Semiempirical calculations on the interaction between dimethyltin(IV) and DNA model system

The interaction between a dinucleotide triphosphate duplex (DD), mimicking the DNA molecule, and the dimethyltin(IV) cation is studied by the semiempirical PM3 method. The results show that the interaction can occur involving the tin atom and the electron-donor centres of DD, requiring in some cases the presence of water molecules. In particular, the binding of the dimethyltin(IV) moiety with two adjacent phosphate oxygen atoms is allowed by the presence of water molecules coordinating to the tin atom. In this case the tin environment shows a geometry in agreement with ¹¹⁹Sn Mössbauer and X-ray data.     

Synthesis,characterization, equilibria and biological activity of dimethyltin(IV) complex with 1,4-piperazine

The interaction of dimethyltin(IV) dichloride (DMT) with 1,4-piperazine (PIP) was investigated. The complex formation equilibria of the complexes formed in solution were investigated. The stoichiometry and stability constants of the complexes formed in solution phase were determined at different temperatures and in solutions of dioxane–water mixtures of different dielectric constants. The equilibrium constant for the displacement of piperazine coordinated to dimethyltin(IV) by inosine as a representative of DNA was calculated. (DMT)(PIP)·3H₂O was synthesized and characterized by elemental analysis, spectral, and thermal techniques. The antitumor activity of the complex was screened.     

Thermodynamic and multinuclear magnetic resonance study of dimethyltin (IV) complexes with some imidazoles in aqueous solutions

The interaction between imidazole (L1), 2-isopropylimidazole (L2), 2-amino-benzimidazole (L3) and 2-(2-pyridyl)benzimidazole (L4) (L in general), and dimethyltin chloride in water have been investigated at 25 degrees C and ionic strength of 0.1 M sodium nitrate using the potentiometric technique. The results showed the formation of 1:1 and 1:2 (organotin:ligand) complexes and the corresponding stability constants were determined. The effect of the pKa values of the respective ligands on the stability constants of its complex species was elucidated. The concentration distribution of the complexes in solution was evaluated. Also, their solid complexes of the general formula in diethylether-dichloromethane, give 1:2 (organotin:Ligand) [(L)2 (CH3)2 SnCl2.zH2O][L = L1, z = 0 and L = L2, z = 1] and 1:1 [L (CH3)2 SnCl2.zH2O][L = L3, z = 0 and L = L4, z = 2]. The separated solid products were characterized by elemental analyses (C, H, N, Cl), IR, mass spectra, thermogravimetric analysis (TGA) and magnetic susceptibility. The participation of the ligand functional groups in bonding to the organotin (IV) was discussed. Conductivity and 1H-NMR spectra were used to confirm the behaviour of these complexes in solution.     

Coordination properties of bidentate (N,O) and tridentate (N,O,O) heterocyclic alcohols with dimethyltin(IV)

The complex-formation equilibria of dimethyltin(IV) (DMT) with 4-hydroxymethyl imidazole (HMI) and 2,6-dihydroxymethyl pyridine (PDC) have been investigated. Stoichiometry and stability constants for the complexes formed were determined at different temperatures and 0.1?mol?L^?1 NaNO₃ ionic strength. The concentration distribution of the complexes in solution was evaluated as a function of pH. The effect of dioxane as a solvent on both protonation constants and formation constants of DMT complexes with HMI and PDC are discussed. The thermodynamic parameters ΔH° and ΔS° calculated from the temperature dependence of the equilibrium constants were investigated.     

The interaction of rhodium(III) with DNA by circular dichroism studies. Comparative behaviour of dimethyltin(IV) and thallium(I)

Summary The effect of RhCl₃ on DNA helix conformation was studied by circular dichroism spectroscopy and compared to the behaviour of Me₂SnCl₂ and TINO₃; the latter metal-DNA systems have been further studied by ultraviolet and thermal denaturation techniques. Both rhodium(III) and tin(IV) react with the bases of DNA and induce appreciable alterations of the double-helical conformation. Rhodium(III) at low binding ratio causes a stabilization of the DNA B conformation, while at higher structural changes are interpreted in terms of a B to C transition. Tin(IV) produces a form geometry; only at high binding ratios does interaction with the phosphate groups seem to occur. The data for thallium(I) are interpreted in terms of a preferential interaction with the phosphate groups of the DNA chain, causing a stabilization of the double-helical structure of DNA.     

Synthesis and characterization of diorganotin(IV) complexes of tridentate Schiff bases: crystal structure of [N-(3-hydroxypyridine-2-yl)-5-chlorosalicylideneiminato]dimethyltin(IV)

Some five-coordinated dimethyltin(IV) complexes of the type Me₂SnL (where L is the anion of a bifunctional tridentate Schiff base) were synthesized. These Schiff bases are N-(3-hydroxypyridine-2-yl)-3-methoxysalicylideneimine, HOC₆H₃OCH₃CH=NC₅H₃NOH (1), N-(3-hydroxypyridine-2-yl)-3-ethoxysalicylideneimine, HOC₆H₃OC₂H₅CH=NC₅H₃NOH (2), N-(3-hydroxypyridine-2-yl)-5-chlorosalicylideneimine, HOC₆H₃ClCH=NC₅H₃NOH (3), and N-(3-hydroxypyridine-2-yl)-3-methoxy-5-bromosalicylideneimine, HOC₆H₂OCH₃BrCH=NC₅H₃NOH (4). Dimethyltin(IV) complex of 3 (3a) was characterized by single crystal X-ray diffraction method and a coordination geometry that is nearly halfway between trigonal–bipyramidal and square pyramidal arrangement was found. Dimethyltin complexes of (1), (2), and (4) were also prepared and characterized by the comparison of their elemental analysis and ¹H-NMR-, IR-, UV- and mass spectral data with those of (3a). For example, in the ¹H-NMR spectra, the ²J(¹¹⁹Sn-¹H) in the Sn-CH₃ moiety have values between 80 Hz and 90 Hz, typical of five-coordinated tin species. By using these values in Lockart’s Equations, H₃C–Sn–CH₃ angles in the complexes were estimated to lie between 130° and 145°. X-ray diffraction value for 3a, confirms this estimate within 3.4% relative deviation (129.7° exp. Vs. 134.9° estimate).     

The crystal structure of dichlorobis(2-imidazolidone)dimethyltin

The results of a single-crystal X-ray diffraction study of the 1:2 adduct between dichlorodimethyltin(IV) and 2-imidazolidone are reported, together with some preliminary IR data. The complex is hexacoordinate and with a distorted cis-octahedral geometry.     

Synthesis and thermodynamic studies of the dinuclear adducts between dimethyltin(IV) dichloride with SalenH2 and MII(Salen) complexes in chloroform

A UV-Vis spectrophotometric study of adduct formation of SalenH₂ (1) and M^II(Salen), where M?=?Mn (2), Fe (3), Co (4), Ni (5) and Cu (6) as donors with Me₂SnCl₂ as acceptor have been investigated in chloroform. Adducts (1a–6a) have been characterized by ¹H, ¹³C and ¹¹⁹Sn NMR, IR and electronic spectroscopy and microanalysis. Formation constants and thermodynamic parameters were measured for 1 : 1 and 2 : 1 adducts at various temperatures (T?=?278 to 308 K). The data refinement was carried out with the SQUAD 84 program. The trend of formation constants of M^II(Salen) complexes with Me₂SnCl₂ follows the order: Mn>Fe>Cu>Co>Ni. The formation constants for the free 1 and M^II(Salen) with Me₂SnCl₂ changes according to the following trend: M^II(Salen)>SalenH₂     

Synthesis of sitting‐atop type adducts of diphenyl and dimethyltin(IV) dihalides with meso‐tetraarylporphyrins

Some molecular adducts of dimethyltin(IV) dichloride, diphenyltin(IV) dichloride and diphenyltin(IV) dibromide with para‐substituted meso‐tetraphenylporphyrin have been prepared. This adducts with general formula [(Me₂SnCl₂)₂H₂T(4‐X)PP], [(Ph₂SnCl₂)₂H₂T(4‐X)PP], and [(Ph₂SnBr₂)₂H₂T(4‐X)PP]; {X= CH₃O, CH₃, H, and Cl} have been synthesized and characterized by means of ¹H NMR, UV‐Vis, and elemental microanalysis methods.     

[5‐Bromo‐N‐(2‐carboxylatophenyl)salicylideniminato]dimethyltin(IV)

The structure of the title di­methyl­tin(IV) complex, [2‐(5‐bromo‐2‐oxido­benzyl­idene­amino)­benzoato‐κ³O,N,O′]di­methyl­tin(IV), [Sn(CH₃)₂(C₁₄H₈BrNO₃)], features centrosymmetric dimers disposed about a central Sn₂O₂ core. Each Sn centre has seven‐coordinate pentagonal–bipyramidal geometry, taking into account two moderately long Sn—O contacts about an inversion centre [2.679 (4) and 2.981 (4) Å]. The methyl groups are in an axial orientation.