Tetrahedral Geometry Research Articles

Synthesis, structure, and cytotoxicity of some triorganotin(iv) complexes of 3-aminobenzoic acid-based Schiff bases

Abstract Six new triorganotin(iv) complexes of 3-aminobenzoic acid-based Schiff bases, 3-(R′-CH═N)C6H4COOSnR3 (1–6) (R′, R = 5-Br-2-HOC6H3, Ph (1); 3,5-Br2-2-HOC6H2, Ph (2); 4-NEt2-2-HOC6H3, Cy (3); 3-OCH3-2-HOC6H3, Cy (4); 2-HOC10H6, Ph (5); 2-HOC10H6, Cy (6)), have been synthesized by the one-pot reaction of equimolar 3-aminobenzoic acid, substituted 2-hydroxybenzaldehyde (or 2-hydroxy-1-naphthaldehyde) and triorganotin(iv) hydroxide, and characterized by elemental analysis, FT-IR, NMR spectroscopy, and X-ray single crystal diffraction. The NMR data (1 J(119Sn–13C) and 119Sn chemical shifts) suggested that these organotin(iv) complexes are all four-coordinated in CDCl3 solution. In the crystalline state, the tin atoms in 1–4 and 6 are four-coordinated and possess a distorted tetrahedral geometry. Complex 5 with crystalline solvents (CH3OH and CHCl3) exhibits a zigzag chain, and the five coordination atoms on the tin atom are arranged in a trigonal bipyramidal geometry in which the carboxylate oxygen atom and the phenolic oxygen atom of the adjacent ligand occupy the axial positions. In all complexes, the 3-(arylmethyleneamino)benzoate ligands are coordinated with tin atoms in monodentate mode. Their cytotoxicity against two human cancer cell lines (A549 and HeLa), UV-Vis, and fluorescence have been determined, and the results reveal that complexes 1–6 have higher cytotoxicity than cisplatin and may be explored for potential blue luminescent materials.

Titelbild: Stable Luminescent [Cu(NN)(PP)]+ Complexes Incorporating a β‐Cyclodextrin‐Based Diphosphane Ligand with Metal‐Confining Properties (Angew. Chem. 6/2023)

Encapsulation makes the difference!. A β-cyclodextrin-based diphosphane ligand with metal confining properties is key in the stabilization of heteroleptic Cu(I) complexes. In their Research Article (e202214638), Nicola Armaroli, Béatrice Delavaux-Nicot, Jean-François Nierengarten, Dominique Armspach et al. show how encapsulation of the metal-bound diimine ligand moiety in the cyclodextrin cavity influences their electronic properties. In particular, flattening of the metal tetrahedral geometry in the excited state is largely prevented thus resulting in enhanced luminescent properties. Encapsulation makes the difference!. A β-cyclodextrin-based diphosphane ligand with metal confining properties is key in the stabilization of heteroleptic Cu(I) complexes. In their Research Article (e202214638), Nicola Armaroli, Béatrice Delavaux-Nicot, Jean-François Nierengarten, Dominique Armspach et al. show how encapsulation of the metal-bound diimine ligand moiety in the cyclodextrin cavity influences their electronic properties. In particular, flattening of the metal tetrahedral geometry in the excited state is largely prevented thus resulting in enhanced luminescent properties. Aerogels Organic Electronics Membranes

Synthesis, Spectral Studies and Antimicrobial Activity of Zinc(II) Azide Complexes with N,N-Donor and N,N,S-Donor Schiff Base Ligands Derived from 2-Pyridinecarboxaldehyde

Two water soluble Zn(II) Schiff base complexes of composition [Zn(L1)3][Zn(N3)4] (1) and [Zn(L2)2][Zn(N3)4] (2) were synthesized using bidentate N,N-donor (L1) and tridentate N,N,S-donor (L2) of Schiff base ligands viz. (E)-1-phenyl-N-(pyridin-2-ylmethylene)methanamine (L1) and (E)-2-((pyridin-2-ylmethylene)amino)benzenethiol (L2). Different spectroscopic tools such as FT-IR, UV-Vis, 1H NMR and fluorescence spectroscopy have been employed to characterize complexes 1 and 2. Efforts for getting single crystals suitable for X-ray crystal structure could not be achieved. However, from the spectroscopic data and on the basis of the structures of the related zinc(II) complexes reported earlier in the literature, the complexes could be proposed to adopt six coordinated octahedral geometries in one zinc centre coordinated to the ligands and while the other zinc centre has four azides (N3) terminally coordinated resulting in the octahedral and tetrahedral metal geometries around zinc metal atoms. The compounds behave as electrolytes in acetonitrile solution. In vitro antimicrobial activity of the Zn(II) complexes were studied against some microbes like Aspergillus niger, Fusarium ventricossum and Fusarium chlamydosporum. Effective antifungal activity of complex 2 was found against the tested fungal strains.

Synthesis, Characterization of New Ligand Derived from 4-aminoantipyrine and its Complexes with Few Metallic Ions and Evaluation of their Activity as Anticancer

A new heterocyclic ligand (LH) derived from 4-aminoantipyrene was prepared through the reaction of 2-mercaptobenzothiazole with 4-amino-antipyrene dissolved in absolute ethanol as the first step to form compound-A, while the second step involved the reaction of O-phenylenediamine with benzil to produce compound -B, the third step involved the reaction of the products of the first and second steps to give the ligand as a final product. Five complexes, Ni (II), Cu (II), Zn(II), Cd (II) and Ag (I) were synthesized from the reaction of the ligand (LH) with its ionic salts. The ligand and its prepared complexes are characterized by proton nuclear magnetic resonance (1H-NMR), fourier-transform infrared spectroscopy (FTIR), UV-vis spectroscopy and X-rays as well as used other techniques such as quantitative analysis of the elements china health and nutrition survey (CHNS), field emission scanning electron microscope (FESEM) as well as molar conductivity and magnetism sensitivity, in addition to measuring melting points. These techniques were used to determine the structures and geometry of the prepared compounds. FTIR spectra showed that the ligand behaves as a tetra-dentate ligand and that the ratio of ligand to metal is (1:1) for all the prepared complexes according to the molar ratio calculations, which were confirmed by quantitative analysis of the elements CHNS and atomic absorption measurements. The molar conductivity results showed that all the non-electrolytic complexes except the zinc (II) and cadmium (II) complexes were ionic in a 1:1 ratio. From the foregoing, it is proved that the complexes have tetrahedral geometry, with the exception of the Ni(II) and Cu(II) complexes, which are octahedral. The anticancer activity of the ligand and its complex with silver was further evaluated using breast cancer cell lines and compared to the normal cell line. The study showed good results by treating infected cells compared to normal cells.

Local Structure in α-BIMEVOXes (ME = Ge, Sn).

The BIMEVOXes are among the best oxide ion conductors at low and intermediate temperatures. Their high conductivity is associated with local defect structure. In this work, the local structures of two BIMEVOX compositions, Bi2V0.9Ge0.1O5.45 and Bi2V0.95Sn0.05O5.475, are examined using total neutron and X-ray scattering methods, with both compositions exhibiting the ordered α-phase at 25 °C and the disordered γ-phase at 700 °C. While the diffraction data for the α-phase do not allow for the polar (C2) and nonpolar (C2/m) structures to be readily distinguished, measurements of dielectric permittivity suggest the α-phase is weakly ferroelectric in character, consistent with calculations of spontaneous polarization based on a combination of density functional calculations and machine learning methodology. Reverse Monte Carlo (RMC) analysis of total scattering data reveals Ge preferentially adopts tetrahedral geometry at both temperatures, while Sn is found to predominantly adopt octahedral coordination in the α-phase and tetrahedral coordination in the γ-phase. In all cases, V polyhedra are found to consist of tetrahedral, pentacoordinate, and octahedral geometries, as also predicted by the crystallographic analysis and confirmed by 51V solid state NMR spectroscopy. Although similar long-range structures are observed at room temperature, the oxide ion vacancy distributions were found to be quite different between the two studied compositions, with a nonrandom deficiency in vacancy pairs in the second-nearest shell along the ⟨100⟩ tetragonal direction for BIGEVOX10, compared with a long-distance (>8.0 Å) ordering of equatorial vacancies for BISNVOX05. This is attributed to the differences in the preferred coordination geometries of the substituent cations in the two systems. Impedance spectroscopy measurements reveal both compositions show high conductivity in the order of 10-1 S cm-1 at 600 °C.

Development of New Azomethine Metal Chelates Derived from Isatin: DFT and Pharmaceutical Studies

Through the condensation of isatin (indoline-2, 3-dione) and aniline in a 1:1 ratio, a Schiff base ligand was synthesized and characterized via (1H-NMR, mass, IR, UV-Vis) spectra. Elemental analyses, spectroscopy (1H-NMR, mass, UV-Vis), magnetic susceptibility, molar conductivity, mass spectra, scanning electron microscope (SEM), and thermal analysis have all been used to characterize a series of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) metal complexes derived from the titled ligand. The metal-to-ligand ratio is 1:1, according to the analytical data. The Schiff base ligand displayed bidentate behavior with NO coordination sites when it bonded to metal ions, as seen by the IR spectra. The magnetic moment measurement and UV-Vis spectral investigation showed the octahedral geometry of the Cr(III), Fe(III), Co(II), Ni(II), and Zn(II) complexes, whereas they suggested the tetrahedral geometry of the Mn(II), Cu(II), and Cd(II) complexes. The thermal analysis study confirmed the presence of both hydrated and coordinated water molecules in all the compounds, except for the Mn(II) complex, and showed that the complexes decomposed in three or five decomposition steps leaving the corresponding metal oxide as a residue. The ligand and its metal complexes' antibacterial efficacy were evaluated. The findings showed that the metal complexes had stronger antibacterial properties than the ligand alone. The ligand and its metal complexes' anticancer properties were also investigated. A DFT investigation is also reported to gather information regarding the electronic features of the ligand and its metal complexes. Finally, drug-likeness and ADME characteristics were also calculated as parameters.

Probing the Magnetization Relaxation Dynamics of Four-Coordinate Lanthanide(III) Complexes

The reaction of bulky trimethylsilylanilide (N-TMSA) ligand with various lanthanide salts led us to isolate unusual and unique four-coordinate monomeric Ln(III) complexes which are challenging to isolate and not surprisingly rare in the literature. The single crystal X-ray diffraction unveils that all the complexes are monomeric and isostructural with the general molecular formula of [Ln(N-TMSA)3(THF)] where Ln = Dy (1) or Yb (2). Both complexes are found to possess distorted tetrahedral geometry. For all the complexes, detailed dc and ac susceptibility measurements were performed and both 1 and 2 show frequency-dependent out-of-phase susceptibility signals only in the presence of an optimum external magnetic field. The experimental observations are well supported by theoretical calculations and developed magneto-structural correlation using the various model complexes.

Stable Luminescent [Cu(NN)(PP)]+ Complexes Incorporating a β-Cyclodextrin-Based Diphosphane Ligand with Metal-Confining Properties.

A β-cyclodextrin-based diphosphane with metal-confining properties was efficiently synthesized thanks to an unprecedented Smiles-like rearrangement of diphenyl-(2-phosphanylphenyl)phosphane in the presence of excess n-BuLi. The cis-chelating bidentate ligand is capable of forming very stable heteroleptic [Cu(NN)(PP)]+ complexes in which a metal-bound diimine ligand (bpy, phen, or mmp) is located within the cyclodextrin cavity. As a result of ligand encapsulation, flattening of the metal tetrahedral geometry in the excited state is disfavored, thereby resulting in enhanced luminescent properties.

Stable Luminescent [Cu(NN)(PP)]+ Complexes Incorporating a β‐Cyclodextrin‐Based Diphosphane Ligand with Metal‐Confining Properties

AbstractA β‐cyclodextrin‐based diphosphane with metal‐confining properties was efficiently synthesized thanks to an unprecedented Smiles‐like rearrangement of diphenyl‐(2‐phosphanylphenyl)phosphane in the presence of excess n‐BuLi. The cis‐chelating bidentate ligand is capable of forming very stable heteroleptic [Cu(NN)(PP)]+ complexes in which a metal‐bound diimine ligand (bpy, phen, or mmp) is located within the cyclodextrin cavity. As a result of ligand encapsulation, flattening of the metal tetrahedral geometry in the excited state is disfavored, thereby resulting in enhanced luminescent properties.

Zinc(II) Complex Containing Oxazole Ring: Synthesis, Crystal Structure, Characterization, DFT Calculations, and Hirshfeld Surface Analysis.

A new complex of Zn(II), with 5-chloro-2-methylbenzoxazole ligand (L), has been synthesized by the reaction of zinc dichloride with the ligand (L= C8H6ClNO) in ethanol solution: dichloridobis(5-chloro-2-methyl-1,3-benzoxazole)-zinc(II), C16H12Cl4N2O2Zn. The synthesized complex has been fully characterized by elemental analysis, molar conductivity, FT‑IR, UV‑Vis, and single-crystal X-ray diffraction (XRD). The XRD analysis reveals that the complex has a 1:2 metal-to-ligand ratio. The zinc(II) complex has a distorted tetrahedral geometry with two coordinated nitrogen atoms from the ligand. Density Functional Theory (DFT) calculations were performed at the B3LYP level of theory using the LANL2DZ basis set for metal complex and the6-31G(d)basis set for non-metal elements to determine the optimum geometry structure of the complex, and the calculatedHOMOandLUMOorbital energies were presented. A natural bond orbital (NBO) analysis was carried out on the molecules to analyze the atomic charge distribution before and after the complexation of the ligand. The Hirshfeld surface mapped over dnorm, shape index, and curvature exhibited strongH...Cl/Cl...H and H...H intermolecular interactions as the principal contributors to crystalpacking.

Fine Structure and the Huge Zero-Field Splitting in Ni2+ Complexes.

We perform a thorough study of the ground state magnetic properties of nickel-based 3d8 complexes. This includes an in-depth analysis of the contribution of the crystal field, spin exchange and spin-orbit interactions to the ground state magnetic properties. Of particular interest to the current investigation are the presence and occurrence of non-trivial zero-field splitting. The study focuses on the cases of Ni2+ ideal octahedral, trigonal bipyramidal, square planar and tetrahedral geometries. We provide results for the complete energy spectrum, the fine structure related to the ground state and the second set of excited states, low-field magnetic susceptibility and magnetization. In addition, we examine the zero-field fine structure in square pyramidal, trigonal pyramidal and trigonal planar complexes. The obtained results unequivocally show that a moderate or highly coordinated 3d8 complex can neither exhibit spin-orbit-driven large and giant magnetic anisotropy nor a huge zero-field splitting. Moreover, in the trigonal bipyramidal coordination, a fine structure associated to the ground state cannot result from the spin-orbit coupling alone.

Boronic acid derived salicylidenehydrazinopyridine (BOSPY) complexes with aggregation-induced emission for fluorescence imaging of cellular organelles

A series of boronic acid derived salicylidenehydrazinopyridine complexes have been synthesized from the condensation of 2-hydrazinopyridine or 2-hydrazinoquinoline and salicylaldehyde then followed by complexation with various boronic acids. Their X-ray structures demonstrate that the boron atoms adopt a tetrahedral geometry and the aryl substituents from arylboric acids along the vertical axis gave the molecule stereotactic structure and induced molecular chirality. These dyes have good solubility on organic solvents due to the nonplanar curved structure and the presence of axial-substituted groups that provide steric protection. They have strong visible-light absorption, weak emission and large Stoke shifts in organic solvents. Interestingly, molecular aggregates of these new boron complexes experienced the transformation from H-type aggregation to J-type aggregation and exhibited strong aggregation-induced emission (AIE) activities. These novel AIE dyes showed great potential as bioimaging dyes, and two complexes were mainly distributed in lipid droplets of cells in colocalization experiments.

Synthesis, structures, antioxidant, and antifungal activities of organotin(IV) complexes derived from 1-(3′-carboxyphenylhydrazono)naphthalene-2-one

In this study, the hydrazone ligand 1-(3′-carboxyphenylhydrazono)naphthalene-2-one (H2L) was employed to generate three new organotin(IV) compounds with the general formula of [R x SnIV(HL) y ] (where R = Me, x = y = 2 (1); R = n-Bu, x = 3, y = 1 (2), and R = Ph, x = 3, y = 1 (3)). The single-crystal structures of 1 and 3 were examined to establish the coordination environment about Sn(IV). Compound 1 possesses a hepta-coordinate homo-polymer with a chromophoric coordination environment of Me2SnIVO5. Compound 3, on the other hand, has monomeric distorted tetrahedral geometry with Ph3SnO chromophoric unit. The 119Sn-NMR signals in the spectra of 1–3 are found to be at 145.5, 120.1, and −104.4 ppm, respectively, indicating that they are isostructural and adopt four-coordinate tetrahedral geometry in solution. The bioactivities of 1 and 3 among the three are distinct. The antioxidant activity of 1 in ethanol is the highest, with a 45.64% DPPH-scavenging efficiency, whereas 3 shows excellent antifungal efficacy against Penicilium chrysogenum, with a 21 mm inhibited zone at 750 μg/mL, which is significantly higher than that of standard drug amphotericin-B. Thus, the compounds could be treated as potential antioxidant and antifungal agents.

Spectroscopic, computational, anti-bacterial studies of bivalent metal complexes of N-picolyl-amine dithiocarbamate

This study reports the synthesis of seven picolylamine dithiocarbamate complexes of M(II) {M =CoII (1), NiII (2), CuII (3), PdII (4), ZnII (5), CdII (6) and HgII (7)}. CHN analysis, conductivity measurements, magnetic susceptibility measurement, FT-IR, 1H and 13C-NMR, SEM, and XRD were used to investigate the structural geometries of the complexes. The dithiocarbamate ligand coordinates to the M(II) ion in a bidentate mode through sulfur atoms forming a square planar or tetrahedral geometry. Moreover, the surface structural analysis revealed nano-pattern properties. For instance, complexes of Cd(II) and Hg(II) showed a nano-flower pattern, averaging 2–5 µm. Furthermore, the obtained complexes exhibited biological activity properties. The results showed that the new metal (II) compounds possessed remarkable antibacterial inhibition activity against both Gram-positive and Gram-negative bacteria. Additionally, the complexes [Ni(PA-dtc)2], [Cu(PA-dtc)2], and [Pd(PA-dtc)2] were theoretically studied and their quantum parameters were evaluated using Gaussian 09 program at B3LYP/SDD level of theory. The optimized structures of all of the three complexes showed square planar geometry. The calculated bond lengths showed close values, specifically for CSS and CN group, which suggests a partially double bond character. Other quantum parameters have evaluated and showed similar properties such as the total energy, HOMO-LUMO energy gap, Affinity, Hardness, and dipole moment.

One pot synthesis of two potent Ag(I) complexes with quinoxaline ligand, X-ray structure, Hirshfeld analysis, antimicrobial, and antitumor investigations

In one pot, the self-assembly of AgNO3 and 2-chloroquinoxaline (2Cl-quinox) in water–ethanol mixture afforded two novel crystalline Ag(I) complexes. The major product is the polymeric complex [Ag(2Cl-quinox)(NO3)]n; (1), while the minor product (2) comprises two molecules which are the monomeric [Ag(2Cl-quinox)2(NO3)]; (2a) and polymeric [Ag(2Cl-quinox)(NO3)]n; (2b) complexes. The single crystal X-ray structure revealed that 1 and 2b are made up of two-dimensional infinite sheets. In contrast, 2a is a monomeric complex which has a highly distorted tetrahedral geometry around Ag(I) center. In all cases, the 2Cl-quinox molecule acts as a terminal monodentate ligand. Complexes 1 and 2b have similar molecular structures and also have almost similar crystal packing. Using Hirshfeld surface analysis, the O…H hydrogen bonds and π–π stacking interactions contributed significantly to the molecular packing. Both complexes have broad-spectrum action towards multi drug-resistance bacteria. The most effective function of 2 is against Proteus morganii, with a MIC value of 8 μg/mL. Complex 2 (IC50 = 5.93 ± 0.52 μg/mL) has remarkably greater cytotoxic effect against lung carcinoma (A-549) than cis-platin (IC50 = 7.5 ± 0.69 μg/mL) and AgNO3 (IC50 = 14.7 ± 0.53 μg/mL). The higher Ag-content in 2 could be the main reason for its higher cytotoxicity than 1.

Crystal structure of poly[(μ6-benzene-1,3,5-tricarboxylato)tris(1-methylpyrrolidin-2-one)nitratodizinc(II)

The asymmetric unit of the title compound, [Zn2(C9H3O6)(NO3)(C5H9NO)3] n , I, consists of two different zinc(II) ions bridged by the carboxylate group of benzene-1,3,5-tricarboxylate (BTC3−). The Zn1 center is tetra-coordinated by the carboxylate O atoms of three symmetrically equivalent BTC3− anions and one nitrate O atom in a distorted tetrahedral geometry with Zn—Ocarboxylate bond lengths (average value 1.958 Å) slightly shorter than the Zn—Onitrate distance [2.013 (6) Å]. The Zn2 center is hexa-coordinated by three O atoms from the carboxylic groups of different BTC3− linkers and three O atoms of 1-methylpyrrolidin-2-one (NMP) in a slightly distorted octahedral geometry with nearly equivalent Zn—O bond lengths (average values of 2.091 and 2.088 Å, respectively). Linking of the paddle-wheel dizinc building units by the three carboxylate groups of the BTC3− molecule results in the formation of the three-dimensional coordination framework.

Ag(I), In (III), and Sn (II) chelates of azo mesalamine drug: Characterization, DFT studies, molecular docking and biological evaluation

A new set of Ag(I), In (III) and Sn (II) chelates based on azo dye ligand of 5‐aminosalicylic acid (H2L) were prepared. The structures of this novel chelates have already been confirmed by elemental analysis, thermo‐gravimetric analysis, molar conductance, X‐ray diffraction (XRD), UV–Vis, Fourier‐transform infrared spectroscopy (FT‐IR), and mass spectra. The lower conductivity values showed the non‐electrolytic nature. The kinetic and thermodynamic parameters were determined through using Coats–Redfern model, also, potential application; the antibacterial activity of the target compounds was tested by examining their effect on the development of various strains of bacteria. Utilizing UV–visible absorption measurements, we investigated the interaction between calf thymus DNA and the evaluated compounds. According to the findings, the intercalative binding approach, the chelates interact with DNA by assessing the binding constants. Additionally, the in vitro antimicrobial properties of the ligand and its metal chelates were evaluated. The theoretical density functional theory (DFT) simulations for the azo dye ligand (H2L) were completed by using B3LYP/6‐311G++ (d,p) basis functions, and the B3LYP/LanL2DZ for Ag(I), In (III), and Sn (II) chelatesshows that the uninuclear Ag(I) and Sn(II) chelates under consideration have a tetrahedral geometry. Although the experimental data are in agreement with the octahedral shape for binuclear In (III) chelate. Molecular docking simulations were carried out using molecular operating environment (MOE) software for the ligand and its chelates. Docking simulation results indicated that the Ag(I) chelate was more potent and exhibited a higher affinity for the (3QKK) protein than the In (III) and Sn (II) chelates. This is in agreements with the biological evaluations under studies.

Synthetic Exploration of Bis(phenolate) Aza-BODIPYs and Heavier Group 13 Chelates

A series of boron, aluminum, gallium, and indium chelates containing the underexplored bis(phenolate) aza-dipyrromethene (aza-DIPY) core were prepared. These compounds were found to possess near-infrared absorption and emission profiles in the 710 to 770 nm domain and exhibit quantum yield values up to 14%. X-ray diffraction analysis revealed that heavier group 13 bis(phenolate) aza-DIPY chelates possessed octahedral geometries with either THF or pyridine groups occupying the axial positions as opposed to the tetrahedral geometry of the boron chelate.

Synthesis, Characterization and Biological Studies of Bimetallic Complexes Containing Co(II), Cd(II) and Hg(II) and {N, N’,-Bis (Benzylidene)-1,3,-Diamine} Schiff Base in 1:2 Ratio

A new series of bimetallic complexes of Co(II), Cd(II) and Hg(II) with Schiff base ligand (N,N',-Bis(Benzylidene)-1,3-Phenylenediamine, {BENDAMB (1,3)} have been synthesized and characterized by elemental analysis, molar conductance, magnetic moment measurements, IR, Electronic and 1H NMR spectral studies. The softness parameter TEn of complexes have also been calculated to derive the binding side of the thiocyanate ligand. The spectral data shows that the Schiff base ligand is linked with comparatively harder metal Co2+ whereas SCN present as terminal. Magnetic susceptibility measurements indicate tetrahedral geometry around Cobalt ion. The softness parameter, suggest cationic-anionic structure for these complexes. Newly synthesized bimetallic complexes have been screened, for their antimicrobial and antifungal activities and was compared with solvent and Schiff base, screening results indicates that, the metal complexes are moderately active compared with those of pure Schiff base, BENDAMB (1,3).

Designing metal chelates of halogenated sulfonamide Schiff bases as potent nonplatinum anticancer drugs using spectroscopic, molecular docking and biological studies

In this contribution, five Ni(II) complexes have been synthesized from sulfonamide-based Schiff bases (SB1–SB5) that comprise bromo or iodo substituents in the salicylidene moiety. The chemical structures of these compounds were extensively elucidated by different analytical and physicochemical studies. All ligands act as bidentate chelators with ON binding mode yielding octahedral, square planar, or tetrahedral geometries. The phenolic OH at δ 12.80 ppm in the free Schiff base SB2 vanishes in the 1H NMRspectrum of diamagnetic complex [Ni(SB2–H)2] favoring the OH deprotonation prior to the chelation with Ni(II) ion. The appearance of twin molecular ion peaks ([M − 1]+ and [M + 1]+) is due to the presence of bromine isotopes (79Br and 81Br) in the mass spectra of most cases. Also, the thermal decomposition stages of all complexes confirmed their high thermal stability and ended with the formation of NiO residue of mass 6.42% to 14.18%. Besides, antimicrobial activity and cytotoxicity of the ligands and some selected complexes were evaluated. Among the ligands, SB4 showed superior antimicrobial efficacy with MIC values of 0.46, 7.54, and 0.95 µM against B. subtilis, E. coli, and A. fumigatus strains, respectively. The consortium of different substituents as two bromine atoms either at positions 3 and/or 5 on the phenyl ring and a thiazole ring is one of the reasons behind the recorded optimal activity. Moreover, there is a good correlation between the cytotoxicity screening (IC50) and molecular docking simulation outcomes that predicted a strong binding of SB2 (16.0 μM), SB4 (18.8 μM), and SB5 (6.32 μM) to the breast cancer protein (3s7s). Additionally, [Ni(SB4–H)2] (4.33 µM) has nearly fourfold potency in comparison with cisplatin (19.0 μM) against breast carcinoma cells (MCF-7) and is highly recommended as a promising, potent, as well as low-cost non-platinum antiproliferative agent after further drug authorization processes.