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In this study five different complexes of Cu(II) were synthesized for the purpose of environmentally notorious mercury sensing and preliminary biological screening. Pyridine‐2,6‐dicarboxylic acid (also known as dipicolinic acid, and abbreviated as H2DPA), 3‐phenyl pyrazole (3‐ppz), 4‐iodo‐1H‐pyrazole (4‐ipz), 4‐nitropyrazole (4‐npz), 4‐bromopyrazole (4‐bpz), and 4‐chloropyrazole (4‐cpz) were chosen as potential ligands. The synthesized complexes labelled as 1–5, namely [Cu(DPA)(3‐ppz)], [Cu(DPA)(4‐ipz)], [Cu(DPA)(4‐npz)], [Cu(DPA)(4‐bpz)], [Cu(DPA)(4‐cpz)], were proposed based on spectroscopic data (FTIR, TGA, and UV‐visible spectroscopy). These complexes feature C=O functionalities that are not involved in coordination and may be used for further applications. The isolated complexes were utilized for detecting Hg(II) ions in water samples. Various concentrations of Hg(II) ions were prepared for detection purposes, and changes in absorption concerning complexes 1–5 were determined using UV‐Visible spectroscopy. It was found that complexes 3 and 4 exhibit efficient sensing abilities towards Hg(II) ions. The antibacterial activities of complexes 1–5 were assessed against S. typhi and E. coli. The complexes 1 and 3 displayed good antibacterial activities against S. typhi (13.67, and 13.56 mm, respectively) while complexes 1, 2 and 4 were found to be efficient against E. coli (11.6, 12.66, 11.31 mm, respectively). The absorption maxima of 2,2‐diphenyl‐1‐picryhydrazyl (DPPH) at 517 nm, considerably shifted upon addition of complexes 1–5. The results reveal that the complexes possess potential free radical scavenging abilities. [ABSTRACT FROM AUTHOR]

Rapid detection of potentially toxic heavy metals like Hg(II) has attracted great attention in the last few decades due to the importance to maintain a safe and sustainable environment for human beings. Coordination chemistry and concepts therein, play an important role in the detection of Hg(II). Size, charge, and nature of the donor atom and the respective cation (metal ion), are crucial in selective interactions between the sensor and metal ions. The sensors designed for the purpose, coordinate to Hg(II) ion through various donor sites, coordination causes a change in the electron density in organic molecules and results in either visible color change or enhancing/quenching fluorescence intensity. Since Hg(II) is soft metal, with d10 electron system, so majority of the sensors have soft donor sites which prefer to coordinate with Hg(II). Oxygen is also present in some chelating ligands which is least preferred coordination site, due to its hard nature. There are several reports of replacing other ligating sites by sulfur for enhanced mercury sensing. In some cases, desulfurization is being detected as clear change in spectral behavior during the sensing process. Efforts are still in progress to design and introduce a sensor with utmost sensitivity and selectivity. In this review, we made an attempt to explain the coordination aspects of Hg(II) detectors, reasons for poor efficiency and possible suggestions to improve the selection criterion of various compounds. It will help researchers to know about important concepts in designing more sensitive and selective sensors for detection of Hg(II) in environmental and biological samples. [ABSTRACT FROM AUTHOR]

Formaldehyde is an organic volatile compound and a commonly used chemical in various construction materials thus causing dwellers to be exposed to it inside a building. Its remediation from indoor air has been carried out through various techniques where potted plants and living walls are at the front foot. It is necessary to study plants under various conditions for their efficiency. We selected three plant species Epipremnum aureum, Chlorophytum comosum, and Spathiphyllum wallisii non-native of Bahrain. These plants were tested under normal conditions in a sealed fumigation box where formaldehyde concentration was kept ∼3 ppm, CO2 ∼ 450 ppm, light intensity 1000 Lx (equal to 13.5 µmol.m−2.s−1), irrigated with tap water. Analysis of Variance (ANOVA) statistical method was performed to test the significant differences of purification efficiencies of the tested indoor plants against HCHO. In addition, the statistical method was used to test the significant difference, if any, of the plants to CO2 emission because of absorbing HCHO. The physical health of plants and their short-term remediation ability reveals that all plants exhibited up to 70% remediation potential and tolerance to remediate the target chemical. It is evident that the impact of local environmental factors on the plants is negligible. NOVELTY STATEMENT: Epipremnum aureum, Chlorophytum comosum, and Spathiphyllum wallisii are non-native plants available in Bahrain for decorative purposes. Their efficiency against formaldehyde under local indoor environment was studied for the first time. Under normal conditions the plant proved to be sufficiently tolerant toward normal conditions. The efficiency in normal soil system is very good. The efficiency of the three species was mutually compared, statistical modeling reveal that they are significantly close to each other in terms of formaldehyde remediation to purify ambient air. [ABSTRACT FROM AUTHOR]

The current investigation describes the synthesis of four novel methylene blue (MB) salts of benzene sulfonate derivatives, featuring bulky anionic groups. The process involves treating chloride salt of MB with sodium salts of 4‐aminobenzene sulfonate, 4‐styrenebenzene sulfonate, 3,7‐naphthalene disulfonate, and anthraquinone‐1,5‐naphthalene disulfonate to substitute the chloride ion with benzoate sulfonate anion in MB‐chloride. The synthesis includes quaternizing MB‐chloride with the corresponding benzene sulfonate in minimal aqueous solvent to promote precipitation. The resultant precipitates were subsequently dissolved in an appropriate solvent to enable the crystallization of the ultimate product. The dissolution occurs either at ambient temperature or with heat. The crystals of the resultant salts were characterized using various analytical techniques like UV‐visible, and FT‐IR spectroscopy, TGA, single crystal X‐ray diffraction and powder X‐ray diffraction analysis. The UV‐visible spectroscopic results, frontier molecular orbital, density of states, molecular electrostatic potentials, and HOMO‐LUMO energy gaps were estimated by DFT. Structural analysis revealed that supramolecular structure of compounds achieved stabilization through electrostatic interactions, a diverse range of both conventional and non‐conventional hydrogen bonds, π–π stacking interactions, and other short‐range interactions. The investigation delves into intricate details and offers a thorough discussion of the fundamental principles that contribute to the formation and stabilization of supramolecular structures. [ABSTRACT FROM AUTHOR]

3-(2-naphthoyl)-1,1-dibutylselenourea was prepared and Sol-gel silica was doped with it. The selenourea organic derivative was characterised in solid state by single-crystal X-ray diffraction, and doped sol-gel materials were characterised by FT-IR and SEM. The doping results were verified from their characteristic prominent bands v(cm−1) = 1753 and 1199 predominantly assigned to C = O and C = Se, respectively. The processed sol-gel was used as adsorbent to investigate its efficiency for removal of M(II) ions from aqueous solution using batch techniques (M = Pb and Zn). The porosity study reveals that the doped sol-gel contains pores which are responsible for the adsorption of metal ions, besides pores present in the material, the ligand possesses active sites (-NH, = O, = Se) readily available for coordination with metal ions, and the material thus acts as efficient chelating agent. Adsorption kinetics, isotherm, effect of equilibration time, initial concentration of adsorbate, and pH on the metal extraction were studied and conditions were optimised. Metal remediation capacity of the hybrid material i.e. sol-gel is pH dependent, and maximum removal was obtained at pH 5 (Pb) and pH 6 (Zn) with in 35 and 15 minutes, respectively. The prepared adsorbent shows rapid equilibrium and enough stability at elevated temperature in the given medium. Desorption of metal ions was carried out in 0.1 M HNO3 solution, and thereafter, sol-gel silica adsorbent was successfully regenerated and reused. [ABSTRACT FROM AUTHOR]

The issue of heavy metals contamination of environmental segments is becoming serious day by day with industrial and electronic developments. Economic growth and environmental issue are parallel in many aspects. For instance, increased number of vehicles and rapid industrialisation are indicators of economic growth. Economic run is important and shall continue because it is associated with global needs while environmental pollution is otherwise. Necessary steps are required to be taken to control the release of unwanted chemicals including heavy metals and arsenic to the environment. Arsenic is present in water both in its organic and inorganic form. Among these forms inorganic arsenic (As(III) and As(V)) are very toxic. WHO has recommended a threshold limit for As(III) in drinking water i.e. 10 ppb (equivalent to 10 μg L−1 or 133 nM). Sensing of arsenic has been made possible due to several techniques with a wide range of detection limit. Herein very recent As(III) sensors with detection limit below 10 ppb, mechanism of detection at certain instances, interferants during measurements and future goals have been discussed. Further, the review article covers literature mostly from 2015 to 2021. [ABSTRACT FROM AUTHOR]

The variant SARS-CoV-2 (COVID-19) has affected the entire globe; it has caused acute respiratory illnesses and has led to massive environmental problems associated with extra medical waste and single-use plastics. Herein the total quantity of waste generated in the selected GCC countries from different sources has been calculated. The popularity of the medical waste issue through using relative search volume was investigated to associate it with the quantities of Waste. Data was collected from the first COVID-19 case in the respective country until March 26, 2022, from the public domains, "Worldmeter", "Our World in Data" and "Google Trends". Autoregressive Integrated Moving Average (ARIMA) was used to predict the amount of CMW. The calculated values are 1107.980 kg/day from the facemask used by the public, 2,554,812 kg from vaccination, 2,595,772 kg from PCR tests, also the predicted daily total amount of COVID-19 related Medical Waste (CMW) by the end of 2022 (December 31, 2022) to be 3667.25 kg/day. The trend in the generation of CMW has been identified in selected countries. Generally, the waste is expected to get minimized, but it is a lesson for future planning. Especially With extensive vaccination, the cases are drastically decreased, and life is resuming in the regions. [ABSTRACT FROM AUTHOR]

The Fe(III), Ni(II) and Zn(II) salts were treated with MB+ to obtain metal complexes MB[FeCl4], (MB)2[NiCl4], MB(ClO4) and to explore the coordination behavior of the organic cation. Crystals were grown by soft grinding and solution techniques. The resultant compounds were fully characterized by UV‐visible spectroscopy, TGA, single crystal and powder XRD. UV‐Visible, Frontier molecular orbital, Density of states, Molecular electrostatic potentials, and band gap were estimated theoretically by DFT. The purity and crystallinity of material was measured with the help of powder X‐ray diffraction analysis while their thermal stability was measured with the help of thermogravimetric analysis. DFT study revealed that the chlorinated metal center helps to stabilize the HOMO and LUMO values which are ultimately responsible for the lower energy gap. Complex (MB)2[NiCl4] has the lowest bandgap 0.48 eV which is due to the presence of one extra MB+ and also due to the electron‐rich nature of Ni(II). The crystal structure of all compounds is stabilized by strong electrostatic, hydrogen bonding, π‐π‐stacking and other short‐interactions. Molecular electrostatic potentials ESP surface shows that chlorinated metal centers are electron rich in nature and more electron density are found in ClO4- ${{ClO}_{4}^{-}}$ center. The supramolecular chemistry of the resultant solids is discussed in detail. [ABSTRACT FROM AUTHOR]

Abstract Metal–organic-frameworks (MOFs) have emerged as promising candidates in different scientific disciplines owing to their intriguing characteristics. Their unique structural properties, including large surface area to volume ratio with multi-functionalities and ultra-high porosity, tunability, uniformity, and easy derivation and fabrication, render them effective materials for sensing applications. The detection of heavy metals in different environmental matrices using various MOF-based sensors is in practice. They include luminescent, electrochemical, electrochemiluminescent, colorimetric, and surface-enhanced Raman scattering, are of great interest. This review elaborates on selected synthetic methods for the fabrication of MOF-based sensors, modification routes for tailoring and enhancing the desired properties, basic characterization techniques, and their limitations in the detection of heavy metals. Also, it emphasizes the use of various types of MOF-based sensors alternatively for the detection of different heavy metals such as Fe(III), Cr(III), Hg(II), Cd(II), and Pb(II) in addition to a normal metal Al(III). A collection of recent references is provided for researchers interested in such applications. Results from the literature have been summarized in tables which give an easy comparison and will help to develop efficient materials. [ABSTRACT FROM AUTHOR]

Coordination complexes (1–4) of 2-amino-4-methylbenzothiazole and 2-amino-3-methylpyridine with Cu(CH3COO)2 and AgNO3 were prepared and characterized by UV/Vis and FT-IR spectroscopy. The molecular structure for single crystals of silver complexes (2 and 4) were determined by X-ray diffraction. The coordination complex (2) is monoclinic with space group P21/c, wherein two ligands are coordinated to a metal ion, affording distorted trigonal geometry around the central Ag metal ion. The efficient nucleophilic center, i.e., the endocyclic nitrogen of the organic ligand, binds to the silver metal. Ligands are coordinated to adopt cis arrangement, predominantly due to steric reasons. The O(2) and O(3) atoms of the N O 3 − group further play an important role in such type of ligand arrangement by hydrogen bonding with the NH2 group of ligands. Complex (4) is orthorhombic, P212121, comprising two molecules of 2-amino-3-methylpyridine as ligand coordinated with the metal ion, affording a polymeric structure. The coordination behavior of the ligand is identical to that in complex 2, wherein ring nitrogen is coordinated to the metal center and bridged to another metal ion through an NH2 group. The resulting product is polymeric in nature with the Ag metal in the backbone and ligand as the bridge. Compounds (2–4) were found to be luminescent, while 1 did not show such activity. All compounds were screened for their preliminary biological activities such as antibacterial, antioxidant and enzyme inhibition. Compounds exhibited moderate activity in these tests. [ABSTRACT FROM AUTHOR]

Formaldehyde evolves from various household items and is of environmental and public health concern. Removal of this contaminant from the indoor air is of utmost importance and currently, various practices are in the field. Among these practices, indoor plants are of particular importance because they help in controlling indoor temperature, moisture, and oxygen concentration. Plants and plant materials studied for the purpose have been reviewed hereunder. The main topics of the review are, mechanism of phytoremediation, plants and their benefits, plant material in formaldehyde remediation, and airtight environmental and health issues. Future research in the field is also highlighted which will help new researches to plan for the remediation of formaldehyde in indoor air. The remediation capacity of several plants has been tabulated and compared, which gives easy access to assess various plants for remediation of the target pollutant. Challenges and issues in the phytoremediation of formaldehyde are also discussed. Novelty statement: Phytoremediation is a well-known technique to mitigate various organic and inorganic pollutants. The technique has been used by various researchers for maintaining indoor air quality but its efficiency under real-world conditions and human activities is still a question and is vastly affected relative to laboratory conditions. Several modifications in the field are in progress, here in this review article we have summarized and highlighted new directions in the field which could be a better solution to the problem in the future. [ABSTRACT FROM AUTHOR]