Synthesis of substituted benzene derivatives by homo- and hetero-coupling of 2-bromobenzaldehyde and bromovinylaldehydes followed by McMurry coupling

A convenient synthetic approach to substituted benzene derivatives by modified Ullmann cross-coupling of 2-bromobenzaldehyde and bromovinylaldehydes followed by intramolecular McMurry coupling has been developed.     

Solving the Liouville equation for conservative systems: Continued fraction formalism and a simple application

There are very few formalisms available to solve the Liouville equation for energy-conserved systems. The continued fraction formalism, introduced through the works of Zwanzig, Mori, Kubo, Lee, Grigolini and others is described here. A detailed discussion is presented on ways to apply the continued fraction formalism to solve for relaxation functions and for the dynamical variable itself for a simple and exactly solvable quantum spin system.     

Supramolecular peptide helix from a novel double turn forming peptide containing a β-amino acid

A single-crystal X-ray diffraction study of the terminally protected tetrapeptide Boc-β-Ala-Aib-Leu-Aib-OMe 1 (Aib: α-aminoisobutyric acid; β-Ala: β-Alanine) reveals that it adopts a new type of double turn structure which self-associates to form a unique supramolecular helix through intermolecular hydrogen bonds. Scanning electron microscopic studies show that peptide 1 exhibits amyloid-like fibrillar morphology in the solid state.     

Simultaneous determination of copper,mercury and antimony in biological samples by neutron activation and substoichiometric extraction

A simple and accurate method has been developed for the determination of copper, mercury and antimony by thermal neutron activation analysis involving substoichiometric extraction technique. The results of analysis indicate that copper, mercury and antimony in biological samples can be determined with an accuracy of 5.3%, 5.5% and 6.2%, respectively. Two samples and a standard can be analysed by the proposed method in about 4 hrs. Part of this work was presented at the International Conference on Modern Trends in Activation Analysis, Saclay, Paris, France, October 2–6, 1972.     

Synthesis, structure and properties of delocalized transition metal chelates: Diazoketiminato chelates of Co(III) and Pt(II)

The reactions of HL 1 [where HL is 1N-(2-pyridyl-2-methyl)-2-arylazoaniline and is formulated as ArN = NC₆H₄N(H)(CH₂C₅H₄N); Ar = C₆H₅ (for HL¹) or p-MeC₆H₄ (for HL²) or p-ClC₆H₄ (for HL³)] with K₂PtCl₄ and Co(ClO₄)₃ · 6H₂O afforded the (L)PtCl and [(L)₂Co]ClO₄ complexes, respectively. The HL ligands bind the platinum(II) and cobalt(III) centres in a tridentate (N,N,N) fashion, forming new diazoketiminato chelates upon dissociating the amino proton. The X-ray structures of (L³)PtCl and [(L³)₂Co]ClO₄ were determined. Redox properties of the new complexes have been examined.     

Constrained photophysics of 3-acetyl-4-oxo-6,7-dihydro-12H indolo-[2,3-a] quinolizine in micellar environments: a spectrofluorometric study

Photophysical properties of 3-acetyl-4-oxo-6,7-dihydro-12H indolo-[2,3-a] quinolizine (AODIQ) have been studied in different aqueous micellar environments using steady-state and time-resolved emission spectroscopy. The charge transfer (CT) fluorescence exhibits appreciable hypsochromic shift, along with an enhancement in the fluorescence intensity in all the micellar media. This is associated with an increase in the fluorescence anisotropy (r), which suggests that the fluorophore molecule experiences motionally restricted environments upon binding with the micelles. Fluorescence spectral position and fluorescence quenching studies suggest that the fluorescing moiety does not penetrate into the core of the micellar units; rather it binds at the micelle-water interfacial region. The binding constant and free energy change during probe-micelle binding have been evaluated from relevant fluorescence data. Light has been thrown on the mode of action of urea on micelle bound probes. The results are interpreted in terms of the model that urea displaces water molecules from the micellar interface and the consequent destabilization leads to the expulsion of the probe molecules from the interfacial region. Polarity and viscosity of the microenvironments around the probe have been determined in the micellar systems.     

Novel bio-inspired deep eutectic solvent and graphene functionalized deep eutectic solvent as an efficient flame retardant material for cotton fabric

Cellulose - In this study, a novel bioinspired deep eutectic solvent (DES) was synthesized and functionalized with graphene to prepare G-DES. DES was synthesized in the presence of choline chloride...     

Bridging the Green Gap: Metal–Organic Framework Heteromultilayers Assembled from Porphyrinic Linkers Identified by Using Computational Screening

In organic photovoltaics, porphyrins (PPs) are among the most promising compounds owing to their large absorption cross-section, wide spectral range, and stability. Nevertheless, a precise adjustment of absorption band positions to reach a full coverage of the so-called green gap has not been achieved yet. We demonstrate that a tuning of the PP Q- and Soret bands can be carried out by using a computational approach for which substitution patterns are optimized in silico. The most promising candidate structures were then synthesized. The experimental UV/Vis data for the solvated compounds were in excellent agreement with the theoretical predictions. By attaching further functionalities, which allow the use of PP chromophores as linkers for the assembly of metal-organic frameworks (MOFs), we were able to exploit packing effects resulting in pronounced redshifts, which allowed further optimization of the photophysical properties of PP assemblies. Finally, we use a layer-by-layer method to assemble the PP linkers into surface-mounted MOFs (SURMOFs), thus obtaining high optical quality, homogeneous and crystalline multilayer films. Experimental results are in full accord with the calculations, demonstrating the huge potential of computational screening methods in tailoring MOF and SURMOF photophysical properties.     

Synthesis and characterization of dimeric μ-oxidovanadium complexes as the functional model of vanadium bromoperoxidase

Two vanadium (IV) complexes [V^IVO(Haeae-sal)(MeOH)]⁺ ( 1 ) and [V^IVO(Haeae-hyap)(MeOH)]⁺ ( 2 ) were prepared by reacting [VO(acac)₂] with ligands [H₂aeae-sal] ( I ) and [H₂aeae-hyap] ( II ) respectively. Condensation of 2-(2-aminoethylamino)ethanol with salicylaldehyde and 2-hydroxyacetophenone produces the ligands ( I ) and ( II ) respectively. Both vanadium complexes 1 and 2 are sensitive towards aerial oxygen in solution and rapidly convert into vanadium(V) dioxido species. Vanadium(V) dioxido species crystalizes as the dimeric form in the solid-state. Single-crystal XRD analysis suggests octahedral geometry around each vanadium center in the solid-state. To access the benefits of heterogeneous catalysis, vanadium(V) dioxido complexes were anchored into the polymeric chain of chloromethylated polystyrene. All the synthesized neat and supported vanadium complexes have been studied by a number of techniques to confirm their structural and functional properties. Bromoperoxidase activity of the synthesized vanadium(V) dioxido complexes 3 and 4 was examined by carrying out oxidative bromination of salicylaldehyde and oxidation of thioanisole. In the presence of hydrogen peroxide, 3 shows 94.4% conversion ( TOF value of 2.739 × 10² h⁻¹) and 4 exhibits 79.0% conversion (TOF value of 2.403 × 10² h⁻¹) for the oxidative bromination of salicylaldehyde where 5-bromosalicylaldehyde appears as the major product. Catalysts 3 and 4 also efficiently catalyze the oxidation of thioanisole in the presence of hydrogen peroxide where sulfoxide is observed as the major product. Covalent attachment of neat catalysts 3 and 4 into the polymer chain enhances substrate conversion (%) and their catalytic efficiency increases many folds, both in the oxidative bromination and oxidation of thioether. Polymer supported catalysts 5 displayed 98.8% conversion with a TOF value of 1.127 × 10⁴ h⁻¹ whereas catalyst 6 showed 95.7% conversion with a TOF value of 4.675 × 10³ h⁻¹ for the oxidative bromination of salicylaldehyde. These TOF values are the highest among the supported vanadium catalysts available in the literature for the oxidative bromination of salicylaldehyde.