Anilate Tethered Neutral Tetrahedral Pd(II) Cages Exhibiting Selective Encapsulation of Xylenes and Mesitylene

The design of porous materials for the recognition of multiple hydrocarbons is highly desirable for the energy-efficient separation and recognition of chemical feedstock. Herein, three new iso-structural porous discrete metal–organic cages of formula {[Pd₃(NiPr)₃PO]₄(R-AN)₆} (R-AN=anilate linkers) for the selective recognition of substituted aromatic hydrocarbons are reported. The tetrahedral cages 1 , 2 , and 3 containing anilate, chloranilate, and bromanilate linkers exhibited selective encapsulation of mesitylene, o-xylene, and p-xylene, respectively, over other analogous aromatic hydrocarbons. These selective encapsulations were driven by the variations in the portal diameters present at each of these cages and their interactions with the hydrocarbon guests. These observations are supported by mass spectrometry, NMR studies, and theoretical binding-energy calculations.     

Synthesis and Coordination Behavior of a New Hybrid Bidentate Ligand with Phosphine and Silylene Donors

This work describes the synthesis and coordination behavior of a new mixed-donor ligand PhC(NtBu)₂SiC₆H₄PPh₂ ( 1 ) containing both silylene and phosphine donor sites. Ligand 1 was synthesized from a reaction of ortho-lithiated diphenylphosphinobenzene (LiC₆H₄PPh₂) with chlorosilylene (PhC(NtBu)₂SiCl). Treatment of 1 with Se and GeCl₂ resulted in Si^IV compounds 2 and 3 by selective oxidation of the silylene donor. This strong σ-donor ligand induces dissociation of CuCl and PhBCl₂ leading to formation of ionic complexes 4 and 5 respectively. The reaction of 1 with ZnCl₂ and AlCl₃ resulted in the formation of chelate complexes 5 and 7 , respectively, while treatment with EtAlCl₂ and GaCl₃ forms monodentate complexes 8 and 9 . X-ray analysis of 4 showed that the copper is in the spiro center of the two five-membered rings. Moreover, the copper(I)chloride has not been oxidized but dissociates to Cu⁺ and [CuCl₂]⁻. All the compounds are well characterized by mass spectrometry, elemental analysis, NMR spectroscopy, and single-crystal X-ray diffraction studies.     

Study of indoor radon and thoron progeny levels in surrounding areas of Nalbari, Assam, India

With the growing understanding of the role of radon and its daughter products as major sources of radiation exposure, the importance of large number of estimation of radon concentration in various parts of the country is realized. Inhalation of radon, thoron and their decay products is the major source of the total radioactive dose received by the human population from natural radiation. The indoor radon and thoron progeny levels in Nalbari area of Assam are studied by using the LR-115 (type II) Solid State Nuclear Track Detector in Plastic Twin Chamber dosimeter. Radon and thoron progeny levels in different types of dwellings for one full calendar year are presented in this paper. For Assam Type (A.T.) houses, indoor radon progeny concentrations vary from 0.17 to 0.64 mWL with an annual geometric mean of 0.27 mWL and that for Reinforced Cement Concrete (R.C.C.) houses vary from 0.22 mWL to 0.60 mWL with the annual geometric mean of 0.37 mWL. The thoron progeny levels in A.T. houses also vary from 0.01 to of 0.05 mWL with an annual geometric mean of 0.02 mWL and that for R.C.C. houses vary from 0.02 to 0.08 mWL with the annual geometric mean of 0.04 mWL.      

A Facile One‐Pot Route for the General Synthesis of Triazole Linked Chiral 2‐Substituted Benzimidazoles

One‐pot protocol for the synthesis of novel class of triazole linked 2‐sugar and 2‐aryl substituted benzimidazoles has been developed. The rapid and simple method involves copper (I) catalyzed simultaneous formation of benzimidazole and triazole rings at room temperature and in high yield.     

Montmorillonite Supported Borohydride: A New Reducing Agent for Reductions Under Phase Transfer Conditions

A few cyclic and acyclic ketones were reduced in dichloro-methane, using reducing agents prepared from reusable montmorillonite clay supported phase transfer catalyst. A high percentage of axial attack (76–100%) by hydrides on substituted cyclohexanones observed, has been rationalised on the basis of a four center cyclic transition state for the clay absorbed ketone.     

Mono- and Di-valent Salts as Modifiers of PEO-PPO-PEO Block Copolymer Interactions with Silica Nanoparticles in Aqueous Dispersions

Colloidal stabilization of nanoparticle dispersions is central to applications including coatings, mineral extraction, and dispersion of oil spills in oceanic environments, which often involves oil-mineral-aggregates (OMAs). We have an ongoing interest in the modulation of amphiphile micellization and adsorption behavior in aqueous colloidal dispersions in the presence of various additives. Here we evaluate the effect of added salts CaCl₂, MgCl₂, and NaCl on the micellization and adsorption behavior of the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer Pluronic P105 (EO₃₇PO₅₆EO₃₇). In 0.10 wt% silica nanoparticle (10.6 nm average diameter) dispersion, adsorbed block copolymer layer formation begins at a critical surface micelle concentration (csmc) of 0.02 wt%, well below the critical micellization concentration of Pluronic P105 in water. Dye solubilization experiments demonstrate an increase in the csmc upon addition of each salt. Each added salt reaches a level of maximum effectiveness in its ability to disfavor Pluronic P105 adsorption at the silica surface. These peak levels occur at concentrations of 0.005, 0.03, and 0.05 M for CaCl₂, MgCl₂, and NaCl, respectively, in the presence of 0.10 wt% silica nanoparticles. We explain these results in the context of an electrostatic displacer mechanism and discuss possible connections to OMA-dispersant formation.     

Carbon Nanotubes-Based Label-Free Affinity Sensors for Environmental Monitoring

Nanostructures, such as nanowires, nanobelts, nanosprings, and nanotubes, are receiving growing interest as transducer elements of bio/chemical sensors as they provide high sensitivity, multiplexing, small size, and portability. Single-walled carbon nanotubes (SWNTs) are one such class of nanostructure materials that exhibit superior sensing behavior due to its large-surface carbon atoms that are highly responsive to surface adsorption events. Further, their compatibility with modern microfabrication technologies and facile functionalization with molecular recognition elements make them promising candidates for bio/chemical sensors applications. Here, we review recent results on nanosensors based on SWNTs modified with biological receptors such as aptamers, antibodies, and binding proteins, to develop highly sensitive, selective, rapid, and cost-effective label-free chemiresistor/field-effect transistor nanobiosensors for applications in environmental monitoring.     

Metal-based anticancer agents: targeting androgen-dependent and androgen-independent prostate and COX-positive pancreatic cancer cells by phenanthrenequinone semicarbazone and its metal complexes

A planar, polycyclic and aromatic hydrocarbon ligand, namely 9,10-phenanthrenequinone semicarbazone, and its transition metal complexes have been synthesized and structurally characterized. The in vitro antiproliferative activity of these compounds against five human cancer cell lines revealed that they were effective against androgen receptor-positive/negative prostate cancer cells as well as COX-positive pancreatic BxPC-3 cancer cell line. The driving force behind such antiproliferative activity seems to be the up-regulated COX expression in these cells, which was amenable for targeting through metal complexation. These structural motifs can, therefore, serve as a starting point for developing novel cytotoxic agents against the growing number of prostate and pancreatic cancers.