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.     

New form of effective potential to calculate polarization effects of theπ-electronic states of organic molecules

A new relation for the contribution of the most important polarization effects in the energy of the -electronic states of organic molecules is derived. For -electronic systems we suggest a correct form of the ejfective potential of the two-panicle polarization interaction of -electrons via the polarizable -core. This form approximates (by the Thomas-Fernti method) the exact contribution of the corresponding exchange polarization diagrams of the Rayleigh-Schrödinger perturbation theory. The potential may be flectively used in ab initio calculations of -electronic systems typically done in the frozen core approximation.Hydrometeorological Institute, Ukraine. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 5, pp. 12–19, September–October, 1993.Translated by L. Smolina     

Spectroscopic manifestation of the accidental degeneracy of π=Δ electronic adiabatic terms of linear triatomic systems

The semiclassical form of the absorption band of a linear triatomic system which corresponds to an electronic transition from the -ground state term to the excited intersection and terms was calculated. The analysis was carried for negligibly small defect of frequencies and in the absence of a shift of the equilibrium position on excitation. The experimentally observed CuCl₂ absorption spectrum was interpreted qualitatively as a , gS transition on the existence of a point of = accidental degeneracy. The 7000–24000 cm^–1 energy interval in the spectrum was analyzed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 2, pp. 222–225, March–April, 1988.     

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.

     

Research on 1-aza two-ring systems

Reduction of 5-[2-(methoxycarbonyl)ethyl]-1,3-dihydropyrrolizines with lithium aluminum hydride gave 5-(-hydroxypropyl)-1,2-dihydropyrrolizines (in 70–90% yields), which have intramolecular -hydrogen bonds in dilute solutions. The parameters of the -hydrogen bonds were determined in the IR spectra, and their enthalpies were found. The data obtained (_OH 95–99 cm^–1, –H 3.05 kJ·mole^–1) show that among compounds with an aliphatic hydroxyl group and a system of electrons, 5-(-hydroxypropyl)-1,2-dihydropyrrolizines have some of the strongest intramolecular -hydrogen bonds.See [1] for communication XVI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 359–363, March, 1978.     

Excited Π states of divinyl chalcogenides and chalcophenes

Electron transitions in divinyl chalcogenides (CH₂=CHXCH=CH₂, where X is S, Se, or Te) have been analyzed using UV absorption spectra of dialkyl and alkyl vinyl chalcogenides. The following relations for the orbital energies are found: ^* < ^* < ^* < ^* for Te and ^* < ^* < ^* < ^* for S and Se. For chalcophenes, a correlation between the energy of the excited state (E ^*) of specific symmetry, the ionization potential (I) and the electron affinity (EA) is obtained:E ^*=const+(I+EA)/2. The electron affinity of divinyl chalcogenides is estimated. The correlation between the excited ^* states of divinyl chalcogenides and chalcophenes is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 831–835, May, 1994.     

Synthesis and chiral-optical properties of (+)-3-methyl-3,4-dihydroisoquinoline-1-thione

(+)-3-Methyl-3,4-dihydroisoquinoline-1-thione was obtained by sulfuration of (+)-3-methyl-3,4-dihydroisoquinolone with phosphorus pentasulfide or by cyclization of (+)--benzylethyl isothiocyante under the influence of polyphosphoric acid. Measurements of the rotatory dispersion and circular dichroism showed the presence of two positive Cotton effects due to n^* and ^* transitions in the thioamide chromophore, as well as Cotton effects apparently due to ^* transitions in the aromatic chromophore.Communication XXXV from the series Stereochemical Investigations. See [11] for communication XXXIV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 94–97, January, 1976.     

Quantum-chemical calculations and interpretations of electronic spectra of phthalocyanines of transition metals and of their ionic forms

The INDO/S method with Zerner's parametrization has been used to calculate the energies and intensities of electronic transitions for a number of metallophthalocyanines of transition metals and their negatively charged ions: CoPC, FePC·L₂, MnPC·L₂, CoPC^–, FePC^–, MnPC^–·L₂, FePC^2–, FePC^–·L₂, and COPC^2– (PC is the macrocyclic phthalocyanines ligand, and L the molecules of axial ligands, in the present instance ammonia molecules). It is shown that within an isoelectronic series of compounds, having the same total number of electrons and the same disposition of pairs of d orbitals, the laws governing the changes in the electronic spectra, related to changes in the d- interactions, can be described theoretically by allowing for configuration interactions of doubly excited configurations in the basis. It is established that in the visible and near UV and IR regions of the spectrum the allowed electronic transitions in compounds of an isoelectronic series, corresponding to an uncharged state of the phthalocyanine ligand, consist of a superposition of the ^* configuration (2a_1u 6e_g) and two types of intramolecular CT configurations: (d 3b_1u) and the double excitation (2a_1u, d 6e_g, 6e_g). Data are obtained for the energy levels of the even electronic states which are responsible for the rapid radiationless deactivation of excited molecules of the phthalocyanines of transition metals.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 6, pp. 651–658, November–December, 1990.     

Ab initio SCF and CI study of the electronic spectrum of pyridine N-oxide

Configuration interaction (CI) studies of ground, n *, * * electronically excited states are reported for pyridine N-oxide. The transition energy to the lowest * excited ¹ B ₂ state is calculated at 4.35 eV, compared to the experimental spectrum range of 3.67–4.0 eV. This state lies below the lowest n * excited ¹ A ₂ state calculated at 4.81 eV above the ground state. The only experimentally reported triplet state at 2.92 eV above the ground state is predicted to be the ³ A ₁ (*) state. The calculated energy lies at 3.27 eV. Numerous other high-lying singlet states as well as the triplet states have also been calculated. The intramolecular charge transfer character of the ground and the excited states have been studied in terms of the calculated dipole moment and other physical properties.     

Molar cotton-mouton constants and anisotropy of magnetic susceptibility of benzyl chlorides and benzyl bromides

Conclusions Due to thearom^–gsC-Hal* interaction, the magnetic susceptibility ellipsoids of -haloalkylbenzenes, with the exception of ,'-p-xylylidene bromide, undergo rearrangement of the semimajor axes with a decrease in the diamagnetic component in direction 1, 4 and along the axis of symmetry of the electrons in the ring.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No No. 7, pp. 1552–1557, July, 1986.     

Homodimerization of spiro{bicyclo[2.2.1]Hepta-2,5-Diene-7,1′-cyclopropane}, catalyzed by group VIII transition metal complexes

Conclusions The homodimerization of spiro{bicyclo[2.2.1]hepta-2,5-diene-7,1-cyclopropane} (I) has been investigated in the presence of Ni-, Fe-, Co-, Rh-, and Ir-based metal complex catalysts. Depending on the nature of the metal and its ligand environment cyclodimerization of (I) can take place via [2+2]-, [2+2+2]-, and [4+4]-cycloaddition schemes, to give high yields of hepta-, octa-, and nonacyclic strained hydrocarbons.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2592–2599, November, 1988.     

The electronic spectrum of acrylonitrile

The vapor absorption spectrum of acrylonitrile CH₂CHCN has been measured in the vacuum ultraviolet region. In addition, an all-valence-electron molecular orbital calculation has been used to calculate the electronic structure and spectrum of the molecule. On the basis of the MO calculation, as well as a vibrational analysis of the observed spectrum, several electronic transitions are assigned. The lowest energy absorption band (2107Å, = 150) is assigned as an n ^* transition. Absorption bands at 2030Å (=1600), 1725Å ( = 2100), and 1570Å ( = 1920) are assigned as 0–0 bands associated with transitions that are, respectively, ^*,^*, and ^* in character.

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Zusammenfassung Das UV-Absorptionsspektrum von dampfförmigen Acrylnitril wurde gemessen und eine CNDO/2-Rechnung für die Elektronenstruktur durchgeführt. Auf dieser Basis konnten unter Zuhilfenahme der Analyse der Schwingungsstruktur im beobachteten Spektrum mehrere Banden zugeordnet werden: die 2107-Å-Bande ( = 150) einem n^*-Übergang, die drei Banden bei 2030Å ( = 1600), 1725Å ( = 2100) und 1570 Å ( = 1920)0-0-Übergängen von ^*-, ^*- bzw. ^*-Banden.

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Résumé Mesure du spectre d'absorption en phase vapeur de l'acrilonitrile CH₂CHCN dans la région de l'ultraviolet. Par ailleurs, la structure électronique et le spectre de la molécule ont été calculés à l'aide d'une méthode des orbitales moléculaires semi-empirique pour tous les électrons de valence. Sur cette base, ainsi que sur une analyse vibrationnelle du spectre expérimental, on procède à l'attribution de plusieurs transitions électroniques. La bande d'absorption de plus basse énergie (2107 Å, = 150) est attribuée à une transition n ^*. Les bandes d'absorption à 2030Å ( = 1600), 1275Å ( = 2100) et 1570Å ( = 1920) sont considérées comme des bandes 0 - 0 associées à des transitions ^*, ^* et ^* respectivement.

     

Infrared spectra of vinyl compounds and the effects of conjugation involving the π-electrons of the vinyl group

Conclusions The frequencies of the =CH₂ group wagging vibration in CH₂=CH-X compounds reflects both the inductive effect of the substituents X, and the effects of, -, ,p- and (d-p)-conjugation in which these substituents take part.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No.l, pp. 152–154, January 1970.     

AM1 study of photoelectron spectra.

The -orbital structure of the monomeric form of the 2,2,4,6-tetrachloro-2,2-dihydro-1,5,2-diazaphosphorinine has been studied by photoelectron spectroscopy and using quantum-chemical calculations by the semiempirical AM1 method. It has been concluded that the electronic and energy characteristics of four higher -MOs (frontier and three next orbitals) of this compound may be interpreted in terms of semipolar bonds formed by three atoms (C, P, and N). For describing two low-lying -MOs of the ⁴,⁵-phosphorine studied, it is necessary to take into account the --interaction.For Part 8, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 827–831, April, 1996.     

Spectroscopic study of organosilicon derivatives of thiophene

Substituents in disubstituted thiophenes have an additive effect on the chemical shifts of the ring hydrogen atoms. The electronic effects of organosilicon substituents are transmitted via inductive and conjugation (d-p interaction) mechanisms. The effect of d-p interaction in the Si-ring bond is absent for Si(OC₂H₅) and SiF₃ substituents.See [1] for communication III.Translated from Khimiya Geterotsiklicheskikh Soedinenli, No. 11, pp. 1483–1488, November, 1972.     

An ab initio study of formamide

Calculated energy and molecular properties of the ground and low-energy excited states of formamide are presented at the ground state geometry. Satisfactory results are obtained except for the ¹* energy which remains too high by 1 eV (which is nevertheless a large improvement over previous calculations). The predicted triplet energies lie at 5.4 eV (³ n*) and 5.8 eV (³*).     

Triplet states via intermediate neglect of differential overlap: Benzene,pyridine and the diazines

The intermediate neglect of differential overlap technique is modified and applied to the calculation of excited triplet states. The resulting method generally reproduces the transition energies of the better-classified observations within a rms error of 1000 cm^–1. Trends are well reproduced, and the calculated orders ofn-* and -* triplet states are in good accord with the experimental information to date.The method is applied to benzene and the azines. The lowest four triplet states of benzene are calculated in good accord with experiment. Pyridine is calculated to have an-* triplet nearly degenerate with the lowest lying -* triplet, corroborating suggestions of Japar and Ramsay based on experimental information. A detailed analysis is made of the diazines, and assignments are suggested for the higher lying triplet states not yet classified or not yet observed.     

Electronic structure and aromaticity of planar singlet π-electron monocyclic π2 carbenes

Induced -electron ring currents and relative diamagnetic susceptibilities of planar singlet -electron monocyclic ² carbenes are calculated in the coupled variant of perturbation theory in the CNO method. It is shown that the parity theorem holds for charged planar ² and ² carbenes formally generated by the detachment of a proton or a hydride ion from alternant hydrocarbons. This leads, in such carbenes, to the same energies of singlet-singlet and singlet-triplet transitions, electric polarizabilities, conjugation energies, -electron ring currents, diamagnetic susceptibilities and current contributions to chemical shifts, whereas the charge contributions to the latter are of opposite signs.Donbas State Academy of Building and Architecture, 1 Derzhavina St., 339023 Makeevka, Donetsk Region, Ukraine. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 32, No. 3, pp. 157–162, May–June, 1996. Original article submitted December 5, 1994.     

Cooligomerization of 1,2-dienes with norbornadienes catalyzed by cobalt complexes

Conclusions Under the action of low-valency cobalt complexes [2 + 2 + 2] cycloaddition of allene, cyclopropylallene, phenylallene, and 1,2-cyclononadiene to norbornadiene and spirocyclo-[2.2.l]hepta-2,5-diene-7,1-cyclopropane takes place with the formation of derivatives of tetracyclo[4.3.0.0^2,4. 1.0^3,7] nonane in high yields.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1346–1356, June, 1988.     

Nature of the pentamethyldisilanyl group in organosilicon compounds

Summary The positige inductive effect of the pentamethyldisilanyl group (CH₃)₃SiSi(CH₃)₂ and the election-acceptor effect of its p-d bond with an aromatic ring are appreciably greater than the analogous effects of the trimethylsilyl group (CH_{3 3}Si, which gives ground for the postulation of the presence of a p-d-d¹ bond in the fragment C_sp ²-Si-Si.