Aarne Pajunen

Salen Complexes with Bulky Substituents as Useful Tools for Biomimetic Phenol Oxidation Research

The catalytic properties of bulky water-soluble Co-, Cu-, Fe- and Mn-salen complexes in the oxidation of phenolic lignin model compounds have been studied in aqueous water--dioxane solutions (pH 3--10). Mn catalysts were found to oxidize coniferyl alcohol in a same reaction time as horseradish peroxidase (HRP) enzyme and Mn and Co catalysts showed different regioselectivity suggesting a different substrate to catalyst interaction in the oxidative coupling. When the oxidation of material more relevant to plant polyphenolics was studied, the results indicated that the complexes catalyze one- and two-electron oxidations depending on the bulk of the substrate.

Synthesis and characterization of bulky salen-type complexes of Co, Cu, Fe, Mn and Ni with amphiphilic solubility properties

Several new bulky salen-type Schiff base ligands and their complexes with first-row transition metals Co, Cu, Fe, Mn and Ni have been synthesized and characterized. The ligands contain tert-butyl and methyl(triphenylphosphonium chloride) substituents in aromatic rings providing flexible solubility properties. Crystal structures of some of the complexes were determined.

A novel type of spiro compound formed by oxidative cross coupling of methyl sinapate with a syringyl lignin model compound. A model system for the β-1 pathway in lignin biosynthesis

Oxidative coupling of methyl (E)-sinapate with 1-(4-hydroxy-3,5-dimethoxyphenyl)ethanol, a syringyl lignin model compound, was carried out with hydrogen peroxide catalyzed by horseradish peroxidase. The main product was a cyclohexadienone spiro compound of a novel type. Mild acidolysis caused the loss of one side chain and yielded a dimeric compound with a 1,2-diarylpropane structure. This is the first example of the formation of this structural type by oxidative coupling in vitro.

The crystal structure of a heteronuclear Pt22CuL4 complex of 1-methyluracil, Cu[Pt(NH3)2(C5H5N2O2)2]2SO4·8H2O

Abstract The crystal structure of heteronuclear bis[bis(μ- 1-methyluracilato- N 3, O 4)- cis -diammineplatinum(II)]- copper(II) sulfate octahydrate, Cu[Pt(NH 3 ) 2 (C 5 H 5 - N 2 O 2 ) 2 ] 2 SO 4 ·8H 2 O, has been determined by X-ray diffraction. The compound crystallizes in space group I 4 1 / a with cell parameters a = 20.470(7), c = 23.509(8) A, V = 9850(6) A 3 , Z = 8. The structure was refined on 2783 reflections to R = 0.045 and R w = 0.064. The deprotonated 1-methyluracilato ligand coordinates to cis -Pt(NH 3 )2 2+ , by N3 and to Cu by O4. Both the Pt and Cu have square-planar coordination spheres with Cu in the inversion center of the trinuclear Pt 2 Cu unit. The PtCu distances within the cation are 2.684(1) A. The non- coordinating O2 oxygens take part in a hydrogen bond network with NII 3 groups of the adjacent molecular cations.

Synthesis and crystal structure of Na[Pd(Hpba)]·2H2O [H4pba = 1,3-propylenebis(oxamic acid)]. The first bis(oxamato)palladium(II) complex and an unexpected trideprotonated form of the ligand

Abstract The complex of formula Na[Pd(Hpba)]·2H2O, in which H4pba is 1,3-propylenebis(oxamic acid), was obtained by reaction of the diethyl ester of the 1,3-propylenebis(oxamic acid) and Na2PdCl4 in basic conditions. The X-ray structure consists of [N,N′-(1,3-propanediyl)bis(oxamato-N,O)]palladate(II) dihydrate anions, sodium cations and water molecules coordinated to the sodium cations, linked together to give rise to polymeric chains [Na(H2O)2Pd(Hpba)]n. Within the [Pd(Hpba)]− anions, Pd(II) atom occupies the N2O2 inner-site of the ligand displaying a distorted square-planar coordination. Interestingly, the ligand coordinates to Pd(II) in an unexpected trideprotonated fashion; the remaining hydrogen atom being located on an amide oxygen atom.

(1,3-Dimethyl-2,6-dioxo-2,3,6,7-tetrahydro-1H-purin-7-yl)(dimethylphenylphosphine)gold(I)

In [Au(PMe 2 Ph)T], where T is the theophyllinate ligand, C 7 H 7 N 4 O 2 - (theophylline = 3,7-dihydro-1,3-dimethyl-1H-purine-2,6-dione), the Au atom is linearly coordinated by the P atom of the dimethylphenylphosphine ligand and the deprotonated N atom at position 7 of the theophyllinate ligand. Bond parameters involving Au are : Au-N 2.071 (9), Au-P 2.233 (3)A and N-Au-P 177.5 (2)°.

Heptahydrated monosodium salt of 6-amino-5-(2-carboxyphenyl)azouracil

The bulky organic molecule in the title compound, sodium 2-[6-amino-2,4(3H,5H)-dioxopyrimidin-5-ylazo]benzoate heptahydrate, Na + .C 11 H 8 N 5 O 4 − .7H 2 O, exists as a monovalent anion with negatively charged carboxylate and uracil groups and a protonated azo group. An intramolecular bifurcated hydrogen bond contributes to the approximate planarity of the anion

Analysis of 1H and 13C{1H} NMR Spectral Parameters and Geometries of Three Isomeric Diphenylbicyclo[2.2.1]Hept-5-Ene-2,3-Dicarboxylic Anhydrides

Abstract Diels-Alder adducts of 1,4-diphenyl-1,3-cyclopentadiene and maleic anhydride were investigated by recording the 1H and 13C{1H} NMR spectra of three isomeric diphenylbicyclo[2.2.1]hept-5-ene endo and exo 2,3-dianhydrides. the spectra were recorded in CD2Cl2 and analysed completely. the effect of the endo and exo configuration of the anhydride ring on the chemical shifts of the bridgehead phenyl protons is discussed. the ortho protons of the exo isomers resonate at higher field than those of the endo isomer, and the resonance pattern of the aromatic protons is narrower in the exo than the endo anhydride. the aromatic regions of the spectra are compared with the same regions of the 1H NMR spectra of the earlier investigated addition products of 1,4-di-p-tolyl-1,3-cyclopentadiene and 1-phenyl-4-p-tolyl-1,3-cyclopentadiene with maleic anhydride. Chemical shifts of the bridge protons are explained on the basis of X-ray data of the compounds and MacroModel calculations on the minimum energy conformations.