A Design Criteria to Achieve Giant Ising-Type Anisotropy in CoII-Encapsulated Metallofullerenes

Discovery of permanent magnetisation in molecules just like in hard magnets decades ago led to the proposal of utilising these molecules for information storage devices and also as Q-bits in quantum computing. A significant breakthrough with a blocking temperature as high as 80 K has been recently reported for lanthanocene complexes. While enhancing the blocking temperature further remains one of the primary challenges, obtaining molecules that are suitable for the fabrication of the devices sets the bar very high in this area. Encouraged by the fact that our earlier predictions of potential single-molecule magnets (SMMs) in lanthanide-containing endohedral fullerenes have been verified, here we set out to undertake a comprehensive study on Co^II-ion-encapsulated fullerene as potential SMMs. To study this class of molecules, we have utilised an array of theoretical methods ranging from density functional to ab initio CASSCF/NEVPT2 methods for obtaining reliable estimate of zero-field splitting parameters D and E. Additionally, we have also employed, for the first time a combination of molecular dynamics based on DFT methods coupled with CASSCF/NEVPT2 methods to seek the role of conformational isomers in the relaxation of magnetisation. Particularly, we have studied, Co@C₂₈, Co@C₃₈ and Co@C₄₈ cages and their isomers as potential target molecules that could yield substantial magnetic anisotropy. Our calculations categorically reveal a very large Ising anisotropy in this class of molecules, with Co@C₄₈ cages predicted to yield D values as high as −127 cm⁻¹. Our calculations on the smaller cages reveal the free movement of Co^II ion inside the cage, leading to the likely scenario of faster relaxation of magnetisation. However, larger fullerene cages were found to solve this issue. Further models with incorporating units such as {CoOZn}, {CoScZnN} inside larger fullerenes yield axial zero-field splitting values as high as −200 cm⁻¹ with negligible E/D values. As these units represent a strong axiality coupled with a viable way to obtain air-stable low-coordinate Co^II complexes, this opens up a new paradigm in the search of SMMs in this class of molecules.     

Chemical Composition and Antioxidant Property of Essential Oil of Callicarpa tomentosa

Chemistry of Natural Compounds -     

Unified approach to the sesquiterpenoids,lauranes and cyclolauranes: Total synthesis of (±)-isolaurene

A general approach to the total synthesis of sesquiterpene, isolaurene (1a) and cyclolaurene (2a) is featured from commercially available 3-methyl cyclopenten-2-one. The strategy includes a Stork-Danheiser sequence concomitant with a Ni(II)-catalyzed conjugate addition of methyl group onto 3-aryl 2-methyl cyclopenten-2-one to afford the advanced intermediate 11. A methyllithium addition onto compound 11 with an eventual dehydration completed the total synthesis of isolaurene (1a) in 5 steps (58.3% overall yields).     

Effect of Cetyltrimethyl Ammonium Bromide on Electrochemical Determination of Dexamethasone

The effect of surfactants on the electrochemical determination of dexamethasone at an edge plane pyrolytic graphite electrode (EPPGE), modified with single‐walled carbon nanotubes (SWNT) has been investigated. The unique electrocatalytic properties of SWNT along with the synergistic adsorption of CTAB on SWNT lead to sensitive voltammetric response of dexamethasone with the reduction peak at ca. ?1195 mV. The limit of detection and sensitivity of dexamethasone is estimated to be 9.1×10^?10 M and 0.727 µA µM^?1 respectively. The SWNT coated EPPGE had good stability and reproducibility. The analytical utility of the developed method was evaluated by applying it for sensing the drug in human body fluids and for the determination of dexamethasone content in several commercially available pharmaceutical preparations. A comparison of the observed results of proposed method with HPLC clearly indicates that the results of both the methods are in good agreement. The product obtained after the reduction of dexamethasone has also been characterized using ¹H NMR and carbonyl group at position 3 has been found to reduce. The method is instant, simple and accurate and can be easily applied for detecting cases of doping.     

A supramolecular hydrogel that responds to biologically relevant stimuli

First demonstration of heat and pH-responsive hydrogel of SDS and a zwitterionic amphiphile, sodium N-(n-dodecyl-2-aminoethanoyl)-L-valinate with very low minimum gelation concentration.     

Production and Characterization of an Alkaline Thermostable Crude Lipase from an Isolated Strain of <Emphasis Type="Italic">Bacillus cereus</Emphasis> C<Subscript>7</Subscript>

A bacterial strain isolated from spoiled coconut and identified as Bacillus cereus was found capable of producing alkaline thermostable extracellular lipase. Optimum temperature, time, and pH for enzyme substrate reaction were found to be 60 °C, 10 min, and 8.0 respectively. Common surfactants except Triton X 100 and cetyltrimethylammonium bromide have no or very little inhibitory effects on enzyme activity. The enzyme was found to be stable in presence of oxidizing agents and protease enzyme. The maximum lipase production was achieved at 30–33 °C, pH 8.0 on 24 h of fermentation using 50 ml medium in a 250-ml Erlenmeyer flask. The superior carbon and nitrogen sources for lipase production were starch (2%) and ammonium sulfate (nitrogen level 21.2 mg/100 ml), peptone (nitrogen level 297 mg/100 ml), and urea (nitrogen level 46.62 mg/100 ml) in combination, respectively. The maximum enzyme activity obtained was 33 ± 0.567 IU/ml.     

Iron(II)‐Based Metalloradical Activation: Switch from Traditional Click Chemistry to Denitrogenative Annulation

A unique concept for the intermolecular denitrogenative annulation of 1,2,3,4‐tetrazoles and alkynes was discovered by using a catalytic amount of Fe(TPP)Cl and Zn dust. The reaction precludes the traditional, more favored click reaction between an organic azide and alkynes, and instead proceeds by an unprecedented metalloradical activation. The method is anticipated to advance access to the construction of important basic nitrogen heterocycles, which will in turn enable discoveries of new drug candidates.     

Measurement of local susceptibility at100Rh in some metallic hosts

The local susceptibilities (T) of isolated Rh impurities in Pb, Ru, Au, Pd, Pt andYb hosts have been measured as a function of temperature. The results show close to unity for Rh in Pb, Ru, Au andYb indicating nonmagnetic behaviour. In contrast, the magnetic response in exchange enhanced d band metal hosts, e.g. Pd andPt, shows Curie-Weiss-like local susceptibility andreflects a large quasi stable 4d magnetic moment on Rh.     

Anisotropic charge transport properties of chrysene derivatives as organic semiconductor: A computational study

We used density functional theory to calculate the angular resolution anisotropic charge mobility of the substituted chrysene molecules, viz, 4,10‐diphenoxychrysene (DPC), 4,10‐bis(phenylsulfanyl)chrysene (BPSC), and ethyl 8,9,12‐trimethoxychrysene‐6‐carboxylate (ETCC). The highest occupied molecular orbital–lowest unoccupied molecular orbital gap for DPC, BPSC, and ETCC was calculated to be 3.92, 3.83, and 3.81 eV, respectively, which inferred the compounds to be wide‐band‐gap semiconductors indicating that the compounds should have high stability in atmospheric conditions. The fact is also supported by electronic band‐structure calculation. In addition, higher electron affinity of studied compounds as compared with the bare chrysene molecule imparts enhancement of n‐type character in the compounds. The maximum hole ( ) and electron mobilities ( ) for DPC compound were found to be 0.739 cm²V^?1s^?1 and 0.319 cm²V^?1s^?1, respectively, at Φ = 0°. On the other hand, in the case of BPSC crystal, comparatively larger anisotropic electron mobility (0.709 cm²V^?1s^?1 at Φ = 0° and Φ = 179.90°) than the hole mobility (0.208 cm²V^?1s^?1 at Φ = 127.19° and Φ = 307.10°) was noted. Similarly, in ETCC, the parallel dimers were found to contribute maximum and of 0.052 and 0.102 cm²V^?1s^?1, respectively, at Φ = 0°. The substitution of ‐SPh in BPSC and ‐OCH₃ and ‐CO₂CH₂CH₃ in ETCC have relatively more impact on band reduction than ‐OPh in DPC, thus facilitating electron transport in BPSC and ETCC.