Mechanisms of the coupling of one-and two-electron reactions in chemical and biochemical processes

The mechanisms of chemical and biochemical reactions in which one-electron stages ae coupled with two-electron stages are examined. The mechanisms of the coupling of the one- and two-electron stages in the electron-transport systems of the living cell are discussed on the basis of an analysis of chemical models. Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine, 1 Murmanskaya ul., Kiev 253094, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 3, pp. 133–144, May–June, 1999.     

Synthesis,Structure and Properties of Some 3d-Element Complexes with 2-[2-(Hydroxybenzylidene)-amino]-2-hydoxymethylpropane-1,3-diol

2-[2-(Hydroxybenzylidene)-amino]-2-hydoxymethylpropane-1,3-diol (HL) reacts with cobalt, nickel, copper and zinc chlorides, bromides and acetates in water–ethanol solutions and gives MLX · nH₂O and ML₂ · nH₂O complexes (M = Co, Ni, Cu, Zn; X = Cl, Br; n = 0–5). Single crystals of CuLBr were grown, and its crystal structure was determined by X-ray diffraction analysis. The crystals are tetragonal, a = 17.024(2), c = 8.720(2) Å, space group P 2₁ c, Z = 8, R ₁ = 0.0349. In the structure of this complex, the copper atom coordinates the deprotonated HL molecule. The coordination polyhedron of the central atom is an elongated tetragonal pyramid. Its base is built of the imine nitrogen atom, phenolic and alcoholic oxygen atoms, and bromine atom. The apex of the pyramid is occupied by the bromine atom of the adjacent complex connected with the initial complex by the plane of sliding reflection. Thus, the crystal contains infinite chains of complexes running along the c axis, the complexes being united by both bridging bromine atoms and O–H···O hydrogen bonds. The conclusions on the compositions and structures of the remaining compounds were made on the basis of elemental and combined thermal analyses, IR spectroscopy, and magnetic chemistry data. The copper halide complexes were found to have dimeric, and the other metal complexes monomeric, structures. In the synthesized complexes, the azomethine HL can function as a bidentate or tridentate ligand. The thermolysis of the coordination compounds proceeds through the stages of elimination of crystal water molecules (75–90°C) or inner-sphere water molecules (145–155°C) and complete thermal destruction (485–550°C).     

Coordination Compounds of Copper(II) with Benzoylhydrazones of Substituted Salicylaldehydes

Benzoylhydrazones of 5-nitro- (H₂L¹), 3-nitro- (H₂L²), 5-chloro- (H₂L³), 5-bromo- (H₂L⁴), and 3,5-dibromosalicylaldehydes (H₂L⁵) react in ethanol with copper acetate to form complexes CuL^1-5. In the presence of amines (A = C₅H₅N, 3-CH₃3C₅H₄N), the above reactions give complexes CuL^1-5A·nH₂O (n = 0, 1). When cuprous bromide or nitrate and benzoylhydrazone H₂L³ were used as starting materials, complexes Cu(HL³)X (X = Br^-, NO₃ ^-) were isolated. The resulting complexes all are polynuclear structures in which azomethines H₂L^1-5 behave as tridentate O,N,O-ligands. Thermolysis of the complexes involves the stages of dehydration (70-90°C), deaquation (120-150°C) or deamination (150-180°C), and complete thermal de- composition (350-500°C).     

Kinetics and mechanism of the photochemical hydrolysis of phosphoenolpyruvic acid

It was established that phosphoenolpyruvic acid, photoexcited by UV light at 20°C, loses its phosphoryl group under the action of acids and bases. Raising the temperature to 50°C induces dissociation of the photoexcited molecule into enolpyruvate and metaphosphate, which in turn phosphorylates HPO₄ ^2– and H₂P₂O₇ ^2– ions and AMP.Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine, 1 Murmanskaya St., 253094 Kiev-94, Ukraine. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 32, No. 5, pp. 287–290, September–October, 1996. Original article submitted December 1, 1995.     

Lanthanide Complexes with N,N′-Bis(2- hydroxybenzylidene)-2-hydroxyphenylmethanediamine

Complexes of lanthanides with N,N-bis(2-hydroxybenzylidene)-2-hydroxyphenylmethanediamine (H₃L) were synthesized and investigated by the elemental, IR, magnetochemical, and thermogravimetric methods. Using the data obtained, they were found to have compositions Ln₂L₂ · nH₂O and La₂L₂ · MCl₂ · 4H₂O (Ln = La³⁺, Pr³⁺, Nd³⁺, Dy³⁺, Er³⁺; M = Cu²⁺, Co²⁺, Ni²⁺; n = 4, 6). Suggestions on their structures were made. In the interval of 20–140°C, these complexes were shown to be high-resistance semiconductors.     

Kinetics and mechanism of the biomimetic reactions of macroergic phosphates

Data on the reactions of phosphates with a macroergic bond (adenosine di- and triphosphate, pyrophosphate, enolophosphates, acyl phosphates, and amidophosphates), which are regarded as models of the respective biochemical processes, are reviewed. The mechanisms of the biomimetic reactions of this type of compound are discussed.Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine, Kiev. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 32, No. 4, pp. 200–210, July–August, 1996. Original article submitted June 14, 1995.