Mala Nath

Organotin(IV) complexes of amino acids and peptides

Abstract A comprehensive review, >120 references, on organotin(IV) complexes of the amino acids and peptides is presented with special reference to their methods of synthesis, structural and thermal properties as well as their solution studies and biological activity. The structures of these complexes are discussed on the basis of IR, electronic, multinuclear (1H-, 13C- and 119Sn-) NMR, X-ray and 119Sn Mossbauer spectral studies.

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

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.

Synthesis, characteristic spectral studies and in vitro antimicrobial and antitumour activities of organotin(IV) complexes of Schiff bases derived from amino-acids

Equimolar reactions of dibutyltin(IV) oxide with Schiff bases derived from amino-acids led to the formation of a new series of dibutyltin(IV) complexes of general formula, Bu2SnL [L=dianion of tridentate Schiff bases derived from the condensation of 2-hydroxy-1-naphthaldehyde or acetyl acetone with glycine (L-1), L-β-alanine (L-2), DL-valine (L-3), DL-4-aminobutyric acid (L-4), L-methionine (L-5), L-leucine (L-6) and phenylglycine (L-7)]. An attempt has been made to prove the structures of the resulting complexes on the basis of elemental analyses, conductance measurements and electronic, IR, multinuclear magnetic resonance (1H, 13C and 117Sn) and 119Sn Mossbauer spectral studies. The complexes have been tested against various bacteria [Streptococcus faecalis, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus penicillin resistance (2500 units)] and fungi (Candida albicans, Cryptococcus neoformans, Sporotrichum schenckii,Trichophyton mentagrophytes and Aspergillus fumigatus). All the complexes showed moderate activity. The cytotoxicity of a few compounds has been screened in vitro against seven human tumour cell lines, viz. MCF-7, EVSA-T, WiDr, IGROV, M19 MEL, A498 and H226. The activities found experimentally were better than those obtained for cisplatin and carboplatin

Comparative study of structure–activity relationship of di- and tri-organotin(IV) derivatives of amino acid and peptides

Novel non-electrolytic di- and tri-organotin(IV) derivatives of the general formula R2Sn(L/HL′) and Ph3Sn(HL/H2L′), where R is n-Bu and Ph, and L/HL is dianion/monoanion of d-penicillamine (H2L-1) and l-carnosine (H2L-2), and HL′/H2L′ is dianion/monoanion of triglycine (H3L-3) have been synthesized in 1:1 molar ratio either at pH 7.0 or pH<2.0. All n-Bu2Sn(IV) derivatives have been synthesized by the reaction of Bu2SnO with amino acid/peptides under azeotropic removal of water. Ph2Sn(IV)/Ph3Sn(IV) derivatives have been synthesized by either sodium chloride method or alkoxide method. The dibutyltin(IV) complexes synthesized at pH<2.0 possess chlorine in the coordination sphere (as revealed from molar conductance measurement in methanol) and a molecule of water in the crystal lattice. The structures of the complexes are discussed on the basis of IR, far-IR, multinuclear (1H-, 13C- and 119Sn-) NMR and 119Sn-Mossbauer spectroscopic studies. All the diorganotin(IV) derivatives possess a distorted trigonal bipyramidal structure in which D-penicillamine/peptides are tridentate coordinating through Namino, C(O)Ocarboxyl and Sthiol/Npeptide. The NH2 group bridging/hydrogen bonding may lead to the associated structure. Whereas a linear polymeric structure with a distorted trigonal bipyramidal environment around tin has been tentatively proposed for Ph3Sn(IV) derivatives in which the ligands may act as bidentate coordinating through Namino and C(O)Ocarboxyl. n-Bu2SnCl(HL-1)·H2O, synthesized at low pH, is dimeric. The anti-inflammatory activity, ALD50 and blood pressure lowering activity of the synthesized derivatives are reported. Some complexes exhibit good anti-inflammatory activities comparable to that of phenylbutazone (a comparative analysis is presented through plots). The triorganotin(IV) derivatives exhibit significantly better activities than the diorganotin(IV) derivatives.

Characteristic spectral studies, and antimicrobial and anti-inflammatory activities of diorganotin(IV) derivatives of dipeptides

Abstract New diorganotin(IV) complexes of general formula R 2 SnL (R= n -Bu and Ph, and L=dianion of alanylphenylalanine (H 2 L-1), phenylalanylleucine (H 2 L-2), phenylalanylphenylalanine (H 2 L-3), glycylleucine (H 2 L-4) and glycylisoleucine (H 2 L-5) have been prepared and characterised by elemental analyses, molar conductance, and the bonding in these complexes is discussed in terms of their IR, far-IR, 1 H-, 13 C- and 117 Sn-NMR, and 119 Sn Mossbauer spectral studies. The monomeric 1:1 complexes have distorted trigonal bipyramidal structure with cis -equatorial organic groups. The complexes, soluble in DMSO, have been screened against a wide spectrum of bacteria ( Escherichia coli, Rhizobium meliloti, Pseudomonas putida and Aeromonas formicans ) and fungi ( Aspergillus niger, Pencillium chrysogenum, Aureobasidium pullulans and Verticillium dahliae ) and are found to be active. The LD 50 values (>500 mg kg −1 ) have also been determined in the albino rats. Some of the complexes also exhibit very high anti-inflammatory activity.

Characteristic spectral studies and in vitro Antimicrobial and in vivo multi‐infection antifungal activities in mice of new organotin(IV) derivatives of heterocyclic amino acids

The nature of the products obtained on reacting R3SnCl (R = Me, Bu and Ph), Ph2SnCl2 and Bu2SnO with amino acids having nitrogen-containing heterocyclic rings; i.e. L-histidine and DL-tryptophan, is shown to depend upon the reaction conditions. Ten new organotin(IV) derivatives of these amino acids have been synthesized and characterized by elemental analyses, molar conductance and electronic spectra, and the bonding in these complexes is discussed in terms of their infrared, far-infrared, 1H and 13C NMR, and 119Sn Mossbauer spectra. The complexes soluble in DMSO have been tested in vitro against a wide spectrum of bacteria and fungi and found to be active. Two complexes, Ph3SnL-1 and Ph3SnL-2, have been found to be slightly active in vivo against a multi-infection fungal model in mice. Copyright

Dibutyltin(IV) Complexes of Schiff Bases Derived from Aminoacids

Abstract Some new dibutyltin (IV) complexes of the general formula, Bu2Sn (ONO) [where, ONO = dianionic tridentate Schiff bases derived from the condensation of salicy-laldehyde, o-hydroxyacetophenone and pyruvic acid with glycine (L1), β-alanine (L2), 2-aminotutyric acid (L3), 4-aminobutyric acid (L4), L-valine (L5), DL-methionine (L6) and phenylglycine (L7)] have been synthesized and characterized by elemental analyses, molar conductance, electronic, infra-red, far-infra-red ana nuclear magnetic resonance spectroscopy. The spectral studies suggested a distorted trigonal bipyramidal geometry around the tin atom.

Spectral and Thermal Studies of Cobalt(II), Nickel(II) and Copper(II) Complexes of Schiff Bases Obtained from o-Hydroxyacetophenone and Amino Acids

Abstract A variety of N-(2-hydroxyphenyl)ethylidene-amino acid Schiff bases (abbreviated as OHACPh:AA) coordinated to cobalt(II), nickel(II) and copper(II) have teen synthesized and characterized by elemental analyses, conductivity measurements and magnetic, electronic and infrared spectral studies. The results suggest that the complexes are four-coordinate with 1:2 (metal:ligand) stoichiometry. The ligands coordinate through the imino nitrogen and carboxylate oxygen.

Diorganotin(IV) Derivatives of Dipeptides Containing at Least One Essential Amino Acid Residue: Synthesis, Characteristic Spectral Data, Cardiovascular, and Anti‐inflammatory Activities

Abstract New diphenyltin(IV) derivatives of the formula Ph2SnL, where L is the dianion of glycyltryptophan (Gly‐Trp), glycylphenylalanine (Gly‐Phe), valylvaline (Val‐Val), alanylvaline (Ala‐Val), and leucylalanine (Leu‐Ala), have been synthesized by the reaction of Ph2SnCl2 and the disodium salt of the respective dipeptides. The bonding and coordination behaviour in these derivatives are discussed on the basis of IR, multinuclear 1H, 13C, and 119Sn NMR and 119Sn Mössbauer spectroscopic studies. These investigations suggest that all the dipeptides in Ph2SnL act as dianionic tridentate ligands coordinating through the COO−, NH2, and Npeptide groups. The 119Sn Mössbauer studies, together with the NMR data, suggest a trigonal‐bipyramidal geometry around tin in Ph2SnL with the phenyl groups and Npeptide in the equatorial positions, whereas a carboxylic oxygen and the amino nitrogen atom occupy the axial positions. The anti‐inflammatory and cardiovascular activities, and toxicity of all the synthesized diphenyltin(IV) derivatives of dipeptides and of n‐dibutyltin(IV) derivatives of dipeptides (synthesized and characterized earlier) viz. Gly‐Trp, Val‐Val, Ala‐Val, glycyltyrosine (Gly‐Tyr), leucyltyrosine (Leu‐Tyr), and leucylleucine (Leu‐Leu) are discussed. The n‐dibutyltin(IV) derivatives exhibit better cardiovascular and anti‐inflammatory activities than the diphenyltin(IV) analogues.

Spectral Studies and Bactericidal, Fungicidal, Insecticidal and Parasitological Activities of Organotin(IV) Complexes of Thio Schiff Bases Having no Donor Atoms.

Twelve new organotin(IV) complexes of the type RnSnLm [where n = 3, m = 1, R = CH3 or C6H5; n = 2, m = 2, R = C6H5 or C4H9 ; L = anion of Schiff bases derived from the condensation of 2-amino-5-(o-anisyl)-l,3,4-thiadiazole with salicylaldehyde (HL-1), 2- hydroxynaphthaldehyde (HL-2) and 2-hydroxyacetophenone (HL-3)] have been synthesized and characterized by elemental analysis, molar conductances, electronic, infrared, far-infrared, 1H NMR and 119Sn Mössbauer spectral studies. Thermal studies of two complexes, viz., Ph3Sn (L-1) and Ph2Sn(L-2)2 have been carried out in the temperature range 25-1000∘C using TG, DTG and DTA techniques. All these complexes decompose gradually with the formation of SnO2 as an end product. In vitro antimicrobial activity of the Schiff bases and their complexes has also been determined against Streptococcus faecalis, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus Penicillin resistance (2500 units), Candida albicans, Cryptococcus neoformans, Sporotrichum schenckii, Trichophyton mentagrophytes and Aspergillus fumigatus. The Schiff bases (HL-1), (HL-2) and the organotin(IV) compounds have also been tested against various important herbicidal, fungicidal, insecticidal species and also for parasitological activity against freeliving nematode.