Self-assembly of extended Schiff base amino acetate skeletons, 2-{[(2Z)-(3-hydroxy-1-methyl-2-butenylidene)]amino}phenylpropionate and 2-{[(E)-1-(2-hydroxyaryl)alkylidene]amino}phenylpropionate skeletons incorporating organotin(IV) moieties: Synthesis, spectroscopic characterization, crystal structures, and in vitro cytotoxic activity

Biologically potent organotin(iv) complexes of N-acetylated β-amino acids with spectroscopic, X-ray powder diffraction and molecular docking studies†

Twelve novel organotin(iv) complexes (1–12) of N-acetylated β-amino acids (L₁–L₈) were synthesized and characterized by elemental analysis, FTIR, multinuclear (¹H, ¹³C, ¹¹⁹Sn) NMR, EI-MS and powder XRD techniques. The XRD results determined lattice parameters, average particle size, and intrinsic strain and confirmed the crystalline nature of complexes as face centered cubic phases. Molecular docking analysis using a catalytic pocket of the α-glucosidase enzyme indicated that most of the compounds displayed a well-fitted orientation and occupied important amino acids in the enzyme's catalytic pocket. Furthermore, in vitro α-glucosidase inhibitory activity results revealed that L₁ and complexes 4, 6 and 10 showed the highest activity with IC₅₀ values of 21.54 ± 0.45, 37.96 ± 0.81 and 35.20 ± 1.02, respectively, compared to standard acarbose with an IC₅₀ value of 42.51 ± 0.21. In addition, in vivo antidiabetic activity of selected compounds using alloxan induced diabetic rabbits showed that L₄ and complexes 4, 6, 10, 12 showed significant activities like standard metformin. Anti-bacterial activity against the selected Gram-positive and Gram-negative bacterial strains has the following order Escherichia coli > Pseudomonas aeruginosa > Staphylococcus aureus > Bacillus subtilis. Similarly, antioxidant activity by the DPPH scavenging method was also studied with following results: triorganotin > diorganotin > ligands.

Novel organotin(iv) complexes of N-acetylated β-amino acids were synthesized and characterized by different techniques. The molecular docking, in vitro α-glucosidase inhibitory, and in vivo antidiabetic activity studies were carried out.

Di-butyltin(iv) complexes with azo-carboxylates: synthesis, characterization, crystal structures and their anti-diabetic assay

The results of the anti-diabetic test of the compounds against the alpha glucosidase enzyme showed that2exhibits promising activity.

o-Vanillin Derived Schiff Bases and Their Organotin(IV) Compounds: Synthesis, Structural Characterisation, In-Silico Studies and Cytotoxicity

Six new organotin(IV) compounds of Schiff bases derived from S-R-dithiocarbazate [R = benzyl (B), 2- or 4-methylbenzyl (2M and 4M, respectively)] condensed with 2-hydroxy-3-methoxybenzaldehyde (oVa) were synthesised and characterised by elemental analysis, various spectroscopic techniques including infrared, UV-vis, multinuclear (¹H, ¹³C, ¹¹⁹Sn) NMR and mass spectrometry, and single crystal X-ray diffraction. The organotin(IV) compounds were synthesised from the reaction of Ph₂SnCl₂ or Me₂SnCl₂ with the Schiff bases (S2MoVaH/S4MoVaH/SBoVaH) to form a total of six new organotin(IV) compounds that had a general formula of [R₂Sn(L)] (where L = Schiff base; R = Ph or Me). The molecular geometries of Me₂Sn(S2MoVa), Me₂Sn(S4MoVa) and Me₂Sn(SBoVa) were established by X-ray crystallography and verified using density functional theory calculations. Interestingly, each experimental structure contained two independent but chemically similar molecules in the crystallographic asymmetric unit. The coordination geometry for each molecule was defined by thiolate-sulphur, phenoxide-oxygen and imine-nitrogen atoms derived from a dinegative, tridentate dithiocarbazate ligand with the remaining positions occupied by the methyl-carbon atoms of the organo groups. In each case, the resulting five-coordinate C₂NOS geometry was almost exactly intermediate between ideal trigonal-bipyramidal and square-pyramidal geometries. The cytotoxic activities of the Schiff bases and organotin(IV) compounds were investigated against EJ-28 and RT-112 (bladder), HT29 (colon), U87 and SJ-G2 (glioblastoma), MCF-7 (breast) A2780 (ovarian), H460 (lung), A431 (skin), DU145 (prostate), BE2-C (neuroblastoma) and MIA (pancreatic) cancer cell lines and one normal breast cell line (MCF-10A). Diphenyltin(IV) compounds exhibited greater potency than either the Schiff bases or the respective dimethyltin(IV) compounds. Mechanistic studies on the action of these compounds against bladder cancer cells revealed that they induced the production of reactive oxygen species (ROS). The bladder cancer cells were apoptotic after 24 h post-treatment with the diphenyltin(IV) compounds. The interactions of the organotin(IV) compounds with calf thymus DNA (CT-DNA) were experimentally explored using UV-vis absorption spectroscopy. This study revealed that the organotin(IV) compounds have strong DNA binding affinity, verified via molecular docking simulations, which suggests that these organotin(IV) compounds interact with DNA via groove-binding interactions.

Dibutyltin(IV) Complexes Derived from L-DOPA: Synthesis, Molecular Docking, Cytotoxic and Antifungal Activity

A series of organotin(IV) complexes was herein prepared and characterized. A one-pot synthetic strategy afforded reasonable to high yields, depending on the nature of the ligand. All new complexes were fully characterized by spectroscopic techniques, consisting of IR, MS and NMR (¹H, ¹³C and ¹¹⁹Sn). The in vitro cytotoxicity tests demonstrated that the organotin complexes produced a greater inhibition, versus cisplatin (the positive control), of the growth of six human cancer cell lines: U-251 (glioblastoma), K-562 (chronic myelogenous leukemia), HCT-15 (colorectal), MCF-7 (breast), MDA-MB-231 (breast) and SKLU-1 (non-small cell lung). The potency of this cytotoxic activity depended on the nature of the substituent bonded to the aromatic ring. All complexes exhibited excellent IC₅₀ values. The test compounds were also screened in vitro for their antifungal effect against Candida glabrata and Candida albicans, showing minimum inhibitory concentration (MIC) values lower than those obtained for fluconazole. A brine shrimp bioassay was performed to examine the toxic properties. Molecular docking studies demonstrated that the organotin(IV) complexes bind at the active site of topoisomerase I in a similar manner to topotecan, sharing affinity for certain amino acid side chains (Ile535, Arg364 and Asp533), as well as for similar DNA regions (DA113, DC112 and DT10).

Fluorescent biogenic Schiff base compounds of dimethyltin

Fluorescent biogenic Schiff base compounds of dimethyltin featuring distinct coordination sphere in solid and solution phase.

Synthesis, photophysical properties and structures of organotin-Schiff bases utilizing aromatic amino acid from the chiral pool and evaluation of the biological perspective of a triphenyltin compound

Five new organotin(IV) complexes of compositions [Me₂SnL¹] (1), [Me₂SnL²]_n (2), [Me₂SnL³] (3), [Ph₃SnL¹H]_n (4) and [Ph₃SnL³H] (5) (where L¹=(2S)-2-((E)-((Z)-4-hydroxypent-3-en-2-ylidene)amino)-3-(1H-indol-3-yl)propanoate, L²=(2S)-(E)-2-((2-hydroxybenzylidene)amino)-3-(1H-indol-3-yl)propanoate and L³=(2S)-(E)-2-((1-(2-hydroxyphenyl)ethylidene)amino)-3-(1H-indol-3-yl)propanoate were synthesized and spectroscopically characterized. The crystal structures of 1-4 were determined. For the dimethyltin derivative 2, a polymeric chain structure was observed as a result of a long Sn∙∙∙O contact involving the exocyclic carbonyl oxygen-atom from the tridentate ligand of a neighboring Sn-complex unit. The tin atom in this complex has a distorted octahedral coordination geometry, in which the long Sn-O bond is almost trans to the tridentate ligand nitrogen-atom. In contrast, the dimethyltin(IV) complexes 1 and 3 displayed discrete monomeric structures where the tin atom has distorted trigonal-bipyramidal geometry with the two coordinating L oxygen atoms defining the axial positions. On the other hand, 4 is a chain polymer in the solid state. The ligand-bridged Sn atoms adopt a trans-Ph₃SnO₂ trigonal-bipyramidal configuration with equatorial phenyl groups. A carboxylato oxygen atom from one and the hydroxyl oxygen of the successive ligand in the chain occupy the axial positions. The solution structures were predicted by the use of ¹¹⁹Sn NMR chemical shifts. The photophysical properties of the complexes were investigated in the solid and in solution. The triphenyltin(IV) compound 4 was tested in detail ex vivo against A375 (human melanoma) cell line, exhibiting an IC₅₀ value of 261nM to induce cell death as assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay without significant alteration of cytolysis as determined by lactate dehydrogenase (LDH) assay. Compound 4-mediated potent cell death was also determined by Live and Dead assay and caspase-mediated cleavage of poly-ADP ribose polymerase (PARP). Potent cell death activity was not observed in primary cells, like blood-derived peripheral mononuclear cells (PBMC). Compound 4 inhibited the diphenyl hexatriene (DPH) binding to cells and decreased the micro viscosity in a dose-dependent manner. Additionally, the ability of 4 and cyclodextrin (CD) to interact was determined by molecular modelling.

Crystal structure of catena-poly[(μ2-acetamido-benzoato-κ2 O:O′)triphenyltin(IV)], C27H23NO3Sn

C27H23NO3Sn, orthorhombic, P212121, a = 8.9287(7) Å, b = 15.0252(12) Å, c = 18.4531(14) Å, V = 2475.6(3) Å3, Z = 4, R gt (F) = 0.0315, wR ref (F 2 ) = 0.0861, T = 296(2) K.

Diorganotin(IV) derivatives of N-methyl p-fluorobenzo-hydroxamic acid: preparation, spectral characterization, X-ray diffraction studies and antitumor activity

Three diorganotin(IV) complexes of the general formula R₂Sn[RcC(O)N(RN)O] (Rc = aryl, RN = Alkyl) have been synthesized by refluxing in toluene the corresponding diorganotin(IV) oxides with the free ligand N-methyl p-fluorobenzohydroxamic acid, using a Dean and Stark water separator. The ligand was derived from the reaction of the corresponding p-fluorobenzoyl chloride and N-methylhydroxylamine hydrochloride in the presence of sodium hydrogen carbonate. The isolated free ligand and its respective diorganotin compounds have been characterized by elemental analysis, IR and ¹H-, ¹³C-, ¹¹⁹Sn-NMR spectroscopies. The crystal structures of the diorganotin complexes have been confirmed by single crystal X-ray diffraction methods. The investigations carried out on the diorganotin(IV) complexes of N-methyl p-fluorobenzohydroxamic acid confirmed a 1:2 stoichiometry. The complex formation took place through the O,O-coordination via the carbonyl oxygen and subsequent deprotonated hydroxyl group to the tin atom. The crystal structures of three diorganotin complexes were determined and were found to adopt six coordination geometries at the tin centre with coordination to two ligand moieties.

Synthesis, Characterization and In Vitro Antibacterial Studies of Organotin(IV) Complexes with 2-Hydroxyacetophenone-2-methylphenylthiosemicarbazone (H(2)dampt)

Five new organotin(IV) complexes of 2-hydroxyacetophenone-2-methylphenylthiosemicarbazone [H₂dampt, (1)] with formula [RSnCl_n-1(dampt)] (where R = Me, n = 2 (2); R = Bu, n = 2 (3); R = Ph, n = 2 (4); R = Me₂, n = 1 (5); R = Ph₂, n = 1 (6)) have been synthesized by direct reaction of H₂dampt (1) with organotin(IV) chloride(s) in absolute methanol. The ligand (1) and its organotin(IV) complexes (2–6) were characterized by CHN analyses, molar conductivity, UV-Vis, FT-IR, ¹H, ¹³C, and ¹¹⁹Sn NMR spectral studies. H₂dampt (1) is newly synthesized and has been structurally characterized by X-ray crystallography. Spectroscopic data suggested that H₂dampt (1) is coordinated to the tin(IV) atom through the thiolate-S, azomethine-N, and phenoxide-O atoms; the coordination number of tin is five. The in vitro antibacterial activity has been evaluated against Staphylococcus aureus, Enterobacter aerogenes, Escherichia coli, and Salmonella typhi. The screening results have shown that the organotin(IV) complexes (2–6) have better antibacterial activities and have potential as drugs. Furthermore, it has been shown that diphenyltin(IV) derivative (6) exhibits significantly better activity than the other organotin(IV) derivatives (2–5).

Structural analysis of organometallic compounds with soft ionization mass spectrometry

The analysis of organometallic compounds with mass spectrometry has some special features in comparison with organic and bioorganic compounds. The first step is the choice of a suitable ionization technique, where the electrospray ionization is certainly the best possibility for most classes of organometallic compounds and metal complexes. Some ionization mechanisms of organometallic compounds are comparable to organic molecules, such as protonation/deprotonation, and adduct formation with sodium or potassium ions; however, in many cases, different mechanisms and their combinations complicate the spectra interpretation. Organometallics frequently undergo various types of adduct and polymerization reactions that result in significantly higher masses observed in the spectra in comparison to molecular weights of studied compounds. Metal elements typically have more natural isotopes than common organic elements, which cause characteristic wide distributions of isotopic peaks; for example, tin has ten natural isotopes. The isotopic pattern can be used for the identification of the type and number of metal elements in particular ions. The ionization and fragmentation behavior also depend on the type of metal atom; therefore, our discussion of mass spectra interpretation is divided according to the different type of organometallic compounds. Among various types of mass spectrometers available on the market, trap-based analyzers (linear or spherical ion-traps, Orbitrap) are suitable to study complex fragmentation pathways of organometallic ions and their adducts, whereas high-resolution and high-mass accuracy analyzers (time-of-flight-based analyzers, or Fourier transform-based analyzers-Orbitrap or ion cyclotron resonance mass spectrometers) provide accurate masses applicable for the determination of the elemental composition of individual ions.

Antimicrobial activity of organotin(IV) complexes with the ligand benzil bis(benzoylhydrazone) and 4,4'-bipyridyl as coligand

Several methyltin(IV) and butyltin(IV) complexes with the ligand benzil bis(benzoylhydrazone) and 4,4'-bipyridyl as coligand were synthesised and characterized by elemental analysis and by IR, (1)H, (13)C and (119)Sn NMR spectroscopies. Some of them were also analyzed using single crystal X-ray diffraction. The title compounds were evaluated for their in vitro antimicrobial properties. All buthyltin complexes showed significant inhibition of Gram positive bacteria, resulting Bacillus subtilis, Sarcina lutea and both methicillin-susceptible and methicillin-resistant Staphylococcus epidermidis the most sensitive strains. Furthermore, they were able to inhibit the growth of Gram negative bacteria, especially Proteus vulgaris, whereas no activity was exhibited against fungi. All methyltin complexes were devoid of antimicrobial properties.

{3-Methyl-2-[(1-oxido-2-naphth-yl)methyl-idene-amino-κO,N]butano-ato-κO}(1H-pyrazole-κN)nickel(II)

In either of the two independent mol­ecules within the asymmetric unit of the title compound, [Ni(C₁₆H₁₅NO₃)(C₃H₄N₂)], the Ni^II atom is coordinated by the two N atoms and two O atoms in a distorted square-planar geometry. The crystal packing is stabilized by strong and weak inter­molecular C—H⋯O hydrogen bonds, as well as weak centroid–centroid π-stacking inter­actions [centroid–centroid separation = 3.526 (3) Å].