Schiff bases are the most widely used versatile ligands, able to coordinate many elements and to stabilize them in various oxidation states. Recently, this class of compounds has been employed as models for biological systems, and in control of stereochemistry in six-coordinate transition metal complexes. Recently, the chemistry of organotin(IV) complexes of Schiff bases has also stemmed from their antitumour, antimicrobial, antinematicidal, anti-insecticidal and anti-inflammatory activities. Furthermore, organotin(IV) complexes of Schiff bases present a wide variety of interesting structural possibilities. Both aliphatic and aromatic Schiff bases in their neutral and deprotonated forms have been used to yield adducts and chelates with variable stoichiometry and different modes of coordination. This critical review (>155 references) focuses upon the chemistry and biological applications of organotin(IV) complexes of Schiff bases reported in the past 15 years. Thermal behavior of these complexes is also discussed.

Chemistry and applications of organotin(IV) complexes of Schiff bases

New di- and triorganotin(IV) complexes of tripodal Schiff base ligand containing three imidazole arms: Synthesis, structural characterization, anti-inflammatory activity and thermal studies

In vitro antioxidant activity for 12 stannoxanes derived from Ph3SnCl (compounds 1-3), Ph2SnCl2 (compounds 4-6), Bu3SnCl (compounds 7-9), and Bu2SnCl2 (compounds 10-12), was assayed qualitatively by the chromatographic profile with 1,1- diphenyl-2-picrylhydrazil (DPPH) method and by two quantitative methods: the DPPH radical scavenging activity and Ferric-Reducing Antioxidant Power (FRAP) assays. The results were compared with those obtained with the starting materials 2-pyridine- carboxylic acid (I), 3-pyridinecarboxylic acid (II) and 4-pyridinecarboxylic acid (III), as well as with standard compounds, such as vitamin C and vitamin E, respectively. The in vitro antiradical activity with DPPH of diphenyltin derivative 5 showed a very similar behavior to vitamin C at a 20 g/mL concentration, whereas according to the FRAP method, compound 8 was better. This difference is due to the mechanism of the antioxidant process. The Structure-Activity Relationships (SAR) for both methods is also reported.

Antioxidant Activity of Butyl- and Phenylstannoxanes Derived from 2-, 3- and 4-Pyridinecarboxylic Acids

Complexes of copper(II) with 5(2′-hydroxyphenyl)-3-(4-x-phenyl)pyrazolines, (C15H12N2OX)2Cu [X =–H,–Cl,–CH3,–OCH3] have been synthesized with their addition complexes with 2,2′-bipyridine, 1,10-phenanthroline and triphenylphosphine. The complexes were characterized by elemental analyses, molecular weight measurement, magnetic, conductivity measurement, IR, electronic, 31P NMR, ESR and FAB mass spectra. The complexes were examined for crystalline/amorphous nature through XRD. Square-planar geometry around copper(II) is suggested with two bidentate pyrazoline ligands. In the additional complexes pyrazoline is monodentate. The bidentate and monodentate behavior of pyrazoline ligands was confirmed by IR and 31P NMR spectral data. All complexes were tested for in vitro antibacterial and antifungal activity and exhibit very good antibacterial and antifungal activity; coordination has a pronounced effect on the microbial activities. The brine shrimp bioassay was also carried out to study their in vitro cytotoxic...

Synthesis, spectroscopic, antimicrobial and anti-inflammatory studies of 5(2′-hydroxyphenyl)-3-(4-x-phenyl)pyrazolinates of copper(II) and their addition complexes with donor ligands

Dichlorobismuth(III) pyrazolinates and chlorobismuth(III) dipyrazolinates of the type BiCl2(C15H12N2OX) and BiCl(C15H12N2OX)2 have been synthesized in dry benzene by reaction of BiCl3 and the sodium salt of pyrazoline in 1 : 1 and 1 : 2 molar ratios at elevated temperature [C15H12N2OX = 3(2′-hydroxyphenyl)-5-(4-X-substituted phenyl) pyrazoline and X = H in compounds 1, 5, CH3 in 2, 6, OCH3 in 3, 7 and Cl in 4, 8, respectively]. These newly synthesized derivatives have been characterized by elemental analysis (C, H, N, Cl and Bi), molecular weight measurements and spectral (IR, 1H NMR, 13C NMR) studies. Selected compounds screened against different bacteria and fungi show potential antibacterial and antifungal activities.

Synthesis, spectral study and antimicrobial activity of bismuth(III) 3(2′-hydroxyphenyl)-5-(4-substituted phenyl) pyrazolinates

Triorganotin(IV) pyrazolinates of the type R3Sn(C15H12N2O · X) [where C15H12N2O · X = 3(2′-hydroxyphenyl)-5(4-X-phenyl)pyrazoline {where X = H (a); CH3 (b); OCH3 (c); Cl (d) and R = Me, Pr n and Ph}] have been synthesized by the reaction of R3SnCl with the sodium salt of pyrazolines in a 1 : 1 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 studies [IR and multinuclear NMR (1H, 13C and 119Sn)]. The bidentate behaviour of the ligands was confirmed by IR, 1H and 13C NMR spectral data. Trigonal bipyramidal structure around tin(IV) atom for R3Sn(C15H12N2O · X) has been suggested. The free pyrazoline and a few triorganotin(IV) pyrazolinates have also been screened for their antibacterial and antifungal activities. Some triorganotin(IV) pyrazolinates exhibit higher antibacterial and antifungal effects than free pyrazoline and some of the antibiotics.

M. Safi Ahmad

Papers

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