Ngoh Khang Goh

Molecular adducts of diorganotin dichloride with N-(2-oxidoarylideneaminoacidato) diorganotin(IV) complexes. Crystal structure of [Ph2Sn(2-OC10H6CH-NCH2COO)]SnPh2Cl2

Abstract Three new dinuclear tin complexes, [Me2Sn(2-OC6H4CH-NCH[Pri]COO)]SnMe2Cl2 (1), [Me2Sn(2-OC10H6CH-NCH2COO)SnMe2Cl2 (2) and [Ph2Sn(2-OC10H6CH-NCH2COO)]SnPh2Cl2 (3), were prepared and characterized by spectroscopic studies and elemental analyses as a 1 : 1 adduct between diorganotin dichloride (acceptor) and bicycloazastannoxide (donor). A full X-ray crystal structure analysis was performed on 3 and the results confirmed that the donor and the acceptor moieties of 3 are bonded with an Sn-O bond distance of 2.307A˚.

Carnivorous pitcher plant uses free radicals in the digestion of prey.

Abstract A study of the involvement of free oxygen radicals in trapping and digestion of insects by carnivorous plants was the main goal of the present investigation. We showed that the generation of oxygen free radicals by pitcher fluid of Nepenthes is the first step of the digestion process, as seen by EPR spin trapping assay and gel-electrophoresis. The EPR spectrum of N. gracilis fluid in the presence of DMPO spin trap showed the superposition of the hydroxyl radical spin adduct signal and of the ascorbyl radical signal. Catalase addition decreased the generation of hydroxyl radicals showing that hydroxyl radicals are generated from hydrogen peroxide, which can be derived from superoxide radicals. Gel-electrophoresis data showed that myosin, an abundant protein component of insects, can be rapidly broken down by free radicals and protease inhibitors do not inhibit this process. Addition of myoglobin to the pitcher plant fluid decreased the concentration of detectable radicals. Based on these observations, we conclude that oxygen free radicals produced by the pitcher plant aid in the digestion of the insect prey.

Phenolic constituents from the leaves of the carnivorous plant Nepenthes gracilis.

Plumbagin, isoshinanolone, epishinanolone, shinanolone, quercetin and kaempferol were isolated from the leaves of Nepenthes gracilis. Spectral data of shinanolone are presented.

The synthesis, structural characterization and biocidal properties of some triorganotin(IV) esters of N-arylidene-ω-amino acids.

The methods of synthesis, elemental analysis, IR and NMR spectroscopic data and fungicidal activity against Ceratocystis ulmi are reported for a series of triorganotin esters of N-arylidene-ω-amino acids of general formula R 3 SnO-CO(CH 2 ) n N = CHAr (R = Ph, n-Bu; Ar = 2-HOC 6 H 4 , 2-HOC 10 H 6 ; n = 1, 2, 3 and 5). The crystal structures for two of the compounds, tributyltin N-2-hydroxynaphthalidene glycinate (1) and tributyltin N-2-hydroxynaphthalidene-β-alaninate (2), have been determined. Although both of these compounds have a trans-R 3 SnO 2 structure, in compound 1 the carboxylate group is monodentate and the fifth coordination position around the tin atom is taken up by a coordinated phenolic group, whereas in 2 the carboxylate group is bridging. These two examples thus correspond to the two different structures reported for trans-R 3 SnO 2 complexes. Both compounds were found to be active against Ceratocystis ulmi, but there was no significant difference in their levels of biological activity against this particular fungus. Apart from compound 1, the other tributyltin compounds reported are believed to adopt the carboxylate bridging mode shown by compound (2). Crystal data: for 1, crystals monoclinic, space group P2 1 /c, a = 12.9435(11) A, b = 13.5769(10) A, c = 15.7715(12) A, β = 108.919(6)°, Z = 4, R f = 0.046 and R w = 0.058 for 1448 significant reflections; for 2, crystals monoclinic, space group C 2/c, a = 24.588(14) A, b = 9.733(3) A, c = 27.611(12) A, β = 113.49(4)°, Z = 8, R f = 0.053 and R w = 0.069 for 3822 significant reflections.

A Gaussian-3 (G3) theoretical study of the interactions between alkali metal cations and polyhydroxyl ligands

Abstract Ab initio molecular orbital calculations at the G3(GCP) level were conducted for the alkali cation–alcohol complexes (M + –L, where M + =Li + , Na + , and K + ; L=methanol, ethylene glycol, propan-1,2-diol, propan-1,3-diol and propan-1,2,3-triol). In general, these cations maximize the number of M + ⋯O interactions with the ligands. The role of intramolecular hydrogen bonding, ligand polarizability, ligand deformations, number of M + ⋯O interactions and the M + ⋯O distances in governing M + –L affinities was discussed. The computationally less expensive G2(MP2,SVP)–FC/ASC models were found to yield affinities in good agreement against the G3(GCP) benchmark, but the agreement deteriorates somewhat with increasing number of M + ⋯O interactions.

Triphenyltin esters of N-(2-carboxybenzylidene)anilines : Synthesis, spectroscopic characterization, X-ray structure analysis and fungicidal activity

Four triphenyltin carboxylates formulated as o-Ph 3 SnOCOC 6 H 4 CH=N-Ar (Ar=C 6 H 5 ; p-CH 3 C 6 H 4 ; o-CH 3 C 6 H 4 ; o-HOC 6 H 4 ) were prepared and spectroscopically characterized. The crystal structure of o-Ph 3 SnOCOC 6 H 4 CH=NC 6 ,H 5 indicates that the tin atom, in each of the two molecules comprising the asymmetric unit, exists in a distorted tetrahedral geometry owing to an intramolecular acyl O...Sn contact. These new triphenyltin carboxylates display marked toxicity against the fungus Ceratocystis ulmi

A chemical equation as a representation of a class of linear Diophantine equations and a system of homogeneous linear equations

A chemical equation, comprising nelements interspersed among mspecies (reactants + products) and where the stoichiometric coefficients are represented by algebraic symbols, is shown to be equivalent to a class of linear Diophantine equations as well as a system of khomogeneous linear equations in munknowns, where k^ n.The use of conservation conditions for the elements in the chemical equation affords a non‐conventional approach for the generation of some of the integral solution sets of the Diophantine equations and the integral solutions of the system of homogeneous linear equations.