One-dimensional description of multidimensional electron transfer reactions in condensed phase

We derive a one-dimensional energy diffusion equation for describing the dynamics of multidimensional electron transfer reactions in condensed phase, which is conceptually simpler and computationally more economic than the conventional approaches. We also obtain an analytical expression for the rate of electron transfer reactions for a general one-dimensional effective potential as well as an energy dependent diffusitivity. As an illustrative example, we consider application to electron transfer in a contact ion pair system modeled through harmonic potentials consisting of two slow classical modes and a high frequency vibrational mode for which the numerical results calculated using the proposed one-dimensional approach are shown to be in good agreement with experimental results. The energy diffusion equation and the rate expression for electron transfer obtained from the present theory, therefore, open up the possibility of describing the dynamics of electron transfer in complex systems, through a simpler approach.     

Mononuclear and binuclear iron(III) complexes incorporating N4O3 coordinating heptadentate ligand: Synthesis,structure and magnetic properties

The N₄O₃ coordinating heptadentate ligand afforded the mononuclear [Fe^III(HL)][BPh₄] (1) and binuclear [Fe₂^IIIL(OAc)₂][BPh₄] (2) complexes. In complex 1, the ligand binds in a trianionic N₂O₃ fashion whereas in the case of 2 the ligand binds in the trianionic N₄O₃ form in which the iron ions are held together by μ-phenoxo and bis μ-acetato bridges. In 1, the Fe(III) center has a trigonal bipyramidal geometry (τ = 0.84) whereas in 2 both the Fe(III) centers have a distorted octahedral geometry. Complex 2 shows an intramolecular weak antiferromagnetic interaction. Gas phase geometry optimizations have been performed using density functional theory without any symmetry constraints. The gas phase optimized structures agree well with the X-ray structure.     

Binuclear cobalt(II/II) and cobalt(II/III) chelates with O<Subscript>2</Subscript>N<Subscript>2</Subscript> ligands: synthesis,structure and magnetic studies

Abstract  The title complexes and have been synthesized in excellent yields by reacting Co(OAc)₂·4H₂O with H₂L¹ and H₂L², respectively, in acetonitrile solution. Here, [L¹]²⁻ and [L²]²⁻ are the deprotonated forms of N,N-bis(2-hydroxybenzyl)-N′,N′-dimethylethylenediamine and N,N-bis(2-hydroxybenzyl)-2-picolylamine, respectively. The crystal structures of and were determined by x-ray crystallography. In , each cobalt atom has distorted trigonal bipyramid geometry, while in , each cobalt atom has distorted octahedral geometry. Variable temperature magnetic moment measurements show weak antiferromagnetic interaction in . The magnetic characterization for is in agreement with the presence of Co(II) and Co(III) centers. Graphical Abstract  The title complexes and have been synthesized in excellent yields by reacting Co(OAc)₂·4H₂O with dianionic N₂O₂ coordinating ligands. In complex 1, each cobalt atom has distorted trigonal bipyramid geometry, while in complex 2, each cobalt atom has distorted octahedral geometry. Variable temperature magnetic moment measurements show weak antiferromagnetic interaction in complex 1. The magnetic characterization for complex 2 is in agreement with the presence of Co(II) and Co(III) centers. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Synthesis, structure, and spectroscopic properties of chiral oxorhenium(V) complexes incorporating polydentate ligands derived from L-amino acids: a density functional theory/time-dependent density functional theory investigation

The oxorhenium(V) complexes [Re (V)O(L A)Cl 2] bearing the (N-2-pyridylmethyl) of l-valine (HL A (1)), l-leucine (HL A (2)), and l-phenylalanine (HL A (3)) and [Re (V)O(L B)Cl] containing the {(N-2pyridylmethyl)-(N-(5-nitro-2-hydroxybenzyl)} of l-valine (H 2L B (1)), l-leucine (H 2L B (2)), and l-phenylalanine (H 2L B (3)) are presented in this article. The complexes are isolated in enantiomeric pure form examined from X-ray structure determination. The complexes are characterized by spectroscopic and electrochemical methods. The molecular structures observed in the solid state are grossly preserved in solution ( (1)H, (13)C, and circular dichroism spectra). Gas-phase geometry optimization and the electronic structures of [Re (V)O(L A (1))Cl 2], [Re (V)O(L A (2))Cl 2], and [Re (V)O(L B (2))Cl] have been investigated with the framework of density functional theory. The absorption and circular dichroism spectra of the complexes were also calculated applying time-dependent density functional theory (TDDFT) using the conductor-like polarizable continuum solvent model to understand the origin of the electronic excitations. The chemical shift ( (1)H and (13)C) as well as (1)H- (1)H spin-spin coupling constant were also computed by the gauge-independent atomic orbital method, and the computed values are consistent with the experimental data.     

2D NMR studies of structural phase transitions in ABF6.6D2O systems

²D NMR studies in single crystals of CoSiF₆.6D₂O, CoTiF₆.6D₂O and ZnTiF₆.6D₂O reveal that all of them transform from rhombohedral to monoclinic symmetry through an intermediate phase as the temperature is lowered from 300 to 100K. The results throw light on the hydrogen bond network in different phases.     

Lithium diffusion in polyether ether ketone and polyimide stimulated by in situ electron irradiation and studied by the neutron depth profiling method

Diffusion of lithium from a LiCl aqueous solution into polyether ether ketone (PEEK) and polyimide (PI) assisted by in situ irradiation with 6.5?MeV electrons was studied by the neutron depth profiling method. The number of the Li atoms was found to be roughly proportional to the diffusion time. Regardless of the diffusion time, the measured depth profiles in PEEK exhibit a nearly exponential form, indicating achievement of a steady-state phase of a diffusion–reaction process specified in the text. The form of the profiles in PI is more complex and it depends strongly on the diffusion time. For the longer diffusion time, the profile consists of near-surface bell-shaped part due to Fickian-like diffusion and deeper exponential part.     

Comparative study on low energy ion beam modification of thermoplastic polymers

ABSTRACT

Polycarbonate (PC) and polyethylene terephthalate (PET) thermoplastic polymer films were irradiated by low energy ion beams such as 100 keV Hydrogen (H⁺) ions and 350 keV Nitrogen (N⁺) ions at varied fluence from 1?×?10¹³ ions/cm² to 5?×?10¹⁴ ions/cm². The depth profile concentration of ions was calculated using Stopping and Range of Ions in Matter (SRIM) software code. Fourier Transform Infrared (FTIR) technique shows decrement in the intensity of peaks and disappearance of peaks mainly related to carbonyl stretching at 1770?cm^?1 and C–C stretching at 1500?cm^?1. Scanning electron microscopy (SEM) of irradiated polymers showed the formation of pores. X-ray diffraction (XRD) analysis has showed decrease in the intensity indicating the decrease in crystallinity after irradiation. Mechanical studies revealed that the molecular weight and microhardness decrease with increase in ion fluence due to increase in chain scission. The contact angle increased with increase in ion fluence indicating the hydrophobic nature of polymer after irradiation. Antibiofilm activity test of irradiated films shows resistance to Salmonella typhi (S. typhi) pathogen responsible for typhoid. The study shows that Nitrogen ion induces more damage compared to Hydrogen ions and PC films get more modified than PET films.     

Inherent stability testing of empagliflozin in the presence of metformin HCl by HPTLC and characterization of degradation products of empagliflozin by LC–ESI–QTOF–MS/MS

JPC – Journal of Planar Chromatography – Modern TLC - A successful attempt has been made to develop and validate a stability-indicating high-performance thin-layer chromatography...     

Antioxidant and anti-inflammatory related activities of selected synthetic chalcones: structure-activity relationship studies using computational tools

Synthetic derivatives of 1-(2-hydroxy-3-(2-hydroxy-cyclohexyl)-4,6-dimethoxy-phenyl)-methanone were evaluated in-vitro for their activities related to antioxidant and anti-inflammatory. The antioxidant potential was determined by calculating reducing potential, OH and DPPH (2,2-diphenyl-1-picryl hydrazine) radical scavenging activities. The in-vitro anti-inflammatory related activities of synthetic chalcones (SCs) were demonstrated by performing inhibition assays of trypsin, beta-glucuronidase and diene conjugates. The results of the various parameters studied shows that the selected derivatives were found to be effective reducing agents and were reactive towards stabilizing the OH and DPPH radicals. The compounds have showed moderate to poor or no inhibition profile towards trypsin and beta-glucuronidase, but were found to be effective inhibitor of dien conjugates (hydroperoxides). An attempt has been made to define structure activity relationship using BioMed CAChe 6.1.10: a computer-aided molecular modeling tool which applies equations from classical and quantum mechanics. The experimental and in silico results of the present investigation shows that the basic nucleus 1-(2-hydroxy-3-(2-hydroxy-cyclohexyl)-4,6-dimethoxy-phenyl)-methanone can be considered as a potential candidate for the design and development of lead antioxidant and anti-inflammatory agents.     

An unreported bis-abeo cembrane-type diterpenoid with antioxidative and anti-lipoxygenase activities from the muricid gastropod mollusc Chicoreus ramosus

Abstract

The chemical analyses of ethyl acetate-methanol (EtOAc-MeOH) extract of muricid gastropod mollusk, Chicoreus ramosus from the southeastern coast of Indian peninsular led to the identification of unprecedented cembrane-type diterpenoid, which was characterized as (3E, 6E, 10E)-8a-butoxy-17(15→14), 20(12→11)-bis-abeo-cembra-3,6,10,14(17),15-pentaene (1). The structure of the studied cembrane was unambiguously assigned through the extensive spectroscopic experimentations. The antioxidant potentials of the bis-abeo cembrane as determined by in vitro 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis-3-ethylbenzothiozoline-6-sulfonic acid diammonium salt radical quenching potentials were greater (IC₅₀?<?0.40?mg/mL) related to α-tocopherol (IC₅₀?>?0.60?mg/mL). The pro-inflammatory anti-5-lipoxygenase potential of studied cembrane was higher (IC₅₀?<?0.80?mg/mL) related to those demonstrated by ibuprofen and sodium salicylate (IC₅₀?>?0.90?mg/mL).