Diorganotin(IV) complexes of dipeptides containing the alpha-aminoisobutyryl residue (Aib): preparation, structural characterization, antibacterial and antiproliferative activities of [(n-Bu)2 Sn(H(-1)L)] (LH=H-Aib-L-Leu-OH, H-Aib-L-Ala-OH)

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.

Synthesis, antibacterial evaluation and QSAR analysis of Schiff base complexes derived from [2,2′-(ethylenedioxy)bis(ethylamine)] and aromatic aldehydes

A novel series of Schiff base complexes (1–34) were synthesized which exhibited good antibacterial activity and compound 30 was found to be the most potent antibacterial agent.

Zinc(II) complexes of Pro-Gly and Pro-Leu dipeptides: synthesis, characterization, in vitro DNA binding and cleavage studies

Dipeptide (Pro-Gly and Pro-Leu) Zinc(II) complexes 1 and 2 were designed and synthesized for potential use as cancer chemotherapeutic agents. In order to augment the DNA recognition of metallonuclease activity, zinc metal ion was tethered to peptide motif to carry out DNA site specific hydrolytic cleavage. The structural formulation of the complexes 1 and 2 was done by elemental analysis, spectroscopic methods (IR, NMR, electronic) and molar conductance measurements. Their in vitro DNA binding profile was investigated by UV-vis titrations, fluorescence titrations and circular dichroism which revealed that these complexes bind to CT DNA by electrostatic interactions via groove binding mode. Zn(II) Pro-Gly complex 1 showed greater binding affinity to CT DNA as compared to the Zn(II) Pro-Leu complex 2 due to steric constraints in the latter. The supercoiled pBR322 DNA cleavage activity of complex 1, ascertained by gel electrophoresis demonstrated efficient DNA cleaving ability via hydrolytic mechanistic pathway. Further, the molecular docking studies confirmed that complex 1 bind to the minor groove of DNA having AT-rich sequences with relative binding energy of -196.72kJmol(-1).

Synthesis, Characterization, and Thermal and Antimicrobial Activities of Some Novel Organotin(IV): Purine Base Complexes

A new series of organotin(IV) complexes with purine bases theophylline (HL1) and theobromine (L2) of the types R3Sn(L1), R2Sn(L1)Cl, R3Sn(L2)Cl, and R2Sn(L2)Cl2(R = C6H5CH2–;p-ClC6H4CH2–) have been synthesized in anhydrous THF. The complexes were characterized by elemental analysis, conductance measurements, molecular weight determinations, UV-vis, IR,1H,13C NMR, and mass spectral studies. Various kinetic and thermodynamic parameters of these complexes have also been determined using TG/DTA technique. The thermal decomposition techniques indicate the formation of SnO2as a residue. The results show that the ligands act as bidentate, forming a five-member chelate ring. All the complexes are 1 : 1 metal-ligand complexes. In order to assess their antimicrobial activity, the ligands and their corresponding complexes have also been testedin vitroagainst bacteria (E. coli, S. aureus, andP. pyocyanea) and fungi (Rhizopus oryzaeandAspergillus flavus). All the complexes exhibit remarkable activity, and the results provide evidence that the studied complexes might indeed be a potential source of antimicrobial agents.

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).

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.

Antioxidant activity of butyl- and phenylstannoxanes derived from 2-, 3- and 4-pyridinecarboxylic acids

In vitro antioxidant activity for 12 stannoxanes derived from Ph₃SnCl (compounds 1-3), Ph₂SnCl₂ (compounds 4-6), Bu₃SnCl (compounds 7-9), and Bu₂SnCl₂ (compounds 10-12), was assayed qualitatively by the chromatographic profile with 1,1-diphenyl-2-picrylhydrazil (DPPH) method and by two quantitative methods: the DPPH radical scavenging activity and Ferric-Reducing Antioxidant Power (FRAP) assays. The results were compared with those obtained with the starting materials 2-pyridine- carboxylic acid (I), 3-pyridinecarboxylic acid (II) and 4-pyridinecarboxylic acid (III), as well as with standard compounds, such as vitamin C and vitamin E, respectively. The in vitro antiradical activity with DPPH of diphenyltin derivative 5 showed a very similar behavior to vitamin C at a 20 μg/mL concentration, whereas according to the FRAP method, compound 8 was better. This difference is due to the mechanism of the antioxidant process. The Structure-Activity Relationships (SAR) for both methods is also reported.

Intramolecular chalcogen-tin interactions in [(o-MeEC6H4)CH2]2SnPh(2-n)Cl(n) (E = S, O, CH2; n = 0, 1, 2) and intermolecular chlorine-tin interactions in the meta- and para-methoxy isomers

Organotin(IV) compounds of the type [(o-MeEC(6)H(4))CH(2)](2)SnPh(2-n)Cl(n) were synthesized, E = O, n = 0 (1), n = 1 (2), and n = 2 (3); E = S, n = 0 (4), n = 1 (5), and n = 2 (6); and E = CH(2), n = 0 (7), n = 1 (8), and n = 2 (9). The dichloro compounds 3 and 6 have been investigated by single-crystal X-ray diffraction and exhibit bicapped tetrahedral geometry at the tin atom as a consequence of significant intramolecular Sn...O (3) and Sn...S (6) secondary bonding, in monomolecular units. Compound 3, when crystallized from a hexane/THF solvent mixture, shows two different conformers, 3' and 3'', in the crystal structure; 3' has two equivalent Sn...O interactions, while 3'' has two nonequivalent Sn...O interactions. Upon the recrystallization of 3 from hexane, only a single structural form is observed, 3'. The Sn...E distances in 3', 3'', and 6 are 71.3, 73.5 and 72.9, and 76.3% of the SigmavdW radii, respectively. The meta- and para-substituted isomers of 3 (10, 11) exhibit a distortion at the tin atom due to self-association via intermolecular Sn...Cl interactions, resulting in polymeric structures. (119)Sn NMR spectroscopy suggests that the intramolecular Sn...E interactions persist in solution for the dichloride compounds 3 and 6.