Heptanuclear Mixed-Valence Co4IIICo3II Molecular Wheel─A Molecular Analogue of Layered Double Hydroxides with Single-Molecule Magnet Behavior and Electrocatalytic Activity for Hydrogen Evolution Reactions.

We present a bifunctional heptanuclear cobalt(II)/cobalt(III) molecular complex formulated as [Co7(µ3-OH)4(H2L1)2(HL2)2](NO3)6·6H2O (1) (where H5L1 is 2,2'-(((1E,1'E)-((2-hydroxy-5-methyl-1,3-phenylene)bis(methanylylidene))bis(azanylylidene))bis(propane-1,3-diol)) and H2L2 is 2-amino-1,3-propanediol). Compound 1 has been characterized by single-crystal X-ray diffraction analysis along with other spectral and magnetic measurements. Structural analysis indicates that 1 contains a mixed-valence Co7 cluster where a central Co(II) ion is connected to six different Co centers (four CoIII and two CoII ions) by four µ3-OH groups, giving rise to a planar heptanuclear cluster that resembles a molecular fragment of a layered double hydroxide (LDH). Two triply deprotonated (H2L1)3- ligands form the outer side of the cluster while two singly deprotonated (HL2)- ligands are located at the top and bottom of the central heptanuclear core. Variable temperature magnetic measurements indicate the presence of weak ferromagnetic CoII···CoII interactions (J = 3.53(6) cm-1) within the linear trinuclear CoII cluster. AC susceptibility measurements show that 1 is a field-induced single-molecule magnet (SMM) with τ0 = 8.2(7) × 10-7 s and Ueff = 11.3(4) K. The electrocatalytic hydrogen evolution reaction (HER) activity of 1 in homogeneous phase shows an overpotential of 455 mV, with a Faradaic efficiency of 81% and a TOF of 8.97 × 104 µmol H2 h-1 mol-1.

Low-Cost and Scalable Ni-Prussian Blue Analogue//Functionalized Carbon Based Na-Ion Systems for all Climate Operations.

Herein, we have developed a sodium ion based aqueous energy storage device with nickel prussian-blue-analogue (Ni-PBA) positive and functionalized carbon-black negative electrodes in 1 M Na2 SO4 electrolyte solution. The components required to develop the device, i. e., stainless steel (SS) current-collectors, absorbent-glass-mat separator, electrolyte, carbon-black, and precursors of Ni-PBA, are all environmentally benign and inexpensive. To minimize the corrosion of pristine-SS, polyaniline coating on the SS surface is applied by in situ electrodeposition method. The full cell exhibits a specific capacity of 28 mAh g-1 with 90 % Coulomb efficiency (@0.2C), an energy density of 34 Wh kg-1 (@20 W kg-1 ), a power density of 100 W kg-1 (@18 Wh kg-1 ) and a good life cycle (70 % capacity-retention over 500 cycles @1.0C rate) within the 0-1.2 V window. The cell performance is further tested under variable temperatures, and 0-50 °C range is reported to be the working window for this cell.

Report on "The Second United Nations World Geospatial Information Congress (UN-WGIC) Pre-Event".

The United Nations Committee of Experts on Global Geospatial Information Management (GGIM) organises the World Geospatial Information Congress (UN-WGIC) once every four years bringing together member states of the UN-GGIM, experts in the field of Geospatial Technologies and its various application domains, commercial geospatial sector, academia, researchers and practitioners from across the globe. India is the proud host of the Second UN-WGIC scheduled for 10-14 October 2022 in Hyderabad, India. The Second UN-WGIC is organised by the United Nations and the Department of Science and Technology (DST), Government of India. Through a series of online virtual pre-events, DST intends to collect and collate various ideas and resource materials including applications and innovations in the field of Geospatial information generation to highlight the vibrant Indian Geospatial Ecosystem. One of the Pre events in India was held during 26th and 27th May, Co-ordinated by Prof. Biplab Biswas, Department of Geography, The University of Burdwan, Burdwan, West Bengal, India. The whole UN-WGIC pre-event was structured into-Inauguration; five technical sessions with presentations from various stakeholders like Government, Industry, Youth, Academics, others; and Conclusion with a detailed discussion over the nature, development and future trend of geospatial ecosystem in India and other countries.

Impacts of a lead smelter in East Java, Indonesia: degree of contamination, spatial distribution, ecological risk, and health risk assessment of potentially toxic elements in soils.

This study investigates the characteristics of potentially toxic elements in soils collected from the vicinity of a lead smelter in East Java, Indonesia. The objective is to assess the impact of the lead smelter on the surrounding soil. The study involves chemical composition analysis, spatial distribution mapping, and potential ecological and health risk assessments. Soil samples were collected from the surface area (0-10 cm) and subsurface (15-30 cm) within radii of 1.5 km, 3 km, and 5 km from the lead smelter. The samples were analyzed for As, Cr, Cu, Ni, Pb, and Zn using energy-dispersive X-ray fluorescence. Principal component analysis (PCA) was performed to identify the sources of potentially toxic elements in the soil. The results indicate severe Pb contamination within a 1.5 km radius of the smelter, with an average contamination factor (Cf) value of 22.0, posing a high potential health risk. The contamination factor indicated that the soils were heavily polluted by As and Pb and moderately polluted by Cu, Ni, and Zn. The results of PCA showed that smelter releases are the main source of potentially toxic element contamination in the soil, accounting for 66.2%. The health risk assessment suggested that the children and adults in the study region were exposed to non-carcinogenic risks caused by As and Pb. Oral ingestion was identified as the primary exposure route impacting health risks. The carcinogenic risk from potentially toxic elements in soil was found to exceed the acceptable level for children and adults in the study region. Therefore, it is necessary for the government to take effective measures, including designing regulations and interventions, and improving lead smelter management to mitigate potential contamination and minimize the impact of lead smelter releases on the surrounding environment, especially to protect human health, particularly that of children.

Arsenic, iron, and manganese in groundwater and its associated human health risk assessment in the rural area of Jashore, Bangladesh.

This study investigated groundwater pollution and potential human health risks from arsenic, iron, and manganese in the rural area of Jashore, Bangladesh. Study results show that the mean value of groundwater pH is 7.25 ± 0.31, with a mean conductivity of 633.94 ± 327.41 µs/cm, while about 73, 97, and 91% of groundwater samples exceeded the Bangladesh drinking water standard limits for As, Fe, and Mn, respectively. Groundwater pollution evaluation indices, including the heavy metal pollution index, the heavy metal evaluation index, the degree of contamination, and the Nemerow pollution index, show that approximately 97, 82, 100, and 100% of samples are in the high degree of pollution category, respectively. Spatial distribution exhibited that the study area is highly exposed to As (73%), Fe (82%), and Mn (46%). In the case of non-carcinogenic health risk via oral exposure, about 94% of samples suggest a high category of risk for infants, and 97% of samples are found to be at high risk for children and adults. The carcinogenic risk of arsenic via an oral exposure pathway suggests that approximately 97% of the samples are found to be at high risk for infants, and all of the samples are at high risk for both adults and children.

Long-term exposure to indoor air pollution and risk of tuberculosis.

Indoor air pollution (IAP) is a recognized risk factor for various diseases. This paper examines the role of indoor solid fuel exposure in the risk of mycobacterium tuberculosis (TB) in Delhi Metropolitan, India. Using a cross-sectional design, subjects were screened for a history of active TB and lifelong exposure to IAP sources, such as solid fuel burning and kerosene. The TB prevalence rate in the study area was 1117 per 100 000 population. Every year, increase in solid fuel exposure was associated with a three percent higher likelihood of a history of active TB. Subjects exposed to solid fuel and kerosene use for both heating home and cooking showed significant associations with TB. Age, household expenditure (a proxy of income), lung function, and smoking also showed significant associations with TB. Smokers and solid fuel-exposed subjects were four times more likely to have a history of active TB than non-smoker and unexposed subjects. These finding calls strategies to mitigate solid fuel exposure, such as use of clean cookstove and ventilation, to mitigate the risk of TB which aligns with the United Nations' goal of "End TB by 2030."

Fine-needle aspiration cytology of retroperitoneal lesions: a 5-year experience with an emphasis on cytohistological discrepancy.

BACKGROUND: The retroperitoneal space contains various organs which can be affected by various non-neoplastic and neoplastic pathological processes. A diagnosis of these retroperitoneal lesions is often difficult. Fine-needle aspiration cytology (FNAC) under image guidance is now becoming an effective tool for the initial evaluation of retroperitoneal lesions. OBJECTIVE: The present study was undertaken to evaluate the role of ultrasound-guided FNAC in the diagnosis of retroperitoneal lesions in comparison to histopathology and to assess the probable causes of failure in cases of pitfalls in cytodiagnosis. MATERIALS AND METHODS: During the study period of 5 years, a total of 104 cases of retroperitoneal lesions were aspirated under USG guidance. Seven cases yielded inadequate material, the remaining 97 cases were included in the study group. RESULTS: Out of 97 cases, the kidney was the most common organ aspirated (27 cases; 27.8%). Malignant lesions (68 cases; 70.1%) were much more frequent than benign or non-neoplastic lesions (29 cases; 29.9%). Tuberculosis was the most common non-malignant lesion (14 cases) and renal cell carcinoma was the most frequent malignant lesion encountered (15 cases). In 5 cases (7.9%), the histological diagnosis showed inconsistent results in comparison to cytodiagnosis. CONCLUSION: USG-guided FNAC is a safe, rapid, relatively cheap and fairly accurate procedure for the assessment of retroperitoneal lesions.

scHD4E: Novel ensemble learning-based differential expression analysis method for single-cell RNA-sequencing data.

Differential expression (DE) analysis between cell types for scRNA-seq data by capturing its complicated features is crucial. Recently, different methods have been developed for targeting the scRNA-seq data analysis based on different modeling frameworks, assumptions, strategies and test statistic in considering various data features. The scDEA is an ensemble learning-based DE analysis method developed recently, yielding p-values using Lancaster's combination, generated by 12 individual DE analysis methods, and producing more accurate and stable results than individual methods. The objective of our study is to propose a new ensemble learning-based DE analysis method, scHD4E, using top performers in only 4 separate methods. The top performer 4 methods have been selected through an evaluation process using six real scRNA-seq data sets. We conducted comprehensive experiments for five experimental data sets to evaluate our proposed method based on the sample size effects, batch effects, type I error control, gene ontology enrichment analysis, runtime, identified matched DE genes, and semantic similarity measurement between methods. We also perform similar analyses (except the last 3 terms) and compute performance measures like accuracy, F1 score, Mathew's correlation coefficient etc. for a simulated data set. The results show that scHD4E is performs better than all the individual and scDEA methods in all the above perspectives. We expect that scHD4E will serve the modern data scientists for detecting the DEGs in scRNA-seq data analysis. To implement our proposed method, a Github R package scHD4E and its shiny application has been developed, and available in the following links: https://github.com/bbiswas1989/scHD4E and https://github.com/bbiswas1989/scHD4E-Shiny.

Socioeconomic inequality and urban-rural disparity of antenatal care visits in Bangladesh: A trend and decomposition analysis.

BACKGROUND: Socioeconomic inequality in antenatal care visits is a great concern in developing countries including Bangladesh; however, there is a scarcity of investigation to assess the factors of inequality and these changes over time. In this study, we investigated the trend of socioeconomic inequalities (2004-2017) in 1+ANC and 4+ANC visits, and extracted determinants contributions to the observed inequalities and urban-rural disparities in Bangladesh over the period from 2011 to 2017. METHODS: The data from the Bangladesh Demographic and Health Surveys (BDHS) conducted in 2004, 2007, 2011 and 2017 were analyzed in this study. The analysis began with exploratory and bivariate analysis, followed by the application of logistic regression models. To measure the inequalities, the Erreygers concentration index was used, and regression-based decomposition analyses were utilized to unravel the determinant's contribution to the observed inequalities. The Blinder-Oaxaca type decomposition is also used to decompose the urban-rural disparity into the factors. RESULTS: Our analysis results showed that the prevalence of 1+ANC and 4+ANC visits has increased across all the determinants, although the rate of 4+ANC visits remains notably low. The magnitudes of socioeconomic inequality in 4+ANC visits represented an irregular pattern at both the national and urban levels, whereas it increased gradually in rural Bangladesh. However, inequalities in 1+ANC visits declined substantially after 2011 across the national, rural and urban areas of Bangladesh. Decomposition analyses have suggested that wealth status, women's education, place of residence (only for 4+ANC visits), caesarean delivery, husband education, and watching television (TV) are the main determinants to attribute and changes in the level of inequality and urban-rural disparity between the years 2011 and 2017. CONCLUSIONS: According to the findings of our study, it is imperative for authorities to ensure antenatal care visits are more accessible for rural and underprivileged women. Additionally, should focus on delivering high-quality education, ensuring the completion of education, reducing income disparity as well as launching a program to enhance awareness about health facilities, and the impact of caesarean delivery.

Anion-directed structural tuning of two azomethine-derived Zn2+ complexes with optoelectronic recognition of Cu2+ in aqueous medium with anti-cancer activities: from micromolar to femtomolar sensitivity with DFT revelation.

Herein, two novel mononuclear transition metal Zn2+ complexes i.e. [Zn(HL)(N3)(OAc)] (NS-1) & [Zn(HL)2(ClO4)2] (NS-2) have been synthesised using a tridentate clickable Schiff base ligand, HL (2-methyl-2-((pyridin-2-ylmethyl)amino)propan-1-ol), and the polyatomic monoanions N3- and ClO4- for NS-1 and NS-2 respectively. Interestingly, NS-1 and NS-2 have been explored for the detection of Cu2+ with an LOD of 48.6 fM (response time ∼6 s) and 2.4 µM respectively through two mutually independent pathways that were studied using sophisticated methods like UV-Vis, cyclic voltammetry, ESI-MS etc. with theoretical DFT support. Herein, both chemosensors are equally responsive towards the detection of Cu2+ in aqueous as well as other targeted real field samples with appreciable recovery percentage (74.8-102%), demonstrating their practical applicability. Moreover, the detection of unbound Cu2+ in a human urine specimen was also analysed which may be helpful for the diagnosis of Cu2+-related disorders like Wilson's disease. Taking one step ahead, TLC strips have been employed for on-field detection of the targeted analytes by contact mode analysis. Additionally, the anti-cancer activity of these complexes has also been studied on breast cancer cells with the help of the MTT assay. It has been found that at a 0.5 mM dose, both NS-1 and NS-2 could kill 81.4% and 73.2% of cancer cells respectively. However, it has been found that NS-1 destroys normal cells together with cancer cells. Hence, NS-2 could be administered as a better anticancer drug for MDA-MB-231 cancer cells in comparison with NS-1. In a nutshell, the present work describes how anion-directed synthesis of two architecturally different metal complexes leads toward the detection of the same analyte via an independent chemodosimetric pathway along with their anti-cancer activities on breast cancer cells.

Prevalence of hemoglobinopathy, ABO and rhesus blood groups in rural areas of West Bengal, India.

BACKGROUND: Hemoglobinopathies are a group of inherited disorders of hemoglobin synthesis. It could be formed a fatal scenario in concern of lacking of actual information. Beside this, ABO and Rh blood grouping are also important matter in transfusion and forensic medicine and to reduce new born hemolytic disease (NHD). MATERIALS AND METHODS: The spectrum and prevalence of various hemoglobinopathies, ABO and rhesus (Rh) blood groups was screened among patients who visited B.S. Medical College and Hospital, Bankura, West Bengal, India. This study was carried out on 958 patients of different ages ranging from child to adults from January to June 2011. High-performance liquid chromatography (HPLC), complete blood count (CBC) and hemagglutination technique were performed for the assessment of abnormal hemoglobin variants, ABO and Rh blood groups, respectively. RESULTS: Results from this study had been shown that there was high prevalence of hemoglobinpathies (27.35%) where ß-thalassemia in heterozygous state occurred more frequent than other hemoglobinopathies. Out of 958 patients, 72.65% were HbAA and 27.35% were hemoglobinopathies individuals where 17.64% ß-thalassemia heterozygous, 2.92% ß-thalassemia homozygous, 3.86% HbAE, 1.15% HbAS trait, 1.25% HbE-ß thalassemia trait and 0.52% HbS-ß thalassemia trait were found. No incidence of HbSS, HbSC, HbCC, HbD and other variants of hemoglobinpathies were observed. The gene frequencies with respect to ABO systems had been shown as O > B > A > AB. Blood group O was the highest (35.8%) and the least percentage distribution was blood group AB (6.68%). Rhesus positive (Rh+) were 97.7%, while the remaining was 2.3% Rhesus negative (Rh-). The frequencies of A(+), B(+), AB(+,) and O(+) blood groups were 22.44%, 33.61%, 6.58%, and 35.07%, respectively. CONCLUSIONS: Remarkable percentages of hemoglobinopathies were prevalent from the present study. An extensive screening of the population is needed to assess the prevalence of hemoglobinopathies, which will help in identification of carriers of hemoglobinopathies and further it will be of assistance in taking adequate therapeutic and preventive measures.

Geographical Appraisal of COVID-19 in West Bengal, India.

Study shows that COVID-19 cases, deaths and recoveries vary in macro level. Geographical phenomena may act as potential controlling factor. The present paper investigates spatial pattern of COVID-19 cases and deaths in West Bengal (WB), India and assumes Kolkata is the source region of this disease in WB. Thematic maps on COVID related issues are prepared with the help of QGIS 3.10 software. As on 15th January 2021, WB has 564032 number of COVID-19 cases which is 0.618% to the total population of the state. However, the COVID-19 case for India is 0.843% and for world is 1.341% to its total population. Lorenz Curve shows skewed distribution of the COVID-19 cases in WB. 17 (90%) districts hold 84.11% of the total population and carry 56.30% of the total COVID-19 cases. However, the remaining two districts-Kolkata and North 24 Parganas-hold remaining 43.70% COVID-19 cases. Correlation coefficient with COVID-19 cases and Population Density, Urban Population and Concrete Roof of their house are significant at 1% level of significance.

Air quality during three covid-19 lockdown phases: AQI, PM2.5 and NO2 assessment in cities with more than 1 million inhabitants.

Implemented quarantine due to the ongoing novel coronavirus (agent of COVID-19) has an immense impact on human mobility and economic activities as well as on air quality. Since then, and due to the drastic reduction in pollution levels in cities across the world, a large discussion has been magnetized regarding if the lockdown is an adequate alternative counter-measure for enhancing air quality. This paper aimed at studying the Air Quality Index (AQI), PM2.5, and tropospheric NO2 levels in three lockdown phases (before, during, and after) among 21 cities around the world. Simple before/after comparison approach was carried out to capture the declining trend in air pollution levels caused by the lockdown restrictions. The results showed that the frequency distribution for NO2 is more variable than that for PM2.5, and the distribution is flatter from 2020 to the baseline 2018-2019 period. Besides, AQI, in most of the cities, has varied from high to mild pollution during the lockdown and was moderate before. Although during the lockdown, a reduction of 3 to 58% of daily NO2 concentrations was observed across the cities, an increase was detected in three cities including Abidjan (1%), Conakry (3%), and Chengdu (10%). Despite this mixed trend, the NO2 time series clearly showed the effect of the unlocking phase where the NO2 levels increased in almost all cities. Similarly, PM2.5 concentrations have increased in the post-lockdown period, with 50% of the cities reporting significant positive differences between the lock and the unlock phase. Then, the levels of PM2.5 were higher at the pre-lockdown phase than at any other time exhibiting a "U" shape. In addition, during Ramadan, it was noted that altered patterns of daily activities in some Islamic cities have a significant negative impact on air quality.

Metal-complexes as ligands to generate asymmetric homo- and heterodinuclear M(A)(III)M(B)(II) species: a magneto-structural and spectroscopic comparison of imidazole-N versus pyridine-N.

Ten hetero- and homodinuclear M(A)(III)M(B)(III) complexes, 1-10, containing the metal centers Fe(III)Zn(II) (1), Fe(III)Cu(II) (2), Fe(III)Ni(II) (3), Fe(III)Fe(II) (4), Fe(III)Mn(II) (5), Cr(III)Ni(II) (6), Cr(III)Zn(II) (7), Ga(III)Ni(II) (8), Co(III)Fe(II) (9), and Mn(III)Mn(II) (10) are described. The tridentate ligation property of the divalent metal complexes tris(1-methylimidazole-2-aldoximato)metal(II) with three facially disposed pendent oxime O-atoms has been utilized to generate the said complexes. Complexes were characterized by various physical methods including MS, IR, UV-vis, Mossbauer and EPR spectroscopy, cyclic voltammetry (CV), variable-temperature (2-290 K) magnetic susceptibility, and X-ray diffraction techniques. Binuclear complexes 1-10 contain three oximato anions as bridging ligands and are isostructural in the sense that they all contain a metal(III) ion, LM(A)(III) (L = 1,4,7-trimethyl-1,4,7-triazacyclononane), in a distorted octahedral environment M(A)(III)N(3)O(3) and a second six-coordinated divalent metal ion, M(B)(II), in a trigonally distorted M(B)(II)N(6) geometry. A comparison of the cyclic voltammograms of the complexes with those of similar systems reveal both ligand-centered and metal-centered redox processes. Complexes 2, 3, 5, and 6 display antiferromagnetic exchange coupling of the neighboring metal centers in the order Fe(III)Mn(II) (5) < Fe(III)Ni(II) (3) < Fe(III)Cu(II) (2) whereas Fe(III)Ni(II) (3) > Cr(III)Ni(II) (6). On the contrary, complex 10, containing high-spin Mn(III) and Mn(II) centers, exhibits ferromagnetic coupling yielding a "high-spin" molecule with an S(t) = (9)/(2) ground state. X-band electron paramagnetic resonance (EPR) spectroscopy for 6, Cr(III)Ni(II) and 3, Fe(III)Ni(II) has been used to establish the electronic ground state in great detail and to complement the magnetic susceptibility measurements. Moreover, computational results have been included to compare the sigma-bonding character of the nitrogen lone pair in imidazole-containing ligand and the analogous pyridine-containing oxime.

A star-shaped heteronuclear Cr(III)Mn(II)3 species and its precise electronic and magnetic structure: spin frustration studied by X-ray spectroscopic, magnetic, and theoretical methods.

Molecular magnets incorporate transition-metal ions with organic groups providing a bridge to mediate magnetic exchange interactions between the ions. Among them are star-shaped molecules in which antiferromagnetic couplings between the central and peripheral atoms are predominantly present. Those configurations lead to an appreciable spin moment in the nonfrustrated ground state. In spite of its topologically simple magnetic structure, the [Cr(III)Mn(II)(3) (PyA)(6)Cl(3)] (CrMn(3)) molecule, in which PyA represents the monoanion of syn-pyridine-2-aldoxime, exhibits nontrivial magnetic properties, which emerge from the combined action of single-ion anisotropy and frustration. In the present work, we elucidate the underlying electronic and magnetic properties of the heteronuclear, spin-frustrated CrMn(3) molecule by applying X-ray magnetic circular dichroism (XMCD), as well as magnetization measurements in high magnetic fields, density functional theory, and ligand-field multiplet calculations. Quantum-model calculations based on a Heisenberg Hamiltonian augmented with local anisotropic terms enable us not only to improve the accuracy of the exchange interactions but also to determine the dominant local anisotropies. A discussion of the various spin Hamiltonian parameters not only leads to a validation of our element selective transition metal L edge XMCD spin moments at a magnetic field of 5 T and a temperature of 5 K but also allows us to monitor an interesting effect of anisotropy and frustration of the manganese and chromium ions.

Exploratory studies on azido-bridged complexes (Ni2+ and Mn2+) as dual colourimetric chemosensors for S2- and Ag+: combined experimental and theoretical outcomes with real field applications.

We report two isostructural dinuclear transition metal complexes [M2(HL)2(N3)4], where M = Ni2+ (BS-1), Mn2+ (BS-2), and HL is (2-methyl-2-((pyridin-2-ylmethyl)amino)propan-1-ol) and investigate them as molecular sensors towards hazardous entities. BS-1 shows high selectivity towards the S2- and Ag+ ions, easily observed by the naked eye colour change and its detection limit in aqueous solutions for the S2- ion was calculated as 0.55 µM with a binding constant of 3.28 × 105 M-1, while the limit for the Ag+ ion is 21.8 µM. Notably, BS-2 shows good selectivity towards the Ag+ ion with a detection limit of 10.84 µM. Spectroscopic and DFT studies shed light on the mechanistic course of interaction between the host and guest entities, suggesting a sulphide-mediated reduction of the azide mechanism. In a nutshell, these simple transition metal complexes were exploited for discriminately detecting hazardous analytes with real field applications in analytical science (via. "Dip-Stick" approach) as well as engineering science, which provides a significant contribution in the recent advancement of supramolecular chemistry.

A magneto-structural study of a hexanuclear (V(IV)=O)6-complex and a tetranuclear mixed-valent [V(III)2V(IV)2] species.

Syntheses, crystal structures, and magnetic properties are reported for a hexametallic and a mixed-valent tetrametallic vanadium cluster, namely [Na(L(1))(6)(V(IV)=O)(6)]ClO(4) (1) and [(L(2))(2)V(III)(2)V(IV)(2)(mu-Cl)(6)Cl(4)] (2), where H(2)L(1) represents N-methyldiethanolamine and H(2)L(2) N'N'-di(3,5-di-tert-butyl-salicylidene)-1,3-diaminobenzene. The structure of the cation in 1 is comprised of a hexagon of six (V(IV)=O) units, in which a sodium ion is encapsulated in the center of the hexagon. Thus, the hexametalate ring contains six d(1) ions, each of which is in an octahedral environment of O(5)N atoms. Magnetic studies reveal the cluster to exhibit ferromagnetic exchange interactions (J = +16.7 +/- 0.3 cm(-1)), which is rationalized by the orthogonal neighboring xy planes of d(1) V(IV)=O ions. The structure of complex 2 can be considered as two mixed-valent face-sharing bioctahedral units of [V(III)(mu-Cl)(3)V(IV)] bridged by two m-phenylene linkers. The V(1)(III)...V(2)(IV) distances of av. 3.10 A preclude metal-metal bonding. Variable-temperature magnetic susceptibility data are fitted to obtain the parameters J(1) = -47.6 cm(-1), J(2) = +1.5 cm(-1), g(V(III)) = 1.95, g(V(IV)) = 1.85 (H = -2J x S(i).S(j)). The ferromagnetic coupling J(2) operates at a distance of approximately 7.09 A between two vanadium centers through the spin polarization mechanism due probably to the topology (1,3-substitution) of the m-phenylene bridges. The X-band electron paramagnetic resonance (EPR) spectrum analyzed with S(t) = 1 shows that the mixed-valent V(III)V(IV) species has indeed been formed and the tetranuclear core remains intact in solution. The hyperfine coupling constants indicate the localized mixed-valence nature of 2.

Polynuclear nickel(II) complexes: a magnetostructural study of Ni(II)4, Ni(II)6, and Ni(II)9 species with oxime ligands.

Syntheses, crystal structures, and magnetic properties are reported for a tetrametallic (complex 1), a nonametallic (complex 2), and two hexametallic (complexes 3 and 4) nickel(II) clusters, namely, [Ni(4)(HL(1))(2)(mu-OAc)(2)(MeOH)] (1), [Ni(9)(L(2))(10)(mu(3)-OH) (2) (mu-OH) (2) (mu-OH (2))(2)(OH(2))(6)](ClO(4)) (4) (2), [Ni(6)(L(2))(9)(L(2)H)(MeOH)(H(2)O)(2)](ClO(4))(3) (3), and [Ni(6)(L(3))(3)(mu(3)-O)(2)](ClO(4))(2) (4), where H(4)L(1) represents N,N'-dimethyl-N,N'-ethylene-bis(5-bromo-3-formyloxime-2-hydroxybenzylamine); HL(2), 1-methylimidazole-2-aldoxime; and H(2)L(3), N,N'-bis(2,3-butanedionemonoxime-2-ene)-3(aminomethyl)benzylamine. The structure of 1 can be considered as two face-sharing bioctahedral units of [Ni(2)(mu-O(phen))(2)(mu-OAc)] bridged by a two-atom (-N-O-) oximate linker. The Ni(II)...Ni(II) distances of av. 2.935 A preclude metal-metal bonding, although they are remarkably short. Variable-temperature magnetic susceptibility data are fitted to obtain the parameters J (1) = +8.0 cm(-1), J(2) = -16.0 cm (-1), and g = 2.19 (H= -2 JS(i) x S(j)). The ferromagnetic coupling J (1) operates between the nickel(II) centers in the face-sharing bioctahedral units, whereas J(2) represents the antiferromagnetic interactions mediated by a single (-N-O-) bridge separating the two nickel centers at a distance of approximately 4.71 A. A rationale for the disparate nature of interactions based on a comparison with those reported in the literature is forwarded. The structure of 2 consists of two [Ni(4)(L(2))(5)] units linked covalently to a central nickel atom by four oximate and two hydroxy oxygen atoms, resulting in a central octahedral NiO(6) core and thus yielding the nonanuclear nickel(II) cluster. The magnetic data were analyzed by a "two-J" model, yielding pairwise antiferromagnetic exchange interactions, J(1) = -24.0 cm (-1) and J(2) = -5.8 cm (-1), between the nickel centers. The spin ground state of S(t) = 1.0 has been confirmed by magnetization measurements (variable-temperature, variable-field) at different fields. The structure of 3 contains six nickel(II) centers, each of which is six-coordinated but with different coordination environments: NiN(6), NiO(6), NiN(3)O(3)(2x), NiN(4)O(2), and NiNO(5). The ground-state spin has been observed to be S(t) = 1.0 with the axial zero-field splitting parameter D = -7.2 cm(-1). Complex 4 is a rare example of dimeric [Ni(3)(mu(3)-O)](4+) units, in which each of six nickel(II) centers is in square-planar geometry with low-spin d(8) Ni(II) centers, thus rendering diamagnetism to complex 4.

Anion-mediated bio-relevant catalytic activity of dinuclear nickel(ii) complexes derived from an end-off compartmental ligand.

Four dinuclear nickel(ii) complexes, namely [Ni4(L)2(H2O)8(µ2-H2O)2](NO3)6(H2O)6 (1), [Ni2(L)Cl2(µ-Cl)(CH3OH)] (2), [Ni2(L)(OAc)2(H2O)2]Br (3) and [Ni2(L)(H2O)4(µ2-OH)] (H2O)X(I)X (4), have been synthesized using a template synthesis technique by adding nickel(ii) salts (nitrate/chloride/bromide/iodide) to the N4O donor end-off compartmental ligand (HL) obtained via the condensation of 2-(2-pyridyl)ethylamine and 2,6-diformyl-4-isopropyl phenol in methanol. All complexes were characterized with the help of typical physicochemical techniques, and their solid-state structures were assigned from single crystal X-ray analysis. The variable temperature magnetic study reveals that the two nickel centers are antiferromagnetically coupled with J values ranging from -5 to -15 cm-1 in the complexes. The catecholase-like activity of complexes 1-4 was studied using 3,5-di-tert-butylcatechol (3,5-DTBC) as the model substrate in N,N-dimethylformamide (DMF) medium. Complex 1 shows the catecholase activity, while the other complexes were found to be inactive. The phosphatase-like activity of the complexes was also investigated in a 97.5% (v/v) DMF-water mixture using the disodium salt of 4-nitrophenylphosphate (4-NPP) as the model substrate and the reactivity trend was 4 > 1 > 3 > 2. The reasons behind the activity, inactivity and activity trend have been explored. It has been assumed that the anions associated with the complexes are supposed to play a crucial role in the whole event. Complex 1 showed catalytic promiscuity, whereas complexes 2, 3 and 4 should be considered only as the potential hydrolytic catalyst.

Radical-ligand-derived C-N coupling, Ga(III)-radical vs low-spin Co(III)-radical reactivity.

The redox-active ligand 2-(3,5-dimethoxyanilino)-4,6-di- tert-butylphenol, H 2L (OCH3), results in, as expected, a trisradical complex with a low-spin Co(III) center, [Co (III)(L (OCH3) (*)) 3] ( 1), whereas the Ga(III) center yields a coordinated new hexadentate monoradical ligand, [Ga (III)L (*) 1] ( 2), presumably due to the ligand-derived redox activity involving C-H activation.