Saira Shahzadi

Structural chemistry of organotin(IV) complexes

The amazing structural diversity in organotin compounds is discussed in the systems containing -O and -S donor ligands. It is demonstrated that there exist a fascinating range of structural diversity for organotin(IV) complexes, including differences in coordination number and molecular geometry. The difference in structure is correlated with the nature of tin and ligand bonded R groups. Despite the large number of different structures found in organotin(IV) carboxylates, there is limited range of coordination geometries about the Sn atom. The four coordinated Sn atom in triorganotin(IV) complexes is invariably distorted tetrahedral and five coordinated Sn is distorted trigonal bipyramidal. A large range has been observed for diorganotin carboxylate structures, where five, six and seven coordinate geometries have been reported. The Sn atom in mono-organotin has only been demonstrated to exist in distorted octahedral geometries (the single exception being a pentagonal bipyramidal geometry). In the case of organotin(IV) complexes of S donor ligands, it has been shown that there exists a rich diversity in Sn atom geometries and coordination modes of the sulfur donor ligands themselves. As in related carboxylate systems, the assignment of coordination numbers to the Sn centers in some compounds is controversial. As a general trend, it has been shown that, the overall coordination number at the Sn atom decreases with the increasing number of organic substituents at the Sn atom. This phenomenon is usually achieved by increased asymmetry in the mode of coordination of the sulfur donor ligands.

Organotin(IV) Derivatives as Biocides: An Investigation of Structure by IR, Solution NMR, Electron Impact MS and Assessment of Structure Correlation with Biocidal Activity

A brief account is given of the synthesis, structural chemistry and the antibacterial, antifungal and cytotoxic effects of organotin complexes of 2-[(2,4-dichloroanilinocarbonyl)]benzoic acid. The unimolar and bimolar substitution products have been characterized by elemental analysis and spectral studies, including IR, 1H NMR, 13C NMR, 119Sn NMR, and mass spectra. The data support the binding of the oxygen atom to the tin atom in [R2Sn(OOCR’)2] and [R3Sn(OOCR’)] (R = Me, Bu, and Ph, R’ = 2-[(2,4-dichloroanilinocarbonyl)]benzoic acid). Based on these studies, with a coordination number of four, a distorted tetrahedral geometry has been proposed for the resulting derivatives in solution. The free ligand (R’/COOH) and its respective tin complexes were tested in vitro against a number of microorganisms to assess their biocidal properties and to correlate them with the structures of the derivatives.

Di- and triorganotin(IV) complexes of 2-aminobenzoic acid with and without triphenylphosphine: synthesis, spectroscopy, semi-empirical study, and antimicrobial activities

Eight organotin carboxylates have been synthesized in quantitative yield by reaction of NaL (L = 2-aminobenzoate) with the di- and triorganotin chlorides and triphenylphosphine. All the complexes have been characterized by elemental analysis, IR, multinuclear NMR (1H, 13C, and 119Sn), and mass spectrometry. The spectroscopic data indicate 1 : 2/1 : 1 M : L stoichiometry in 1, 3, 5, and 7 and 1 : 2 : 1/1 : 1 : 1 M : L : PPh3 stoichiometry in 2, 4, 6, and 8. FT-IR spectra clearly demonstrate metal attachment with both oxygens of the ligand and bidentate coordination in 1, 3, 5, and 7 while monodentate ligand for 2, 4, 6, and 8. In solid state, 1, 2, 5, and 6 exhibit six coordination whereas 3, 4, 7, and 8 show five coordination. The structural behavior is confirmed by semi-empirical study. NMR data reveal four-coordinate geometry in solution. These complexes were screened for antimicrobial activity in vitro. The screening tests show that tributyltin carboxylates are more potent antibacterial and fungicidal agents than corresponding methyl derivatives, and triphenylphosphine enhances the antibacterial and fungicidal activities of these complexes.

Synthesis, characterization, semi-empirical study, and biological activities of organotin(IV) complexes with cyclohexylcarbamodithioic acid as biological active ligand

Cyclohexylcarbamodithioic acid has been synthesized by the reaction of cyclohexylamine with carbon disulfide at room temperature. Its complexes have been synthesized by the reaction of cyclohexylcarbamodithioic acid with organotin(IV) chlorides in 1 : 1/1 : 2 molar ratio. The ligand and complexes have been characterized by elemental analysis, infrared (IR), and multinuclear (1H, 13C, and 119Sn) NMR spectroscopy. Elemental data show good agreement between calculated and found values of carbon, hydrogen, nitrogen, and sulfur. IR data show that the ligand is bidentate and complexes exhibit a five-coordinate geometry in the solid state, which is also confirmed by semi-empirical studies. NMR data show that the complexes exhibit tetrahedral geometry in solution state. The ligand and its complexes were screened for their in vitro mutagenic, antimicrobial, MIC, antioxidant activities, and cytotoxicity. Biological screening data demonstrate that complexes show significant activity against various bacterial and fungal strains and are good antioxidants. The cytotoxicity data show positive lethality for complexes as compared to ligand and can play a very significant role in drug development.

Organotin(IV) Complexes of Aniline Derivatives. I. Synthesis, Spectral, and Antibacterial Studies of Di- and Triorganotin(IV) Derivatives of 4-Bromomaleanilic Acid

Organotin(IV) derivatives of the general formulae R2SnL2 and R3SnL where R = Me, n‐Bu, n‐Oct, Ph and Bz and HL = 4‐bromomaleanilic acid have been synthesised. These compounds were characterized by elemental analyses, infrared, multinuclear (1H, 13C, 119Sn) NMR and mass spectrometry. Biological screenings were performed in order to establish their biological activity.

Oxovanadium(IV) complexes of non-steroidal anti-inflammatory drugs: Synthesis, spectroscopy, and antimicrobial activity

Oxovanadium(IV) complexes with four different non-steroidal anti-inflammatory drugs have been synthesized. These complexes were characterized by different analytical techniques such as CHN, IR, UV-Vis spectroscopy, and mass spectrometry. The IR data show the bidentate nature of the ligands and reveal hexacoordinate geometry in the solid state. The complexes were tested for their biological activity against six different bacterial strains and plant pathogens, and all complexes showed good biological activity with few exceptions

Synthesis, characterization, biological activities, crystal structure and DNA binding of organotin(IV) 5-chlorosalicylates

New organotin(IV) carboxylates, R2SnL2 (R=n-Bu: 1), R2Sn(Cl)L (R=n-Bu: 2), and R3SnL (R=Me: 3; n-Bu: 4; Ph: 5) have been synthesized by stirring 5-chloro-2-hydroxybenzoic acid HL with KOH and R2SnCl2 (R=n-Bu)/R3SnCl (R=Me, n-Bu, Ph) in methanol at room temperature. The complexes along with ligand have been characterized by FTIR, (1H, 13C) NMR, EI-MS, and single-crystal XRD crystallography. FTIR data indicated bidentate coordination of carboxylate. NMR data suggested six- or five-coordinate geometry of organotin(IV) carboxylates. Single-crystal XRD of 1 demonstrated skew-trapezoidal geometry around the tin center, with the basal plane occupied by four oxygens and the two butyl groups lying in distorted axial position. Complexes 1, 2, and 5 exhibited interaction with SS-DNA (salmon sperm) and suggests intercalating mode of binding. The complexes displayed significant antimicrobial activities against bacterial and fungal strains as compared to free ligand. The hemolytic activity of the complexes was lower compared to Triton-X 100 (positive control, 100% lysis) and higher than phosphate-buffered saline (negative control, 0% lysis). Complex 4 was the most potent inhibitor of bacterial/fungal growth. Graphical abstract

Review: structural diversity in organotin(IV) dithiocarboxylates and carboxylates

Organotin(IV) complexes are known for their outstanding structural diversity and applications. Organotin(IV) carboxylates and dithiocarboxylates form an important class of organotin(IV) compounds. The structural diversity of these compounds emanates from several features including flexibility in coordination geometries, coordination numbers, and versatility of the ligands to engage in different modes of chelation from monodentate to bidentate. Triorganotin(IV) complexes with various ligands mostly demonstrate tetrahedral or trigonal bipyramidal symmetry with some distortions, while diorganotin(IV) and chlorodiorganotin(IV) complexes have variation of geometries and coordination numbers. Some monoorganotin(IV) complexes have also been reported with pentagonal bipyramidal geometries.

Homobimetallic complexes containing Sn(IV) with acetylene dicarboxylic acid: their syntheses and structural interpretation by spectroscopic, semi-empirical, and DFT techniques

Homobimetallic carboxylates with general formulae (R3Sn)2 L (where R = Me, n‐Bu, Ph and L = acetylene dicarboxylate dianion) have been synthesized by refluxing disodium salt of acetylene dicarboxylic acid with triorganotin chlorides in 1 : 2 (L : M) molar ratio in methanol under reflux. These complexes have been characterized by elemental analyses, FTIR, and multinuclear NMR (1H, 13C) spectroscopies. DFT calculations have been performed for structural elucidation and results were compared with semi‐empirical data. FTIR data indicate bidentate chelation of the ligand with tin and the complexes exhibit five‐coordinate geometry in the solid state. Such coordination behavior is also supported by DFT and semi‐empirical studies. NMR data confirm four‐coordinate geometry in solution.

Synthesis and spectroscopic and thermogravimetric characterization of heterobimetallic complexes with Sn(IV) and Pd(II); DNA binding, alkaline phosphatase inhibition and biological activity studies

A palladium complex, [KLCSS]2Pd (1), has been prepared by stirring sarcosine (HLH), KOH and CS2 in methanol and subsequently treating with palladium(II) chloride. Six heterobimetallic derivatives of the type [R2(Cl)SnLCS2]2Pd (R = Me: 2; Bu: 3; Ph: 4)/[R3SnLCS2]2Pd (R = Me: 5; Bu: 6; Ph: 7) were also synthesized by stirring sarcosine (HLH) with KOH and CS2 in methanol followed by an addition of R2SnCl2/R3SnCl and then PdCl2. FT-IR data demonstrated bidentate binding of dithiocarbamate and carboxylate with four- and five-coordinate environments around Pd(II) and Sn(IV) centers, respectively, in the solid state. UV–visible studies verified the square planar arrangement around Pd(II) in solution. The magnitude of 2J(119Sn-1H) demonstrates a distorted trigonal bipyramidal geometry around tin(IV) in solution. Elemental analysis (C, H, N, and S), mass spectroscopic (EI-MS and ESI), and thermogravimetric analyses verified the chemical composition of products. Complexes 1–7 exhibited interaction with salmon sperm DNA (SS-DNA). The palladium complex 1 had shown higher potential to bind with SS-DNA and to inhibit the alkaline phosphatase when compared to the heteronuclear products (2–7). However, the antifungal/antibacterial activities of the bimetallic complexes (2–7) were significantly higher than the palladated derivative 1. The in vitro hemolytic activity investigations on human red blood cells showed that bimetallic derivative 2 with chlorodimethyltin(IV) exhibited the lowest hemolytic effects (17.55%), while 5 having trimethyltin(IV) center exhibited the highest hemolytic activity (78.64%). A palladium complex and its heterobimetallic (Sn, Pd) derivatives were synthesized and characterized by spectroscopic and thermogravimetric analyses. The palladium complex showed higher potential to bind with SS-DNA and to inhibit the alkaline phosphatase (ALPs) relative to the heteronuclear products (2–7). However, the bimetallic derivatives displayed significantly higher antifungal/antibacterial activities than the palladium complex 1.