Bioactive versatile azomethine complexes of organotin(IV) and organosilicon(IV)

Diorganotin(IV) and diorganosilicon(IV) derivatives of the types R₂MCl(TSCZ) and R₂M(TSCZ)₂ (where TSCZ is the anion of a thiosemicarbazone ligand, R=Ph or Me and M=Sn or Si) have been synthesized and characterized by elemental analyses, molecular weight determinations and conductivity measurements. The mode of bonding has been established on the basis of IR and ¹H, ¹³C ²⁹Si and ¹¹⁹Sn NMR spectroscopic studies. Some of the representative complexes have also been evaluated for their antimicrobial effects on different species of pathogenic fungi and bacteria in vivoas well as in vitro.The results of these investigations are reported. © 1998 John Wiley & Sons, Ltd.     

Microwave‐assisted synthesis and insecticidal properties of biologically potent organosilicon(IV) compounds of a sulfonamide imine

Microwave‐assisted synthesis and spectroscopic studies of dimethyl‐, diphenyl‐ and triphenyl‐silicon(IV) chelates derived from the reactions of organochlorosilanes with the sodium salt of a biologically active nitrogen donor ligand N^∩NH are described. The resulting products have been isolated and characterized by elemental analyses, molecular weight determinations and conductance measurements. On the basis of electronic, infrared, ¹H, ¹³C and ²⁹Si NMR spectral studies, trigonal bipyramidal and octahedral geometries have been suggested for the resulting complexes. The biological activity of the ligand and its corresponding complexes has been examined with regard to antifungal and antibacterial activity against pathogenic fungi and bacteria, and the results are quite encouraging. All the compounds have also been found to act as nematicides and insecticides, by reducing the number of nematodes (Meloidogyne incognita) and insects (Trogoderma granarium). Copyright © 2005 John Wiley & Sons, Ltd.     

Organosilicon(IV) and organotin(IV) complexes as biocides and nematicides: synthetic,spectroscopic and biological studies of N∩N donor sulfonamide imine and its chelates

A brief account is given of the synthesis and stereochemistry and the antibacterial, antifungal, nematicidal and insecticidal behaviour of organosilicon(IV) and organotin(IV) complexes of a biologically potent ligand, 2‐acetylfuransulfaguanidine. The unimolar and bimolar substitution products have been characterized by elemental analyses, conductance measurements, molecular weight determinations, and spectral studies, viz. IR, ¹H NMR, ¹³C NMR, UV, ²⁹Si NMR and ¹¹⁹Sn NMR spectra. The data support the binding of the nitrogen atom to the metal atom in R₃M(N^∩N), [R₂M(N^∩N)₂ and R₂M(N^∩N)Cl [(R = Me/Ph and M = Si(IV) and Sn(IV)] types of complex. Based on these studies, with coordination number five and six a trigonal bipyramidal and an octahedral geometry have been proposed for the resulting derivatives. The free ligand (N^∩NH) and its respective metal complexes were tested in vitro against a number of microorganisms to assess their antimicrobial properties. The results are indeed positive. In addition to these studies, the complexes also show good nematicidal and insecticidal properties. The results of these findings have been discussed in detail. Copyright © 2004 John Wiley & Sons, Ltd.     

Fungicidal,bactericidal and antifertility activities of diorganosilicon(IV) complexes derived from benzothiazolines

Synthetic, structural and biological aspects of trigonal-bipyramidal, Me₂S(N—S)CI and octahedral, Me₂Si(N—S)₂ types of diorganosilicon(IV) complexes of heterocyclic benzothiazolines (N—SH) are described. The complexes were characterized by elemental analysis, molecular weight determination, conductance measurements and electronic, infrared, ¹H and ¹³C NMR spectroscopic studies. Some ligands and their corresponding dimethylsilicon(IV) complexes have been tested for their effects on several pathogenic fungi and bacteria and found to be quite active in this respect. Antifertility activity in male mice of some representative ligands and their silicon complexes was also evaluated and discussed.     

Synthesis and characterization of pentagonal bipyramidal organotin(IV) complexes of 2,6-diacetylpyridine Schiff bases of S-alkyl- and aryldithiocarbazates

New organotin(IV) complexes with empirical formula Sn(SNNNS)R₂, where SNNNS is the dianionic form of 2,6-diacetylpyridine Schiff bases of S-methyldithiocarbazate (H₂dapsme) or S-benzyldithiocarbazate (H₂dapsbz) and R = Ph or Me, have been prepared and characterized by IR, UV-Vis, NMR and Mössbauer spectroscopic techniques and conductance measurements. The molecular structures of the Sn(dapsme)R₂ (R = Ph and Me) have been determined by single crystal X-ray diffraction techniques. Both complexes have a distorted pentagonal-bipyramidal geometry in which the tin is coordinated by a dinegatively charged pentadentate chelating agent via pyridine nitrogen, two azomethine nitrogens, and two thiolate sulfurs. The five donors (N₃S₂) provided by the Schiff base occupy the equatorial plane close to a pentagonal planar array while the carbanion ligands occupy axial sites.     

Antimicrobial activity of organotin(IV) compounds: a review

A comprehensive review on antimicrobial activity of organotin(IV) compounds is presented. Copyright © 2008 John Wiley & Sons, Ltd.     

New di‐ and triorganotin(IV) carboxylates derived from a Schiff base: synthesis,characterization and in vitro antimicrobial activities

A new carboxylic acid, 2‐{[5‐(2‐nitrophenyl)furan‐2‐yl]methyleneamino}benzoic acid (HOBZ), has been produced by reacting 5‐(2‐nitrophenyl)furfural with 2‐aminobenzoic acid. Reactions of NaOBZ with organotin chlorides led to formation of [Me₃Sn(OBZ)] ( 1 ), [Bu₃Sn(OBZ)] ( 2 ), [Me₂Sn(OBZ)₂] ( 3 ) and [Bu₂Sn(OBZ)₂] ( 4 ). Complexes 1 , 2 , 3 , 4 have been characterized using elemental analyses and infrared, ¹H NMR, ¹³C NMR, ¹¹⁹Sn NMR and ¹¹⁹Sn Mössbauer spectroscopies. In the solid state, the OBZ ligands might coordinate to tin in an anisobidentate fashion via the carboxylate group. The in vitro antimicrobial activity of all compounds has been screened against the following fungi: Aspergillus niger, A. flavus, A. parasiticus, Penicillium citrinum, Candida dubliniensis, C. lusitaniae, C. albicans, C. tropicalis, C. parapsilosis and C. glabrata; and against the following bacteria: Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, Streptococcus sanguinis, Escherichia coli, Citrobacter frendii, Salmonella typhimurium and Pseudomonas aeruginosa. Complexes 2 and 4 exhibited higher biocide activity in comparison to 1 and 3 and to the control drugs nystatin and miconazole nitrate for the yeasts, and chloramphenicol and ampicillin for the bacteria. The biological activity of 2 was superior to that of 4 . In addition, the toxicity of HOBZ, NaOBz and 1 , 2 , 3 , 4 were determined using Chlorella vulgaris, revealing low toxicity of the complexes at MIC₅₀ concentrations. We also performed cell viability studies, using XTT assay, displaying no change in the mitochondrial function after 2–4 h of exposure of the microorganism to the complexes at MIC₅₀ concentrations. The butyl‐containing complexes 2 and 4 display greater lipophilicities than do the methyl analogues 1 and 3 , thereby endowing 2 and 4 with superior abilities to cross the microbe cell membrane, the possible mechanism of action. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis,spectroscopic characterization,biological screening and in vitro cytotoxic studies of 4‐methyl‐3‐thiosemicarbazone derived Schiff bases and their Co (II), Ni (II), Cu (II) and Zn (II) complexes

A series of twenty compounds inclusive of bidentate Schiff bases derived from condensation of 4‐methyl‐3‐thiosemicarbazide with substituted derivatives of napthaldehyde/benzaldehyde/salicylaldehyde and their mononuclear Co (II), Ni (II), Cu (II) and Zn (II) complexes in molar ratio (1:1) were synthesized and characterized. The coordination behavior, modes of bonding and overall geometry of the compounds was known from the elemental analysis, spectral techniques (IR, UV–Vis, ¹H NMR, ¹³C NMR, ESR and ESI‐mass), magnetic moment measurements, molar conductance, thermal and powder XRD studies. The studies revealed octahedral geometry for all the complexes where ligands coordinated in a neutral bidentate manner (NS) via nitrogen atom of azomethine group and sulphur atom of thione group with the metal centre. In vitro biological effects of the compounds were tested against four bacterial species and two fungal strains. The results indicated that the metal complexes showed a marked enhancement in biocidal activity in comparable with the parent Schiff bases. In vitro anticancer activity against the malignant tumor cell lines; human alveolar adenocarcinoma epithelial cell line (A549), human breast adenocarcinoma cell line (MCF7), human prostate cancer cell line (DU145) and human normal lung cell line (MRC‐5) using MTT assay, exposed compound 16 as a leading member with lowest IC₅₀ value of 10.6 ± 0.14 μM against (A549) cell line.     

Organotin(IV) complexes of dibasic tridentate Schiff bases containing ONO donor atoms

Organotin(IV) Schiff base complexes of the type (L)SnR₂ [where R?CH₃, C₆H₅ or CH₂CH₂CO₂ CH₃], (LH)Sn(C₆H₅)₃ and (L)SnCl(CH₂CH₂CO₂ CH₃) [where LH₂?2-N-salicylideneimino-2-methyl-1-propanol, derived from the condensation of salicylaldehyde and 2-amino-2-methyl-1-propanol] have been prepared and characterized on the basis of their elemental analyses, IR, ¹H, ¹³C and ¹¹⁹Sn NMR studies. In these mononuclear complexes the Schiff base acts either as a dianionic tridentate or as a monobasic bidentate moiety by coordinating through an alkoxy group, an azomethine nitrogen and a phenoxide ion to tin. Sulphur dioxide inserts in the tin–methyl/–phenyl bond in the above Schiff base complexes to give tin–O–sulphinates of formulae (L)RSn(SO₂R) and (LH)(C₆H₅)₂Sn(SO₂C₆H₅).     

Antioxidative vs cytotoxic activities of organotin complexes bearing 2,6‐di‐tert‐butylphenol moieties

Two series of organotin(IV) complexes with Sn–S bonds on the base of 2,6‐di‐tert‐butyl‐4‐mercaptophenol ( L ¹ SH ) of formulae Me₂Sn(L¹S)₂ ( 1 ); Et₂Sn(L¹S)₂ ( 2 ); Bu₂Sn(L¹S)₂ ( 3 ); Ph ₂ Sn(L¹S)₂ ( 4 ); (L¹)₂Sn(L¹S)₂ ( 5 ); Me₃Sn(L¹S) ( 6 ); Ph₃Sn(L¹S) ( 7 ) (L¹ = 3,5‐di‐tert‐butyl‐4‐hydroxyphenyl), together with the new ones [Me₃SnCl(L²)] ( 8 ), [Me₂SnCl₂(L²)₂] ( 9 ) ( L ²  = 2‐(N‐3′,5′‐di‐tert‐butyl‐4′‐hydroxyphenyl)‐iminomethylphenol) were used to study their antioxidant and cytotoxic activity. Novel complexes 8 , 9 of Me_nSnCl_4 ? n (n = 3, 2) with Schiff base were synthesized and characterized by ¹H, ¹³C NMR, IR and elemental analysis. The crystal structures of compounds 8 and 9 were determined by X‐ray diffraction analysis. The distorted tetrahedral geometry around the Sn center in the monocrystals of 8 was revealed, the Schiff base is coordinated to the tin(IV) atom by electrostatic interaction and formation of short contact Sn–O 2.805 Å. In the case of complex 9 the distorted octahedron coordination of Sn atom is formed. The antioxidant activity of compounds as radical scavengers and reducing agents was proved spectrophotometrically in tests with stable radical DPPH, reduction of Cu²⁺ (CUPRAC method) and interaction with superoxide radical‐anion. Moreover, compounds have been screened for in vitro cytotoxicity on eight human cancer cell lines. A high activity against all cell lines with IC₅₀ values 60–160 nM was determined for the triphenyltin complex 7 , while the introduction of Schiff base decreased the cytotoxicity of the complexes. The influence on mitochondrial potential and mitochondrial permeability for the compounds 8 and 9 has been studied. It is shown that studied complexes depolarize the mitochondria but don't influence the calcium‐induced mitochondrial permeability transition.     

Antimicorbial effects of newly synthesized organotin(IV) and organolead(IV) derivatives

Triorganotin(IV) and triorganolead(IV) derivatives of the types Me₃Sn(SCZ) and Ph₃Pb(SCZ) (where SCZ^? is the anion of a semicarbanzone ligand) have been synthesized by substitution reactions of trimethyltin chloride and triphenyl-lead chloride with semicarbazones derived from heterocyclic ketones. The resulting complexes have been characterized by elemental analyses, molecualr weight determinations and conductivity measurements. The mode of bonding has been established on the basis of infrared and ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopic studies. Some respresentative complexes have also been evaluated for their antimicrobial effects on different species of pathogenic fungi and bacteria; the results of these investigations have been reported in the present paper.     

Synthesis,spectral and antimicrobial studies of diorganotin(IV)3(2′‐hydroxyphenyl)‐5‐(4‐substituted phenyl) pyrazolinates

Diorganotin(IV) dipyrazolinates of the type R₂Sn(C₁₅H₁₂N₂OX)₂ [where C₁₅H₁₂N₂OX = 3(2′‐Hydroxyphenyl)‐5(4‐X‐phenyl)pyrazoline {where X = H ( a ); CH₃ ( b ); OCH₃ ( c ); Cl ( d ) and R = Me, Prⁿ and Ph}] have been synthesized by the reaction of R₂SnCl₂ with sodium salt of pyrazolines in 1:2 molar ratio, in anhydrous benzene. These newly synthesized derivatives have been characterized by elemental analysis (C, H, N, Cl and Sn), molecular weight measurement as well as spectral [IR and multinuclear NMR (¹H, ¹³C and ¹¹⁹Sn)] studies. The bidentate behaviour of the pyrazoline ligands was confirmed by IR, ¹H and ¹³C NMR spectral data. A distorted trans‐octahedral structure around tin(IV) atom for R₂Sn(C₁₅H₁₂N₂OX)₂ has been suggested. The free pyrazoline and diorganotin(IV) dipyrazolinates have also been screened for their antibacterial and antifungal activities. Some diorganotin(IV) dipyrazolinates exhibit higher antibacterial and antifungal effect than free ligand and some of the antibiotics. Copyright © 2006 John Wiley & Sons, Ltd.     

Studies on some oxovanadium(IV) complexes of acyl pyrazolone analogues

A series of novel bidentate pyrazolone based Schiff base ligands were synthesized by interaction of 4-benzoyl-3-methyl-1-(4′-methylphenyl)-2-pyrazolin-5-one with various aromatic amines like aniline, o-,m-,p-chloroaniline and o-,m-,p-toluidine in a ethanolic medium. All of these ligands have been characterized on the basis of elemental analysis, IR and ¹H NMR data. The molecular geometries of five of these ligands have been determined by single crystal X-ray study. Crystallographic study reveals that these ligands exist in the amine-one tautomeric form in the solid state. NMR study also suggests the existence of the amine-one form in solution at room temperature. Ab initio calculations for representative ligand HL¹ has been carried out to know the coordination site of the ligand. Novel vanadium Schiff base complexes of these ligands with general formula [OV(L^1–7)₂(H₂O)] have been prepared by interaction of aqueous solution of vanadyl sulfate pentahydrate with DMF solution of the appropriate ligands. The resulting complexes have been characterized on the basis of elemental analysis, vanadium determination, molar conductance and magnetic measurements, thermo gravimetric analysis, infrared and electronic spectral studies. Suitable distorted octahedral structures have been proposed for these complexes.     

Synthesis,antimicrobial activity and molecular docking of di‐ and triorganotin (IV) complexes with thiosemicarbazide derivatives

Six organotin (IV) complexes with two ligands derived from 2,3‐butanedione and thiosemicarbazide have been synthesized and fully characterized by several spectroscopic techniques, including ¹¹⁹Sn NMR and single crystal X‐ray diffraction. Reactions of the ligand diacetyl‐2‐(thiosemicarbazone)‐3‐(3‐hydroxy‐2‐naphthohydrazone), L¹H₂, with SnR₂Cl₂ (R = Me, Bu, Ph) lead to the obtaining of complexes 1 – 3 with general formula [SnR₂L¹] (R = Me 1 , R = Bu 2 , R = Ph 3 ), in which the ligand is doubly deprotonated and behaves as a N₂SO donor, whereas from the reactions of diacetyl‐2‐thiosemicarbazone, HATs, with the same organotin precursors any complex could be isolated. By contrast, reaction of HATs with SnR₃Cl induces the ligand cyclization to form a 1,2,4‐triazine‐3‐thione that binds to the metal as a monoanionic donor in a mono or bidentate manner to form compounds 4 – 6 with formula [SnR₃L²] (R = Me 4 , R = Bu 5 , R = Ph 6 ). The antimicrobial activity of the ligands and the six complexes was tested towards bacteria and fungi, including clinical isolated strains. The results show that the ligands are devoid of activity, except HATs that displays activity against Bacillus subtilis. Conversely, the complexes exhibit good antimicrobial properties against Gram positive and negative bacteria, yeasts and moulds. The best results are obtained for complexes [SnBu₃L²] 5 and [SnPh₃L²] 6 , indicating that their more lipophilic nature could play an important role in the ease of microbial cell penetration. In some cases, these complexes display similar or higher activity than that of ampicillin and miconazole, used as antibacterial and antifungal positive controls, respectively. Docking study with DHPS protein (S. aureus) has shown that out of six drugs, the compound 6 has the best binding affinity (?8.5 Kcal/mol).     

Structural and conformational analysis of neutral dinuclear diorganotin(IV) complexes derived from hexadentate Schiff base ligands

The synthesis of three hexadentate Schiff base ligands has been carried out, which contain two sets of ONO donor atoms. These were reacted with diorganotin(IV) dichloride derivatives (R = Me, nBu, Ph) to prepare seven dinuclear diorganotin(IV) complexes in moderate yields. Aside from IR and NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopic studies, mass spectrometry and elemental analysis, four tin complexes were characterized by X-ray diffraction analysis. The spectroscopic analyses showed that in solution the tin atoms have five-coordinate environments with a distorted trigonal bipyramidal geometry. Each tin atom is coordinated to the nitrogen atom and forms covalent bonds with two oxygen atoms and two carbon atoms. Due to the presence of a methylene group as bridge between the two ONO chelates, the overall molecular structures can have cis or trans conformation, having either mirror or C₂-symmetry. While in solution a fast equilibrium can be supposed, in the solid state different intermediate conformations have been detected. Furthermore, for the dialkyltin derivatives Sn?O intermolecular interactions were found allowing for a dimeric or crinkled polymeric organization, whereas for the diphenyltin derivatives no such interactions were observed.     

Synthesis,characterization and biological studies of oxovanadium(IV) complexes with triazole‐derived Schiff bases

A series of triazole‐derived Schiff bases (L¹–L⁵) and their oxovanadium(IV) complexes have been synthesized. The chemical structures of Schiff bases were characterized by their analytical (CHN analysis) and spectral (IR, ¹H and ¹³C NMR and mass spectrometry) data, and oxovanadium(IV) complexes were elucidated by their physical (magnetic susceptibility and conductivity), analytical (CHN analysis), conductance measurements and electronic spectral data. The molar conductivity data indicate the oxovanadium(IV) complexes to be non‐electrolyte. The Schiff bases act as bidentate and coordinate with the oxovanadium(IV)‐forming stoichiometry of a complex as [M (L‐H)₂] where M = VO and L = L¹–L⁵ in a square‐pyramidal geometry. The agar well diffusion method was used for in vitro antibacterial screening against E. coli, S. flexenari, P. aeruginosa, S. typhi, S. aureus and B. subtilis and for antifungal activity against T. longifucus, C. albican, A. flavus, M. canis, F. solani and C. glaberata. The biological activity data show the oxovanadium(IV) complexes to be more antibacterial and antifungal than the parent Schiff bases against one or more bacterial and fungal strains. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis,spectral and biological studies of organotin(IV) complexes of heteroscorpionate

A heteroscorpionate ligand, potassium hydrobis(benzoato)(salicylaldehyde)borate (KL), has been synthesized. This was converted into organotin complexes R₂SnL₂ and R₃SnL complexes by mixing and stirring with a methanolic solution/suspension of organotin chloride. The ligand and its complexes were characterized by elemental analyses and spectral studies (IR, ¹H NMR, ¹³C NMR, ESI mass spectra and Thermo gravimetric analysis (TGA)). Antibacterial and antifungal studies of these compounds were evaluated by the disc diffusion method at variable concentration against three species of bacteria (Staphylococcus aureus, Klebsiella pneumonia and Bacillius subtillis) and two species of fungi (Asperjillius fiavus and Candida albicans). It was found that triorganotin derivatives (R₃SnL) of the ligand were more effective as compared with diorganotin derivatives (R₂SnL₂). The organotin complexes of borates were tested for their algicidal activity on the cyanobacterial strains Aulosira fertilissma, Anabaena species, Anabaena variabilis and Nostoc muscorum and showed high to moderate toxicity towards the above species. The ligand and its complexes were also tested for its pH effect on soil in vitro for a duration of more than one month and it was found that they are able to kill pests without damaging the soil quality. Copyright © 2006 John Wiley & Sons, Ltd.