Sulphated alumina tungstic acid (SATA): a highly efficient and novel heterogeneous mesostructured catalyst for the synthesis of pyrazole carbonitrile derivatives and evaluation of green metrics

A novel mesostructured catalyst sulphated alumina tungstic acid (SATA) has been prepared by an easy route. Various techniques such as IR, XRD, SEM, EDX, TEM, TGA and BET were used to characterize the synthesized catalyst. The catalytic activity of the meso material has been explored by synthesizing a series of new pyrazole carbonitrile derivatives from aromatic aldehydes, ethylcyanoacetate, phenylhydrazine/hydrazine hydrate in ethanol under reflux conditions. Furthermore, the “greenness” of this protocol when estimated by green metrics, displayed satisfactory results. The protocol is free from column chromatography, and toxic solvents and is more efficient as compared to reported ones.

A novel mesostructured catalyst sulphated alumina tungstic acid (SATA) has been prepared by an easy route.     

Synthesis of N-aryl β-amino acid derivatives via Cu(ii)-catalyzed asymmetric 1,4-reduction in air

In the presence of the inexpensive and stable stoichiometric reductant polymethylhydrosiloxane (PMHS) as well as certain amounts of appropriate alcohol and base additives, the non-precious metal copper-catalyzed asymmetric 1,4-hydrosilylation of β-aryl or β-alkyl-substituted N-aryl β-enamino esters was well realized to afford a diverse range of N-aryl β-amino acid esters in high yields and excellent enantioselectivities (26 examples, 90–98% ee). This approach tolerated the handling of both catalyst and reactants in air without special precautions. The chiral products obtained have been successfully converted to the corresponding enantiomerically enriched β-lactam and unprotected β-amino acid ester, which highlighted the synthetic utility of the developed catalytic procedure.

Non-precious metal copper-catalyzed asymmetric 1,4-hydrosilylation of β-aryl or β-alkyl-substituted N-aryl β-enamino esters proceeded in air in high yields and excellent enantioselectivities (26 examples, 90–98% ee).     

Highly-efficient removal of Pb(ii), Cu(ii) and Cd(ii) from water by novel lithium,sodium and potassium titanate reusable microrods

In this work, we report on the efficient removal of heavy metal ions with nanostructured lithium, sodium and potassium titanates from simulated wastewater. The titanates were obtained via a fast, easy and cost effective process based on extraction of sulfate ions from the crystals of titanyl sulfate and their replacement with hydroxyl groups of NaOH, LiOH and KOH solutions leaving the Ti–O framework intact. The as-prepared titanates were carefully examined by scanning and transmission electron microscopy. Furthermore, the effect of contact time, pH, annealing temperature, together with adsorption in real conditions including competitive adsorption and reusability were studied. It was found that the maximum adsorption capacity, as calculated from the Langmuir adsorption model, is up to 3.8 mmol Pb(ii) per g, 3.6 mmol Cu(ii) per g and 2.3 mmol Cd(ii) per g. Based on the characterization results, a possible mechanism for heavy metal removal was proposed. This work provides a very efficient, fast and convenient approach for exploring promising materials for water treatment.

This work provides a very efficient, fast and convenient approach for exploring promising materials for water treatment.     

Two Cu(ii)-triadimenol complexes as potential fungicides: synergistic actions and DFT calculations

Two Cu(ii) complexes, namely, [CuL₄(H₂O)₂]·2NO₃·2CH₃OH 1 and [CuL₂(CH₃COO)₂] 2, (L = (1S,2R)-1-(4-chlorophenoxy)-3,3-dimethyl-1-(1,2,4-triazol-1-yl)butan-2-ol, triadimenol, a commercial 1,2,4-triazole pesticide) were synthesized and characterized by elemental analysis, IR spectra, UV-Vis spectra and single crystal X-ray diffraction. Crystal structural analysis shows that the different types of salts (copper acetate is covalent, while copper nitrate is ionic) contribute to different crystal structures: complex 1 consists of one copper cation, four ligands, two coordinated water molecules, two free nitrate anions and two uncoordinated methanol molecules. Complex 2 is composed of one copper cation, two ligands and two acetate anions, without free molecules. The two complexes and the ligand triadimenol were also screened for antifungal activities against four selected fungi. The antifungal results reveal that both the complexes show better bioactivities in comparison with L, and that complex 1 has higher bioactivities than complex 2. To elaborate the reasons of the enhanced bioactivities after complexation, the interaction levels between Cu²⁺ cation and triadimenol, as well as the density functional theory (DFT) method were carried out. The results indicate that three factors made the antifungal activities stronger after forming Cu(ii) complexes: new active site of copper cation, synergic interactions between Cu²⁺ cation and L, and improved penetration of the metal complexes into the lipid membranes.

Two Cu(ii) complexes of triadimenol show greater antifungal activities than the ligand triadimenol. Moreover, the synergistic interactions and DFT calculations were both carried out to elucidate the reasons for the enhanced bioactivities.     

Removal of Pb(ii) and Cd(ii) from wastewater using arginine cross-linked chitosan–carboxymethyl cellulose beads as green adsorbent

A one pot approach has been explored to synthesize crosslinked beads from chitosan (CS) and carboxymethyl cellulose (CM) using arginine (ag) as a crosslinker. The synthesized beads were characterized by FTIR, SEM, EDX, XRD, TGA and XPS analysis. The results showed that CS and CM were crosslinked successfully and the obtained material (beads) was analyzed for adsorption of Cd(ii) and Pb(ii) by using batch adsorption experiments; parameters such as temperature, contact time, pH and initial ion concentration were studied. Different kinetic and thermodynamic models were used to check the best fit of the adsorption data. The results revealed that the kinetics data of the adsorption of Pb(ii) and Cd(ii) ions shows the best fit with the pseudo second order model whereas the thermodynamics data shows the best fit with the Langmuir isotherm with maximum adsorption capacities of 182.5 mg g⁻¹ and 168.5 mg g⁻¹ for Pb(ii) ions Cd(ii) ions, respectively. For the recovery and the regeneration after the one use of the beads, several adsorption–desorption cycles were carried out to check the reusability and recovery of both the metal ion and the adsorbent without the loss of maximum adsorption efficiency.

Remediation of Pb(ii) and Cd(ii) containing wastewater by arginine crosslinked chitosan/carboxymethyl cellulose beads.     

Correction: Removal of Pb(ii) and Cd(ii) from wastewater using arginine cross-linked chitosan–carboxymethyl cellulose beads as green adsorbent

Correction for ‘Removal of Pb(ii) and Cd(ii) from wastewater using arginine cross-linked chitosan–carboxymethyl cellulose beads as green adsorbent’ by Kaiser Manzoor et al., RSC Adv., 2019, 9, 7890–7902.

The authors regret that an incorrect version of the SEM image shown in Fig. 3b was included in the original article. The correct version of Fig. 3 is presented below.Open in a separate windowFig. 3SEM micrographs of (a) CS, (b) CM, (c) CS-ag-CM, (d) Pb(II)/Cd(II)-CS-ag-CM(e) Pb(II)/Cd(II)-CS-ag-CM and EDX spectrum of (f) CS-ag-CM and (g) Pb(II)/Cd(II)-CS-ag-CM.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

Theoretical and experimental investigation of anticancer activities of an acyclic and symmetrical compartmental Schiff base ligand and its Co(ii), Cu(ii) and Zn(ii) complexes

A compartmental Schiff base ligand, 2,2′-((((((2-hydroxypropane-1,3-diyl)bis(oxy))bis(2,1-phenylene))bis(methylene))bis(azanylylidene))bis(methanylylidene))bis(4-bromophenol) (H₃L^Br) and its complexes with cobalt(ii), copper(ii) and zinc(ii) including, [Co(HL^Br)] (1), [Cu₂(L^Br)(μ-1,3-OAc)]·MeOH (2) and [Zn(HL^Br)] (3) were prepared using template synthesis and characterised by elemental analysis, FT-IR and ¹H NMR spectroscopies and single-crystal X-ray diffraction. In the structure of complexes 1 and 3 the metal atom has a MN₂O₂ environment with tetrahedral geometry while complex 2 has a binuclear structure with a MNO₄ environment and square planar geometry around the copper atom. The ability of all compounds to interact with the nine biomacromolecules (BRAF kinase, CatB, DNA gyrase, HDAC7, rHA, RNR, TrxR, TS and Top II) are investigated by docking calculations. For examination of the docking results, the in vitro activities of eight compounds against the human leukemia cell line K562 was investigated by evaluation of IC₅₀ values and mode of cell death (apoptosis).

A compartmental Schiff base ligand and its copper, cobalt and zinc complexes were prepared. The in vitro activities of all compounds against the human leukemia cell line K562 were investigated along with docking and DFT studies.     

Uniform Cu/chitosan beads as a green and reusable catalyst for facile synthesis of imines via oxidative coupling reaction

A nonprecious metal and biopolymer-based catalyst, Cu/chitosan beads, has been successfully prepared by using a software-controlled flow system. Uniform, spherical Cu/chitosan beads can be obtained with diameters in millimeter-scale and narrow size distribution (0.78 ± 0.04 mm). The size and morphology of the Cu/chitosan beads are reproducible due to high precision of the flow rate. In addition, the application of the Cu/chitosan beads as a green and reusable catalyst has been demonstrated using a convenient and efficient protocol for the direct synthesis of imines via the oxidative self- and cross-coupling of amines (24 examples) with moderate to excellent yields. Importantly, the beads are stable and could be reused more than ten times without loss of the catalytic performance. Furthermore, because of the bead morphology, the Cu/chitosan catalyst has greatly simplified recycling and workup procedures.

Uniform, spherical Cu/chitosan beads prepared using a software-controlled flow system as a green and conveniently recyclable catalyst for the efficient synthesis of various imines in short reaction time.     

A facile green and one-pot synthesis of grape seed-derived carbon quantum dots as a fluorescence probe for Cu(ii) and ascorbic acid

In this study, an on–off–on fluorescence probe for the detection of trace Cu(ii) and ascorbic acid (AA) based on biomass-derived sulfur and nitrogen double heteroatom-doped carbon dots (N,S-CDs) was designed. For the first time, the probe (N,S-CDs) was prepared from grape seeds and thiourea as the precursor. Cu(ii) was added to the carbon point solution, the fluorescence intensity (FL) of N,S-CDs was strongly quenched (switch OFF) and the fluorescence probe turned to “ON” (switch ON) with the addition of AA. Under the optimal conditions, the as-synthesized N,S-CDs had a good detection performance for Cu(ii) and AA assay with the linearity ranges from 150–500 μg mL⁻¹ and 0.1–400 μg mL⁻¹, and the LODs were 0.048 mg L⁻¹ and 0.036 mg L⁻¹, respectively. The as-prepared N,S-CDs exhibited a low cytotoxicity and a good biocompatibility, which show their potential for application in the biological imaging of living cells.

In this study, an on–off–on fluorescence probe for the detection of trace Cu(ii) and ascorbic acid (AA) based on biomass-derived sulfur and nitrogen double heteroatom-doped carbon dots (N,S-CDs) was designed.     

Facile and green preparation of solid carbon nanoonions via catalytic co-pyrolysis of lignin and polyethylene and their adsorption capability towards Cu(ii)

Carbon nanomaterials, such as carbon nanoonions (CNOs), possess promising applications in various fields. There are urgent demands to synthesize carbon nanomaterials from a green and renewable carbon source. In this study, solid CNOs with relatively uniform size distribution (with diameters of about 30–50 nm), abundant structure defects and oxygen-containing surface functional groups (such as –OH and –COOH) are developed from co-pyrolysis of lignin (LG) and polyethylene (PE) in the presence of Ni-based catalysts. The type of catalyst, the concentration of catalyst and catalytic co-pyrolysis temperature play important roles in the morphologies and properties of CNOs as confirmed by TEM and SEM. Furthermore, the produced CNOs can act as a low-cost and highly-efficient adsorbent to remove Cu(ii) from aqueous solution according to a homogeneous monolayer, chemical action-dominated, endothermic and spontaneous process. The theoretical maximum adsorption capacity of CNOs calculated from the Langmuir model is 100.00 mg g⁻¹. Surface deposition, complexation, π electron–cation interaction and electrostatic interaction are responsible for the adsorption of Cu(ii) using the prepared CNOs.

Solid carbon nanoonions with relatively uniform size distribution, abundant structure defects and oxygen-containing surface functional groups can be prepared from lignin with the introduction of polyethylene and Ni-based catalysts.     

Nano-Fe3O4@walnut shell/Cu(ii) as a highly effective environmentally friendly catalyst for the one-pot pseudo three-component synthesis of 1,3-oxazine derivatives under solvent-free conditions

Fe₃O₄@walnut shell/Cu(ii) as an eco-friendly bio-based magnetic nano-catalyst was prepared by adding CuCl₂ to Fe₃O₄@walnut shell in alkaline medium. A series of 2-aryl/alkyl-2,3-dihydro-1H-naphtho[1,2-e][1,3]oxazines were synthesized by the one-pot pseudo three-component reaction of β-naphthol, formaldehyde and various amines using nano-Fe₃O₄@walnut shell/Cu(ii) at 60 °C under solvent-free conditions. The catalyst was removed from the reaction mixture by an external magnet and was reusable several times without any considerable loss of its activity. This protocol has several advantages such as excellent yields, short reaction times, clean and convenient procedure, easy work-up and use of an eco-friendly catalyst.

Fe₃O₄@walnut shell/Cu(ii) as an eco-friendly bio-based magnetic nano-catalyst was prepared by adding CuCl₂ to Fe₃O₄@walnut shell in alkaline medium.

Biopolymers, especially cellulose and its derivatives, have some unparalleled properties, which make them attractive alternatives for ordinary organic or inorganic supports for catalytic applications.¹ Cellulose is the most abundant natural material in the world and it can play an important role as a biocompatible, renewable resource and biodegradable polymer containing OH groups.² Walnut shell is a natural, cheap, and readily available source of cellulose. Fe₃O₄ nanoparticles are coated with various materials such as surfactants,³ polymers,^4,5 silica,⁶ cellulose⁷ and carbon⁸ to form core–shell structures. Magnetic nanoparticles as heterogeneous supports have many advantages such as high dispersion in reaction media and easy recovery by an external magnet.⁹ Cu(ii) as a safe and ecofriendly cation is a good Lewis acid and can activate the carbonyl group for nucleophilic addition reactions.¹⁰1,3-Oxazines moiety has gained great attention from many organic and pharmaceutical chemists due to their broad range of biological activities such as anticancer,¹¹ anti-bacterial,¹² anti-tumor¹³ and anti-Parkinson''s disease.¹⁴Owing to the biological importance of benzo-fused 1,3-oxazines, various methods have been developed for the synthesis of these compounds. Some shown protocols for the synthesis of various 2-aryl/alkyl-2,3-dihydro-1H-naphtho[1,2-e][1,3]oxazines via a Mannich type condensation between a 2-naphthol, formaldehyde and a primary amine were reported. This protocol has been catalyzed by KAl(SO₄)₂·12H₂O (alum),¹⁵ ZrOCl₂,¹⁶ polyethylene glycol (PEG),¹⁷ thiamine hydrochloride (VB₁)¹⁸ and CCl₃COOH.¹⁹ Other methods of synthesis of oxazines are aza-acetalizations of aromatic aldehydes with 2-(N-substituted aminomethyl) phenols in the presence of an acid as catalyst²⁰ and electrooxidative cyclization of hydroxyamino compounds.²¹However, some of these catalysts have limitations such as inefficient separation of the catalyst from reaction mixtures, unrecyclable and environmental limitations. Therefore, the development of green and clean methodology for the preparation of 2-aryl/alkyl-2,3-dihydro-1H-naphtho[1,2-e][1,3]oxazine derivatives is still an interesting challenge.Herein, we wish to report the preparation of Fe₃O₄@nano-walnut shell/Cu(ii) as a new and bio-based magnetic nanocatalyst and its using for one-pot synthesis of 1,3-oxazine derivatives via condensation of β-naphthol, primary amine and formaldehyde.     

Natural phosphate-supported Cu(ii), an efficient and recyclable catalyst for the synthesis of xanthene and 1,4-disubstituted-1,2,3-triazole derivatives

Cu(NO₃)₂ supported on natural phosphate, Cu(ii)/NP, was prepared by co-precipitation and applied as a heterogeneous catalyst for synthesizing xanthenes (2–3 h, 85–97%) through Knoevenagel–Michael cascade reaction of aromatic aldehydes with 1,3-cyclic diketones in ethanol under refluxing conditions. It was further used for regioselective synthesis of 1,4-disubstituted-1,2,3-triazoles (1–25 min, 95–99%) via a three-component reaction between organic halides, aromatic alkynes and sodium azide in methanol at room temperature. The proposed catalyst, Cu(ii)/NP, was characterized using X-ray fluorescence, X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, Brunauer–Emmett–Teller, Barrett–Joyner–Halenda and inductively coupled plasma analyses. Compared to other reports in literature, the reactions took place through a simple co-precipitation, having short reaction time (<3 hours), high reaction yield (>85%), and high recyclability of catalyst (>5 times) without significant decrease in the inherent property and selectivity of catalyst. The proposed protocols provided significant economic and environmental advantages.

Cu(NO₃)₂ supported on natural phosphate, Cu(ii)/NP, was prepared by co-precipitation and characterized. The Cu(ii)/NP catalyzed the synthesis of xanthenes and triazoles. The proposed protocols provided significant economic and environmental advantages.     

Synthesis and characterization of a novel CNT-FeNi3/DFNS/Cu(ii) magnetic nanocomposite for the photocatalytic degradation of tetracycline in wastewater

Herein, Cu(ii) complexes were anchored within the nanospaces of a magnetic fibrous silicate with a high surface area and easily accessible active sites via a facile approach, leading to the successful synthesis of a novel potent nanocatalyst (FeNi₃/DFNS/Cu). Furthermore, FeNi₃/DFNS/Cu was supported on carbon nanotubes (CNTs) via an usual nozzle electrospinning method (CNT-FeNi₃/DFNS/Cu). In addition, its performance as a photocatalyst for the degradation of tetracycline was tested in a batch reactor. Tetracycline is an antibiotic that is commonly utilized in veterinary medicine and in the treatment of human infections, but is hazardous to aquatic environments. However, the usual processes for the removal of tetracycline are not efficient. The eco-friendly attributes of this catalytic system include high catalytic activity and ease of recovery from the reaction mixture using an external magnet, and it can be reused several times without significant loss in its performance. Also, protocols such as hot filtration, and mercury poisoning provided complete insight into the nature of this heterogeneous catalyst.

Herein, Cu(ii) complexes were anchored within the nanospaces of a magnetic fibrous silicate with a high surface area and easily accessible active sites via a facile approach, leading to the successful synthesis of a novel potent nanocatalyst (FeNi₃/DFNS/Cu).     

Synthesis,structural characterization and Cu(ii) adsorption behavior of manganite (γ-MnOOH) nanorods

New alternatives for the removal of transition metal ions that present an environmental risk are required. The chemical adsorption of these ions on surfaces with chemisorbent properties represents a promising area of research. In this work, manganite (γ-MnOOH) nanorods were synthesized, with a surface area of 20.22 m² g⁻¹, pore size of 32.18 nm and pore volume of 0.1627 cm³ g⁻¹. After chemical and structural characterization of the manganite sample, it was evaluated as an adsorbent of Cu(ii) from aqueous solution. The equilibrium adsorption data were well fitted by the Langmuir isotherm, and the results indicated that the maximum adsorption capacity of Cu(ii) was 11.926 mg g⁻¹. Cu(ii) ion adsorption on the manganite surface is a spontaneous and exothermic process (ΔG°< 0 and ΔH°< 0). The negative value of ΔS° suggests the stability of the adsorption process without structural change at the manganite–aqueous solution interface. A scheme for chemisorption of Cu(ii) ions on the hydroxylated surface of manganite is proposed.

Manganite (γ-MnOOH) nanorods were synthesized and Cu(ii) adsorption on their hydroxylated surface was a spontaneous process (ΔG° < 0).     

Cytotoxic effect,generation of reactive oxygen/nitrogen species and electrochemical properties of Cu(ii) complexes in comparison to half-sandwich complexes of Ru(ii) with aminochromone derivatives

This paper describes the synthesis of new 6-aminoflavone (6AFl (3)) and 6-aminochromone (6AC (4)) complexes with Cu(ii) and Ru(ii) ions ([Cu(6AC)₂Cl₂] (3a), [Cu(6AFl)₂Cl₂] (4a), [Ru(p-cymene)(6AC)Cl₂] (4b)) and comparison of their properties with the previously described 7-aminoflavone (7AFl (1)) and 7-amino-2-methylchromone (7A2MC (2)) analogues. The cytotoxic effect of all these complexes against two human leukaemia cell lines (HL-60 and NALM-6), melanoma WM-115 cells and COLO205 cells, is determined. The cytotoxicity of copper(ii) complexes, especially [Cu(6AFl)₂Cl₂] (3a) was higher than ruthenium(ii) complexes with the same ligands. Their cytotoxic potency was also stronger in comparison to the referential agents like cisplatin. The pro-oxidative properties were determined for the most active complexes and their ability to generate ROS (reactive oxygen species)/RNS (reactive nitrogen species) in cancer cells was confirmed. The type of ligand and the chemical structure of the tested complexes had an influence on the level of ROS/RNS generated in cancer cells. The redox properties of the copper complex compounds were evaluated by cyclic voltammetry, and compared with the data for Ru(ii) complexes. The reduction and oxidation processes of Ru(iii)/Ru(ii) and Cu(ii)/Cu(i) were described as quasi-reversible.

New Cu(ii)/Ru(ii) complexes with 6-aminoflavone/chromone derivatives as ligands were synthesized and characterized. Their cytotoxicity, pro-oxidative and redox properties were investigated.     

A novel square-planar Pt(ii) complex as a monomeric and dimeric G-quadruplex DNA binder

A novel phenanthroimidazole ethylenediamine Pt(ii) complex with coumarin derivative (1) was synthesized and showed higher affinity, selectivity and thermal stabilization for mixed-type dimeric G-quadruplexes (G2T1) over monomeric G-quadruplexes (G1) and duplex DNA. Complex 1 could bind to G-quadruplexes via end-stacking and external-binding modes.

A phenanthroimidazole ethylenediamine Pt(ii) complex with coumarin derivative (1) showed high binding properties and thermal stabilization for dimeric quadruplexes G2T1.

G-quadruplex DNA, as a noncanonical secondary DNA structure, is formed by G-rich sequences widespread in biologically important regions of the human genome. Its stabilization at telomeric regions can inhibit telomerase activity and interfere with telomere biology, which makes it a potential target for the development of new anticancer therapies.^1,2 However, bioinformatic studies have shown that over 700, 000 DNA sequences within the human genome have potential to form G-quadruplex structures.³ So it is crucial to selectively bind the different sequences and conformations of G-quadruplexes. The ca. 200 bases of the single-stranded overhang of telomeric DNA can potentially fold into multimeric telomeric G-quadruplexes consisting of several consecutive G-quadruplex units linked by TTA spacers.^4,5 Moreover, multimeric G-quadruplexes could be formed by telomeric DNA and r(GGGGCC)_n RNA repeats, being relevant in amyotrophic lateral sclerosis.^6,7 Thus it is significant to design some binders for selectively binding and stabilizing multimeric G-quadruplexes.Many square-planar Pt(ii) complexes, such as square-planar platinum(ii) phenanthroline complexes, have been reported as good binders of G-quadruplexes for possessing a large electron deficient π-aromatic surface, positively charged substituents and a positively charged center.^8–12 Some Pt(ii) complexes have been modified with a pendant cyclic amine or pyridine side arm and exhibited high affinity for human telomeric G-quadruplexes.^8–10 Other structurally analogous Pt(ii) complexes, including ones with phenanthroimidazol,¹¹ dipyridophenazine,¹² and C-coordinated phenylpyridine ligands,¹² have exhibited considerably stronger interactions with G-quadruplex DNA for possessing an extended π-surface. Though a few small molecules have been studied to specifically bind multimeric G-quadruplex structures,^13–18 most square-planar Pt(ii) phenanthroline complexes have been discussed to selectively bind monomeric G-quadruplexes rather than multimeric G-quadruplexes.It has been reported that an excellent binder of monomeric G-quadruplexes, such as TMPyP4 and azatrux, could also show high binding properties toward multimeric G-quadruplexes, and even result in the significant differences of the binding properties toward multimeric G-quadruplexes and monomeric G-quadruplexes.¹⁹ With this thought in mind, together that the coumarin derivatives possess a π-surface and an amino substituent, we chose phenanthroimidazole ethylenediamine with coumarin derivative L previously reported²⁰ as a ligand, synthesized its Pt(ii) complex 1 (Scheme 1), and systematically studied its binding affinities, selectivities and thermal stabilization towards human telomeric dimeric quadruplexes G2T1 and monomeric quadruplexes G1.Open in a separate windowScheme 1Synthesis of complex 1. Reagents and conditions: (a) K₂PtCl₄, aqueous DMSO, 140 °C, 2 h; (b) ethylenediamine, EtOH, 80 °C, 12 h.Complex 1 was synthesized according to the synthetic route in Scheme 1. Phenanthroimidazole with coumarin derivative L reacted with K₂PtCl₄ in aqueous DMSO and got a red solid of Pt(ii) complex 2. Complex 2 reacted with ethylenediamine in ethanol and got the crude product, which was washed with CHCl₃ to afford complex 1 as a red solid in 39% yield. Complex 1 was fully characterized by ¹H NMR, MS (LR and HR), IR and elemental analysis (seeing ESI^†).^‡The binding effect of complex 1 on the structures of dimeric G-quadruplexes G2T1 was investigated by circular dichroism (CD) spectra. At first, addition of complex 1 led no significant changes in the ellipticity of antiparallel G2T1, and only induced minor changes in the negative ellipticity at 265 nm (Fig. S3^†). These results suggest that complex 1 brought about no structural changes and low binding affinity toward antiparallel G2T1. Subsequently, for mixed-type G2T1, addition of complex 1 led to the increasement of the band with maximum at 291 nm and the shoulder at 270 nm and the shift of the maximum band from 291 nm to 287 nm (Fig. 1a). These results show that complex 1 strongly bound with mixed-type G2T1.Open in a separate windowFig. 1(a) CD spectra of mixed-type G2T1 (3.0 μM) in the presence of complex 1: (1) 0 equiv.; (2) 2 equiv.; (3) 4 equiv. and (4) 8 equiv., respectively. (b) CD-melting profiles at 290 nm for mixed-type G2T1 (3.0 μM) with complex 1 (0, 12 and 24 μM, respectively). Values are the average ± SD of three independent measurements.Thermal stabilization of complex 1 towards mixed-type G2T1 was further assessed by CD-melting assays (Fig. 1b and S4^†). Complex 1 displayed a ΔT_m value being 9.0 °C at 4 : 1 complex-to-G2T1 ratio. And the values of ΔT_m increased with the increasing amounts of complex 1. A higher thermal stabilization (ΔT_m = 11.5 °C) was observed at 8 : 1 complex-to-G2T1 ratio, which suggests that complex 1 exhibited comparable thermal stabilization with those mixed-type G2T1 binders reported in the literature.^16,17,19,21 In contrast, complex 1 had negligible thermal stabilization towards monomeric quadruplexes G1 (ΔT_m = 1.2 °C, Fig. S5a^†) and double-stranded (ds) DNA (ΔT_m = −2.9 °C, Fig. S5b^†). These results show that complex 1 had the preferential thermal stabilization towards mixed-type G2T1 over G1 and ds DNA.Based on higher thermal stabilization of complex 1 towards mixed-type G2T1 over G1, the binding selectivity of complex 1 was further confirmed for mixed-type G2T1 by gel electrophoresis (Fig. 2). The gel reveals that addition of complex 1 to mixed-type G1 led to no appearance of any new band (lane 2–3). However, the presence of complex 1 increased the mobility of the mixed-type G2T1 (lane 5). These results suggest that complex 1 could form a compact complex with G2T1 rather than G1,^14,16 which was further verified by incubating complex 1 with a mixture of G1 and G2T1 and then analysing their gel electrophoresis. Obviously, a mixture of G1 and G2T1 in the absence of complex 1 gave the characteristic bands corresponding to intramolecular G1 and G2T1 (lane 6). When complex 1 added to a mixture of G1 and G2T1, a new band corresponding to the complex of G2T1 with complex 1 (G2T1 + 1) appeared and became more intense with the increasing amounts of complex 1 (lanes 7 to 9). However, no new band appeared corresponding to the complex of G1 and complex 1 (lanes 7 to 9). These results indicate that complex 1 had higher binding selectivity towards G2T1 over G1.Open in a separate windowFig. 2Native gel electrophoretic analysis of G1, G2T1 and their mixture in the presence of complex 1 in Tris–HCl buffer (10 mM, 100 mM KCl and pH 7.0). Lanes 1–3: G1 (16 μM) in the presence of complex 1 (0, 16 and 32 μM); lanes 4–5: G2T1 (8 μM) in the presence of complex 1 (0 and 8 μM); lanes 6–9: mixtures of G1 (16 μM) and G2T1 (8 μM) in the presence of complex 1 (0, 8, 16 and 32 μM, respectively); lane 10: DNA ladder.The binding affinities of complex 1 towards mixed-type G2T1 and G1 were determined by UV-Vis titrations (Fig. 3 and S6a^†). The gradual addition of G2T1 and G1 to complex 1 resulted in considerable hyperchromicity, a noticeable red-shift at ca. 449 nm (15 nm for G2T1 and 11 nm for G1) and the appearance of a new and strong absorbance peak at ca. 481 nm (Fig. 3a and S6a^†), which suggests that complex 1 could interact with G2T1 and G1. Then the data of UV-Vis titrations were also used to calculate the binding constant (K) of complex 1 and the number of binding sites towards G2T1 and G1 by Scatchard eqn (1a):²²r/C_f = nk − rK1ar = C_b/C_DNA1bC_b = C_t (A − A₀)/(A_max − A₀)1chere, C_t is the total complex concentration, C_b is bound complex concentration, C_f is free complex concentration, A and A_max are the observed and maximum absorption values of complex 1 at ca. 481 nm with addition of DNA, and A₀ is the absorption value of complex 1 at ca. 481 nm without addition of DNA. In eqn (1a), r represents the number of moles of bound complex per mole of DNA, D_f represents the concentration of unbound complex, K is the binding constant, and n is the number of complex-binding sites on the G-quadruplex. The plot of r/D_fversus r gives the binding constant. The results were presented in Fig. 3b and Fig. 3b, the Scatchard plots had no single linear relationship but two regression curves, which suggests the existence of two types of binding sites in the interaction of complex 1 and DNA. The binding stoichiometries of complex 1 were 1.0 : 1 for G2T1 and 1.1 : 1 for G1, respectively, when [1]/[DNA] was lower than 1.0. And the binding stoichiometries of complex 1 were 1.5 : 1 for G2T1 and 1.7 : 1 for G1, respectively, when [1]/[DNA] was higher than 1.0 (†). These results show that complex 1 had higher binding affinity towards G2T1 over G1 and CT DNA. The K_a value of complex 1 towards mixed-type G2T1 was (9.70 ± 0.26) μM⁻¹ (13,19,21,23Open in a separate windowFig. 3(a) UV-Vis titrations of 20 μM complex 1 in the presence of mixed-type G2T1 (from 0–25 μM). (b) Scatchard plots for complex 1 with G2T1 and G1. The absorbance values at ca. 481 nm were used to construct the Scatchard plots. Values are the average ± SD of three independent measurements.Binding parameters obtained from UV-Vis titrations^a

Appraisal of Cu(ii) adsorption by graphene oxide and its modelling via artificial neural network

Graphene oxide (GO), as an emerging material, exhibits extraordinary performance in terms of water treatment. Adsorption is a process that is influenced by multiple factors and is difficult to simulate by traditional statistical models. Artificial neural networks (ANNs) can establish highly accurate nonlinear functional relationships between multiple variables; hence, we constructed a three-layered ANN model to predict the removal performance of Cu(ii) metal ions by the prepared GO. In the present research work, GO was prepared and characterized by FT-IR spectroscopy, SEM, and XRD analysis techniques. In ANN modeling, the Levenberg–Marquardt learning algorithm (LMA) was applied by comparing 13 different back-propagation (BP) learning algorithms. The network structure and parameters were optimized according to various error indicators between the predicted and experimental data. The hidden layer neurons were set to be 12, and optimal network learning rate was 0.08. Contour and 3-D diagrams were used to illustrate the interactions of different influencing factors on the adsorption efficiency. Based on the results of batch adsorption experiments combined with the optimization of influencing factors by ANN, the optimum pH, initial Cu(ii) ion concentration and temperature were anticipated to be 5.5, 15 mg L⁻¹ and 318 K, respectively. Moreover, the adsorption experiments reached equilibrium at about 120 min. Combined with sensitivity analysis, the degree of influence of each factor could be ranked as: pH > initial concentration > temperature > contact time.

Graphene oxide (GO), as an emerging material, exhibits extraordinary performance in terms of water treatment.     

Several coumarin derivatives and their Pd(ii) complexes as potential inhibitors of the main protease of SARS-CoV-2, an in silico approach

The global pandemic of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) caused many fatalities among people and significantly influenced the global economy. Since efficient treatment is not available, the computational methods in biology and chemistry are a promising starting point towards adequate medication. Three previously synthesized coumarin derivatives and their Pd(ii) complexes were examined for the binding affinity towards the M^pro protein of SARS-CoV-2 by molecular docking and compared to two Food and Drug Administration (FDA) drugs, cinanserin and chloroquine. All of the investigated compounds bind to the active position of the mentioned protein. Coumarin–Pd(ii) complexes showed higher binding affinities compared to the approved drugs. The bindings of the bis(3-(1-((3-chlorophenyl)amino)ethylidene)-chroman-2,4-dione) palladium(ii) complex, its corresponding ligand, and cinanserin to SARS-CoV-2 M^pro were further subjected to the molecular dynamics simulations. The binding free energies, computed by MM/PBSA approach were analyzed in detail and the importance of specific interactions outlined. These results showed that the molecules bearing structural similarity to the approved drugs and their complexes have the potential to inhibit the functional activity of SARS-CoV-2 protease and further experimental studies should be undertaken.

Coumarin derivatives and their Pd(ii)-complexes have shown a higher binding potential towards SARS-CoV-2 M^pro than chloroquine/cinanserin along with lower toxicity.     

Selective oxidation of alcohols and sulfides via O2 using a Co(ii) salen complex catalyst immobilized on KCC-1: synthesis and kinetic study

The aim of this study was to immobilize a Co(ii) salen complex on KCC-1 as a catalyst that can be recovered (Co(ii) salen complex@KCC-1). Field-emission transmission electron microscopy, FT-IR spectroscopy, thermogravimetric analysis, elemental analysis, atomic absorption spectroscopy, and XRD were used to confirm the structure and chemical nature of Co(ii) salen complex@KCC-1. The oxidation efficiency was obtained for an extensive range of sulfides and alcohols using this sustainable catalyst, alongside O₂ as an oxygen source and isobutyraldehyde (IBA) as an oxygen acceptor, with superior selectivity and conversion for the relevant oxidation products (sulfoxides and ketones or aldehydes) under moderate conditions. The μ-oxo and peroxo groups on the ligands of the Co complex appeared to be responsible for the superior activity of the catalyst. Essential factors behind the oxidation of alcohol and sulfoxides were investigated, including the catalyst, solvent, and temperature. In this paper, molecular oxygen (O₂) was used as a green oxidant. Furthermore, kinetic studies were conducted, revealing a first-order reaction for the oxidation of both benzyl alcohol and sulfide. The reaction progressed at mild temperature, and the catalyst could be easily recovered and reused for numerous consecutive runs under the reaction conditions, without any substantial reduction in the functionality of the catalytic system.

The aim of this study was to immobilize a Co(ii) salen complex on KCC-1 as a catalyst that can be recovered (Co(ii) salen complex@KCC-1).     

Simultaneous removal of tetracycline and Cu(ii) by adsorption and coadsorption using oxidized activated carbon

Co-contamination of antibiotics and heavy metals prevails in the environment. To overcome the obstacle of low metal uptake on activated carbon and to achieve simultaneous removal of tetracycline (TC) and Cu(ii) from water, coconut shell based granular activated carbon (GAC) treated with nitric acid was utilized. GAC property characterization showed that oxidation treatment distinctly decreased the surface area of GAC and significantly increased the content of oxygen containing functional groups. The oxidized GAC exhibited greater adsorption capacity for individual TC and Cu(ii). Kinetics studies demonstrated that although the overall removal rate of coexisting TC and Cu(ii) decreased, the ultimate removal efficiency was further enhanced in the binary system. The adsorption isotherms were well described by Langmuir and Freundlich models. Moreover, the maximum adsorption capacities of coexisting TC and Cu(ii) with oxidized GAC kept increasing within a pH range of 3.0–6.0, indicating an electrostatic repulsion mechanism as well as a competition for adsorption sites. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis revealed that the enhanced removal of TC and Cu(ii) was very likely as a result of coadsorption by forming TC–Cu(ii) complexes bridging between the adsorbate and the adsorbent.

The enhanced coadsorption of TC and Cu(ii) was likely due to the formation of a TC–Cu(ii) complex bridging.