Search

Foremost, practical applications of spin‐crossover (SCO) materials require control of the nature of the spin‐state coupling. In existing SCO materials, there is a single, well‐defined dimensionality relevant to the switching behavior. A new material, consisting of 1,2,4‐triazole‐based trimers coordinated into 1D chains by [Au(CN)2]− and spaced by anions and exchangeable guests, underwent SCO defined by elastic coupling across multiple dimensional hierarchies. Detailed structural, vibrational, and theoretical studies conclusively confirmed that intra‐trimer coupling was an order of magnitude greater than the intramolecular coupling, which was an order of magnitude greater than intermolecular coupling. As such, a clear hierarchy on the nature of elastic coupling in SCO materials was ascertained for the first time, which is a necessary step for the technological development of molecular switching materials. [ABSTRACT FROM AUTHOR]

An extended nitro-functionalised 1,2,4-triazole ligand has been used to induce considerable lattice distortion in a 2-D Hofmann framework material via competing supramolecular interactions. Single crystal X-ray diffraction analyses on [Fe3(N-cintrz)6(Pd(CN)4)3]·6H2O (N-cintrz: (E)-3-(2-nitrophenyl)acrylaldehyde) reveal a substantial deviation from a regular Hofmann structure, in particular as the intra- and inter-layer contacts are dominated by hydrogen-bonding interactions rather than the typical π-stacking arrays. Also, the 2-D Hofmann layers show an assortment of ligand conformations and local FeII coordination environments driven by the optimisation of competing supramolecular contacts. Temperature-dependent magnetic susceptibility measurements reveal a two-step spin crossover (SCO) transition. Variable temperature structural analyses show that the two crystallographically distinct FeII centres, which are arranged in stripes (2 : 1 ratio) within each Hofmann layer, undergo a cooperative HS ↔ HS/LS ↔ LS (HS = high spin, LS = low spin) transition without periodic spin-state ordering. The mismatch between crystallographic (2 : 1) and spin-state (1 : 1) periodicity at the HS : LS step provides key insight into the competition (frustration) between elastic interactions and crystallographically driven order. [ABSTRACT FROM AUTHOR]

A 3-D FeII Hofmann-type framework material has been prepared which contains a three-connecting pyridyl-donor ligand with amide functionality and [Au(CN)2]− metallo-ligands. The FeII sites display a rare FeII(py)3(N≡C⋯)3 coordination environment, which we show for the first time to be conducive to spin crossover (SCO). [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the chemical properties of atmospheric particulate matter collected during post biomass burning events from November to December 2015. The types of particulate samples collected from the study area were total suspended particulates (TSP) and particulates less than 2.5 µm (PM2.5). Multiple methods were used for the qualitative and quantitative characterization. Fifteen major and minor trace metal analyses were performed using acid digestion followed by inductively coupled plasma mass spectrometry analysis. Infrared spectroscopy was used for the identification of functional groups of organic compounds present in the samples. In addition, field emission scanning electron microscopy–energy dispersive X-ray spectroscopy was used for morphological characterization and microanalysis of individual particles. The average measured concentration of trace metals in TSP and PM2.5follows the order of Zn > Fe > Al > Cu > Pb > Mn > V > Cr > Ni > Sn > As > Hg > Cd > Ag > Co. Enrichment factor analysis showed strong anthropogenic contributions of Hg, Ag, Zn, Cd, Pb, As, Cu, and Sn in the samples. Field emission scanning electron microscopy–energy dispersive X-ray spectroscopy shows that three types of particles were present that originated from crustal and anthropogenic sources. Furthermore, the infrared measurements indicate that most compounds were organic acids and aromatic hydrocarbons. [ABSTRACT FROM PUBLISHER]

Vegetation is one of the natural sources which contribute to the amount of surface active agent into the environment. It is believed that surfactants can be derived from various kinds of sources such as biomass burning or soil and these excessive level of surfactants emitted into the atmosphere can influence both cloud formation and climate. The objective of this study was to determine the concentration of both anionic and cationic surfactants as well as levoglucosan from vegetation and soot and at different weather conditions around the tin mine lakes environment. The samples were prepared by cutting several parts of tropical plant species, namelyCinnamomum Iners, Gliricidia SepiumandHopea Odorata, which were mainly leaves and stems. After that, samples were allowed to dry in an oven at a temperature of 40°C for 2 h. The concentrations of levoglucosan and surfactant such as methylene blue active substance (MBAS) and disulphine blue active substance (DBAS) were analysed through the colorimetric method. The results showed that higher concentrations for both anionic and cationic surfactants were found inC.Inersleaves which give the concentrations of 86.92 ± 38.99 and 22.33 ± 10.59 µg/g. It was noted that the concentrations of anionic and cationic surfactants in this research were correlated to each other, indicating the possibility of similar sources that affect both levels of surfactants in the vegetation. In addition, the highest level of levoglucosan was dominated by the leaves fromG.Sepiumspecies with the concentration of 25.62 ± 12.65 mg/g, respectively. A positive significant correlation (r = 0.8447, 0.8355 andp = 0.0001 < 0.05) between anionic surfactants and levoglucosan was also discovered in this study. [ABSTRACT FROM AUTHOR]

The multi-genre Persian text Chachnama, written in Uch in 1226, represents a unique formulation of a possible future for a Muslim polity at the frontier and under immense duress. In its explicit linkage of a Muslim with a local pre-Islamic past within the site and milieu of its production, the Chachnama presents the beginnings of a new political theology. Long understood as a translation of an earlier text, it is instead a specifically imagined text that found political and romantic resonance in the histories of Uch and Sindh through the centuries. This article provides a close reading of the text to elucidate the ways in which it participates in varied genres and the socio-political claims it makes on historiography. It further traces the historiography surrounding the text and highlights the ways in which classificatory schema (such as genre) operate on analytical understandings of narratives. [ABSTRACT FROM PUBLISHER]

An introduction is presented to this issue arising from a panel at the 39th Annual South Asia Conference on studies of Indic Medieval texts and their later influence on Indic society.

Review: 93 refs. [ABSTRACT FROM AUTHOR]

Foremost, practical applications of spin-crossover (SCO) materials require control of the nature of the spin-state coupling. In existing SCO materials, there is a single, well-defined dimensionality relevant to the switching behavior. A new material, consisting of 1,2,4-triazole-based trimers coordinated into 1D chains by [Au(CN) 2 ] - and spaced by anions and exchangeable guests, underwent SCO defined by elastic coupling across multiple dimensional hierarchies. Detailed structural, vibrational, and theoretical studies conclusively confirmed that intra-trimer coupling was an order of magnitude greater than the intramolecular coupling, which was an order of magnitude greater than intermolecular coupling. As such, a clear hierarchy on the nature of elastic coupling in SCO materials was ascertained for the first time, which is a necessary step for the technological development of molecular switching materials., (© 2021 Wiley-VCH GmbH.)

A 3-D FeII Hofmann-type framework material has been prepared which contains a three-connecting pyridyl-donor ligand with amide functionality and [Au(CN)2]- metallo-ligands. The FeII sites display a rare FeII(py)3(N[triple bond, length as m-dash]C)3 coordination environment, which we show for the first time to be conducive to spin crossover (SCO).

A family of iron(III) spin crossover complexes with different counteranions, [Fe(qsal-F) 2 ]A (qsal-F = 4-fluoro-2-[(8-quinolylimino)methyl]phenolate; A = PF 6 - 1 , OTf - 2 , NO 3 - 3 , ClO 4 - 4 , BF 4 - 5 , or NCS - 6 ) have been prepared. All compounds are isostructural and crystallize (triclinic P 1̅ space group) with two independent iron(III) centers (Fe1 and Fe2) in the asymmetric unit. No solvent molecules are found in the crystal lattice, allowing us to directly probe the relative influence of anion variation on the spin crossover characteristics. The crystal packing is governed by three types of π-π interactions (type A, type B, and type C), which form undulating 1D chains. Additional interactions (π-F, C-H···O/F, and P4AE) connect the neighboring chains to form a complex supramolecular network. Hirshfeld surface analysis supports these findings. The anions are located between the cationic [Fe(qsal-F) 2 ] + chains; hence, similar interchain distances ( d chain ) are observed irrespective of the anion. However, the interplane distances ( d plane ) are influenced by the crystal packing and increase proportionally with the anion size. Magnetic studies reveal that smaller anions tend to stabilize the low-spin state (NO 3 - 3 , ClO 4 - 4 , and BF 4 - 5 ), while larger anions (PF 6 - 1 and OTf - 2 ) exhibit lower transition temperatures ( T onset for 1 = 200 K and T for 2 = 190 K) and gradual spin crossovers. The anomaly is 6 , where, despite having the smallest anion, it exhibits the lowest transition temperature with magnetic hysteresis in the first step ( T 1/2 ↑ = 170 K and T 1/2 ↓ = 157 K). This suggests the size, shape, and supramolecular connectivity of the anion all influence the magnetic properties.