Synthesis, characterization and in vitro cytotoxicity of new organotin(IV) derivatives of N-methylglycine

Tin(II) and Tin(IV) Complexes Incorporating the Oxygen Tripodal Ligands [(η5-C5R5)Co{P(OEt)2O}3]-, (R = H, Me; Et = -C2H5) as Potent Inflammatory Mediator Inhibitors: Cytotoxic Properties and Biological Activities against the Platelet-Activating Factor (PAF) and Thrombin

Metal complexes displaying antiplatelet properties is a promising research area. In our methodology, Platelet-Activating Factor (PAF), the most potent lipid pro-inflammatory mediator, serves as a biological probe. The antiplatelet activity is exerted by the inhibition of the PAF-induced aggregation in washed rabbit platelets (WRPs) and in rabbit plasma rich in platelets (rPRPs). Herein, the synthesis and biological investigation of a series of organometallic tin(II) and tin(IV) complexes, featuring the oxygen tripodal Kläui ligands [(η⁵-C₅R₅)Co{P(OEt)₂O}₃]^-, {R = H, (L_OEt^-); Me (L*_OEt^-)}, are reported. Reaction of NaL_OEt (1a) and NaL*_OEt (1b) with SnCl₂, yielded the rare four-coordinate L_OEtSnCl (2a) and L*_OEtSnCl (2b) complexes. Accordingly, L_OEtSnPh₃ (3a) and L*_OEtSnPh₃ (3b) were prepared, starting from Ph₃SnCl. Characterization includes spectroscopy and X-ray diffraction studies for 2a, 2b and 3b. The antiplatelet activity of the lead complexes 2b and 3a (IC₅₀ = 0.5 μΜ) is superior compared to that of 1a and 1b, while both complexes display a pronounced inhibitory activity against thrombin (IC₅₀ = 1.8 μM and 0.6 μM). The in vitro cytotoxic activities of 3a and 2b on human Jurkat T lymphoblastic tumor cell line is higher than that of cisplatin.

Unfolding biological properties of a versatile dicopper(II) precursor and its two mononuclear copper(II) derivatives

Synthesis, inter-conversions and biological study of the dichloro bridged dicopper(II) compound [CuLCl]₂ (1) and its two mononuclear derivatives [CuLCl(H₂O)]·H₂O (2) and [CuLCl(py)] (3) (HL=2-(2-pyridylmethyleneamino)benzenesulfonic acid) are described. The dimeric compound 1 collapses into monomers 2 and 3 in the presence of coordinating solvents, water and pyridine, respectively, and 1 is regenerated upon simple stirring of 2 or 3 in methanol. The reactions of 1 with neutral (present study) and charged (earlier studies) ligands result in monomeric and multimeric compounds, respectively, attesting that it is a versatile dicopper(II) precursor. The anticancer activity of these copper complexes (1-3) was screened against lung (A-549) and breast (MDA-MB-231) human cancer cell lines. The IC₅₀ (half maximal inhibitory concentration) value for one (3) of the compounds suggests preferential cytotoxicity against breast cancer MDA-MB-231 cell line. Furthermore, the IC₅₀ value obtained for complex 3 is found to be almost two-fold times cytotoxic than the standard drug cisplatin. In addition, the underlying possible mechanism of its apoptosis-inducing efficacy in MDA-MB-231 cells has been rationalized by using flow cytometry (FACS) and Hoechst 33342/propidium iodide (PI) fluorescence staining. The stimulation of apoptotic induction for complex 3 has further been affirmed by reactive oxygen species (ROS) generation and mitochondrial aggregations studies.

Variation of the Molecular Conformation, Shape, and Cavity Size in Dinuclear Metalla-Macrocycles Containing Hetero-Ditopic Dithiocarbamate-Carboxylate Ligands from a Homologous Series of N-Substituted Amino Acids

A homologous series of dithiocarbamate ligands derived from N-substituted amino acids was reacted with different diorganotin dichlorides to give 18 diorganotin complexes. Spectroscopic and mass spectrometric analysis evidenced the formation of assemblies with six-coordinate tin atoms embedded in skewed-trapezoidal bipyramidal coordination environments of composition C₂SnS₂O₂. Single-crystal X-ray diffraction analysis for three of the compounds revealed a one-dimensional polymeric structure for the complex with the ligand derived from 5-aminopentanoic acid, which through further intermolecular Sn···O interactions generated an overall two-dimensional coordination polymer containing 40-membered hexanuclear tin macrocycles. On the contrary, the ligands derived from 6-aminohexanoic and 8-aminooctanoic acid provided the expected 22- and 26-membered dinuclear macrocyclic structures. Density functional theory calculations for a representative series of macrocyclic complexes of composition [Me₂SnLx]₂ with Lx = ¯S₂CN(Me)-(CH₂)_x-COO¯ (x = 3-12) enabled a detailed analysis of the variations in the molecular conformation, shape, and cavity size of the macrocycles in dependence of the aliphatic spacer. Because of odd-even effects, the difunctional ligands can adopt either a curved or a twisted-pincer shape, while the SnS_xO_4-x (x = 0-4) moieties can act either as linear or angular tectons with varying connectivity angles.

Sulfonated Schiff base Sn(IV) complexes as potential anticancer agents

Syntheses, crystal structures and biological activities of the diphenoxo-bridged diorgano dinuclear Sn(IV) compounds [Sn(Et)₂(HL)(H₂O)]₂ (1) and [Sn(n-Bu)₂(HL)(H₂O)]₂ (2) derived from the Schiff base 2-[(2,3-dihydroxyphenyl)methylideneamino]benzenesulfonic acid trihydrate (H₃L·3H₂O) are described. The monoprotonated form (HL^2-) of the Schiff base behaves as O,O'-bidentate ligand, chelating the metal by the two phenoxo oxygen atoms. The hexacoordinated metal centres in 1 and 2 are bridged by a phenoxo oxygen and the remaining coordination positions are fulfilled by the other phenoxo oxygen, two organic groups (ethyl for 1 and n-butyl for 2) and a water molecule. A two dimensional zigzag sheet in 1 and three dimensional polymeric networks in H₃L·3H₂O and 2 are stabilized by a number of non-covalent, H-bonding and π⋯π stacking interactions. The DNA binding activities of these complexes have been studied by UV-vis and fluorescence spectroscopies. Their antiproliferative efficacies have been evaluated on A-549, HeLa and MDA-MB-231 cancer cell lines by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. IC₅₀ values (1.35±0.23, 2.43±0.54 and 1.74±0.04μM for 2) are indicative of a substantial cytotoxicity of 2, mainly towards the A-549 lung cancer cell line. The greater antiproliferative efficacy of 2has further been studied by fluorescence activated cell sorting (FACS) and nuclear morphology by Hoechst/propidium iodide (PI) double staining method. The possible mode of the apoptotic pathway for 2has been substantiated by the reactive oxygen species (ROS) generation studies.

A sulfonated Schiff base dimethyltin(iv) coordination polymer: synthesis, characterization and application as a catalyst for ultrasound- or microwave-assisted Baeyer–Villiger oxidation under solvent-free conditions

The sulfonated Schiff base dimethyltin(iv) coordination polymer is an efficient heterogeneous catalyst for the peroxidative Baeyer–Villiger oxidation of ketones, under ultrasound or microwave irradiation and solvent- and additive-free conditions.

Preparation, Characterization, and Antimicrobial Activities of Bimetallic Complexes of Sarcosine with Zn(II) and Sn(IV)

Heterobimetallic complexes of Zn(II) and Sn(IV) with sarcosine have been synthesized at room temperature under stirring conditions by the reaction of sarcosine and zinc acetate in 2 : 1 molar ratio followed by the stepwise addition of CS₂ and organotin(IV) halides, where R = Me, n-Bu, and Ph. The complexes were characterized by elemental analysis, FT-IR and NMR (¹H, ¹³C) spectroscopy. IR data showed that the ligand acts in a bidentate manner. NMR data revealed the four coordinate geometry in solution state. In vitro antimicrobial activities data showed that complexes (3) and (4) were effective against bacterial and fungal strains with few exceptions.

Octa-n-butyl-1κC,2κC,3κ,4κC-bis-(μ-2,3-dibromo-propionato)-1:2κO:O',3:4κO:O'-bis-(2,3-dibromo-propionato)-1κO,3κO-di-μ(3)-oxido-1:2:4κO:O:O,2:3:4κO:O:O-tetra-tin(IV)

In the centrosymmetric tetra­nuclear title complex, [Sn₄(C₄H₉)₈(C₃H₃Br₂O₂)₄O₂], one of the two independent Sn atoms is five-coordinated by one O atom of the carboxyl­ate anion, two bridging O atoms and two n-butyl groups in a C₂SnO₃ distorted trigonal bipyramidal geometry. The other Sn atom also has a distorted trigonal bipyramidal geometry, being coordinated by two O atoms of two carboxyl­ate anions, one bridging O atom and two butyl groups. An inter­esting feature of the crystal structure is the short Sn⋯O [2.756 (4) Å] and O⋯O [2.608 (3) Å] inter­actions. The –BrCH₂—CHBr– segments of the two carboxyl­ate anions are disordered over two positions [site occupancies of 0.60 (1)/0.40 (1) and 0.53 (2)/0.47 (2)]. Weak non-directional C—H⋯O inter­actions lead to the formation of infinte chains along the a axis; other weak inter­molecular C—H⋯π inter­actions are also present.

Applications of heteronuclear NMR spectroscopy in biological and medicinal inorganic chemistry

There is a wide range of potential applications of inorganic compounds, and metal coordination complexes in particular, in medicine but progress is hampered by a lack of methods to study their speciation. The biological activity of metal complexes is determined by the metal itself, its oxidation state, the types and number of coordinated ligands and their strength of binding, the geometry of the complex, redox potential and ligand exchange rates. For organic drugs a variety of readily observed spin I = 1/2 nuclei can be used (1H, 13C, 15N, 19F, 31P), but only a few metals fall into this category. Most are quadrupolar nuclei giving rise to broad lines with low detection sensitivity (for biological systems). However we show that, in some cases, heteronuclear NMR studies can provide new insights into the biological and medicinal chemistry of a range of elements and these data will stimulate further advances in this area.

Spectral analysis andin vitrocytotoxicity profiles of novel organotin(IV) esters of 2-maleimidopropanoic acid

Six novel triorganotin(IV) 2-maleimidopropanoato complexes: R3SnOCOCH3(CH)(COCH)2, (R: Me(l), Et(2), n-Pr(3), n-Bu(4), Ph(5), Bz(6) have been synthesized. Their solid-state configuration has been determined by FT IR and lI9mSn Mössbauer spectroscopy. The tin(IV) atom is five-coordinated in all the complexes with 2-maleimidopropanoic acid behaving as a monoanionic bidentate ligand coordinating the tin(IV) atom through a chelating or bridging carboxylate group. The solution-state configuration has been elucidated by means of 1H-, 13C- and 119Sn-NMR spectroscopy which assigned a tetrahedron. Elemental analysis and FAB MS data also supported a 1:1 metal to ligand stoichiometry. The title complexes have been screened in vitro for anti-tumour, anti-fungal, anti-leishmanial and urease inhibition activities and displayed promising results.

Synthesis and characterization of di-phenyl-tinIV-salicyliden-ortho-aminophenols: Analysis of in vitro antitumor/antioxidant activities and molecular structures

The one pot reactions carried among salicylaldehyde 1, ortho-aminophenols 2a-2g, and di-phenyl-tin(IV) oxide 3 led to seven di-phenyl-tin(IV) compounds 4a-4g in good yields (97-83%). All compounds were analyzed by IR, 1H, 13C, 119Sn NMR spectroscopy, mass spectrometry and elemental analyses; furthermore, in the case of compounds 4b, 4c, 4e and 4g by X-ray diffraction. Compounds 4a-4g were tested in vitro against six human tumor cell lines U251, PC-3, K-562, HCT-15, MCF-7 and SKLU-1 to assess their in vitro antitumor activity. The results suggest biological specificity towards U251, MCF-7 and SKLU-1 cells at doses below 2.5 microM, which are lower than cis-platin IC50's in the three cell lines. Since the inhibitory concentration values for the series were alike to Ph(2)SnCl(2) is feasible that only the Ph(2)Sn moiety is responsible for those activities, further experiments are under research. Besides, 4a-4g were tested for their antioxidant efficiency in rat brain homogenate showing that 4g is more active (IC50=3.01 microM) than the flavone quercetin (natural antioxidant, IC50=4.11 microM) on inhibition of thiobarbituric acid reactive substances (TBARS). The TBARS activity (IC50) correlates with the ortho-aminophenol substitutions and a linear combination among sigma Hammett, one bond tin coupling constants and tin chemical shifts against the measured IC(50-TBARS) was found. This correlation gave basis that the implied molecular variables can become trackers for the calculation of TBARS inhibitory concentrations in similar systems. Moreover, there seemed to be an inverse structure-response behavior among activities, since the 4g derivative is the less active compound for cytotoxic assays meanwhile it is the best in antioxidant tests.

Synthesis, spectral characterization and biological studies of some organotin(IV) complexes of L-proline, trans-hydroxy-L-proline and L-glutamine

New organotin(IV) complexes of the general formula R3Sn(L) (where R=Me, n-Bu and HL=L-proline; R=Me, Ph and HL=trans-hydroxy-L-proline and L-glutamine) and R2Sn(L)2 (where R=n-Bu, Ph and HL=L-proline; R=Ph, HL=trans-hydroxy-L-proline) have been synthesized by the reaction of RnSnCl(4-n) (where n=2 or 3) with sodium salt of the amino acid (HL). n-Bu2Sn(Pro)2 was synthesized by the reaction of n-Bu2SnO with L-proline under azeotropic removal of water. The bonding and coordination behavior in these complexes have been discussed on the basis of IR and 119Sn Mössbauer spectroscopic studies in the solid-state. Their coordination behavior in solution has been discussed with the help of multinuclear (1H, 13C and 119Sn) NMR spectral studies. The 119Sn Mössbauer and IR studies indicate that L-proline and trans-hydroxy-L-proline show similar coordination behavior towards organotin(IV) compounds. Pentacoordinate trigonal-bipyramidal and hexacoordinate octahedral structures, respectively, have been proposed for the tri- and diorganotin(IV) complexes of L-proline and trans-hydroxy-L-proline, in which the carboxylate group acts as bidentate group. L-glutamine shows different coordination behavior towards organotin(IV) compounds, it acts as monoanionic bidentate ligand coordinating through carboxylate and amino group. The triorganotin(IV) complexes of L-glutamine have been proposed to have trigonal-bipyramidal environment around tin. The newly synthesized complexes have been tested for their antiinflammatory and cardiovascular activities. Their LD50 values are >1000 mg kg-1.