Formation of different products during photo-catalytic reaction on TiO<Subscript>2</Subscript> suspension in water with and without 2-propanol under diverse ambient conditions

Studies on photo-catalytic reduction of CO₂ using TiO₂ photo-catalyst (0.1%, w/v) as a suspension in water was carried out at 350 nm light. CO₂ from both commercially available source, as well as generated in situ through 2-propanol oxidation, was used for this study. The photolytic products such as hydrogen (H₂), carbon monoxide (CO) andmethane (CH₄) generated were monitored in TiO₂ suspended aqueous solution with and without a hole scavenger, viz., 2-propanol. Similar photolytic experiments were also carried out with varying ambient such as air, O₂, N₂ and N₂O. The yields of CO and CH₄ in all these systems under the present experimental conditions were found to be increasing with light exposure time. H₂ yield in N₂-purged systems containing 2-propanol was found to be more as compared to the without 2-propanol system. The rate of H₂ production in N₂-purged aqueous solutions containing 0.1% TiO₂ suspension were evaluated to be 0.226 and 5.8 μl/h, without and with 0.5 M 2-propanol, respectively. This confirmed that 2-propanol was an efficient hole scavenger and it scavenged photo-generated holes (h⁺), allowing its counter ion, viz., e⁻, to react with water molecule/H⁺ to yield more H₂. The formation of both CO and CH₄ in the photolysis of CO₂-purged aqueous solutions containing suspended TiO₂ in absence of 2-propanol reveal that the generation of CH₄ is taking place mainly through CO intermediate. In presence of air/O₂, the yield of H₂ in the system without 2-propanol was observed to be negligible as compared to the system containing 2-propanol in which low yield of H₂ was obtained with a formation rate of approx. 0.5 μl/h.     

Anion-pi interactions in cyanuric acids: a combined crystallographic and computational study

Several structures of pi complexes of isocyanuric acid and of several thio derivatives with anions have been computed by using high level ab initio calculations. The nature of the complexes has been studied by means of the method of molecular interaction potential with polarization (MIPp) and Bader's theory of atoms-in-molecules. These molecules form favorable complexes with anions and can be used as binding units for building receptors for the molecular recognition of anions. In several cases, the anion-pi interaction has been demonstrated experimentally by means of X-ray crystallography.     

Laser-induced electron impact ionization in a reflectron time-of-flight mass spectrometer

Some details of the generation of electrons by impinging a laser beam on a metal surface are described. It is shown that highly efficient electron generation is observed only during the laser pulse. Therefore, this technique delivers intense pulses of electrons. The process is investigated and different ion source set-ups are discussed. In conjunction with a time-of-flight mass spectrometer this technique can be used to produce mass spectra of different samples ranging from simple organic molecules to peptides.     

Study of the Release Mechanism of Terminalia chebula Extract from Nanoporous Silica Gel

Sol/gel-derived silica gel was prepared at room temperature from tetraethyl orthosilicate precursor. The extracts of Terminalia chebula (Haritoki) were entrapped into the porous silica gel. Fourier transform infrared analysis revealed the proper adsorption of herbal values in the nanopores of the silica gel. Porosity was estimated by transmission electron microscope studies. The release kinetics of the extract in both 0.1 N HCl, pH 1.2, and Phosphate-buffer saline (PBS), pH 7.2, were determined using UV–Vis spectroscopy. Different dissolution models were applied to release data in order to evaluate the release mechanisms and kinetics. Biphasic release patterns were found in every formulation for both the buffer systems. The kinetics followed a zero-order equation for first 4 h and a Higuchi expression in a subsequent timeline in the case of 0.1 N HCl. In the case of PBS, the formulations showed best linearity with a first-order equation followed by Higuchi’s model. The sustained release of the extract predominantly followed diffusion and super case II transport mechanism. The release value was always above the minimum inhibitory concentration.     

Dimethylaminoalkyl chalcogenolate palladium(II) complexes as an efficient copper- and phosphine-free catalyst for Sonogashira reaction

N,N-Dimethylaminoalkyl chalcogenolate Pd(II) complexes [PdCl(E^∩NMe₂)]_n has been investigated as a moisture/air-stable and robust catalyst for Sonogashira cross-coupling reaction in the absence of copper and phosphine ligand. The dimeric palladium(II) complex of selenium containing ligand shows the best catalytic activity as compared with monomeric and trimeric complexes. The variety of functional groups are tolerated under optimized catalytic systems and provide excellent yields of the products.     

Linear {NiII–LnIII–NiII} Complexes Containing Twisted Planar Ni(μ‐phenolate)2Ln Fragments: Synthesis,Structure, and Magnetothermal Properties

Sequential reaction of a multisite LH₄ ligand {2‐[2‐hydroxy‐3‐(hydroxymethyl)‐5‐methylbenzylideneamino]‐2‐methylpropane‐1,3‐diol} with appropriate lanthanide salts followed by the addition of Ni(NO₃)₂ ? 6 H₂O in a 4:1:2 stoichiometric ratio in the presence of triethylamine afforded four heterobimetallic trinuclear complexes [Ni₂Gd(LH₃)₄] ? 3 NO₃ ? 3 MeOH ? H₂O ? CH₃CN ( 1 ), [Ni₂Tb(LH₃)₄] ? 3 NO₃ ? 3 MeOH ? CH₃CN ( 2 ), [Ni₂Dy(LH₃)₄] ? 3 NO₃ ? 3 MeOH ? H₂O ? CH₃CN ( 3 ), and [Ni₂Ho(LH₃)₄] ? 3 NO₃ ? 3 MeOH ? H₂O ? CH₃CN ( 4 ). Complexes 1 – 4 possess linear trimetallic cores with a central lanthanide ion. Magnetic studies revealed a predominant ferromagnetic interaction between the Ni and Ln centers. Alternating current susceptibility measurements of complex 3 showed a small frequency dependence of the out‐of‐phase signal, χ′′_M , under zero direct current field, but without achieving a net maximum above 2 K. Magnetic studies on 1 revealed that it has a significant magnetocaloric effect.     

Incommensurate Phase in Λ-cobalt (III) Sepulchrate Trinitrate Governed by Highly Competitive N−H⋅⋅⋅O and C−H⋅⋅⋅O Hydrogen Bond Networks**

Phase transitions in molecular crystals are often determined by intermolecular interactions. The cage complex of [Co(C₁₂H₃₀N₈)]³⁺ ⋅ 3 NO₃⁻ is reported to undergo a disorder-order phase transition at T_c1 ≈133 K upon cooling. Temperature-dependent neutron and synchrotron diffraction experiments revealed satellite reflections in addition to main reflections in the diffraction patterns below T_c1. The modulation wave vector varies as function of temperature and locks in at T_c3≈98 K. Here, we demonstrate that the crystal symmetry lowers from hexagonal to monoclinic in the incommensurately modulated phases in T_c1<T<T_c3. Distinctive levels of competitions: trade-off between longer N−H⋅⋅⋅O and shorter C−H⋅⋅⋅O hydrogen bonds; steric constraints to dense C−H⋅⋅⋅O bonds give rise to pronounced modulation of the basic structure. Severely frustrated crystal packing in the incommensurate phase is precursor to optimal balance of intermolecular interactions in the lock-in phase.     

Spectral editing in solid-state MAS NMR of quadrupolar nuclei using selective satellite inversion

A sensitivity enhancement method based on selective adiabatic inversion of a satellite transition has been employed in a (pi/2)CT-(pi)ST1-(pi/2)CT spectral editing sequence to both enhance and resolve multisite NMR spectra of quadrupolar nuclei. In addition to a total enhancement of 2.5 times for spin 3/2 nuclei, enhancements up to 2.0 times is reported for the edited sites in a mixture of rubidium salts.     

High resolution 1H NMR of a lipid cubic phase using a solution NMR probe

The cubic mesophase formed by monoacylglycerols and water is an important medium for the in meso crystallogenesis of membrane proteins. To investigate molecular level lipid and additive interactions within the cubic phase, a method was developed for improving the resolution of (1)H NMR spectra when using a conventional solution state NMR probe. Using this approach we obtained well-resolved J-coupling multiplets in the one-dimensional NMR spectrum of the cubic-Ia3d phase prepared with hydrated monoolein. A high resolution t-ROESY two-dimensional (1)H NMR spectrum of the cubic-Ia3d phase is also reported. Using this new methodology, we have investigated the interaction of two additive molecules, L-tryptophan and ruthenium-tris(2,2-bipyridyl) dichloride (rubipy), with the cubic mesophase. Based on the measured chemical shift differences when changing from an aqueous solution to the cubic phase, we conclude that L-tryptophan experiences specific interactions with the bilayer interface, whereas rubipy remains in the aqueous channels and does not associate with the lipid bilayer.