Chaveng Pakawatchai

Solvent-assisted mechanochemical synthesis of metal complexes

The application of solvent-assisted mechanochemical synthesis to the study of metal complex formation is illustrated by examples involving complexes of silver halides with ethylenethiourea.

Cyanogenic and non-cyanogenic glycosides from Manihot esculenta

In addition to lotaustralin and linamarin, a novel cyanogenic glycoside, 2-((6-O-(beta-D-apiofuranosyl)-beta-D-glucopyranosyl)oxy)-2-met hylbutanenitrile , two novel non-cyanogenic glycosides, (2S)-((6-O-(beta-D-apiofuranosyl)-beta-D- glucopyranosyl)oxy)butane and 2-((6-O-(beta-D-apiofuranosyl)-beta-D-glucopyranosyl)oxy)propane, and a simple non-cyanogenic glycoside, ethyl beta-D-glucopyranoside, were isolated from an ethanolic extract of the fresh root cortex of Manihot esculenta. From a methanolic extract of the fresh leaves of this species lotaustralin and linamarin, and two flavonoid glycosides, kaempferol-3-O-rutinoside and quercetin-3-O-rutinoside were isolated.

The coordination chemistry of mono and bis(di-2-pyridylamine)copper(II) complexes: preparation, characterization and crystal structures of [Cu(L)(NO2)2], [Cu(L)(H2O)2(SO4)], [Cu(L)2(NCS)](SCN)·0.5DMSO and [Cu(L)2(SCN)2]

Abstract The crystal structures of two mono(dpyam)copper(II) complexes, [Cu(dpyam)(NO2)2] (1) and [Cu(dpyam)(H2O)2(SO4)] (2) and two dithiocyanate compounds containing bis(dpyam)copper(II) units, [Cu(dpyam)2(NCS)](SCN)·0.5DMSO (3) and [Cu(dpyam)2(SCN)2] (4) have been determined by X-ray crystallography. The second orthorhombic form of the monomeric Cu(II) complex 1 was obtained by the reaction of di-2-pyridylamine (dpyam) with CuCl and NaNO2 in water–methanol solution. Each copper(II) ion in 1 exhibits a tetrahedrally-distorted square base of the CuN2O2 chromophore, with off-the-z-axis coordinated nitrito groups weakly bound in approximately axial positions. Complex 2 is an example of a polymeric copper(II) derivative containing the bidentate bridging sulfate ligand in the long-bonded axial positions. Each copper(II) ion in 2 shows an elongated tetragonal octahedral stereochemistry. The CuN4N′ chromophore of 3 involves a square-based pyramidal structure, slightly distorted towards a trigonal bipyramidal stereochemistry, τ=0.13. One of the SCN− anions is bonded to the copper(II) ion via the N atom in the axial position of the square pyramid. Complex 4 is centrosymmetric and octahedrally elongated, with the SCN− anions coordinating in axial positions via the S atom. The structures of complexes 1–4 and their ESR and electronic reflectance spectra are compared with those of related complexes.

Preparation, crystal structure, spectroscopic and magnetic characterisation of acetatobis(di-2-pyridylamine)copper(II) tetrafluoroborate and μ-carbonato-tetrakis(di-2-pyridylamine) dicopper(II) bistetrafluoroborate tetrahydrate

Abstract The crystal structures of [Cu(dpyam)2(O2CCH3)][BF4] (1) and [Cu2(dpyam)4(CO3)][BF4]2·4H2O (2) have been determined by X-ray analysis. 1 involves the distortion of the CuN4O2 chromophore towards a square pyramidal (4+1+1*) stereochemistry which is best described as involving a square-pyramidal distorted octahedral stereochemistry of the six-coordinate CuN4OO′ chromophore. Compound 2 has a dinuclear cation with five-coordinate copper(II) ions bridged asymmetrically by a bidentate carbonate ligand. Both copper(II) ions predominantly involve the distorted square-pyramidal (4+1) stereochemistry of the CuN3ON′ chromophore. The polycrystalline ESR spectra of 1 and 2 are exchange coupled and temperature independent. In 2 the room temperature effective magnetic moment of 1.34 μB indicates the partial spin pairing by antiferromegnetic coupling.

Synthesis, crystal structures and magnetism of planar and roof-shaped hydroxo-bridged dinuclear copper(II) compounds with di-2-pyridylamine as a ligand

Abstract The compounds [Cu(dpyam)(OH)Br] 2 (H 2 O) 4 ( 1 ), [Cu(dpyam)(OH)(CF 3 SO 3 )] 2 ( 2 ) and [Cu 2 (dpyam) 2 (OH) 2 (OH 2 )]Br 2 (H 2 O) 2 ( 3 ) have been synthesized and their crystal structures determined by X-ray crystallographic methods. Compound 1 crystallises in the triclinic system, space group P 1 . The lattice constants are a =8.892(1), b =9.346(1), c =9.358(1) A, α =112.2(1), β =108.3(1), γ =95.8(2)° with Z =1 and R 1 =0.0292. Compound 2 crystallises in the triclinic system, space group P 1 . The lattice constants are a =8.1616(5), b =9.4156(6), c =10.2921(6) A, α =72.58(2), β =72.48(4), γ =73.19(2)° with Z =1 and R 1 =0.0595. Crystals of 3 are orthorhombic with space group Cmc 2 1 . The lattice constants are a =15.979(1), b =8.550(1), c =18.237(1) A with Z =4 and R =0.0623. Compound 1 contains a dinuclear [Br(dpyam)Cu(OH) 2 Cu(dpyam)Br] unit with a dihedral angle between the CuO 2 planes of 179.9°. Each copper atom is in a square-pyramidal coordination environment; the basal plane consists of two bridging hydroxo groups and two dpyam ligands coordinated through their nitrogen atom. The fifth axial coordination site of each copper(II) ion is occupied by a Br atom, at a weak semi-coordination distance of 2.803(2) and 2.804(2) A. For compound 2 , the coordination geometry around each copper(II) ion is distorted elongated octahedral, CuN 2 O 4 . The equatorial positions are occupied by the two nitrogen atoms of dpyam and the two oxygen atoms of the bridging hydroxo groups, where the apical positions are occupied by oxygen atoms from both triflate groups. In the dinuclear units of compound 3 the triply-bridged Cu(II) ions show a distorted square pyramidal coordination. The fifth apical ligand is a longer bonded bridging water molecule for 3 , at distances of 2.220(2) A, which joins the basal CuN 2 O 2 planes in a roof-shaped configuration (dihedral angle 135.8 o ). The CuCu distances are 2.993(2), 2.964(2) and 2.849(2) A for compounds 1 , 2 and 3 , respectively. The magnetic susceptibility measurements revealed a ferromagnetic interaction between the Cu(II) atoms for compound 2 , with a singlet–triplet energy gap ( J ) around 83 cm −1 . Compound 1 has an antiferromagnetic interaction with a J of −48.6 cm −1 , whereas compound 3 is very weakly antiferromagnetic with J =−0.6 cm −1 .

Studies on complex formation between curcumin and Hg(II) ion by spectrophotometric method: a new approach to overcome peak overlap.

Complex formation between curcumin and Hg(II) ion MeOH/H2O (1: 1 v/v) was investigated and monitored by the spectrophotometric method. The absorption peak of unreacted curcumin which was close and overlapped with that of the complex, was removed by calculation using Microsoft Excel, thereby, allowing determination of the stoichiometry of the complex by the mole-ratio and the Job’s continuous variation methods. Both methods indicated that a 1:1 complex of curcumin and Hg(II) was formed in solution. The formation constant of the 1:1 Hg(II) complex was obtained from two methods, the equilibrium concentration calculation and the linear plot of Benesi-Hildebrand equation, as log K = 4.44 ± 0.16 and 4.83 ± 0.02, respectively. The structure is proposed as a tetrahedral complex of Hg(II) with one curcumin and two chloride ions as ligands.

Drastic steric effects from, respectively, a hydrogen, a methyl and an ethyl group on the coordination network of a zinc(II)–4,4′-bipyridine–carboxylato ternary system

The combination of a [zinc(II)–4,4′-bpy] coordination moiety with, respectively, formato, acetato and propionato ligands leads to the formation of the compounds {[Zn3(4,4′-bpy)3.5(µ-O2CH)4 (H2O)2](ClO4)2(H2O)2}n (1), {[Zn3(4,4′-bpy)3(µ-O2CCH3)4(H2O)2](PF6)2(H2O)2}n (2) and {[Zn3(4,4′-bpy)4(µ-O2CCH2CH3)4](ClO4)2(4,4′-bpy)2(H2O)4}n (3). The molecular structures determined by single-crystal X-ray diffraction data reveal significant changes, which are apparently due to the sole different steric hindrance between a H atom (formato, compound 1), a methyl group (acetato, compound 2) and an ethyl group (propionato, compound 3). The three coordination materials have been fully characterized and their thermal decomposition behavior has been investigated. The 3D (1), 1D (2) and 2D (3) networks exhibit voids that contain the counter-ions and guest molecules as well, namely water for compounds 1 and 2, and water/4,4′-bpy for compound 3.

Photoactive azoimine dyes: 4-(2-Pyridylazo)-N,N-diethylaniline and 4-(2-pyridylazo)-N,N-dimethylaniline: Computational and experimental investigation

4-(2-Pyridylazo)-N,N-dimethylaniline and 4-(2-pyridylazo)-N,N-diethylaniline, two photoactive azoimine dyes, were prepared from the reaction of 2-aminopyridine with N,N-dialkyl-1,4-nitrosoaniline at room temperature. Structural characterizations of these dyes using single crystal X-ray diffraction, (1)H NMR, elemental analysis, mass spectroscopy and IR spectroscopy have been carried out. The X-ray structure indicates a trans configuration around the azo group. The photochemical behavior of these compounds differs from that of 2-phenylazopyridine, the non-dialkylamino substituent compound. The synthesized compounds show emission spectra at room temperature while 2-phenylazopyridine does not. The excitation spectra of these compounds differ from their absorption spectra which can be explained on the basis of the trans to cis photoisomerization which is supported by the TD-PBE0/6-31G(d,p) calculations. Both oxidation of the dialkylamino substituents (-NR(2); R=-CH(3) and -C(2)H(5)) and reduction of -N=N-/-N=N-(-) and -N=N-(-)/-N=N-(2-) were observed in the cyclic voltammogram indicating a π-acidity of both dyes.

Clauraila E from the roots of Clausena harmandiana and antifungal activity against Pythium insidiosum

A new carbazole alkaloid named clauraila E (1) together with 8 known compounds were isolated from the methanol extract of the roots of Clausena harmandiana. All compounds were evaluated for antifungal activity against Pythium insidiosum using disc diffusion assay. Pythium insidiosum is a fungus-like microorganism, for which antifungals available now are not effective. It was found that compounds 3, 6, 7 and 9 could inhibit the mycelia growth of P. insidiosum. The results show convincingly that they may be lead to compounds for the development of probiotic or novel antifungal drugs.

Synthesis of gem-difluoromethylenated polycyclic cage compounds.

The synthesis of gem-difluoromethylenated polycyclic cage compounds, utilizing PhSCF2SiMe3 as a gem-difluoromethylene building block, is described. The fluoride-catalyzed nucleophilic addition of PhSCF2SiMe3 to both maleic anhydride-cyclopentadiene and maleic anhydride-cyclohexadiene adducts was accomplished with high stereoselectivity to provide the corresponding adducts that were treated with Grignard reagents, followed by acid-catalyzed lactonization to afford the corresponding γ-butyrolactones, each as a single isomer. These γ-butyrolactones underwent intramolecular radical cyclization to give the corresponding tetracyclic cage γ-butyrolactones, which were employed as precursors for the synthesis of gem-difluoromethylenated tetracyclic cage lactols or tetracyclic cage furans, upon treatment with Grignard reagents.