Second sphere interaction in fluoroanion binding: Synthesis, spectroscopic and X-ray structural study of trans-dichlorobis(ethylenediamine) cobalt(III) terafluoroborate

Trans-dichlorobis(ethylenediamine) cobalt(III) terafluoroborate was synthesised and detailed packing analysis was undertaken to delineate the topological complimentarity of [trans-Co(en)₂Cl₂]⁺ and BF₄⁻ ions by second sphere coordination. The complex was completely characterised by elemental analyses, solubility product measurement and spectroscopic studies (IR, UV–Vis, multinuclear NMR). In the crystal lattice, discrete ions [trans-Co(en)₂Cl₂]⁺ and BF₄⁻ are arranged in A–B–A–B pattern (in both a and c directions of the lattice) forming columns of anions and cations. Crystal lattice is stabilized by electrostatic forces of attraction and hydrogen bonding interactions, i.e. N–HF⁻ and N–HCl involving second sphere coordination. It appears that the topological features of [trans-Co(en)₂Cl₂]⁺ are conducive for generating second sphere interactions. This strategy may be used as a viable method for the capture of other fluoroanions.     

Time-resolved luminescence detection of peroxynitrite using a reactivity-based lanthanide probe

Peroxynitrite (ONOO⁻) is a powerful and short-lived oxidant formed in vivo, which can react with most biomolecules directly. To fully understand the roles of ONOO⁻ in cell biology, improved methods for the selective detection and real-time analysis of ONOO⁻ are needed. We present a water-soluble, luminescent europium(iii) probe for the rapid and sensitive detection of peroxynitrite in human serum, living cells and biological matrices. We have utilised the long luminescence lifetime of the probe to measure ONOO⁻ in a time-resolved manner, effectively avoiding the influence of autofluorescence in biological samples. To demonstrate the utility of the Eu(iii) probe, we monitored the production of ONOO⁻ in different cell lines, following treatment with a cold atmospheric plasma device commonly used in the clinic for skin wound treatment.

Reactivity-based europium(iii) probe displays excellent selectivity for peroxynitrite (ONOO⁻), enabling its time-resolved luminescence detection in living cells.     

The effect of cold trap adsorbents on the gas chromatographic analysis of ambient VOCs under Peltier cooling conditions

In this work, the relative analytical performance of the GC-based detection method was investigated with a major focus on cold trap (CT) adsorbent materials against four aromatic volatile organic compounds (VOCs) (e. g., benzene, toluene, xylene, and styrene). A series of calibration experiments were hence conducted under cryofocusing conditions formed by the Peltier cooling system in a thermal desorber (TD) unit. During the course of this study, comparative calibration datasets were acquired for each of the three CT types: (i) CT (I) = Carbopack B + Carbopack C, (ii) CT (II) = Carbopack B + Carboxen 1000, and (iii) CT (III) = Tenax TA. All calibration datasets were obtained under subambient temperature (-10 degrees C) conditions controlled by the Peltier cooling system. The reliability of the calibration data was also assessed in an ancillary experiment with the aid of the modified injection through a thermal desorber (MITD) method. The results demonstrated that the GC detection properties of different VOCs were not altered significantly between different CT applications under Peltier conditions, although relative sensitivity could be distinguished moderately depending on the CT type.     

DNA directed self-assembly of anisotropic plasmonic nanostructures

Programmable positioning of one-dimensional (1D) gold nanorods (AuNRs) was achieved by DNA directed self-assembly. AuNR dimer structures with various predetermined inter-rod angles and relative distances were constructed with high efficiency. These discrete anisotropic metallic nanostructures exhibit unique plasmonic properties, as measured experimentally and simulated by the discrete dipole approximation method.     

Terpenoid composition and antifungal activity of three commercially important essential oils against Aspergillus flavus and Aspergillus niger

Hydro-distilled essential oils extracted from three commercially important aromatic plants were analysed by capillary gas chromatography-flame ionization detector and gas chromatography/quadrupole mass spectrometry and subjected to antifungal activity. Fifteen compounds, which accounted for 97.8% of Acorus calamus root oil composition have been identified. Besides the major constituent (Z)-asarone (81.1-92.4%), (Z)-methyl isoeugenol (1.8-2.1%), (Z)-isoelemicin (1.2-1.3%), (E)-asarone (1.0-2.6%), (E)-methyl isoeugenol (0.2-0.4%), (Z)-β-ocimene (0.2-0.4%), elemicin (0.2-0.3%), linalool (0.1-0.9%) and kessane (t-0.2%) were identified. Monoterpenes constituted the main fraction of Origanum vulgare essential oil attaining 90.5% of the total oil composition. p-Cymene (10.3%) was the major component of the monoterpene hydrocarbon fraction while thymol (53.2%) and carvacrol (3.9%) were the most abundant oxygenated monoterpenes among the 33 identified constituents. Cinnamomum tamala leaf oil contained (E)-cinnamaldehyde as the principal component. Quantitative variations in (Z)-cinnamaldehyde (5.8-7.1%), linalool (6.4-8.5%) and (E)-cinnamyl acetate (4.7-5.2%) were significant. The antifungal activity of the hydro-distilled essential oils of A. calamus, O. vulgare and C. tamala were evaluated against Aspergillus flavus and Aspergillus niger. Disc diffusion method was used for the determination of the inhibitory effect. O. vulgare essential oil exhibited the highest activity. Moreover, all three essential oils inhibit the growth of A. flavus and A. niger.     

Supramolecular assembly of Hoechst-33258 with cucurbit[7]uril macrocycle

Molecular assemblies of potential guest molecules through non-covalent host-guest interactions have found immense use in many applied areas. In this study supramolecular interaction of a biologically important dye Hoechst-33258 (H33258) has been investigated in aqueous solutions at different pHs, in the presence of a macrocyclic host, namely, cucurbit[7]uril (CB7). The pH dependent emission behaviour of H33258 is inherently connected with its protolytic equilibria which allow the dye in different geometrical conformations. This pH dependent structural orientation is greatly affected by the complexation with CB7. The significant structural changes in the monocationic H33258 brought out by CB7 at pH 7 have been documented in the fluorescence emission and lifetime data, which are comparatively less affected in case of the dicationic form, which is prominent in dye solutions at pH 4.5. The strong ion-dipole interactions provided by the carbonyl portals of the CB7 host adequately stabilize the CB7-H33258 complex, both in 1:1 and 2:1 stoichiometries at both the pH conditions. The Job's plot method, fluorescence anisotropy, NMR measurements and geometry optimization calculations confirm the stoichiometric arrangement and are found to be tunable with the addition of metal ions. The non-covalently stabilized assembly brings out large enhancement in the fluorescence emission due to the unique structural orientation attained by H33258, which reduces the non-radiative relaxation pathways. Comparison of the spectral data of the dye at different pH conditions in the absence and presence of CB7 proposes a large upward pK(a) shift due to CB7 encapsulation, thus providing a handy tool to modulate the photophysical characteristics of the guest molecules.     

Redox-switchable superhydrophobic silver composite

Unique packaging of Ag(2)O on the surface of polycrystalline AgCl allows fabrication of a new useful, superhydrophobic composite material. This pure inorganic material with surface porosity of submicrometer aperture size fabricates air pockets, which make the composite material superhydrophobic. The new material behaves like lotus leaves, butterfly wings, or water strider's leg in relation to superhydrophobicity. Visible light induces photoreduction of solid Ag(2)O surface layer and generates Ag(0), making the composite surface superhydrophilic. Reoxidation of Ag(0) on the composite surface gives back the hydrophobicity that represents the redox-switchable wetting property of the material.     

Copper(I) and copper(II) complexes of diamino-dithioether ligands

Summary Copper(II) salts were reacted with two diamino-dithioether ligands, i.e. 1,3-di(o-aminophenylthio)propane (abbreviated H₂L¹) and 1,2-di(o-aminophenylthio)xylene (abbreviated H₂L²). Mixtures of copper(I) and copper(II) complexes were obtained with Cl^– and ClO ₄ ^– counterions. The major products were the copper(I) complexes, which were obtained pure after recrystallisation from MeCN-MeOH. The ligands lose two protons from the amine functions to form copper(I) complexes of general formula [CuL]X, where X = ClO ₄ ^– or Cl^–. The complexes were oxidised to [CuL]X₂ with H₂O₂ in DMF. Cu(NO₃)₂ on the other hand gave [CuH₂LNO₃]NO₃.     

Supramolecular Linear Conglomerates Formed by β-Cyclodextrin Dimers and Sodium Deoxycholate

The formation of supramolecular structures by the complexation of two bile salts--sodium cholate (NaC) and sodium deoxycholate (NaDC)--with four new head-to-head g -cyclodextrin dimers was studied by NMR techniques. All dimers form 1:2 (dimer:bile salt) stoichiometry complexes with NaC. With NaDC, linear supramolecular conglomerates of an n : n stoichiometry were obtained for all dimers. ROESY spectra confirmed the presence of electrostatic interactions when a protonated amino group is present in the linking group. The dependence of the pseudo-equilibrium constants with the electrostatic interactions and steric hindrance is discussed.