Estimation of underground water radon danger in Bakreswar and Tantloi Geothermal Region,India

The main aim of the study is to present an evaluation of radon concentration in underground water of Bakreswar and Tantloi geothermal region which is mainly used for drinking purposes of the local people. Water samples were collected from tube-wells at 173 different locations. The radon (²²²Rn) concentration level was observed to fluctuate widely between 3.3 and 803.8 Bq/l with an average of 106.8 Bq/l. Nearly 42% of the samples had radon concentration above the safe limit of 100 Bq/l recommended by World Health Organisation (WHO) and European Union Commission (EU). Considering the WHO and International Commission on Radiological Protection recommended water consumption rate for adults (730 l/year) the corresponding total annual effective dose of the samples were estimated to assess the probable health risk. Total annual effective dose of the samples were varied between 16.72 and 4079.47 µSv/year with an average value of 541.92 µSv/year. About 95% samples exceed the WHO and EU Commission proposed safe limit of 100 µSv/year.     

Atomically Precise Nanocluster Assemblies Encapsulating Plasmonic Gold Nanorods

The self‐assembled structures of atomically precise, ligand‐protected noble metal nanoclusters leading to encapsulation of plasmonic gold nanorods (GNRs) is presented. Unlike highly sophisticated DNA nanotechnology, this strategically simple hydrogen bonding‐directed self‐assembly of nanoclusters leads to octahedral nanocrystals encapsulating GNRs. Specifically, the p‐mercaptobenzoic acid (pMBA)‐protected atomically precise silver nanocluster, Na₄[Ag₄₄(pMBA)₃₀], and pMBA‐functionalized GNRs were used. High‐resolution transmission and scanning transmission electron tomographic reconstructions suggest that the geometry of the GNR surface is responsible for directing the assembly of silver nanoclusters via H‐bonding, leading to octahedral symmetry. The use of water‐dispersible gold nanoclusters, Au_≈250(pMBA)_n and Au₁₀₂(pMBA)₄₄, also formed layered shells encapsulating GNRs. Such cluster assemblies on colloidal particles are a new category of precision hybrids with diverse possibilities.     

Structural features and dye-sensitized solar cell performance of chemically synthesized F doped ZnO particles

Journal of Solid State Electrochemistry - In dye-sensitized solar cell (DSSC) application, the particulate morphologies of photo-anode facilitate efficient dye loading and thus lead to better...     

Pincer ligand coordination at Co3 and Ru6 clusters: Syntheses, reactivity studies, and X-ray diffraction structures of [PhCCo3(CO)8]2(dppx) and [Ru6(μ6-C)(CO)16]2(dppx)

The reaction of the pincer diphosphine ligand 4,6-bis(diphenylphosphinomethyl)-m-xylene (dppx) with the metal cluster compounds PhCCo₃(CO)₉ and Ru₆(μ₆-C)(CO)₁₇ has been explored. Both clusters react with dppx to afford the simple substitution products [PhCCo₃(CO)₈]₂(dppx) and [Ru₆(μ₆-C)(CO)₁₆]₂(dppx), where two cluster units are tethered by the pincer ligand. The molecular structures of the title products and the 2:1 cluster-pincer ligand stoichiometry have been established by X-ray crystallography. The stability of [PhCCo₃(CO)₈]₂(dppx) and [Ru₆(μ₆-C)(CO)₁₆]₂(dppx) has been investigated under gentle thermolysis conditions (ca. 55–65°C). Both dppx-substituted clusters are unstable with [PhCCo₃(CO)₈]₂(dppx) decomposing and [Ru₆(μ₆-C)(CO)₁₆]₂(dppx) transforming into the diphosphine-bridged cluster Ru₆(μ₆-C)(CO)₁₅(μ-dppx) as the major observable product. The identity of the latter cluster has been ascertained by IR and NMR spectroscopies and mass spectrometry.     

Assembling metals (Co II and Mn II) with pyridylcarboxylates in the presence of azide: synthesis, structural aspects and magnetic behavior of three coordination polymers

The reaction between Co(NO3)2.6H2O and substituted pyridylcarboxylic acid [nicotinic acid (Hnic) or trans-3-pyridylacrylic acid (Htpa)] in the presence of NaN3 under hydrothermal conditions yielded [Co(1.5)(nic)2 (Hnic)(N3)]n (1) and [Co(1.5)(tpa)2 (N3)(H2O)]n (2), respectively. Single crystal structure analyses reveal that both complexes are 3D complicated coordination polymers. The basic repeating units in both of the complexes are Co(3) trinuclear clusters containing syn-syn bridging carboxylate and end-on azido linker. A similar reaction using MnCl2.4H2O in presence of equimolar amounts of Htpa and NaN3 yielded a 2D corrugated sheet [Mn(tpa)2]n (3) containing no azide. Complex 3 can also be synthesized under hydrothermal conditions using Natpa in the absence of NaN3. Surprisingly, the same reaction at room temperature yielded a known mononuclear complex [Mn(tpa)2(H2O)4]. Variable temperature magnetic studies down to 2 K revealed the dominant antiferromagnetic nature of the first two complexes with a ferrimagnetic type of behavior despite the facts that they are homometallic and homospin systems. The susceptibility data in both cases were analyzed by a Co3 trinuclear model as well as considering inter-trimer interactions. Complex 3 is weakly antiferromagnetic in nature with an exchange parameter of J = -2 cm(-1) through the syn-anti bridging carboxylate pathway.     

Stereoselective total synthesis of (+)-(6R,2′S)-cryptocaryalactone and (−)-(6S,2′S)-epi cryptocaryalactone

The total synthesis of (+)-(6R,2′S)-cryptocaryalactone and (−)-(6S,2′S)-epi cryptocaryalactone is reported based on stereoselective reduction of δ-hydroxy β-keto ester to install 1,3-polyol system, cis Wittig olefination, and lactonization as the key steps. The synthesis of (−)-(6S,2′S)-epi cryptocaryalactone is also reported using syn-benzylidene acetal formation and a preferential Z-Wittig olefination reaction and lactonization as the key steps.     

Design and synthesis of (E)-4-((3-ethyl-2,4,4-trimethylcyclohex-2-enylidene)methyl)benzoic acid

(E)-4-((3-Ethyl-2,4,4-trimethylcyclohex-2-enylidene)methyl)benzoic acid, 6, was synthesized in 87% starting from β-cyclocitral. The target compound 6 was synthesized starting from 1 via a Grignard reaction to form alcohol 2. Compound 2 was converted to Wittig salt 3 by treatment with aldehyde 4 in butyllithium and hexane at −78 °C to form ester 5. Ester 5 was saponified and, following acidification, acid 6 was isolated as white solid yield 87%.     

Sequence-dependent clustering properties of nucleotides fragments in an ionic solution

The chemical nature of the DNA bases is an important factor in sequence-mediated association of DNA molecules. Nucleotides are the fundamental DNA elements and the base identity impacts the molecular properties of nucleotide fragments. It is interesting to study the fundamental nature of nucleotides in DNA, on the basis of base-specific interactions, association, and modes of standard atomic or molecular interactions. With all-atom molecular dynamics simulations of model dinucleotide and tetranucleotide systems having single-stranded dinucleotide or tetranucleotide fragments of varying sequences, we show how the base identity and interactions between the different bases as well as water may affect the clustering properties of nucleotides fragments in an ionic solution. Sequence-dependent differential interactions between the nucleotide fragments, ionic concentration, and elevated temperature are found to influence the clustering properties and dynamics of association. Well-known epigenetic modification of DNA, that is, cytosine methylation also promotes dinucleotide clustering in solution. These observations point to one possible chemical nature of the DNA bases, as well as the importance of the base pairing, base stacking, and ionic interactions in DNA structure formation, and DNA sequence-mediated association. Sequence- and the ionic environment-mediated self-association properties of the dinucleotides indicate its great potential to develop biological nanomaterials for desired applications.     

Stability and bonding of carbon(0)-iron−N2 complexes relevant to nitrogenase co-factor: EDA-NOCV analyses

The factors/structural features which are responsible for the binding, activation and reduction of N₂ to NH₃ by FeMoco of nitrogenase have not been completely understood well. Several relevant model complexes by Holland et al. and Peters et al. have been synthesized, characterized and studied by theoretical calculations. For a matter of fact, those complexes are much different than real active N₂-binding Fe-sites of FeMoco, which possesses a central C(4-) ion having an eight valence electrons as an μ₆-bridge. Here, a series of [(S₃C(0))Fe(II/I/0)-N₂]^n- complexes in different charged/spin states containing a coordinated σ- and π-donor C(0)-atom which possesses eight outer shell electrons [carbone, (Ph₃P)₂C(0); Ph₃P→C(0)←PPh₃] and three S-donor sites (i.e. ^-S-Ar), have been studied by DFT, QTAIM, and EDA-NOCV calculations. The effect of the weak field ligand on Fe-centres and the subsequent N₂-binding has been studied by EDA-NOCV analysis. The role of the oxidation state of Fe and N₂-binding in different charged and spin states of the complex have been investigated by EDA-NOCV analyses. The intrinsic interaction energies of the Fe−N₂ bond are in the range from −42/−35 to −67 kcal/mol in their corresponding ground states. The S₃C(0) donor set is argued here to be closer to the actual coordination environment of one of the six Fe-centres of nitrogenase. In comparison, the captivating model complexes reported by Holland et al. and Peter et al. possess a stronger π-acceptor C-ring (S₂C_ring donor, π-C donor) and stronger donor set like CP₃ (σ-C donor) ligands, respectively.