Tri-n-butyltin(IV) derivatives of L-cysteine ethyl ester, N-acetyl-L cysteine and α-glutamyl cysteinyl glycine (glutathione reduced)

Nickel(II) complexes of biologically active glutathione: spectroscopic, kinetics of thermal decomposition and XRPD studies

Nickel(II) complexes of reduced glutathione (GSH) of general composition Na[Ni(L)(X)]H(2)O, where H(2)L=GSH; X=NO(3)(-), SCN(-), CH(3)CO(2)(-), Cl(-) have been synthesized and characterized by elemental analysis, infrared spectra, electronic spectra, magnetic susceptibility measurements, thermal and X-ray powder diffraction studies. Infrared spectra indicate deprotonation and coordination of cysteinyl sulphur and carboxylate oxygen of glycine residue with nickel ions. It indicates the presence of water molecule in all the complexes which has been supported by TG/DTA. The thermal behavior of complexes shows that water molecule is removed in first step-followed removal of anions and then decomposition of the ligand molecule in subsequent steps. General mechanisms describing the decomposition of the solid complexes are suggested. Kinetic and thermodynamic parameters were computed from the thermal decomposition data. The room temperature magnetic moment values for all the complexes lie in the range of 2.2-2.4BM, indicating departure from spin only values due to second order Zeeman effect. The electronic spectra indicate planar coordination geometry for all the complexes. Crystal data for Na[Ni(L)(CH(3)CO(2)(-))]H(2)O: tetragonal, space group P4/m, a=8.2004A, b=8.2004A, c=16.0226A, V=1077.47A(3), Z=2. Crystal data for Na[Ni(L)(Cl(-))]H(2)O: cubic, space group Pm3, a=16.1055A, b=16.1055A, c=16.1055A, V=4178.38A(3), Z=6. Crystal data for Na[Ni(L)(NO(3)(-))]H(2)O: tetragonal, space group P4/m, a=7.2121A, b=7.2121A, c=12.0200A, V=625.22A(3), Z=2.

Intramolecular Chalcogen−Tin Interactions in (o-MeE-C6H4)CH2SnPh3-nCln (E = S, O; n = 0, 1, 2), Characterized by X-ray Diffraction and 119Sn Solution and Solid-State NMR

Organotin(IV) compounds of the type (o-MeE-C6H4)CH2SnPh3-nCln were synthesized, E = O, n = 0 (1), n = 1 (2), n = 2 (3) and E = S, n = 0 (4), n = 1 (5), n = 2 (6). The complexes exhibit significant trigonal bipyramidal pentacoordination at tin as a consequence of intramolecular Sn-O (1-3) and Sn-S (4-6) interactions upon substitution of the phenyl groups by chloro groups. The intramolecular Sn-O distances in 1, 2, and 3 are 83%, 75%, and 79% of the sum of the van der Waals radii. The equivalent Sn-S values for 4, 5, and 6 are 90%, 73%, and 71%, respectively. The geometry of compound 3 is complicated by intermolecular dimerization via bridging chlorines creating a distorted octahedral geometry at tin. The related dichloro sulfur compound 6 also exhibits an intermolecular association in the form of Sn-Cl-H hydrogen bonding leading to a polymeric structure in the solid state. CPMAS 119Sn NMR spectroscopy suggests that the intramolecular Sn-E interactions persist in solution and also facilitated the discovery of a new crystalline form of 4, 4', that contains a Sn-S distance which is 95% the sum of the van der Waals radii.

Mechanism of augmentation of organotin decomposition by ferripyochelin: formation of hydroxyl radical and organotin-pyochelin-iron ternary complex

Pyochelin (PCH), a kind of siderophore secreted by Pseudomonas aeruginosa, was recently found to have triphenyltin (TPT)-decomposing capacity. In this work, significant augmentation of TPT decomposition by ferripyochelin (FePCH), the chelating compound of PCH with iron, was demonstrated in Tris-HCl buffer (pH 8.0). The generation of hydroxyl radical (HO.) in the presence of FePCH was observed. Inhibition of HO. generation by adding catalase and HO. scavengers (methanol and dimethyl sulfoxide) decreased TPT decomposition, while an increase in HO. formation in the presence of H(2)O(2) enhanced its decomposition. Our findings indicated that HO. generated in the reaction system was responsible for the enhanced TPT decomposition by FePCH versus PCH. The existence of the TPT-pyochelin-iron ternary complex was demonstrated by electron spray ionization-mass spectrometry, tandem mass spectrometry, and (1)H nuclear magnetic resonance. On the basis of the above results, HO. produced in the presence of FePCH was deduced to be in close proximity to TPT and has more opportunity to attack the Sn-C bond, which resulted in the enhanced organotin decomposition. The information obtained may have considerable environmental significance.

Cobalt(II) complexes of biologically active glutathione: spectroscopic and molecular modeling studies

Cobalt(II) complexes of reduced glutathione (GSH) of general composition Na[Co(L)(X)].nH2O (where H2L = GSH; X = Cl-, NO3-, NCS-, CH3CO2-, HCO2-, ClO4- and n = 0-4) have been synthesized and characterised by elemental analyses, vibrational spectra, electronic spectra, magnetic susceptibility measurements, thermal studies and molecular modeling studies. Electronic spectra indicate planar geometry for all the complexes. Infrared spectra indicate the presence of H2O molecules (except perchlorate complex) in the complexes that has been supported by TG/DTA. The room temperature magnetic moment values for all complexes lie in the range of 2.60-2.80 BM range indicating departure from spin only values due to second order Zeeman effect. Thermal decomposition of all the complexes proceeds via first order kinetics. The Na[Co(L)(Cl)].2H2O complex has the minimum activation energy and Na[Co(L)(CH3CO2)].3H2O has the maximum activation energy. The molecular modeling calculation for energy minimization optimizes geometry of the metal complexes.