Masahiro Kataoka

Geometrical structures and spectra of corannulene and icosahedral c60

Abstract On the basis of the second-order Jahn-Teller theory and the semiempirical SCF MO method, the ground states of both corannulene and icosahedral C60 are predicted not to undergo any bond distortions accompanied with molecular-symmetry reductions. The π-type electronic spectra for corannulene calculated by using the energetically most favorable geometrical structures obtained by the SCF MO method are in good agreement with experimental data.

New modes of thermal reactions of cyclic sulfur ylides. Solvent uptake and spiro-compound formation

Abstract The thermal reaction of 1-cyano-2-methyl-3,4-dihydro-2-thianaphthalene( 3a ) in toluene afforded 1-benzyl-1-cyano-2-thiochroman( 6a ) together with 1-cyano-1-methyl-2-thiochroman( 4a ), whereas the thermal reaction in ethanol gave the spiro-compound( 8a ) in 82.7% yield. The structure of the spiro-compounds was established by their spectral data and chemical reactions.

Magnetic Susceptibility and Aromaticity in the Excited States of Benzene

A numerical method for obtaining the change in energy due to a magnetic field of given strength is applied to calculations of π-electronic delocalisation susceptibilities of the low-lying excited states of benzene. It is found that the delocalisation susceptibilities of the excited states of benzene are quite different from those of the ground state. On the basis of the calculated results, the aromaticity of the excited states of benzene is discussed.

Magnetic properties of dicyclopentapyrenes and their congeners

Abstract The magnetic susceptibilities for dicyclopentapyrenes, dicyclopentanthanthrenes, and their congeners have been examined by use of the modified London-Hoarau method in the framework of the Wheland-Mann-type SCF MO approximation. Dicyclopenta[cd, mn]pyrene is calculated to be more diamagnetic than dicyclopenta[cd, jk]pyrene and dicyclopenta[cd, fg]pyrene. This agrees with the experimental data. Further, the calculated results have suggested that the presence or absence of perimeter delocalization contributes to the magnetic properties of the molecules.

Potential energy profiles along the doubly degenerate vibrational modes in conjugated molecules

In order to predict the molecular symmetries and the geometrical structures of conjugated molecules having the doubly degenerate first-order Jahn-Teller active modes (Q1 and Q2) or the doubly denegerate modes through which the second-order vibronic couplings occur (Q′1 and Q′2), the potential energy curves along these modes are expressed as the power series, including up to the third power. It is shown that although there are cases in which we cannot practically differentiate between the potential energy profiles along Q1, and Q2 or Q′1 and Q′2, in so far as we can differentiate between them, a potential energy minimum should always be located along Q1 or Q′1 that distorts a molecule in a more symmetrical way. This is in agreement with the available experimental facts. Finally on the basis of the perturbation theory, the coefficients of various powers (up to the third power) in the expansion of the electronic part of potential energy in the power series of the relevant mode are expressed in terms of the zeroth-order electronic wavefunctions and energies.

A new theoretical approach to the empirical resonance energies of the aromatic hydrocarbons

In the framework of the Hückel MO approximation, the differences in total binding energy between a given molecule and the corresponding distorted Kekulé-type structure are calculated for a variety of benzenoid hydrocarbons. The total binding energy is assumed to be given by the sum of the π-electron and σ-electron binding energies. It is shown that there is a good linear relationship between the calculated differences in total binding energy and the π-electron delocalization energies (DE) as obtained by using the simple Hückel MO method. This provides a physical basis for the use of the π-electron DE as a theoretical index to the empirical resonance energy (RE). Further, by examining the changes in π-electron binding energy between a given molecule and the corresponding distorted Kekulé-type structure, it is concluded that in benzenoid hydrocarbons the main contributor to the RE is not the π-electron DE but the compressional energy of σ bonds.

Novel rearrangements of cyano-stabilised cyclic sulfur ylides, 2-alkyl-1-cyano-3,4-dihydro-1H-2-thionianaphthalen-1-ides: spiro-compound formation and ring expansion reactions

Thermal reaction of 1-cyano-2-methyl-3,4-dihydro-1H-2-thionianaphthaalen-1-ides 1 in ethanol afforded the spiro compounds 3 in good yields, which underwent thermal rearrangement and Diels–Alder reaction to give tetrahydro-3-benzothiepine 4 and a pair of cycloadducts 6 and 7, respectively. Treatment of 1 with succinimide similarly provided 3via the processes of protonation, ylide formation and [2,3]sigmatropic rearrangement. In contrast, treatment of 1a with N-chlorosuccinimide, chloramine B or T formed the chloroketenimine 16via an S→N [2,3]sigmatropic rearrangement of the exo-methanide 15. The exo-ylide 19 generated by deprotonation of the sulfonium salt 18 with sodium hydride underwent a similar [2,3] rearrangement to give the ketenimine 20. Hydrolysis of the ketenimines 16 and 20 with dilute hydrochloric acid produced amides 17 and 21, respectively. Reactions of 1 with dimethyl acetylenedicarboxylate proceeded via Michael addition followed by two different routes of ring-expansion to give the nine-membered cyclic sulfides 30 and the eight-membered cyclic sulfur ylides 32.

Bond distortions in nonbenzenoid phanes

The C–C bond alternations in syn-[2.2]azulenophane, syn-[2.2]cycloprop[f]indenophane, and [2.2]pentalenophane have been investigated by use of second-order Jahn–Teller theory and the Pariser–Parr–Pople-type SCF MO method. It has been shown that syn-[2.2]azulenophane suffers no bond distortions, whereas syn-[2.2]cycloprop[f]indenophane suffers a2 bond alternation, which is attributed to transannular interaction. Further, in [2.2]pentalenophane and [2.2]-s-indacenophane, C2h and D2 bond-alternating structures are obtained, the transannular interaction stablising the D2 more than the C2h structures.

Reexamination of the symmetry rule for bond distortions in conjugated hydrocarbons

Pariser–Parr–Pople-type SCF MO calculations with the electron correlation effect given by the Brillouin-Wigner second-order perturbation method with Epstein–Nesbet energy denominators and by the Pople–Seeger–Krishnan correction show that the symmetry rule for bond distortions in conjugated hydrocarbons is effective for predicting the geometrical structures of [4n+2]annulenes.

Geometrical structures and magnetic properties of trinaphtho[abc, ghi, mno][18]annulene and its congeners

Pariser–Parr–Pople-type SCF MO and semiempirical magnetic-susceptibility calculations show that trinaphtho[abc,ghi,mno]- and two kinds of triazuleno[abc,ghi,mno][18]annulenes have large diamagnetic susceptibilities and aromatic-islands structures in which three naphthalenes or three azulenes are linked by three olefinic bridges, whereas tripentaleno[abc,ghi,mno]- and triheptaleno[abc,ghi,mno][18]annulenes have small diamagnetic susceptibilities and polyolefine structures where bond alternations are distributed all over their molecular planes.