Reactivity of pyrrole pigments,XXI: Structure and reactivity of Cu(II) and Zn(II) bilindione chelates

Summary Several Mn, Cu, and Zn chelates of etiobiliverdin-IV-, mesobiliverdin-IX, and its dimethyl ester are studied. The results show that the chemical constitution of the Cu biliverdin chelate corresponds to a formal metal oxidation state of (II) coordinated to a neutral radical of the NH trideprotonated biliverdin. The reactivity of the Cu(II) bilindione chelates in nucleophilic solvents agrees with that expected for a neutral radical structure of the ligand; in CH₃OH, they undergo oxidation towards dimethoxybilipurpurins. The magnetic behaviour of Cu(II) etiobiliverdinate-IV- in the solid state shows an intramolecular weak antiferromagnetic coupling d⁹Cu-to--radical (J=–23 cm^–1) and an intermolecular weak antiferromagnetic coupling -radical-to--radical (J=–45 cm^–1). The analogy of this magnetic behaviour to that of the cation radical of metalloporphyrins is discussed.

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Reaktivität von Pyrrolpigmenten, 21. Mitt.: Struktur und Reaktivität von Cu(II)- und Zn(II)-Chelaten von Bilindionen

Zusammenfassung Einige Mn, Cu and Zn Chelate von Etiobiliverdin-IV-, Mesobiliverdin-IX und seinem Dimethylester werden untersucht. Im Komplex koordiniert ein Metallatom (mit der Formalladung II) mit einem Neutralradikal des dreifach NH-deprotonierten Bilindions. Die Reaktivität des Komplexes gegenüber nukleophilen Lösungmitteln entspricht erwartungsgemäß dem eines neutralen -Radikals; in CH₃OH wird er zu Dimethoxybilipurpurin oxidiert. Bei Cu(II)-Etiobiliverdinat-IV beobachtet man im festen Zustand neben schwacher, antiferromagnetischer Kupplung zwischen d⁹Cu und -Radikal (J=–23 cm^–1) auch eine schwache, intermolekulare, antiferromagnetische Wechselwirkung zwischen zwei -Radikalen (J=–45 cm^–1). Dieses magnetische Verhalten wird dem des -Kationradikals von Metalloporphyrinen gegenübergestellt.

     

Reactivity of pyrrole pigments. Part 9 MINDO/3 calculations on dipyrrolic partial models of bile pigments

The applicability of the MINDO/3 method is evaluated for calculations on dipyrrolic partial structures of bile pigments. It is shown that this method cannot be used for an accurate conformational analysis. However, when applying the frontier orbital model for reactivity parameters, a good picture of the HOMO and the LUMO distribution can be obtained in this type of molecules.

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Reaktivität von Pyrrolpigmenten, 9. Mitt. MINDO/3-Rechnungen von dipyrrolischen Partialmodellen von Gallenpigmenten

Zusammenfassung Es werden die Einsatzmöglichkeiten von MINDO/3 für den Fall dipyrrolischer Partialstrukturen der Gallenpigmente aufgezeigt. Die Methode ist für eine genaue Konformationsanalyse nicht geeignet. Unter Verwendung der Reaktionsparameter des Frontier-Orbital-Modells läßt sich jedoch ein gutes Bild der HOMO- und LUMO-Verteilung für diesen Verbindungstyp gewinnen.

     

Isomerization of (Het)arylbenzoins in Basic Media

The isomerization of the hetaryl analogs of unsymmetrical benzoins on heating in basic media is a convenient preparative method for the production of -hydroxyacyl derivatives of -excessive heterocycles. The motivating force here for the isomerization is the formation of a thermodynamically more stable product. It was established that isomerization is promoted by increase in the difference between the electron-donating characteristics of the (het)aryl residues     

Reactivity of pyrrole pigments,XIX. On the structure of Cu(II) and Zn(II) chelates of dipyrrins in solution

Summary The Cu(II) and Zn(II) chelates of 1,2,3,7,9-pentamethyldipyrrin and 1,2,3,7,9-pentamethyl-8-sulfodipyrrin are studied. When metal acetates are used for the formation of the metal complexes, dipyrrinate metal acetates could be detected as precursors of thebis-dipyrrinates.

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Reaktivität von Pyrrolpigmenten, 19. Mitt. Über die Struktur von Cu(II)- und Zn(II)-Chelaten von Dipyrrinen in Lösung

Zusammenfassung Die Cu(II)- und Zn(II)-Chelate von 1,2,3,7,9-Pentamethyldipyrrin und 1,2,3,7,9-Pentadimethyl-8-sulfodipyrrin wurden untersucht. Bei Einsatz von Metalldiacetaten für die Komplexbildung wurden Dipyrrinmetallacetate als Vorläufer derbis-Dipyrrinate nachgewiesen.

     

1,4-dioxins from methyl phenylchloropyruvate. Competition of the Darzens, Favorskii, and Gabriel reactions

The reaction of methyl phenylchloropyruvate with potassium phthalimide and sodium imidazolide leads to isomeric 2,5-dimethoxycarbonyl-3,6-diphenyl- and 2,6-dimethoxycarbonyl-3,5-diphenyl-1,4-dioxins.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1042–1056, August, 2000.     

Physicochemical properties of π-π complexes of zinctetraphenylporphyrin with aromatic molecules

Features of the solvation of zinctetraphenylporphyrin (ZnTPP) in benzene, toluene,ortho-, meta-, andpara-xylenes were studied by a thermogravimetric method. The temperature ranges of the stability and the compositions of the corresponding specific - complexes were determined from the results of the thermogravimetric investigation of the crystallosolvates of the metalloporphyrin with the solvent molecules, and the energy characteristics of the intermolecular metalloporphyrin—solvent interactions were calculated.Institute of the Chemistry of Nonaqueous Solutions, Russian Academy of Sciences, 153018 Ivanovo. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1545–1548, July, 1992.     

Inclusion of dynamic σ-π polarization in π-electronab initio calculations

Summary A method is presented, whereby dynamic - polarization, i.e. the correlation effect expressed by simultaneous (-*, -*) excitations, can be approximately included in a multi-reference configuration interaction (MRCI) or multi-configurational self-consistent field (MC-SCF) calculation, without need to explicitly correlate the sigma orbitals. The method, which we call the capacitance matrix method, is based on the use of conventional one-electron integrals, from which a polarization potential (SPP) contribution is computed and added to the one- and two-electron Hamiltonian. In the present form, the method requires one parameter for each type of atom, and one for each type of bond. These parameters were adjusted to reproduce the dynamic - polarization energy, computed by restricted multi-reference CI calculations, of a number of states of different hydrocarbons, and the agreement was within a few percent. Using the same parameters in CAS (Complete Active Space) SCF calculations of various states of benzene gives excitation energies, when SPP is included, which is comparable to those obtained by much more elaborate MRCI calculations.     

Some peculiarities of π—π interactions between tetraphenylporphine metal complexes and aromatic solvents

The — complexes of metal tetraphenylporphinates with benzene, toluene, and xylenes were characterized by means of thermogravimetry. The ability of metalloporphyrins to form — complexes with certain -donor molecules depends largely on the -acceptor capacity of the macroheterocycle, and on the peculiarities of the metal—porphyrin coordinative linkage. Stoichiometry, energy parameters, and thermal stability of the - complexes of metalloporphyrins with various aromatic ligands are determined to a great extent by the molecular structure of solvents.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp.850–853, May, 1993.     

Die Acetalgruppe, 1. Mitt. Acetale von Halogenmethyl-arylcarbinolen

Several halomethyl-arylcarbinols were prepared, and the influence of substituents on enantiomer selectivity in the acetalisation reaction with [2S-(2,3a,4,7,7a)]-octahydro-7,8,8-trimethyl-4,7-methanobenzofuran-2-ol was examined.

Unserem sehr verehrten Lehrer, Herrn Prof. Dr.Otto Hromatka, mit den besten Wünschen zum 80. Geburtstag gewidmet.     

Quantum-chemical study of manifestations of conjugation in molecules containing conjugated C=C and C=O bonds

Based on the MNDO calculations of the electronic structure of the molecules of acrolein, glyoxal, and butadiene, possible mechanisms of the conjugation in systems containing conjugated C=C and C=O bonds have been analyzed. In the electronic ground state ofs-trans-acrolein, the , -conjugation is very small, whereas in the first excited electronic state, the conjugation is substantial, In the ground state ofs-trans-glyoxal, the ,-conjugation should manifest itself clearly but should be weaker than in butadiene, whereas in the first excited electronic state, this conjugation should be more pronounced, Alternation of double and single bonds in the classic structural formula of a molecule does not ensure that this molecule exhibits the properties of a -conjugated system even in planar conformations.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1648–1652, July, 1996.     

Complexation of monosubstituted benzenes and methanes by cyclotetrachromotropylene in aqueous solution: Substituent effects on π-π and Ch-π interactions

The stability constantsK of 11 complexes formed in aqueous solution between several monosubstituted benzenes (C₆H₅X) and methanes (CH₃X) as guests and cyclotetrachromotropylene as host were determined by proton NMR spectroscopy. Variations ofK with the substituent X are attributed to the electronic effect of X and the presence of C–H or aromatic bonds, if any, interacting with the host bonds.     

Charge control of phenol complexation with unsaturated compounds containing organosilicon substituents. Thiophene derivatives

The frequency shifts of the O-H stretching modes and the resonance components _R of these shifts in the IR spectra of H-complexes of phenol with thiophene derivatives having organic and organosilicon substituents have been analyzed. Relationship of and _R parameters to values calculated by nonempirical methods that characterize the electronic effect of organic substituents on the effective charges of the thiophene ring atoms has been established. It has been shown that in the complexation of phenol (hard acid) with thiophene derivatives charge control prevails over frontier orbital control. The changes in the effective charges of the thiophene ring atoms due to the effect of organosilicon substituents have been calculated.For the previous publication of this series see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2163–2168, December, 1994.This work was supported by the Russian Foundation for Basic Research, Project No. 93-03-18725.     

Quantum-chemical study of allylic and vinylic compounds of fifth-group elements

Energies and oscillator strengths of the long-wave electronic transitions for several conformers of allyl- and vinylamine and allyl- and vinylphosphine have been calculated by the semiempirical quantum-chemical MNDO method. The electronic structure of these molecules is discussed in detail, and the spectral and conformational effects ofn, and , conjugation are analyzed. Some suggestions concerning possible conjugation effects in the allylic compounds of As, Sb, and Bi are made.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1551–1554, September, 1993.     

Konformationen diastereoisomererBis-(alkylaryl)-ether

Summary X-ray-analysis of the meso-ether2 showed the existence of two bridged species in the unit cell besides the expected molecule. The additional bonds between the 9- and 10-positions of the anthracene moieties were extraordinarily long. This fact leads to conclusions on the reactive behaviour of alkylaryl carbinoles upon acid-catalysed etherification.

     

Complexation of Paraquat Dication with Disodium 1,8-Disulfonato-3,4,5,6-Acridinetetracarboxylic Acid in Water

Disodium 1,8-disulfonato-3,4,5,6-acridinetetracarboxylic acidforms a complex of 1 : 1 stoichiometry with paraquatdication in water. The stability constant of thecomplex is 1.2 × 10⁴ M^-1 at 25 °C.     

On the Distribution of π-Electrons into Rings of Conjugated Hydrocarbons Containing a Linear Polyacene Fragment

Summary. A method for assessing the -electron contents (EC) of rings of benzenoid hydrocarbons, based on the examination of their Kekulé structures, was recently put forward by Balaban and Randi. We now show that all hexagons belonging to a linear polyacene fragment of a conjugated hydrocarbon (not necessarily benzenoid) have mutually equal EC-values.     

Screened potential in π-electron systems and its application to the estimation of excitation energies

A diagrammatic technique was developed for the estimation of the screened potential of -electron systems. The screened potential was expanded in terms of the polarization propagators which were constructed from either the singlet, , or triplet vertex part, . These vertex parts correspond to the singlet or triplet excitations, respectively, in the Random Phase Approximation (RPA) containing exchange diagrams. The excitation energies were calculated by using the screened potential in the framework of RPA with exchange. The excitation energies of several conjugated molecules with or without a hetero atom are in agreement with the experimental data.     

Triterpene glycosides ofFatsia japonica. I. Isolation and structure of glycosides fromFatsia japonica seeds

The known triterpene glycosides hederagenin 3-O--L-arabinopyranoside, hederagenin 3-O-\-D-glucopyranoside, oleanolic acid 3-O--sophoroside, hederagenin 3-O--sophoroside, and their 28-O--gentiobiosyl esters, respectively, in addition to the new triterpene glycoside 3-O--sophorosyl-28-O--L-rhamnopyranosyl-(14)-O--gentiobiosyl hederagenin are isolated fromFatsia japonica (Araliaceae) seeds. The structures of these glycosides are established using chemical and spectral methods.Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 131–133, March–April, 2000.     

Calculation of some electronic excited states of formaldehyde

The optimized MO's of several excited states of formaldehyde have been calculated by means of a large basis set of modified Gaussian functions; particular attention has been paid to the * transition. The total energy of the various states has been obtained as the sum of the SCF and correlation energies; the last one has been calculated as a functional of the electronic density. The calculated values for the transition energies are in good agreement with the experiment. A strong interaction of the * state with the continuum is evidentiated; this fact can justify the absence of the * band in the absorption spectrum.