Synthesis, characterization and antitumour activity of 7,7-di-n-butyl-5,9-dioxo-6,8-dioxa-7-stanna-spiro[3,5]nonane, a di-n-butyltin(IV) analog of “paraplatin”, and of a series of di-n-butyltin(IV) derivatives of mono- and disubstltuted malonic acids

Poly Organotin Acetates against DNA with Possible Implementation on Human Breast Cancer

Two known tin-based polymers of formula {[R₃Sn(CH₃COO)]_n} where R = n-Bu– (1) and R = Ph– (2),were evaluated for their in vitro biological properties. The compounds were characterized via their physical properties and FT-IR, ¹¹⁹Sn Mössbauer, and ¹H NMR spectroscopic data. The molecular structures were confirmed by single-crystal X-Ray diffraction crystallography. The geometry around the tin(IV) ion is trigonal bi-pyramidal. Variations in O–Sn–O···Sn′ torsion angles lead to zig-zag and helical supramolecular assemblies for 1 and 2, respectively. The in vitro cell viability against human breast adenocarcinoma cancer cell lines: MCF-7 positive to estrogens receptors (ERs) and MDA-MB-231 negative to ERs upon their incubation with 1 and 2 was investigated. Their toxicity has been studied against normal human fetal lung fibroblast cells (MRC-5). Compounds 1 and 2 exhibit 134 and 223-fold respectively stronger antiproliferative activity against MDA-MB-231 than cisplatin. The type of the cell death caused by 1 or 2 was also determined using flow cytometry assay. The binding affinity of 1 and 2 towards the CT-DNA was suspected from the differentiation of the viscosity which occurred in the solution containing increasing amounts of 1 and 2. Changes in fluorescent emission light of Ethidium bromide (EB) in the presence of DNA confirmed the intercalation mode of interactions into DNA of both complexes 1 and 2 which have been ascertained from viscosity measurements. The corresponding apparent binding constants (K_app) of 1 and 2 towards CT-DNA calculated through fluorescence spectra are 4.9 × 10⁴ (1) and 7.3 × 10⁴ (2) M⁻¹ respectively. Finally, the type of DNA binding interactions with 1 and 2 was confirmed by docking studies.

Self-assembly of dialkyltin(IV) moieties and aromatic dicarboxylates to complexes with a polymeric or a discrete trinuclear macrocyclic structure in the solid state and a mixture of fast interchanging cyclooligomeric structures in solution

It is well-known that the structures of trialkyltin(IV) carboxylates can be either monomeric, polymeric, or cyclooligomeric in the solid state. In contrast, all dialkyltin(IV) dicarboxylates characterized so far in the solid state have monomeric or polymeric structures, however, for some cases it has been proposed that their solution-state structure is cyclooligomeric. In order to generate more information on this subject, dimethyl- and di-n-butyltin(IV) complexes with phthalic and isophthalic acid have been prepared and analyzed both in solution and in the solid state. The solid-state structures of the two dialkyltin(IV) phthalates examined herein contain polymeric molecular chains, however, with supramolecular Sn.O' interactions, which result in the generation of cyclooligomeric units. This provides evidence for the presence of discrete cyclooligomeric structures in solution, which are involved in fast dynamic exchange equilibria as evidenced by (1)H, (13)C, and (119)Sn NMR spectroscopy. In the case of the two dialkyltin(IV) isophthalate complexes studied herein (R = Me, n-Bu), only the di-n-butyltin derivative is soluble and NMR spectroscopy as well as FAB(+) spectrometry indicates the formation of cyclic dinuclear, trinuclear, and/or tetranuclear species in solution, which may be involved also in fast dynamic exchange equilibria. In the solid state, however, discrete cyclotrinuclear units can be identified, in which the 24-membered macrocyclic cavity is almost completely planar, having six oxygen atoms directed into its interior and six Sn-n-butyl groups approximately perpendicular to the molecular plane. The diameter of the cyclic cavity can be described by the transannular O.O distances that vary from 7.68 to 7.84 A, being large enough for the introduction of linear alkyl groups. This can be demonstrated by the supramolecular structure of this compound, which contains a new type of bis[2]pseudorotaxane formed between two molecules through mutual threading via two of the Sn-butyl groups. Such a supramolecular entity has been unknown so far, since the usual composition of bis[2]pseudorotaxanes is the trimolecular combination of a macrocyclic ring system with two threads.

Interaction of bis(ethylene)tin(bis(salicylidene)ethylenediamine) with DNA

The fluorescence spectral characteristics and interaction of bis(ethylene)tin(bis(salicylidene)ethylenediamine) [Et2Sn(salen)] with DNA are described. The polarity of the solvent has a strong effect on the fluorescence characteristics of Et2Sn(salen). Et2Sn(salen) bound to DNA showed a marked decrease in the fluorescence intensity with a bathochromic shift of the excitation and emission peaks. A hypochromism in the UV absorption spectra was also observed. KI quenching and competitive binding to DNA between Et2Sn(salen) and ethidium bromide (EB) were studied in connection with other experimental observations to show that the interactive model between Et2Sn(salen) and DNA is an intercalative one. The pH and salt effect on the fluorescence properties was also investigated. The intrinsic binding constant was estimated to be 1.071 x 10(5) mol L(-1) in base pairs and the binding site number is 1.98, respectively. A linear relationship between F/F0 and the concentration of calf thymus DNA covers 5.1 x 10(-6) - 2.41 x 10(-4) mol L(-1), which can be utilized for determining traces of calf thymus DNA with a detection limit of 1.1 x 10(-7) mol L(-1) in base pairs.