Ligand Complexes Research Articles

Sunlight-boosted recovery of precious metal ions from E-waste using tannin-grafted mesoporous silica

The escalating demand and dwindling reserves of precious metals request efficient recycling techniques from electron waste. Addressing this need, we introduce a new method utilizing tannin-grafted mesoporous silica for the sunlight-boosted recovery of precious metals. Our strategy leverages the inherent photoreactivity of tannins, enabling metal–ligand complexation and plasmonic enhancement of chemical reduction. The result is a marked increase in the adsorption capacity and the high selectivity towards precious metal ions in electronic waste. Our robust covalent bonding approach concentrated tannic acids onto silica at a high density (500,000 per square micrometer), which significantly boosted the adsorption of gold ions up to an 11-fold increase, even amidst a mixture of nine other metal species. Impressively, we achieved a maximum adsorption capacity of 68.4 mmol per gram, equivalent to 13.4 g of gold per gram of adsorbent. Also, the adsorption rates for platinum and palladium ions were enhanced by 2.6 and 3.0 times, respectively. The underlying mechanism includes the visible-light-driven plasmonic hot electron transfer that affords nearly perfect selectivity for gold ions (approximately 99%). These findings not only advance the field of metal recovery from electronic waste but also offer an environmentally benign and cost-effective solution that harnesses renewable solar energy.

Ionic Liquid Crystals Based on Loop-Shaped Copper(I) Complexes.

This paper describes the synthesis and characterization of liquid crystals based on loop-shaped cationic copper(I) complexes of a multidentate ligand. Their synthesis involves the one-pot reaction of an alkyloxy-decorated pyridine-aldehyde unit with a diamine (2,2'-(ethylenedioxy)bis(ethylamine)) spacer to form in situ a pyridine-imine quadridentate-N4-donor ligand, L, which is able to chelate a copper(I) center associated with various noncoordinating anions. All of these compounds were characterized by NMR, IR, and electronic absorption spectroscopy, and more particularly by X-ray diffraction and mass spectroscopy, enabling unambiguous assignment of the [ML]+ mononuclear nature of the cationic components. The presence of six flexible alkyloxy chains at each end of the ligand associated with the rigidity of the core complex causes induction of a liquid crystal state with a columnar self-organized architecture, where the columns are packed in a hexagonal two-dimensional network.

Synthesis and characterizations of Hg (II) Complex of Macrocyclic complexes compounds Tetradecahydrodibenzo hexaazacyclooctadecine with HgX2 (X= Cl, Br) by Hirshfeld analysis and antimicrobial activity

This study examines the synthesis and characterization of a macrocyclic complex molecule having the general formula [M-LX2], where M =Hg (II) with schiff base Tetradecahydrodibenzo hexaazacyclooctadecine ligands. Resulted from the interaction between mercury and the diethyl triamine and benzene- 1, 2 diol in an ethanolic solution. Schiff base and its novel mercury (II) Complexes were studied vibrational in the solid state using spectral, 1H-NMR, IR, UV, and antimicrobial activity approaches. We were able to establish the coordination mode of the metal in complexes by comparing the changes in the ligands' and complexes' FT-IR and UV-Visible spectra.
 Keywords: MERCURY (II), Schiff bases, IR, 1H-NMR, PXRD Spectroscopy.

A structural basis for the activation of peroxisome proliferator-activated receptor gamma (PPARγ) by perfluorooctanoic acid (PFOA)

Perfluorooctanoic acid (PFOA) is a widespread environmental pollutant of the perfluoroalkyl substance (PFAS) class that is extremely resistant to environmental and metabolic degradation, leading to bioaccumulation. PFOA exposure has been linked to many health effects including endocrine disruption and metabolic dysregulation, but our understanding of the molecular mechanisms resulting in these outcomes remains incomplete. One target affected by PFOA is the ligand regulated nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ) which plays a critical role in controlling metabolic homeostasis through regulating processes such as adipogenesis, glucose homeostasis, inflammation and osteogenesis. It has been previously established that PFOA activates PPARγ through binding to the PPARγ ligand binding domain (PPARγ LBD) leading to increased expression of PPARγ controlled target genes. However, the mechanism by which PFOA achieves this has remained elusive. Here, we employed a combination of X-ray crystallography and fluorescence polarization assays to provide a structural basis for PFOA mediated activation of PPARγ via binding to the PPARγ LBD. Using X-ray crystallography, the cocrystal structure of the PPARγ LBD:PFOA complex was solved. This revealed that PFOA occupies three distinct sites, two within the PPARγ LBD and one within the activation function 2 (AF2) on the protein surface. Structural comparison of PFOA binding with previously reported PPARγ:ligand complexes supports that PFOA activates PPARγ by a partial agonist mechanism at micromolar concentrations. Fluorescence polarization assays also revealed that PFOA binding to the AF2 is unlikely to occur in a cellular context and confirmed that PFOA behaves as a partial agonist in vitro, weakly recruiting a coactivator peptide to the AF2 of the PPARγ LBD. This discovery provides an advancement in understanding PFOA mediated regulation of PPARγ, giving new insight regarding regulation of PPARγ by PFAS and PFAS substitutes in general and can be applied to the design and assessment of safer PFAS.

Structure, Antioxidant Activity and Antimicrobial Study of Light Lanthanide Complexes with p-Coumaric Acid.

This paper presents the results of a study of the effects of the lanthanide ions Ce3+, Pr3+, Nd3+ and Sm3+ on the electronic structure and antioxidant and biological (antimicrobial and cytotoxic) properties of p-coumaric acid (p-CAH2). Structural studies were conducted via spectroscopic methods (FTIR, ATR, UV). Thermal degradation studies of the complexes were performed. The results are presented in the form of TG, DTG and DSC curves. Antioxidant properties were determined via activity tests against DPPH, ABTS and OH radicals. The reducing ability was tested via CUPRAC assays. Minimum inhibitory concentrations (MICs) of the ligand and lanthanide complexes were determined on E. coli, B. subtilis and C. albicans microorganisms. The antimicrobial activity was also determined using the MTT assay. The results were presented as the relative cell viability of C. albicans, P. aeruginosa, E. coli and S. aureus compared to controls and expressed as percentages. In the obtained complexes in the solid phase, lanthanide ions coordinate three ligands in a bidentate chelating coordination mode through the carboxyl group of the acid. Spectroscopic analysis showed that lanthanide ions increase the aromaticity of the pi electron system of the ligand. Thermal analysis showed that the complexes are hydrated and have a higher thermal stability than the ligand. The products of thermal decomposition of the complexes are lanthanide oxides. In the aqueous phase, the metal combines with the ligand in a 1:1 molar ratio. Antioxidant activity tests showed that the complexes have a similar ability to remove free radicals. ABTS and DPPH tests showed that the complexes have twice the ability to neutralise radicals than the ligand, and a much higher ability to remove the hydroxyl radical. The abilities of the complexes and the free ligand to reduce Cu2+ ions in the CUPRAC test are at a similar level. Lanthanide complexes of p-coumaric acid are characterised by a higher antimicrobial capacity than the free ligand against Escherichia coli bacteria, Bacillus subtilis and Candida albicans fungi.

Oxygen-Donor Metalloligands Induce Slow Magnetization Relaxation in Zero Field for a Cobalt(II) Complex with {CoO4} Motif.

Most 3d metal-based single-molecule magnets (SMMs) use N-ligands or ligands with even softer donors to impart a particular coordination geometry and increase the zero-field splitting parameter |D|, while complexes with hard O-donor ligands showing slow magnetization relaxation are rare. Here, we report that a diamagnetic NiII complex of a tetradentate ligand featuring two N-heterocyclic carbene and two alkoxide-O donors, [LO,ONi], can serve as a {O,O'}-chelating metalloligand to give a trinuclear complex [(LO,ONi)Co(LO,ONi)](OTf)2 (2) with an elongated tetrahedral {CoIIO4} core, D = -74.3 cm-1, and a spin reversal barrier Ueff = 86.9 cm-1 in the absence of an external dc field. The influence of diamagnetic NiII on the electronic structure of the {CoO4} unit in comparison to [Co(OPh)4]2- (A) has been probed with multireference ab initio calculations. These reveal a contrapolarizing effect of the NiII, which forms stronger metal-alkoxide bonds than the central CoII, inducing a change in ligand field splitting and a 5-fold increase in the magnetic anisotropy in 2 compared to A, with an easy magnetization axis along the Ni-Co-Ni vector. This demonstrates a strategy to enhance the SMM properties of 3d metal complexes with hard O-donors by modulating the ligand field character via the coordination of diamagnetic ions and the benefit of robust metalloligands in that regard.

Stereoselective Syntheses of Organophosphorus Compounds

The review is devoted to the theoretical and synthetic aspects of the stereochemistry of organophosphorus compounds. Organophosphorus compounds are not only widely exist in biologically active pharmaceuticals and agrochemicals, but also have widespread applications in material science and organic synthesis as ligands for transition metal complexes. One of the mainstreams for the development in this field is the creation of biologically active organophosphorus compounds that are searched and used as drugs or plant-protecting agents, which leads to the elaboration of advanced methods and monitoring, yielding up-to-date approaches to perform synthesis in an environmentally friendly manner. The review consists of two parts. The first part presents methods for the asymmetric synthesis of organophosphorus compounds using asymmetric organocatalysis and metal complex catalysis. In the review is described the nature of the chirality generation in the prebiotic period, the mechanisms of asymmetric induction, and double stereodifferentiation are discussed. The use of these methods for the preparation of chiral phosphorus analogs of natural compounds (phosphono-isonorstatin, phosphono-GABOB, phosphacarnitine, bis-phosphonates, and others) is described. Some data concerning of λ5-phosphanediones as metaphosphate anion analogues are also reported. The second part of the presented review shows examples of the use of these methods for the synthesis of phosphorus analogues of natural compounds—chiral phosphonoamino acids and hydroxyphosphonates: phosphonoaspartic acid, phosphonoglutamic acid, phosphonohomoproline, chiral bis-phosphonates. The reaction of dehydration aromatization with the formation of pho sphono isoindolinones, including isoindolinone bis-phosphonates, has been studied. Some of the synthesized compounds showed biological activity as protein tyrosine phosphatase inhibitors. A phosphonic analogue of iso-norstatine was synthesized. A stereoselective method for the synthesis of tetradecapentaenoic acid derivatives was developed.

Synthesis, characterisation, and anticancer and antioxidant activities of novel complexes of palladium and an organic Schiff-base ligand

Treatment of the Schiff base 2-N-(salicylidene) benzothiazole (SabtH) with palladium chloride afforded the neutral 2-N-(salicylidene) benzothiazole palladium(II) complex. This was then treated with one molar equivalent of either ethylenediamine or 1,10-phenanthroline, yielding the neutral mixed ligand complexes 1 and 2, respectively. The prepared organic ligand and its mixed ligand complexes were characterised via UV-Vis, FTIR, 1H-NMR, and 13C-NMR spectroscopy. The antiproliferative activities of 1 and 2 were tested against MCF-7 (breast) and HT-29 (colon) cancer cells using an MTT assay. 1 showed strong antiproliferative activity against both MCF-7 and HT-29 cancer cells, with IC50 values of 74.6 ± 8.35 and 174 ± 20.28 µg/mL, respectively. In addition, 2 exhibited the maximum antioxidant activity, with an EC50 value of 1029 ± 196.76 µg/mL.
 KEY WORDS: 2-N-(Salicylidene) benzothiazole, 1,10-Phenanthroline, Palladium mixed ligand complexes, Anticancer, Antioxidant activity
 Bull. Chem. Soc. Ethiop. 2024, 38(3), 605-613. 
 DOI: https://dx.doi.org/10.4314/bcse.v38i3.5

Synthesize, structural inspection, stoichiometry in solution and DFT calculation of some novel mixed ligand complexes: DNA binding, biomedical applications and molecular docking approach

Mixed ligand chelates of Pd(II), Cu(II), VO(II), and Ag(I) with (BIP = 4,6-dimethyl-N-(octahydro-2H-benzimidazol-2-ylidene)pyrimidin-2-amine) as a main ligand and (Phen = 1, 10-phenanthroline) as a second ligand were synthesized. The recently prepared chelates were investigated through CHN analysis, (NMR, Ft-IR, Mass, and UV–Vis) spectra, magnetic moments, molar conductance, TGA, Job s methods and DFT study. The (CHN and Mass) analysis, result expose the formation of structures (1 M: 1BIP: 1Phen) chelates. The two studied ligands are established to perform in as a neutral bi-dentate approach, concluded four N2 atoms for two ligands. The study of the molar conductance indicated the non-electrolytic features for (Cu(II) and VO(II)) chelates and the electrolytic features for (Ag(I) and Pd(II)) chelates. Thermo-dynamic and Kinetics factors for various thermal degradation phases were calculated. B3LYP/LANL2DZ/6–311 g(d,p) theoretical study has been applied for estimating the MEP, FMO analysis and quantum chemical reactivity descriptors of studied molecules. Practical and computational detail reveals that BIPPCu and BIPPVO complexes possess octahedral geometry around the metal center, BIPPAg complex shows a tetrahedral configuration, and BIPPPd complex has distorted square planar geometry. In vitro anti-microbial and anti-cancer for the studied structures were applied against various strains of microbes and cancer cell lines. The results revealed that all tested chelates showed a higher activity than the free BIP. The tested complexes have been studied to antioxidant potential using DPPH study. The binding of tested chelates with DNA was studied through applying electronic absorption, gel electrophoresis as well as viscosity study, in addition to the intercalating, minor groove and electrostatic approach of DNA interacting were recommended. The studied compounds explained dynamic satisfying performing. Also, the crystal structures of DNA (PDB ID: 454D), human coronavirus Nl63 nucleocapsid protein (PDB ID: 5EPW), breast cancer protein (PDB ID: 3HB5), and Escherichia coli (PDB ID: 2VF5) was performed by molecular docking simulation. Data of docking simulation suggestions are which tested compounds have biological behavior as well as have obvious benefit in the pharmaceutical business.

Investigation of phytochemicals isolated from selected Saudi medicinal plants as natural inhibitors of SARS CoV-2 main protease: In vitro, molecular docking and simulation analysis

The escalation of many coronavirus variants accompanied by the lack of an effective cure has motivated the hunt for effective antiviral medicines. In this regard, 18 Saudi Arabian medicinal plants were evaluated for SARS CoV-2 main protease (Mpro) inhibition activity. Among them, Terminalia brownii and Acacia asak alcoholic extracts exhibited significant Mpro inhibition, with inhibition rates of 95.3 % and 95.2 %, respectively, at a concentration of 100 µg/mL. Bioassay-guided phytochemical study for the most active n-butanol fraction of T. brownii led to identification of eleven compounds, including two phenolic acids (1, and 2), seven hydrolysable tannins (3–10), and one flavonoid (11) as well as four flavonoids from A. asak (12–15). The structures of the isolated compounds were established using various spectroscopic techniques and comparison with known compounds. To investigate the chemical interactions between the identified compounds and the target Mpro protein, molecular docking was performed using AutoDock 4.2. The findings identified compounds 4, 5, 10, and 14 as the most potential inhibitors of Mpro with binding energies of −9.3, −8.5, −8.1, and −7.8 kcal mol−1, respectively. In order to assess the stability of the protein–ligand complexes, molecular dynamics simulations were conducted for a duration of 100 ns, and various parameters such as RMSD, RMSF, Rg, and SASA were evaluated. All selected compounds 4, 5, 10, and 14 showed considerable Mpro inhibiting activity in vitro, with compound 4 being the most powerful with an IC50 value of 1.2 µg/mL. MM-GBSA free energy calculations also revealed compound 4 as the most powerful Mpro inhibitor. None of the compounds (4, 5, 10, and 14) display any significant cytotoxic activity against A549 and HUVEC cell lines.

Oxovanadium (IV) Complexes of α-Amino Acid Schiff Bases and Polypyridyl Ligands: Synthesis, Characterization and Antimicrobial Activity

Oxovanadium(IV) complexes of the type [VO(L)(bpy)] (V-1 to V-5) have been synthesized and characterized by FTIR and UV-Vis spectra, molar conductance, melting points, and magnetic susceptibilities measurements, where L= N-salicylidene-β-alanine (sal-ala), N-salicylidene-glycine (sal-gly), N-salicylidene-DL-β-phenylalanine (sal-pheala), N-salicylidene-leucine (sal-leu), and N-salicylidene-DL-methionine (sal-met), and bpy is 2,2´-bipyridine. The infrared spectral data reveals that the tridentate nature of the amino acid-based Schiff base ligand and the coordination of the ligand through azomethine nitrogen, phenolic oxygen and carboxylate oxygen with vanadyl (VO2+) ion. All of these complexes were determined to be non-electrolyte in nature, according to conductivity measurements. The magnetic moment measurements have been attributed that these complexes are paramagnetic and have d1 configuration of vanadium (IV) ion. In Virto antimicrobial activity of the synthesized complexes was evaluated against two gram-positive (Bacillus subtilis and Staphylococcus aureus) and two gram-negative (Escherichia coli, Proteus vulgaris) bacterial strains.

Reactivity and zinc affinity of dipyrromethenes as colorimetric sensors: structural and solvation effects

A wide range of dipyrromethenes (17 objects) with different nature, number, and attachment positions of alkyl, aryl, and meso-aza substituents was synthesized, and the effect of molecular structure features on their spectral properties was analyzed. It is shown that, chromophores absorb in a wide spectral range from ∼ 420 to ∼ 600 nm due to the structural modification of the dipyrromethene ligand backbone. Partially alkylated dipyrromethenes containing 4–5 methyl substituents absorb in the region from 421 to 436 nm. For fully alkylated dipyrromethenes, the band maximum position shifts to the region from 437 to 446 nm for ligands with 4,4′-substituents in the sequence: methyl, ethyl, propyl, butyl, amyl, hexyl, heptyl. The most significant spectral responses in the form of a red shift of 100 nm (in DMF) are observed when four methyl substituents in the 3,3′,5,5′-positions are replaced by phenyl groups. The replacement of the methine meso-spacer by a nitrogen atom leads to an additional red shift by another 70 nm. Particular attention is paid to the comparative analysis of the effect of structural factors on the coloristic and spectral responses of the complexation of dipyrromethene ligands with zinc(II) acetate and the stability of the resulting complexes [ZnL2], for which the lgKo values are varied from 6.4 to 10.9. The auxochromic action of Zn2+ cations shifts the band maxima of electronic absorption spectra to the long wavelength region by 20–76 nm relative to the spectra of the ligands. The highest complexation constant lgKo is 10.9 was obtained for the reaction of Zn(AcO)2 with hexamethylsubstituted dipyrromethene. Ligands with partially methylated pyrrole nuclei and extended alkyl and benzyl substituents form less stable complexes. The greatest effect of lowering the [ZnL2] stability is produced by the introduction of an electron-withdrawing aryl substituent into the meso-spacer of the dipyrromethene ligand (lgKo is 6.4).

Trinuclear nickel (II) string complexes and copper (II) coordination polymer with pyrazine modulated unsymmetrical dipyridylamino ligand: Synthesis, structure and bioactivity properties with molecular docking

The unsymmetrical pyrazine-modulated ligand, N-(pyridine-2-yl)pyrazin-2-amine (Hppza) (1), its 1D straight-chain copper (II) coordination polymer [Cu2(Hppza)2∙(NO3)4]n (2) and trinuclear metal string [Ni3(µ3-ppza)4Cl2] (3) and [Ni3(µ3-ppza)4(NCS)2] (4) complexes have been successfully synthesized and structurally characterized. The free ligand Hppza (1) exhibits anti-syn conformation. In an asymmetric unit of 2, there are two kinds of Cu(II) atoms, both of which have elongated octahedral coordination geometry, and the copper(II) centers are linked by oxygen atoms of one nitrate anion. There are only minor differences in Ni…Ni bond lengths between pyrazine-modulated ligand complexes of [Ni3(μ3-ppza)4×2] (X = Cl− (3), NCS− (4)) and their unmodulated analogs, while the distances between the terminal nickel atoms and the axial ligands 3 and 4 are shorter. The results of magnetic susceptibility measurements showed an antiferromagnetic exchange constant (J) of about J = –199.2 cm–1 for 3 and J = –178.0 cm–1 for 4. The electrochemical properties of nickel strings of Hppza differ significantly from their unmodulated counterparts. The activities of ligands and their metal complexes against various proteins that are AChE (PDB ID: 4M0E), BChE (PDB ID: 5NN0), α-Gly (PDB ID: 1UAS), hCA I (PDB ID: 2CAB), and hCA II (PDB ID: 3DC3) were compared, and then the ADME/T properties of molecules were examined. Afterward, the interactions occurring in the docking calculation were examined in detail with the Protein-Ligand Interaction Profiler (PLIP) service. These complexes were inhibitors of BChE, hCA I and II, α-glycosidase and AChE enzymes for complex 3 and 5 with Ki values of 12.65 and 42.95 μM for hCA I, 3.64 and 15.84 μM for hCA II, 5.44 and 50.07 μM for BChE, 15.85 and 4.77 μM for α-glycosidase and 8.58 and 86.24 μM for AChE, respectively.

Microwave-assisted synthesis, spectral characterization, and biological activities of complexes of a Schiff base derived from S-benzyl dithiocarbazate

Co(II), Ni(II), Zn(II), and Cd(II) complexes were synthesized from a Schiff base ligand, benzyl-2-(1-(thiophen-2-yl)propylidene)hydrazine-1-carbodithioate (BTPHC), by conventional as well as microwave irradiation methods. The ligand and its metal complexes were characterized by spectroscopic techniques (FT-IR, UV-vis, mass spectrometry, and 1H NMR) and powder X-ray diffraction. Based on magnetic measurements and spectral data, octahedral environments for Co(II) and Ni(II) complexes and tetrahedral environments for Zn(II) and Cd(II) complexes are proposed. The metal(II) complexes were active toward bacterial and fungal strains. Antidiabetic studies showed that the Cd(II) complex possesses greater potential as an antidiabetic agent than the other metal complexes and the ligand. Antioxidant studies indicate that the Zn(II) and Cd(II) complexes possess high radical scavenging activities. The synthesized ligand and metal(II) complexes were screened for their anticancer properties against two human cancer cell lines MCF-7 and HeLa using an MTT cell viability assay. The Ni(II) complex excelled in halting the proliferation of HeLa and MCF-7 cancer cell lines with IC50 values of 46.63 µM and 80.90 µM, respectively, whereas it displayed insignificant cytotoxicity against the human normal embryonic kidney cell line (HEK293) with IC50 = 300.41 µM.

Synthesis and Characterization of 4-(1-(2H benzo[d][1,2,3]triazol-2-ylimino)ethyl)benzonitrile and amino acid alanine and its Metal Complexes

The biological actions of transition metal ion complexes with mixed ligands are very different. Amino acid and azomethine containing Schiff bases are very useful building blocks for ternary complexes. The interaction of two ligands 4-(1-(2H-benzo[d][1,2,3]triazol-2-ylimino)ethyl)benzonitrile as L1 and an amino acid alanine as L2, with newly synthesized cuprous chloride solution in a 1:1:1 molar ratio using standard reflux approach has been attempted to create unique metal(I) complexes. Elemental analysis, molecular weight, magnetic moment, thermal analysis and spectroscopic methods are used to characterize the produced ligand and metal(I) complexes. Bacillus subtilis, Escherichia coli and Candida albicans were used as test organisms in antibacterial tests of the produced compounds. Antibacterial and antifungal activity of the metal (I) complexes have been shown to be very high against ciprofloxacin, ketoconazole.

Synthesis, Spectral Characterization, Antibacterial and Anticancer Evaluation of Novel Isoniazid based Schiff Base Ligand derived Transition Metal Complexes

A novel isoniazid based Schiff base ligand was synthesized by the condensation of 5-acetyl-N-(adamantan-2-yl)thiophene-2-carboxamide (1 mmol) and isoniazid (1 mmol). Metal complexes were prepared by reacting the Schiff base with metal(II) chloride (M = Ni2+, Cu2+ and Co2+), formed the novel metal coordination compound. The synthesized ligand and metal complexes were characterized by 1H NMR, mass spectral, UV-visible, IR & EPR spectral studies, themogravimetric analysis, cyclic voltametry and were screened with both Gram-positive and Gram-negative bacterias to evaluate the antibacterial activity by disc diffusion method. The zone of inhibition of the antibacterial assay demonstrated that all the three metal(II) complexes are active against the four bacterias, showed increased activity with increase in concentration and is more active against S. aureas at all concentrations. The systhesized complexes were also evaluated for its anticancer activities, only Ni(II) and Co(II) complexes showed the moderate levels of cytotoxicity activity.

Ligand Relay Catalysis Enables Asymmetric Migratory Hydroarylation for the Concise Synthesis of Chiral α-(Hetero)Aryl-Substituted Amines.

Complementary to the design of a single structurally complex chiral ligand to promote each step in transition-metal catalysis, multiligand relay catalysis through dynamic ligand exchange with each step in the catalytic cycle promoted by its best ligand provides an attractive approach to enhance the whole reaction reactivity and selectivity. Herein, a regio- and enantioselective NiH-catalyzed migratory hydroarylation process with a simple combination of a chain-walking ligand and an asymmetric arylation ligand, producing high-value chiral α-(hetero)aryl-substituted amines and their derivatives under mild conditions, is reported. The potential synthetic applications of this transformation are demonstrated by the concise synthesis of (S)-nicotine and a CDK8 inhibitor.

Spectroscopic and biological studies of mixed ligand complexes of transition metal (II) ions with chloroquine and ketoprofen

To create fresh transition metal complexes of chloroquine and ketoprofen, we combined Ni(II), Co(II), Cu(II), and Zn(II). Metal analysis, IR, UV-vis, and X-ray diffraction (XRD) spectrum analyzes of the complexes were utilized to characterize them. The octahedral geometry was proposed for all compounds on the basis of the UV-vis and magnetic susceptibility data. The practical size of the ligands and complexes with crystallinity structure was in the nano range according to the XRD data. The antibacterial and antifungal activities of the ligands and their metal complexes have been examined.

On Haptotropic Rearrangements of Diphosphene and Diarsene Ligands in Titanium Complexes.

Dipnictenes of the type RE=ER (E=P, As, Sb, Bi) are the isovalence electronic heavier analogs of alkenes. Although diphosphenes and dipnictenes in general show a variety of binding modes in metal complexes, little is known about haptotropic shift reactions involving these ligands. Herein, we report an unprecedented η2 to η1 rearrangement of the dipnictene ligands in titanocene complexes of the type Cp2Ti(Pn2Ar2) (Pn=P, As; Ar=2,4,6-Me3-C6H2, Mes; 2,6-iPr2-C6H3, Dip; 2,4,6-iPr3-C6H2, Tip), initiated by Lewis basic ligands (L=MeCN, PMe3, AdNC, CO). In the presence of L the dipnictene ligand changes its hapticity from η2 to η1 and complexes of the general form Cp2Ti(L)(Pn2Ar2) with a succinctly different electronic structure are obtained. Electronically, the new complexes are best described as biradicaloids with antiferromagnetically coupled (via a π-bond) [Cp2TiIII]⋅+ and [Pn2Ar2]⋅- fragments. However, the biradical character of these systems is affected by the electronic features of the co-ligand and significantly decreases moving from PMe3/MeCN (σ-donors) to CNAd/CO (σ-donors/π-acceptors).

Glycerol as Ligand in Metal Complexes—A Structural Review

The molecule glycerol (H3gly) plays a key role in sustainable and green chemistry. Having been discovered for over 200 years and produced from vegetable oils and animal fats by hydrolysis, saponification and transesterification reactions, this natural triol is today employed in a wide range of cosmetic, food, polymer and pharmaceutical applications. Moreover, it is an essential C3 precursor in the chemical industry, used in the production of several intermediates and it avoids the need for petroleum-based precursors. Less famous but just as exciting, in the domain of coordination chemistry, glycerol is also proving to be a suitable ligand, capable of binding to one or more metal centres, either directly in its triol H3gly form (rather rare), or in its various deprotonated glycerolate forms, such as [H2gly]−, [Hgly]2− and [gly]3− (in most cases). Since the 1970s, various molecular structures prepared from glycerol and metallic and organometallic precursors, ranging from mononuclear complexes to sophisticated aggregates and coordination polymers, have been isolated and characterised. On the basis of the single-crystal X-ray diffraction structures described so far in the literature and deposited in the Cambridge Structural Database, in this structural inventory, we review the different modes of coordination of glycerol and glycerolates with metals.