Metal Coordination Complexes Research Articles

Implications of non-native metal substitution in carbonic anhydrase - engineered enzymes and models.

The enzyme carbonic anhydrase has been intensely studied over decades as a means to understand the role of zinc in hydrating CO2. The naturally occurring enzyme has also been immobilized on distinct heterogeneous platforms, which results in a different hybrid class of catalysts that are useful for the adsorption and hydration of CO2. However, the reusability and robustness of such natural and immobilized systems are substantially affected when tested under industrial conditions, such as high temperature and high flow rate. This led to the generation of model systems in the form of metal-coordination complexes, metal-organic frameworks, metallo-peptide self-assembled supramolecules and nanomaterials that mimic the primary, and, to some extent, secondary coordination sphere of the active site of the natural carbonic anhydrase enzymes. Furthermore, the effects of zinc-substitution by other relevant transition metals in both the naturally occurring enzymes and model systems has been reported. It has been observed that some other transition metal ions in the active site of carbonic anhydrase and its models can also accomplish similar activity, established by various reaction probes and ideas. Herein, we present a comprehensive highlight about substituting zinc in the active site of the modified enzymes and its biomimetic model systems with non-native metal ions and review how they affect the structural orientation and reactivity towards CO2 hydration. In addition, the utility of artificially engineered carbonic anhydrases towards a number of non-natural reactions is also discussed.

Recyclable All‐in‐One Organo‐Photo‐Auxiliaries Enabling (sp3)C−(sp3)C Coupling Reactions with Diverse Functionalities

AbstractPhotochemical C−C coupling reactions can be tailored to industrial chemical processes and preparations of pharmaceuticals. Recent approaches in this area are limited to using precious transition metal coordination complexes that facilitate light absorption and redox processes with benchtop chemicals. Herein, we propose a paradigm that involves all‐in‐one organo‐photo‐auxiliaries, thio‐heteroarenes, which exhibit unique photophysical properties. These thio‐heteroarenes were employed to prepare several all‐in‐one ionic photo‐salts from commercially available alkyl/benzyl and heterocyclic halides via aromaticity‐mediated nucleophilic substitution reactions. From the library of >30 salts, we performed on‐demand photochemical C−C coupling reactions to isolate numerous symmetrical and unsymmetrical diary/alkyl‐ethanes with yields up to 84% and mass balance as high as 96%. We also investigated the influence of structural features/properties on the outcomes of the photochemical C−C coupling reactions. The current photochemical C−C method was successful in the isolation of >30 photoproducts, including the natural product Brittonin A, a precursor of Imipramine, and derivatives of the bioactive Honokiol Analogues. Furthermore, transient absorption spectroscopy and time‐dependent density functional theory calculations were used to decipher the nature of light‐promoted electronic transitions.

Solubility-Enhanced Iron Complex Posolytes for Redox Flow Batteries

Redox flow batteries (RFBs) are promising stationary energy storage devices for renewables. Commercial RFBs possess potential disadvantages such as cost and resource constraint due to the use of vanadium. Therefore, organic compounds and metal coordination complexes have drawn much attention as redox active materials for RFB electrolytes. We focus on less expensive terpyridine iron complexes that have higher redox potential of approximately 1 V (vs. SHE) as an active material for both aqueous and non-aqueous RFB posolytes.[1] However, terpyridine iron complexes generally possess low solubility in nonaqueous and aqueous solvents. In this study, we improved the solubility of the complexes by multi-componentization based on asymmerizing molecular structures and using the diverse ion effect as shown in Figure 1, and then explored an application as active materials in posolytes.Symmetric terpyridine-iron complexes, [Fe(R-tpy)2](PF6)2 (R-tpy: substituted terpyridine ligand), were synthesized by simple mixing with R-tpy ligands and an iron source in high yields of 96-98%. Cyclic voltammogram of a butoxy-substituted complex, [Fe(BuOtpy)2]2+ (1BuO), shows redox potentials of 0.57 V (vs Fc/Fc+) in CH3CN. The Fe2+/Fe3+ redox couple shifts to a higher potential compared to 0.72 V (vs Fc/Fc+) for the parent complex, [Fe(tpy)2]2+ (1H), because of the electron-donating substituent on the ligand. The solubility of 1BuO·(PF6)2 in CH3CN was estimated as 0.13 M by a UV-Vis method using a calibration curve, which is comparable to that of 1H·(PF6)2 (0.16 M). Such a low solubility of 1BuO·(PF6)2 is due to a stronger lattice energy derived from a tight packing between the iron complex cations and PF6 −. The mixing of 1H and 1BuO produced a mixture containing a new asymmetric complex [Fe(BuOtpy)(tpy)]2+. The solubility of the mixture increased to 0.49 M, which enhances a theoretical volumetric capacity of posolytes three times than those of the single-component ones (Figure 2). Further solubility improvement was achieved using complexes substituted with poly(ethylene glycol)-type chains. Reference [1] A. Okazawa, T. Kakuchi, M. Okubo, APL Mater. 11, 110901 (2023). Figure 1

Toughening of anti-freezing ionic hydrogels with Zr4+-dicarboxylic acid coordination complex for low temperature sensing applications

Conductive hydrogels are widely used in electronic skin, wearable sensing devices, human–machine interfaces, and soft robots because of their high elasticity, biocompatibility, and conformability in interfacial contact. However, hydrogels lose electrical conductivity and flexibility due to water crystallization at low temperatures, which severely limits their applications in the frigid regions. In this study, we propose to design a metal–ligand ionic hydrogel (PAASP-Zr-LiCl) through the formation of a stable coordination bond between the dicarboxylic acid group monomer poly(N-acryloyl aspartic acid) (PAASP) and zirconium ion (Zr4+). Zr4+–COO- metal-coordination complex as physical cross-linking points of the network can effectively improve the mechanical properties of hydrogels. By introducing lithium chloride (LiCl), the hydrogel obtained excellent anti-freezing properties (crystallization temperature < -80 °C) and high ionic conductivity (8.45 S/m). The LiCl molecules enhance the interaction between the polymer network and water molecules. The ionic hydrogel-based strain sensors exhibited a high gauge factor of 3.21. Combining hydrogel sensors with soft grippers can realize continuous and stable monitoring of grasping objects at low temperature of −30 °C. By integration of excellent flexibility (elongation at break 837.4 %), good ionic conductivity, high sensitivity, and excellent anti-freezing properties, the anti-freezing ionic hydrogel has a wide range of applications in the frigid regions of the plateau.

Supramolecular Spin Chains via Radical-Radical Contacts Stabilizing Ferromagnetic Interactions Between Heisenberg or Ising-Like Spins.

A new paramagnetic ligand, 4-(2'-4-(2''-furyl)-pyrimidyl)-1,2,3,5-dithiadiazolyl (furylpymDTDA) and three transition metal coordination complexes, M(hfac)2(furylpymDTDA) M=Mn, Co, Ni; hfac=1,1,1,5,5,5-hexafluoroacetylacetonato-), are reported. The solid-state structures are influenced by the geometry of the coordination sphere of the M(II) centers: trigonal (Mn) vs. octahedral (Co and Ni). While the hs-Mn(II) complex exhibits pairwise multi-centre 2-electron bonds (i. e., pancake bonds) between the planar π radical DTDA moieties, the hs-Co(II) and Ni(II) complexes crystallize with close contacts between coordinated furylpymDTDA radical ligands that define linear 1D arrays of molecular units. The magnetic data for the hs-Co(II) and Ni(II) complexes indicate ferromagnetic (FM) interactions between molecular units, apparently mediated by radical-radical contacts along the supramolecular chains. Computational analysis suggests proximity between regions of large α- and β-spin density on neighbouring molecular sites enabling FM exchange, in accordance with the McConnell I mechanism. The magnetic data for the Ni(II) complex are consistent with a Heisenberg spin chain, whereas the hs-Co(II) complex exhibits Ising-like spin chain behaviour and a magnetic phase transition to an FM ordered state at 4.6 K.

Water-Soluble Curcumin Derivatives Including Aza-Crown Ether Macrocycles as Enhancers of their Cytotoxic Activity.

The synthesis of three novel curcumin derivative compounds, featuring aza-crown ether macrocycles of various sizes (aza-12-crown-4, aza-15-crown-5, and aza-18-crown-6), is described. The incorporation of these aza-crown macrocycles significantly enhances their water solubility, positioning them as groundbreaking instances of curcumin derivatives that are fully soluble in aqueous environments. These curcumin ligands (L1, L2, and L3) were then reacted with zinc acetate to afford the coordination metal complexes (L1-Zn, L2-Zn, and L3-Zn). Comprehensive characterization of all compounds was achieved using various analytical techniques, including 1D and 2D NMR spectroscopy, ATR-FTIR spectroscopy, mass spectrometry (ESI+), elemental analysis and UV-Vis spectroscopy. The in vitro cytotoxic activity of both, ligands and complexes were evaluated on three human cancer cell lines (U-251, MCF-7, and SK-LU-1). Compared to conventional curcumin, these compounds demonstrated improved antiproliferative potential. Additionally, a wound healing assay was conducted to assess their antimigration properties. The obtained results suggest that these modifications to the curcumin structure represent a promising approach for developing therapeutic agents with enhanced cytotoxic properties.

Binding Mechanisms and Therapeutic Activity of Heterocyclic Substituted Arylazothioformamide Ligands and Their Cu(I) Coordination Complexes.

Finding new sources of biologically active compounds for anticancer or antimicrobial therapies remains an active area of research. Azothioformamides (ATFs) with a 1,3 N=N-C=S heterodiene backbone are a new class of biologically active compounds that chelate metals (e.g., Cu) forming stable ATF metal coordination complexes. In this study, ATF ligands were prepared with pyrrolidine, piperidine, N-methylpiperazine, and morpholine substituents on the formamide as to add more heterocyclic drug-like character for biological studies. Formamide derivatives were then complexed with various Cu(I) salts to form coordination complexes. Cu(I) salts were selected as to create potential bioactive compounds with less toxicity. Binding association constants of each Cu(I) salt to ATF ligands were extrapolated from UV-vis titration studies and were corroborated with DFT calculations using a hybrid functional B3LYP method. It was observed that the smaller pyrrolidine functionalized ATFs bound to the Cu(I) salts had stronger binding than any of the larger six-membered-ring heterocycles with association values in the 104 - 105 M-1 range. The ATF-Cu(I) salt coordination complexes were then evaluated for antimicrobial activity against two bacteria (Staphylococcus aureus, Escherichia coli), one yeast (Candida albicans), four human cancer lines (A-549, K-562, HT-1080, MDA-MB-231), and two normal human lines (MRC-5, HFF). The ATF ligands themselves were inactive against all microbes and most human lines except K-562 cells, which were sensitive to three of the four ligands (IC50's = 7.0-25.5 μM). Most ATF-Cu(I) complexes showed low to medium micromolar activity against Candida albicans (IC50's 2.6-24.8 μM) and Staphylococcus aureus (IC50's = 3.4-37.7 μM), with increasing activity corresponding to complexes with higher binding association constants. The antiproliferative properties of ATF-Cu(I) metal salt complexes against mammalian cells were mixed, with low to medium micromolar activity across all cell lines. Notably, several ATF-Cu(I) salt coordination complexes showed submicromolar activity against the HT-1080 fibrosarcoma line (0.52-0.69 μM). The results demonstrate promising activity of ATF-Cu(I) complexes, particularly with pyrrolidine as the formamide component. These studies suggest that the stronger binding association values correlate to higher levels of biological activity.

Voltammetric Investigations of Low-Coordinate Manganese As an Electrocatalyst for Organic Coupling and Functionalization

Earth-abundant, first row, low coordinate transition metal complexes are considered promising candidates for the electrocatalysis of many organic reactions. The use of transition metal catalysts is no stranger to the field of synthetic organic chemistry; however, many of the existing catalysts require the use of rare and expensive metals such as platinum, palladium, ruthenium, and iridium. In this study, we seek to identify and understand the mechanism by which an Mn(I) complex may act as an electrocatalyst for simple organic coupling and C-H functionalization reactions, beginning with the radicalization of benzyl bromide and benzyl chloride as representative organic halide substrates. The careful design and evaluation of this manganese complex has the potential to offer an effective non-toxic 3d metal electrocatalyst, provided that common transition metal behaviors, such as disproportionation or carbon-metal bond formation, are avoided. Initial characterization of the complex by cyclic voltammetry (CV) demonstrates general reversibility of the catalyst, while additions of benzyl halide exhibit the execution of the electron transfer and catalytic step. Electrochemical simulations run in parallel with CV experiments provide supplementary guidance into the relationship between the substrate and catalyst. Additional studies conducted using bulk electrolysis, mass spectrometry, nuclear magnetic resonance, and density functional theory (DFT) calculation will help to further characterize the mechanism and supporting details. Elucidation of the catalytic mechanism will allow us to use this electrocatalyst in a series of synthetic organic conditions and aid in our advancement toward sustainable organometallic catalysis.

Exploring the Reactivity and Stability of Transition Metal Coordination Complexes in Catalysis

Transition metallic coordination complexes assume a pivotal part in diverse reactant cycles in view in their capacity to paintings with an volume of substance modifications. The reactivity and balance of those complexes are earnest elements that have an impact on their functionality and software in synergist applications. This hypothetical offers a format of the key additives affecting the reactivity and balance of transition steel coordination complexes in catalysis. The stability of metal complex is addressed by double unmistakable views like thermodynamic and dynamic strong characteristics. The dating among's balance and reactivity of coordination composites portrayed in the assessment. These evaluation moreover selects the components manipulating the steadiness of steel complexes just like that through metallic particles, ligands, bonding among metal particles and ligands, etc. Likewise, strategies open on behalf of affirmation of stability coefficients passed comprehensively.

Time-Resolved X-ray Emission Spectroscopy and Synthetic High-Spin Model Complexes Resolve Ambiguities in Excited-State Assignments of Transition-Metal Chromophores: A Case Study of Fe-Amido Complexes.

To fully harness the potential of abundant metal coordination complex photosensitizers, a detailed understanding of the molecular properties that dictate and control the electronic excited-state population dynamics initiated by light absorption is critical. In the absence of detectable luminescence, optical transient absorption (TA) spectroscopy is the most widely employed method for interpreting electron redistribution in such excited states, particularly for those with a charge-transfer character. The assignment of excited-state TA spectral features often relies on spectroelectrochemical measurements, where the transient absorption spectrum generated by a metal-to-ligand charge-transfer (MLCT) electronic excited state, for instance, can be approximated using steady-state spectra generated by electrochemical ligand reduction and metal oxidation and accounting for the loss of absorptions by the electronic ground state. However, the reliability of this approach can be clouded when multiple electronic configurations have similar optical signatures. Using a case study of Fe(II) complexes supported by benzannulated diarylamido ligands, we highlight an example of such an ambiguity and show how time-resolved X-ray emission spectroscopy (XES) measurements can reliably assign excited states from the perspective of the metal, particularly in conjunction with accurate synthetic models of ligand-field electronic excited states, leading to a reinterpretation of the long-lived excited state as a ligand-field metal-centered quintet state. A detailed analysis of the XES data on the long-lived excited state is presented, along with a discussion of the ultrafast dynamics following the photoexcitation of low-spin Fe(II)-Namido complexes using a high-spin ground-state analogue as a spectral model for the 5T2 excited state.

The effect of halides on Cd(II)-based metal coordination complexes with indazole and benzimidazole skeletons: Crystal structure, Hirshfeld surface analysis and properties

A set of Cd(II)-based metal coordination complexes with indazole and benzimidazole scaffolds, namely, [Cd(IZBI)Cl2]n·H2O (1) [Cd(IZBI)Br2]n·H2O (2) [Cd(IZBI)I2]·H2O (3) (IZBI stands for 3-(1H-benzimidazol-2-yl)-1H-indazole), were obtained through solvothermal reaction conditions. They have been structurally characterized by elemental analysis, single-crystal X-ray diffraction and IR spectra. Single-crystal X-ray diffraction analysis reveals that complexes 1–3 show one-dimensional polymeric, dimeric and mono-nucleic features, respectively, which indicates that the halide anions affect the final structure of metal coordination complexes. The luminescent maximal peaks can be observed 448, 456 and 462 nm for complexes 1–3, respectively. Compared with the emission peak of IZBI, there exist bathochromic phenomena for metal coordination complexes 1–3, where the red-shifted values can be observed to be 46, 54 and 60 nm, respectively. The order of the photoluminescent emission peaks is summarized as the following: 3 > 2 > 1. The single-crystal X-ray diffraction analysis shows that it occurs the order of the dihedral angles between the pyrazole and imidazole rings (3 < 2 < 1). The Hirshfeld analysis demonstrates that there is a positive correlation between the sequence of H∙∙∙C/C∙∙∙H intermolecular contacts and the dihedral angles formed between the pyrazole and imidazole rings, which is negative correlation with the positions of the luminescent maxima. Additionally, the thermostable behaviors of these complexes were inspected in detail.

Flexible, self-healing, and degradable polymeric dielectrics cross-linked through metal–ligand for resistive memory device

The ability to self-heal is a crucial feature in nature, where living organisms can repair themselves when subjected to minor injuries. With an increasing emphasis on environmental sustainability, the concept of biomimetic self-healing polymeric materials has emerged as a prominent trend, promising to significantly extend the lifespan and reliability of products. Studies have shown that one-third of proteins in living organisms require metal cofactors to function properly. It is known that protein-metal interactions can enhance the performance of certain biomaterials, and different choices of metals and ligands can create diverse material properties, influencing characteristics such as hardness, toughness, adhesion, and self-healing abilities. Gelatin is a natural polymer derived from the hydrolysis of collagen, and its unique amino acid structure has led to a wide range of applications. In this research, by introducing aluminum ions that form metal coordination complexes with the carboxyl groups in gelatin, an elastic network with self-healing properties was constructed. This gelatin-based material was utilized as an insulating layer in resistive switching devices. Furthermore, by employing a gelatin substrate of the same composition, the device demonstrated strong interfacial adhesion. The device based on the self-healing gelatin film exhibited excellent electrical performance and mechanical properties. Even after self-healing, it maintained a high ON/OFF ratio of up to 105 and a concentrated distribution of switching parameters. Supported by compelling physical and electrical evidence, this study showcases significant development opportunities for biomimetic materials in green electronic devices.

Solid State and Solution Structures of Lanthanide Nitrate Complexes of Tris-(1-napthylphosphine oxide).

Coordination complexes of lanthanide metals with tris-1-naphthylphosphine oxide (Nap3PO, L) have not been previously reported in the literature. We describe here the formation of lanthanide(III) nitrate complexes Ln(NO3)3L4 (Ln = Eu to Lu) and the structures of [Ln(NO3)3L2]·2L (Ln = Eu, Dy, Ho, Er) and L. The core structure of the complexes is an eight-coordinate [Ln(NO3)3L2] with the third and fourth ligands H-bonded via their oxygen atoms to one of the naphthyl rings. The structures are compared with those of the analogous complexes of triphenylphosphine oxide and show that the Ln-O(P) bond in the Nap3PO complexes is slightly longer than expected on the basis of differences in coordination numbers. The reaction solutions, investigated by 31P and 13C NMR spectroscopy in CD3CN, show that coordination of L occurs across the lanthanide series, even though complexes can only be isolated from Eu onwards. Analysis of the 31P NMR paramagnetic shifts shows that there is a break in the solution structures with a difference between the lighter lanthanides (La-Eu) and heavier metals (Tb-Lu) which implies a minor difference in structures. The isolated complexes are very poorly soluble, but in CDCl3, NMR measurements show dissociation into [Ln(NO3)3L2] and 2L occurs.

Smart bistable coordination complexes

AbstractSmart molecules have attracted increasing attention due to their transformative role in creating the next generation of smart structures and devices. Smart bistable coordination complexes are a class of functional complexes which have two stable states that can be reversibly switched in response to external stimuli. Such bistable molecules play a vital role in various applications, such as sensors, data storage, spintronics, smart windows, optical switches, information encryption and decryption, displays, actuators, etc. Herein, the recent research studies into the development of these smart bistable metal coordination complexes are reviewed. According to the different external stimuli, these smart bistable coordination systems have been classified and summarized, including light‐responsive systems, thermally‐responsive systems, electrically‐responsive systems, mechanically‐responsive systems, and some other cases. These systems are further subdivided according to the changes in signals (e.g., color, fluorescence, spin state, crystalline phase) under external stimuli. The design principles of each type of smart bistable metal complexes as well as their broad and innovative applications are comprehensively described. Finally, the challenges and opportunities in this field are briefly analyzed and discussed.

Zinc(II) Iminopyridine Complexes as Antibacterial Agents: A Structure-to-Activity Study.

Antibiotic resistance is currently a global health emergency. Metallodrugs, especially metal coordination complexes, comprise a broad variety of candidates to combat antibacterial infections. In this work, we designed a new family of Schiff base zinc(II) complexes with iminopyridine as an organic ligand and different inorganic ligands: chloride, nitrate, and acetate. The antibacterial effect of the Zn(II) complexes was studied against planktonic bacterial cells of Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) strains. The results showed a moderate biocide activity in both types of planktonic bacteria, which arises from the metal complexation to the Schiff base ligand. Importantly, we confirmed the crucial effect of the metal, with Zn(II) improving the activity of Cu(II) counterparts previously reported. On the other hand, the impact of the inorganic ligands was not significant for the antibacterial effect but was relevant for the complex solubility. Finally, as proof of concept of topical antibacterial formulation, we formulated an emulsion containing the most lipophilic Zn(II) complex and confirmed a sustained release for 24 h in a vertical cell diffusion assay. The promising activity of iminopyridine Zn(II) complexes is potentially worth exploring in more detailed studies.

Mn-L-based multifunctional molecular spintronic device: A first-principles investigation

A transition metal coordination complex Mn-L-based multifunctional molecular spintronic device is proposed and its spin-polarized transport properties in two magnetic configurations (parallel and anti-parallel alignments) are evaluated using the first-principles density functional theory and non-equilibrium Green’s function method. Four high-performance physical effects, including spin-filtering, spin-rectifying, giant magnetoresistance and negative differential resistance, are revealed in the proposed device. The physical mechanisms are analyzed through the spin-resolved bias-dependent transmission spectra, and projected device density of states spectra. These results demonstrate that the proposed system holds great promise in developing the multifunctional molecular spintronic devices.

Electropolymerization stabilized bipolar metal coordination complex for high-performance dual-ion batteries

Metal coordination complexes with remarkable redox activity and high working voltage are plagued by their limited specific capacity and sever dissolution problem. A bipolar cobalt-based coordination polymer (CoL) bearing both p-type and n-type active centers was synthesized via the in-situ electropolymerization method with collective merits of multiple redox sites, dual-ion storage capability, and excellent chemical stability. As-prepared electrodes delivered remarkable performances including a high discharge specific capacity of 192.13 mAh/g (at 0.05 A/g), stable cycling over 2000 cycles with 89% capacity retention (at 5A/g), and excellent rate capability. Moreover, the dual-ion storage processes were unveiled by ex-situ Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis. It provides insight to design and synthesis of electropolymerized bipolar electrode for high performance dual-ion batteries.

Exploring the Use of Intracellular Chelation and Non-Iron Metals to Program Ferroptosis for Anticancer Application.

The discovery of regulated cell death (RCD) revolutionized chemotherapy. With caspase-dependent apoptosis initially being thought to be the only form of RCD, many drug development strategies aimed to synthesize compounds that turn on this kind of cell death. While yielding a variety of drugs, this approach is limited, given the acquired resistance of cancers to these drugs and the lack of specificity of the drugs for targeting cancer cells alone. The discovery of non-apoptotic forms of RCD is leading to new avenues for drug design. Evidence shows that ferroptosis, a relatively recently discovered iron-based cell death pathway, has therapeutic potential for anticancer application. Recent studies point to the interrelationship between iron and other essential metals, copper and zinc, and the disturbance of their respective homeostasis as critical to the onset of ferroptosis. Other studies reveal that several coordination complexes of non-iron metals have the capacity to induce ferroptosis. This collective knowledge will be assessed to determine how chelation approaches and coordination chemistry can be engineered to program ferroptosis in chemotherapy.

Coordinated metal complexes with curcumin Schiff base: Synthesis, investigation, antibacterial screening, antioxidant studies, molecular docking and density function theory calculations

Condensation of curcumin with furfuryl amine led to the synthesis of H2L Schiff base in a 1:1 Molar ratio. Subsequently, complexes of this Schiff base with several transition metal ions were prepared also in one‐to‐one molar ratio. Multiple characterization techniques were employed to identify the structure of all compounds. Infrared, UV, proton magnetic resonance spectroscopic tests, elemental analysis, mass spectrometry, thermal analysis, molar conductivity, and density function theory (DFT) calculations were utilized to gain a comprehensive understanding of their structures. Except for the nickel (II) complex, which exhibits non‐electrolyte behavior, all complexes were found to exhibit electrolytic behavior based on molar conductivity studies. Additionally, thermogravimetric analysis was employed to learn more about the complexes' thermal breakdown and the Schiff base ligand's thermal behavior. From DFT studies, some parameters were obtained as bond angles and lengths, chemical hardness, softness, energy levels of highest occupied molecular orbital and lowest unoccupied molecular orbital, electrophilic index, dipole moment, electronegativity, and other variables. Against one or more bacterial species, it was discovered that the antibacterial activity of the metal complexes was superior to that of the free Schiff base. Furthermore, the complexes exhibited notable antioxidant activity according to the results obtained using DPPH scavenging. Overall, a detailed characterization of the synthesized compounds was performed, revealing their structural features, functional properties, and potential applications. Lastly, research on molecular docking was investigated toward all compounds against 3C1L antioxidant protein receptor.

Cadmium and silver complexes of a pyridine containing ligand: syntheses, structural studies, biological activity and docking studies.

The current study aimed to synthesize seven new metal coordination complexes (Q1-Q7) with potential biomedical applications. Novel mononuclear, polynuclear and mixed-ligand coordination compounds of the elements, cadmium(ii) and silver(i) derived from a pyridine containing ligand (2,4,6-tris-(2-pyridyl)-1,3,5-triazine (TPT)) have been synthesized successfully with the general formulae [Cd(TPT)Cl6]·H2O and [Ag x (TPT) y (L)2(ClO4)](ClO4) z (x = 1,2,3, y = 1,2,3, L = PPh3 or phen, z = 1,2). The structural features were fully characterized using various spectroscopic techniques, such as infrared, ultraviolet-visible spectroscopy, 1D and 2D-NMR (1H, 13C, 31P, 1H-1H COSY and 1H-13C HSQCAD), CHN analysis, molar conductance (Λ), thermogravimetric analysis (TGA), and powder X-ray diffraction analysis. The structure of complex Q6 was also confirmed by single-crystal X-ray analysis. The luminescence and electrochemical properties of complexes, in solution, have been studied. X-ray crystallographic determination of the [Ag(TPT)(PPh3)2]ClO4·EtOH (Q6) complex shows that the Ag+ cation is bonded to one tridentate TPT ligand through NNN set of donor atoms and two triphenylphosphine ligands, giving the Ag+ a distorted trigonal bipyramidal geometry. X-ray powder diffraction analysis showed that metal complexes Q3, Q6 and Q7 display crystalline peaks. The complexes were evaluated for their in vitro antibacterial efficacy against various bacterial and fungal species. The in vitro efficacy against the MCF-7 human breast cancer cell line was assessed to determine the anticancer activities. The tri-nuclear silver complex Q3 shows great potential as a therapeutic candidate for treating breast cancer, since it exhibits a half-maximal inhibition concentration (IC50) of 13.45 ± 0.9 μM. Molecular docking simulations were also carried out to evaluate the interaction strength and properties of the metal complexes with selected cancer and bacteria relevant proteins namely cyclin-dependent kinase 2 (CDK2), cyclin-dependent kinase 6 (CDK6), signal transducer and activator of transcription 3 (STAT3), and beta-lactamases from Escherichia coli and Staphylococcus aureus.