis set. Energies, enthalpies and Gibbs free energies of the adsorption processes were calculated. The thermodynamic data showed that the B36 cluster is a good adsorbent only for CO, O2 and NO molecules. The calculated energies of adsorption of N2, H2O and H2 on the B36 cluster were positive values. CO molecule is adsorbed via the carbon atom more effectively, while the nitrogen atom of NO is adsorbed better than the oxygen atom. Also, when NO and O2 are adsorbed synchronously via both atoms, they dissociate. The edge boron atoms of the B36 cluster showed more reactivity than the inner atoms.

Hydroxy, carboxylic and amino acid functionalized superparamagnetic iron oxide nanoparticles: Synthesis, characterization and in vitro anti-cancer studies

Abstract: Superparamagnetic iron oxide nanoparticles were synthesized by simple co-precipitation method and modified with different coating agents such as ascorbic acid, hexanoic acid, salicylic acid, L-arginine and L-cysteine. The synthesized nanoparticles were characterized by various techniques such as FT IR, XRD, VSM, SEM, TEM and thermal analysis. Both bare and coated magnetites were of cubic spinel structure and spherical in shape. All the magnetite nanoparticles showed superparamagnetic behaviour with high saturated magnetization. In vitro cytotoxicity test of bare and coated nanoparticles was performed using adenocarcinoma cells, A549. Cell viability of bare and L-arginine coated magnetite nanoparticles showed IC50 value of 31.2 μg/mL proving the compatibility of nanocarriers when compared to others. Hence, L-arginine coated nanoparticles were used for loading the drug paclitaxel and the observed IC50 value (7.8 μg/mL) shows its potent anti-proliferative effect against A549 lung cancer cell lines. Thus, it can be speculated that the drug paclitaxel loaded L-arginine coated nanoparticles could be used as an effective drug carrier for the destruction of cancer cells.

Hydrogen adsorption of nitrogen-doped carbon nanotubes functionalized with 3d-block transition metals

Abstract: A systematic study of the most stable configurations, calculation of the corresponding binding and free energies of functionalized 3d transition metals (TMs) on (10,0) Single Walled Carbon Nanotube (SWCNT) doped with porphyrin-like nitrogen defects (4ND-CNxNT) using spin-polarized density functional theory (DFT) formalism with flavours of LDA and GGA exchange-correlation (XC) functionals has been made. A thorough analysis showed that the electronic and magnetic properties of SWCNT are dependent on the TMs absorbed wherein, the composite material TM/4ND-CNxNT can act as a medium for storing hydrogen at room temperature manifested through favourable adsorption energy.

Tuning the structural and catalytic properties of ceria by doping with Zr4+, La3+ and Eu3+ cations

Abstract: This work attempts to gain information about the role of trivalent and tetravalent dopants on the structural and catalytic properties of ceria (CeO2). In this study, we have prepared Zr4+, La3+, and Eu3+ doped ceria (CZ, CL, and CE) by coprecipitation method and calcined at 773 K. The physicochemical characterization was achieved by using various techniques, namely, X-ray powder diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area, high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), and electron spin resonance (ESR) spectroscopy. The catalytic efficiency for soot oxidation was evaluated by thermogravimetric (TG) method and compared with undoped CeO2. Doped CeO2 catalysts decreased the soot oxidation temperature by more than 158 K compared to pure ceria. This is ascribed to mutual interaction and synergistic effect between the dopant species and the ceria. Among the synthesized nanocatalysts, the CE sample exhibited better performance. The observed better activity of CE was attributed to the presence of more number of oxygen vacancies, a high specific surface area, and easy reducibility as confirmed from Raman, BET surface area, and TPR measurements, respectively.

Linear sweep anodic stripping voltammetry: Determination of Chromium (VI) using synthesized gold nanoparticles modified screen-printed electrode

Abstract: A highly sensitive electrochemical sensor has been constructed for determination of Cr(VI) with the lowest limit of detection (LOD) reported to date using gold nanoparticles (AuNPs) modified screen-printed electrode (SPE). The modification of SPE by casting pure AuNPs increases the sensitivity for detection of Cr(VI) ion using anodic stripping voltammetry. Cr(VI) ions are reduced to chromium metal on SPE-AuNPs by applying deposition potential of –1.1 V for 180 s. Afterwards, the oxidation peak current of chromium is obtained by linear sweep voltammetry in the range of −1.0 V to 0.2 V. Under the optimized conditions (HClO4, 0.06 mol L−1; deposition potential, –1.1 V; deposition time, 180s; scan rate, 0.1 V s−1), the limit of detection (LOD) was 1.6 pg mL−1. The fabricated electrode was successfully used for detection of Cr(VI) in tap and seawater.

Synthesis, structure analysis, anti-bacterial and in vitro anti-cancer activity of new Schiff base and its copper complex derived from sulfamethoxazole

Abstract: A new bidentate Schiff base ligand (HL1), containing O,N donors was prepared by the reaction of sulfamethoxazole with 5-nitrosalicylaldehyde and characterized by elemental analysis, FT-IR, 1H and13C NMR. The copper complex of this ligand was synthesised by treating DMF-ethanolic mixture solution of the ligand of two equivalents with one equivalent of copper acetate. The complex was characterized on the basis of UV, FT-IR, molar conductance, EPR, magnetic moment and single crystal X-ray diffraction. Interestingly, the crystal structure of the octahedral complex showed two solvent molecules (DMF) as ligands at their axial positions. The molar conductance data revealed that the complex is a non-electrolyte. The Schiff base and its copper complex have been investigated as anti-bacterial and anti-fungal agents against various microorganisms. The in vitro cytotoxicity tests of the ligand and its copper complex were carried out in two different human tumour cell lines, HCT-116 and MDA – MB - 231. The cytotoxicity studies showed that the complex exhibited higher activity than cisplatin and carboplatin towards MDA – MB – 231.

Manganese zinc ferrite nanoparticles as efficient catalysts for wet peroxide oxidation of organic aqueous wastes

Abstract: Manganese substituted zinc nanoparticles, MnxZn1−xFe2O4 (x = 0.0, 0.25, 0.5, 0.75, 1.0) prepared by sol gel method were found to be efficient catalysts for wet peroxide oxidation of 4-chlorophenol. Complete degradation of the target pollutant occurred within 90 min at 70∘C. Zinc substitution enhanced the catalytic efficiency and the unsubstituted ZnFe2O4 oxidized the target compound completely within 45 min. Studies on the effect of reaction variables revealed that only a small amount of the oxidant, H2O2 (3–4 mL) is required for complete degradation of 4-chlorophenol. More than 80% of 4-chlorophenol was removed at catalyst concentrations of 100 mg/L. Direct correlation between the amount of catalyst present and the extent of degradation of 4-chlorophenol was observed, ruling out hesterogeneous-homogeneous mechanism. The catalysts are reusable and complete degradation of target pollutant occurred after five successive runs. The extent of iron leaching was fairly low after five consecutive cycles indicating the mechanism to be heterogeneous.

Designing pH-responsive and dielectric hydrogels from cellulose nanocrystals

Abstract: We report the fabrication and characterization of a pHresponsive hydrogel with improved mechanical and dielectric properties from cellulose nanocrystals. X-ray diffraction and SEM observations were used to analyze the sample morphology. The resulting pH detector exhibits a pronounced change in their swelling index in response to variation in pH. It was used singly and in combination with other nanomaterials to optimize smart material designs. The applications of the developed material are anticipated in chemical, environmental and biological systems.

Effect of surfactants on the morphology of FeSe films fabricated from a single source precursor by aerosol assisted chemical vapour deposition

Abstract: This article presents the fabrication of FeSe thin films from a single source precursor namely (1-(2-fluorobenzoyl)-3-(4-ferrocenyl-3-methylphenyl)selenourea (MeP2F)) by aerosol assisted chemical vapour deposition (AACVD). All the films were prepared via similar experimental conditions (temperature, flow rate, concentration, solvent system and reactor type) except the use of three different concentrations of two different surfactants i.e., triton and span. Seven thin films were characterized with PXRD, SEM, AFM, EDS and EDS mapping. The mechanism of the interaction of surfactant with MeP2F was determined with cyclic voltammetry (CV) and UV-Vis spectroscopy.

Synthesis, Photophysical, Electrochemical and Thermal Studies of Triarylamines based on benzo[g]quinoxalines

Abstract: A series of novel dipolar and nonplanar compounds featuring electron acceptor benzo[g]quinoxaline and various electron donor triarylamine units have been synthesized in good yields and fully characterized. The photophysical, electrochemical and thermal properties of the synthesized compounds are described. The photoluminescence properties of the synthesized molecules are influenced by peripheral amines. The derivatives have high Stokes shifts, low band gap and the Commission Internationale de l’Eclairage (CIE) coordinates are positioned in the green–yellow region of the chromaticity diagram. The ionization potentials and electron affinity were found to be in the range of 5.11–5.60 eV and 2.77–2.93 eV and are comparable to the commonly used hole transporters. Thermal studies also reveal that these synthesized molecules have good thermal stability with 5% and 10% weight loss temperature ranging from 200 to 355°C and 268 to 442°C, respectively.

Synthesis, characterization and study of catalytic activity of Silver doped ZnO nanocomposite as an efficient catalyst for selective oxidation of benzyl alcohol

Abstract: Powder samples of Ag/ZnO nanocomposite containing different amounts of Ag were synthesized by co-precipitation method. The synthesized samples were characterized by XRD, SEM, EDX and TEM techniques. The XRD results revealed that all the samples show wurtzite hexagonal phase of ZnO. The TEM micrographs of the samples showed that size of Ag-ZnO nanoparticles was in the range of 30–50 nm. Catalytic activity was tested using liquid-phase selective oxidation of benzylic alcohols to aldehydes. The influence of some parameters such as optimum weight of Ag, catalyst dosage, oxidant and various solvents were studied. The superior catalytic performance of the Ag/ZnO nanocomposite was observed in microwave condition compared to that performed in reflux condition. The catalysts were recycled three times in the oxidation of alcohols and little change in the conversion efficiency was observed. The highly dispersed Ag metal particles on ZnO surface was considered to be responsible for the catalytic activity.

Effect of optimized structure and electronic properties of some benzimidazole derivatives on corrosion inhibition of mild steel in hydrochloric acid medium: Electrochemical and theoretical studies

Abstract: The corrosion inhibitive action of a few benzimidazole derivatives namely 2-(benzamido) ethylbenzimidazole (BAEBI), 2-(β-benzenesulphonamido) ethylbenzimidazole (BSAEBI), 2-(benzamido) methylbenzimidazole (BAMBI) and 2-(β-benzenesulphonamido) methylbenzimidazole (BSAMBI), towards mild steel in hydrochloric acid has been studied using potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) methods. The results show that these compounds get adsorbed on the mild steel surface following Temkin adsorption isotherm, and act as mixed-type inhibitors. The inhibition efficiencies are found to follow the order, BAEBI > BSAEBI > BAMBI > BSAMBI. This observation is explained in terms of chain length, relative effects of amido and sulphonamido groups, possible structural factors, spatial orientations, energy gap between the frontier molecular orbitals, different intrinsic molecular parameters, like, global hardness and softness, and number of electrons transferred.

Synthesis and bio-catalytic activity of isostructural cobalt(III)-phenanthroline complexes

Abstract: We have synthesized two isostructural mononuclear cobalt(III) complexes [1]NO3⋅3H2O and [1]NO3⋅CH3CO2H⋅H2O {[1] + = [Co(1,10-phenanthroline)2Cl2]+} and characterized by single crystal X-ray structural analyses. Mass spectral studies of the complexes indicate both the compounds to produce identical cationic species viz., [Co(phen)2Cl2]+ in methanol solution. [1]+ has been evaluated as model system for the catechol oxidase enzyme by using 3,5-di-tert-butylcatechol (3,5-DTBC) as the substrate in methanol medium, which revealed that the cationic complex efficiently inhibits catalytic activity with kcat value 9.65 ×102 h−1. [1]+ cleaved pBR 322 DNA without addition of an activating agent. Further, the anti-cancer activity of [1]+ on human hepatocarcinoma cell line (HepG2) has been examined. The induction of apoptosis induced in the cell line was assessed base on the changes in cell morphology, which showed the efficacy of [1] + to induce apoptosis in 53% of cells during 24 h treatment. Interestingly, the observed IC50 values reveal that [1]+ brings about conformational change on DNA strongly and exhibits remarkable cytotoxicity.

Metal–metal multiple bonded intermediates in catalysis

Abstract: Metal–metal bonded Rh2 and Ru2 complexes having a paddlewheel-type structure are exceptional catalysts for a broad range of organic transformations. I review here the recent efforts towards the observation and characterization of intermediates in these reactions that have previously eluded detection. Specifically, mechanistic investigations of carbenoid and nitrenoid reactions of Rh2(II,II)-tetracarboxylate compounds have led to the observation of a metastable Rh2(II,II) carbene complex as well as a mixed-valent Rh2(II,III)-amido intermediate. Related Ru2 nitrido compounds have been studied and found to undergo intramolecular C–H amination reactions as well as intermolecular reaction with triphenylphosphine.

Synthesis of N -acylurea derivatives from carboxylic acids and N,N ′-dialkyl carbodiimides in water

Abstract: Reactions of benzoic acid derivatives and (E)-cinnamic acid derivatives with $N,N^{\prime }$ -dialkyl carbodiimide proceed smoothly at room temperature and in neutral conditions to afford N-acylurea derivatives in high yields. The reaction proceeds smoothly and cleanly under mild conditions and no side reactions were observed.

Studies on ethylbenzene dehydrogenation with CO2 as soft oxidant over Co3O4/COK-12 catalysts

Abstract: Oxidative dehydrogenation of ethylbenzene to styrene has been studied over Co3O4 supported on mesoporous silica (COK-12) with CO2 as soft oxidant in a fixed bed reactor at atmospheric pressure in the temperature range of 723 to 923K. While COK-12 has been prepared by self-assembly method using long chain ionic surfactant i.e., P123 as template, cobalt oxide supported on COK-12 catalysts with variable Co content have been synthesised by simple wet impregnation technique. All the catalysts were characterized by N2 adsorption - desorption, XRD, FT-IR, TPR, UV-Vis and XPS techniques. XRD and pore size distribution studies indicate the intactness of mesoporous structure of SiO2 even after incorporation of Co3O4. Presence of Co3O4 crystallites were observed beyond 5 wt% Co loading. High ethylbenzene conversion and stable styrene yields have been observed over 3% Co3O4/COK-12 catalyst due to the presence of large number of active Co3O4 catalytic sites. Enhancement in the activity has been observed with CO2 as soft oxidant than with N2 as diluent. This is because of the fact that the liberated H2 reacts with CO2 in the form of reverse water gas shift reaction.

A α -cyanostilbene-modified Schiff base as efficient turn-on fluorescent chemosensor for Zn 2 +

Abstract: A novel Schiff base derivative (Z)-3-(4-(hexyloxy)phenyl)-2-(4-((E)-2-hydroxybenzylidene amino)phenyl)acrylonitrile (L) was designed, synthesized and characterized. L was used as a Zn2+ selective, turn-on, fluorescent chemosensor with a detection limit of 0.1 μM in DMF. 1:1 stoichiometric complex formation of L wih Zn2+ was confirmed through fluorescent titration experiments and Job’s plot. The enhancement of fluorescence intensity of L with addition of Zn2+ is the consequence of the inhibited isomerization of the C=N bond, namely chelation-enhanced fluorescence (CHEF) effect.

Sulfanilic acid functionalized mesoporous SBA-15: A water-tolerant solid acid catalyst for the synthesis of uracil fused spirooxindoles as antioxidant agents

Abstract: Incorporating sulfanilic acid as a hydrophobic Bronsted acid inside the nanospaces of SBA-15 led to a water-tolerant solid acid catalyst, SBA-15-PhSO3H, which showed excellent catalytic performance in synthesis of uracil-fused spirooxindoles in aqueous ethanol. The synthesized compounds were evaluated for their antioxidant activity by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging assay.

Electrochemical studies on Li+/K+ ion exchange behaviour in K4Fe(CN)6 cathode material for Li, K-ion battery

Abstract: The electrochemical studies of anhydrous K4Fe(CN)6 is reported. Anhydrous material was produced after dehydrating K4Fe(CN)6.3H2O crystal at 200°C in an open atmosphere. The material, as obtained, was characterized by various spectroscopic techniques, such as UV-Visible, FTIR, powder X-ray diffraction and FESEM-EDX. Electrochemical and Li+/K+ ion exchange behaviour of the synthesized material were studied by cyclic voltametry (CV), chronoamperometry (CA) and galvanostatic charge-discharge method after preparing a laboratory model cell against lithium anode instead of potassium. During anodic scan in the 1st cycle, peak maximum was observed at 3.93 V vs. Li+/Li due to removal of K+ ions from the ferrocyanide matrix, whereas, in the reverse scan (cathodic sweep) as well as in consequent cycles, peak maxima due to Li+ ion insertion and extraction were observed at 2.46 V and 3.23 V vs. Li+/Li, respectively. Cell, assembled using ferrocyanide cathode and lithium anode, shows an open circuit potential of 3.08 V and delivers a maximum capacity of 61 mAh g−1 (theoretical capacity 72 mAh g−1) at a rate of 0.2 C at room temperature.

A novel dinuclear schiff base copper complex as an efficient and cost effective catalyst for oxidation of alcohol: Synthesis, crystal structure and theoretical studies

Abstract: An environmentally friendly protocol is described for an economic, practical laboratory-scale oxidation of primary and secondary alcohols to aldehydes and ketones, using a bis-chloro-bridged binuclear Cu(II) complex [(HL)Cu(μ 2-Cl)2Cu(HL)]*1.5 CH3OH as catalyst. The catalyst was prepared in situ from commercially available reagents and is characterized by single crystal X-ray analysis, FT-IR, UV-visible spectra, mass spectrometry, and powder x-ray diffraction (PXRD). The geometry of the complex has been optimized using the B3LYP level of theory confirming the experimental data. Our results demonstrated well the efficiency, selectivity and stability of this new catalyst in the oxidation of alcohols in ethanol and tert-butyl hydroperoxide (tBuOOH) as a green solvent and oxidant, respectively. Turnover number and reusability have proven the high efficiency and relative stability of the catalyst.

One-pot synthesis of novel pyrimido[4,5- b ]quinolines and pyrido[2,3- d :6,5 d ′]dipyrimidines using encapsulated- γ -Fe 2 O 3 nanoparticles

Abstract: Novel pyrimido[4,5-b]quinolines and pyrido[2,3-d:6,5- $d^{\prime }$ ]dipyrimidine derivatives were synthesized in one-pot, three-component approach using sulfonic acid supported on hydroxyapatite-encapsulated- γ-Fe2O3 [γ-Fe2O3@HAp-SO3H] as magnetically recoverable nanocatalyst. The protocol provided a rapid, useful and green method for the preparation of the products in short reaction times and high yields.

Synthesis of 1-alkyl triazolium triflate room temperature ionic liquids and their catalytic studies in multi-component Biginelli reaction

Abstract: Synthesis of three Brnsted acid-based ionic liquids, namely, 1-ethyl-1,2,4-triazolium triflate (1a), 1-propyl-1,2,4-triazolium triflate (1b) and 1-butyl-1,2,4-triazolium triflate (1c), is described. These ionic liquids have been employed as catalysts for convenient and high-yielding one-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones and 3,4-dihydropyrimidin-2(1H)-thiones, which are Biginelli reaction products. Advantages of the methodology are operational convenience, short reaction times, avoidance of chromatographic purification and non-production of toxic waste. Further, the catalysts are easily recovered and reused without any noticeable diminution in their catalytic activity.

Nickel(II) complexes containing ONS donor ligands: Synthesis, characterization, crystal structure and catalytic application towards C-C cross-coupling reactions

Abstract: Nickel(II) complexes containing thiosemicarbazone ligands [Ni(L)2] (1-3) (L = 9,10-phenanthrenequinonethiosemicarbazone (HL1), 9,10-phenanthrenequinone-N-methylthio semicarbazone (HL2) and 9, 10-phenanthrenequinone-N-phenylthiosemicarbazone (HL3)) have been synthesized and characterized by elemental analysis and spectroscopic (IR, UV-Vis, 1H, 13C-NMR and ESI mass) methods. The molecular structures of complexes 1 and 2 were identified by means of single-crystal X-ray diffraction analysis. The analysis revealed that the complexes possess a distorted octahedral geometry with the ligand coordinating in a uni-negative tridentate ONS fashion. The catalytic activity of complexes towards some C–C coupling reactions (viz., Kumada-Corriu, Suzuki-Miyaura and Sonogashira) has been examined. The complexes behave as efficient catalysts in the Kumada-Corriu and Sonogashira coupling reactions rather than Suzuki-Miyaura coupling.

A novel fluorescent turn-on probe for bisulfite based on NBD chromophore

Abstract: A novel fluorescent turn-on probe (compound 1) for bisulfite based on 7-nitrobenz-2-oxa-1,3-diazole (NBD) chromophore has been developed. Its sensing behavior toward various anions was investigated by absorption and fluorescence techniques. This probe shows a selective, turn-on fluorescent response and ratiometric colorimetric response toward bisulfite in aqueous acetonitrile solutions. The possible recognition mechanism of probe 1toward bisulfite was illustrated by MS spectra analysis and DFT calculations Probe 1 was used to determine bisulfite in real-life samples with good recoveries.

Carbazole-based sensitizers for potential application to dye sensitized solar cells

Abstract: Two push-pull molecules employing carbazole and alkyl thiophene (CAR-THIOHX) or carbazole and triphenylamine (CAR-TPA) as donor moieties, with the cyanoacrylic group as the acceptor, have been designed and synthesized by simple organic transformations. Photophysical and electrochemical studies revealed the potential of these two systems in dye sensitized solar cells (DSSC). Under standard irradiation conditions, CAR-TPA and CAR-THIOHX exhibited 2.12 and 1.83% of overall power conversion efficiencies respectively. The moderate photovoltaic efficiency of the sensitizers has been attributed to the poor light absorption of the sensitizers in the visible region. Density functional theory (DFT) calculations have shown a strong intramolecular charge transfer character, with the HOMOs of both the sensitizers exclusively localized on the corresponding donor moieties and LUMOs on the cyanoacrylic acid acceptor. On the other hand, the calculated high dihedral angle between the carbazole donor and the phenyl bridge for these sensitizers impedes the conjugation along the dyes backbone, and thus leads to less extended and intense absorption spectra in the visible region.

Theoretical Characterization of Hydrogen Bonding Interactions between RCHO (R = H, CN, CF 3 , OCH 3 , NH 2 ) and HOR′(R′ = H, Cl, CH 3 , NH 2 , C(O)H, C 6 H 5 )

Abstract: In this work, density functional theory and ab initio molecular orbital calculations were used to investigate the hydrogen bonded complexes of type RCHO ⋯HOR′ (R = H, CN, CF 3, OCH 3, NH 2, R′ H, Cl, CH 3, NH 2, C(O)H, C 6H 5) employing 6-31 ++g** and cc-pVTZ basis sets. Thus, the present work considers how the substituents at both the hydrogen bond donor and acceptor affect the hydrogen bond strength. From the analysis, it is reflected that presence of –OCH 3 and –NH 2 substituents at RCHO greatly strengthen the stabilization energies, while –CN and –CF 3 decrease the same with respect to HCHO as hydrogen bond acceptor. The highest stabilization results in case of (H 2N)CHO as hydrogen bond acceptor. The variation of the substituents at –OH functional group also influences the strength of hydrogen bond; nearly all the substituents increase the stabilization energy relative to HOH. The analysis of geometrical parameters; proton affinities, charge transfer, electron delocalization studies have been carried out.

Synthesis, crystal structure determination of two-dimensional supramolecular co-ordination polymer of silver(I) with 1,2-Bis(phenylthio)ethane and its Hirshfeld surface analysis

Abstract: The 2-D polymeric complex (I) has the formula [ A g ( p h S E ) ( N O 3 )] n , which has been crystallized from methanol-acetonitrile mixture and characterized by elemental analysis and single-crystal X-ray diffraction analysis. In this polymer, each Ag(I) ion occupies distorted trigonal pyramidal geometry coordinating with two sulphur atoms from two different ligands and two oxygen atoms from two NO3 groups. Each NO3 acts as a bridging ligand coordinating through its two oxygen atoms to different Ag(I) ions. The Ag(I) ion and NO3 group are in plane with torsion angle 176.43∘. All the ligands adopt anti-conformation but the relative orientation of two -S-C-C-S units is perpendicular to one another such that two phenyl rings attached to the two sulphur atoms coordinating to a particular Ag ion lie on the same side. Each NO3 bridges two neighbouring Ag ions belonging to two different -S-Ag-S-C-C-S-Ag-S- tapes running along a-axis where two phenyl rings are not parallel to each other to reduce the steric hindrance and maximize packing. The adjacent chains are fused to form 2D sheet by bridging both through bidentate phSE ligand and NO3 anion stacking in ab plane. The structure consists of 4-c uninodal net where Point symbol for Ag (I) ion and net is (44.62) with sql type topology. X-ray diffraction analysis and Hirshfeld surface analysis give rise to comparable results but in Hirshfeld surface analysis, two-third times more close contacts are obtained. The fingerprint plots demonstrate that these weak non-bonding interactions are important for stabilizing the crystal packing.

Interesting cationic (Li + /Fe 3+ /Te 6+ ) variations in new rocksalt ordered structures

Abstract: A new series of layered oxides, Li3(Li1.5xFe3−(x+1.5x)Tex)O6, (0.1 ≤x≤ 1.0) possessing rocksalt superstructures crystallizing in monoclinic (S.G. C2/m) symmetry is reported here. Investigations based on single crystal and powder X-ray diffraction studies for the x= 1 member, Li3(Li1.5Fe0.5Te)O6, (a= 5.1834(1); b= 8.8858(2); c= 5.16840(8) A; β= 110.660(1)∘) confirmed the stabilization of (Li1.5Fe0.5Te1.0 O6)3− honeycomb arrays with a very high amount of lithium ions. The structure for the x= 0.5 member (Li3.75Fe1.75Te0.5O6) has also been confirmed by the powder X-ray diffraction Rietveld refinements. Li3(Li1.5Fe0.5Te)O6 and Li3(Li0.75Fe1.75Te0.5)O6 oxides exhibited Curie–Weiss behaviour in the temperature range of 50–300 K with negative 𝜃 values. Their respective ionic conductivities were found to be 6.76×10−5 S cm−1 and 2.21 × 10−6 S cm−1 at 573 K. The UV-visible diffuse reflectance measurements for the different members of the series Li3(Li1.5xFe3−(x+1.5x)Tex)O6, 0.1 ≤ x ≤ 1.0) show the expected shifts in their absorption edges based on the increasing amount of Fe3+ ions starting from x= 1.0 member to x= 0.1 member.