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The palladium(0)-catalyzed polyaddition of bifunctional vinyloxiranes [1,4-bis(2-vinylepoxyethyl)benzene (1a) and 1,4-bis(1-methyl-2-vinylepoxyethyl)benzene (1b)] with 1,3-dicarbonyl compounds [methyl acetoacetate (4), dimethyl malonate (6), and Meldrum's acid (8)] was investigated under various conditions. The polyaddition of 1 with 4 was carried out in tetrahydrofuran with phosphine ligands such as PPh 3 and 1,2-bis(diphenylphosphino)ethane (dppe). Polymers having hydroxy, ketone, and ester groups in the side groups (5) were obtained in good yields despite the kinds of ligands employed. The number-average molecular weight value of 5b was higher than that of 5a. The polyaddition of lb and 6 was affected by the kinds of ligands employed. The corresponding polymer 7b was not obtained when PPh 3 and 1,2-bis(diphenylphosphino)ferrocene were used. The polyaddition was carried out with dppe as the ligand and gave polymer 7b in a good yield. The molecular weight of the polymer obtained from 1b and 8 was much higher than those of polymers 5b and 7b. The polyaddition with Pd 2 (dba) 3 . CHCl 3 /dppe as a catalyst (where dba is dibenzylideneacetone) produced polymer 9b in a 92% yield (number-average molecular weight = 45,600). The stereochemistries of all the obtained polymers were confirmed as an E configuration by the coupling constant of the vinyl proton.

Palladium(0)-catalyzed polyaddition of bifunctional vinyloxiranes [1,4-bis(2-vinylepoxyethyl)-benzene (6a) and 1,4-bis(1-methyl-2-vinylepoxyethyl)benzene (6b)] with 1,3-diketones [acetylacetone (2) and 1,3-indandione (8)] as carbon nucleophiles afforded new polymers having an allyl alcohol moiety in the main chain and ketone groups in the side groups. The molecular weights of polymers obtained from 6b were higher than those of polymers from 6a. It was suggested that the cause of formation of lower molecular weight polymers from 6a is the β-hydrogen elimination of the π-allylpalladium intermediate generated by oxidative addition of Pd(0) to 6a. The Pd(0)-catalyzed polyaddition of 6b and 2 gave the corresponding polymer 7b (M n 9800) when Pd 2 (dba) 3 .CHCl 3 /dppf (dba, dibenzylideneacetone; dppf, 1,2-bis(diphenylphosphino)ferrocene) was used as a catalyst. By use of Pd(PPh 3 ) 4 , the polyaddition of 6b and 8 afforded the desired polymer 9b with high molecular weight (M n 67 600). The stereochemistries of all of the obtained polymers were confirmed as being in the E-configuration by the coupling constant of the vinyl proton (-C(OH)CH=CHCH 2 -); the J values were in the range 14.5-15.1. The Z-isomers were observed neither in the 13 C NMR spectra nor in the 1 H NMR spectra.

ESR absorption has been observed in a single-crystal solid solution of acenaphthene in durene under irradiation at 120K with light from a high-pressure mercury lamp. The observed hyperfine structure gives evidence for hyperconjugation of the ethylene group protons. The guest and host molecular planes are nearly parallel to each other, and the guest in-plane axes deviate from the host ones by ca 40°. For comparison, 1,1,2,2-tetradeuteroacenaphthene was also prepared and studied.

We have studied three different subjects, i.e., the ESR line-shape changes, induced circular dichroism (ICD), and suppression of fluorescence quenching, all caused by inclusion complex formation with cyclodextrins.

The radical cations of butatriene (BT +• ) and tetramethylbutatriene (TMBT +• ) have been stabilized in low-temperature halocarbon matrices and studied by ESR spectroscopy. The spectra of BT +• and TMBT +• exhibit isotropic hyperfine splittings of 8.3 G (4H) and 13.0 G (12H), respectively. The skew angles of BT +• (25°) and TMBT +• (50°) are estimated by comparing the experimental hyperfine splittings with those obtained by semiempirical MO calculations.

The ESR spectra of several para-substituted alkyl- and alkenylbenzene radical cations generated by 60 Co γ-ray irradiation in halocarbon marices at 77 K have been studied with the aid of semiempirical MO calculation (1,4-DEB +. ) in CCl 2 FCClF 2 is largely different from that in CCl 3 CF 3 . Further the ethyl and n-propyl groups in 4-ethyltoluene and 4-n-propyltoluene radical cations in CCl 2 FCClF 2 take different conformations from that of 1,4-DEB +. . The conformations of the alkylbenzene radical cations depend strongly both on the amtrices and on the substituent groups. A peculiar radiolytical reaction of 1,4-diisopropylbenzene to a deprotonation-type neutral radical in CCl 2 FCClF 2 has been found, similarly to the case of photolysis

ESR spectra of the radicals of allene (1,2-propadiene) derivatives generated by 60Co γ-ray irradiation in halocarbon matrices have been observed at low temperatures. The geometrical structures of the radicals have been determined from the experimental ESR spectra and with the aid of semiempirical MO calculations invoking the UHF-AM1 and UHF-MNDO methods. After exposure of the allene derivatives to 60Co γ-ray in some halocarbon matrices at 77 K, the temperature raising gave rise to neutral radicals such as allylic and/or deprotonation-type radicals; these thermal reactions have been investigated in detail.

An efficient vector processing algorithm generating PK supermatrices has been developed, in particular aiming at calculations on large molecules. The algorithm utilizes the recurrence relations for electron repulsion integrals. The PK supermatrices are listed in a nearly canonical order so that the Fock matrix generation is efficiently vectorized, no temporary ERI and PK files being used. This is effected by partition of the basis set (atomic orbitals) into subsets of certain appropriate sizes, and the partition approach is named as the three-dimensional partial space method. A high-speed Hartree–Fock calculation including integrals and SCF procedures is achieved. © 1992 by John Wiley & Sons, Inc.

ESR spectra of the radicals of allene (1,2-propadiene) derivatives generated by 60Co γ-ray irradiation in halocarbon matrices have been observed at low temperatures. The geometrical structures of the radicals have been determined from the experimental ESR spectra and with the aid of semiempirical MO calculations invoking the UHF-AM1 and UHF-MNDO methods. After exposure of the allene derivatives to 60Co γ-ray in some halocarbon matrices at 77 K, the temperature raising gave rise to neutral radicals such as allylic and/or deprotonation-type radicals; these thermal reactions have been investigated in detail.

The ESR spectra of several para-substituted alkyl- and alkenylbenzene radical cations generated by 60Co γ-ray irradiation in halocarbon matrices at 77 K have been studied with the aid of semiempirical MO calculations. It has been found that the ethyl conformation of 1,4-diethylbenzene radical cation (1,4-DEB+. ) in CCl2FCClF2 is largely different from that in CCl3CF3. Further the ethyl and n-propyl groups in 4-ethyltoluene and 4-n-propyltoluene radical cations in CCl2FCClF2 take different conformations from that of 1,4-DEB +.. The conformations of the alkylbenzene radical cations depend strongly both on the matrices and on the substituent groups. A peculiar radiolytical reaction of 1,4-diisopropylbenzene to a deprotonation-type neutral radical in CCl2FCClF2 has been found, similarly to the case of photolysis.

ESR spectra of the radical species derived from 60 Co γ-ray irradiation of 1,3,5-cycloheptatriene (1,3,5-CYT) and 1,3-cycloheptadiene (1,3-CYD) in halocarbon matrices have been studied in the temperature range 70–103 K. Ring inversion across the molecular plane occurs in the radical cation 1,3,5-CYT + in CCl 3 CF 3 , the activation energy being 1.7 kcal/mol. Above 90 K, 1,3,5-CYT + is deprotonated thermally in CCl 2 FCClF 2 . No dynamical effect has been observed for 1,3-CYD + .

1,4-Diethylbenzene radical cation generated in six different halocarbon matrices by 60 Co γ-ray irradiation has been studied by ESR at low temperatures. The spectra exhibit drastic variations in different matrices, showing that the conformation of the radical cation is largely dependent on the matrix.

A six-term auxiliary integral expression for the two-electron Gaussian integral is derived on the basis of the Chebyshev polynomial approximation instead of the seven-term Taylor expansion. This expression and the related recurrence formula enable us to perform a high-speed calculation on a vector processing computer.

The radical species derived from cyclopentane, cyclopentenes and cyclohexenes by 60Co γ-ray irradiation at 77 K in halocarbon matrices have been studied by ESR spectroscopy. The electronic and geometrical structures of the radical species are discussed on the basis of the experimental hyperfine coupling constants and semiempirical MO calculations. Exposure of the tetramethylsilane frozen solution containing cyclopentene to 60Co γ-rays produced specifically 3-cyclopenten-l-yl.

The radical anions of nitrobenzene and p-nitrobenzoic acid have been prepared chemically for the first time in aqueous solutions with the aid of micelles. The radicals thus prepared are stable and the resulting ESR spectra are unsymmetrical owing to the suppressed rotational diffusion of the radicals due to incorporation into micelles. The environments surrounding the radicals are discussed in terms of the 14N hyperfine coupling constants and the rotational correlation times. For p-nitrobenzoic acid radical anion, the temperature dependence of the ESR spectrum has been studied.

Equations for solving a quantum beat problem in a three‐level system, which determine two complex variables of time dependence, are rewritten in terms of four real functions constructed from the two complex variables. The Minkowski space is reasonably introduced in order to represent the time evolution of the four real functions as the motion of a four‐dimensional vector, though the equations are irrelevant to the special theory of relativity. It is found that the four‐dimensional vector precesses around the zeroth axis on the cone which is constructed from all of the points whose norms are zero in the Minkowski space, and that the Euclidean norm of the vector decreases with the increase of time. Though the visualized motion of the vector is similar to those in the well‐known magnetic resonance precession model, the picture obtained from the equations for quantum beats cannot be connected with such a phenomenon as photon echo.

The delayed flourescence intensity, I DF , and phosphorescence intensity, I P , of phenanthrene-d 10 in biphenyl were observed at 77 K under various excitation light intensities, I exc . The plots of log I DF versus log I exc and log I P versus log I exc were found to deviate from linearity in the region of high excitation light intensity. The decay curves of delayed flourescence and phosphorescence were observed under various excitation durations and excitation light intensities. It was found that weaker excitation light intensity makes the delayed luminescence decay slower, while shorter excitation duration quickens the decay. The decay curves after successive double-pulse excitation were also observed. It was concluded that all the experimental results could be accounted for in terms of a single model for the emission of delayed flourescence: energy transfer between triplet phenanthrene molecules fixed in space.

The electronic structure of diindeno[1,2,3-cd:1′,2′,3′-lm]perylene (periflanthene) radical anion has been studied on the basis of the ESR, electronic absorption, and linear dichroism spectra. The observed results are interpreted in terms of the SCF MO calculations within the framework of the π-electron approximation.

The highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) are important in chemistry. In this context, we have undertaken resonance Raman (RR) spectroscopic studies on organic radical ions of phenanthrenes, phenazine, bipyridyls, pyrazine, tetramethylpyrazine, alkyl-substituted biphenyls, 4-phenylpyridine, and p-terphenyl [1].

Two new findings are reported on the energy transfer between like molecules in rigid glass at 77 K: The depolarization of the phosphorescence is not mainly caused by the triplet–triplet energy transfer, but essentially by the singlet–singlet transfer. And the concentration where the depolarization starts to take place depends on the individual phosphor compounds.

Temperature and concentration dependences of the delayed luminescence observed in the naphthalene (guest)–biphenyl (host) mixed crystal system have been studied. The presence of the temperature-independent delayed fluorescence (TIDF) and its significance in the evaluation of activation energy have also been confirmed in this system as in the case of the benzo[f]quinoline–biphenyl system previously reported, and the generality of the existence of TIDF as well as its significance in relation to activation energy has been suggested. In addition, some remarks have been made on the nature of TIDF and the decay behavior.

Electron spin resonance absorption has been observed in a single-crystal solid solution of benzo[f]quinoline in biphenyl under irradiation at 120 K with light from a high-pressure mercury lamp. The fine structure of the resonance spectrum observed at 9.25 GHz can be described by the spin HamiltonianH=βH·g·S+D[S_z^2-\frac13S(S+1)]+E(S_x^2-S_y^2) in which S=1, D=±0.09926(18) cm−1, E=\mp0.04781(6) cm−1, gxx=2.0024(6), gyy=2.0018(4), and gzz=2.0018(4); the z axis is normal to the molecular plane, the x and y axes being the in-plane fine-structure principal axes. The principal x axis deviates by ±4° from the biphenyl long axis and the principal z axis by 7° from the biphenyl out-of-plane axis. The phosphorescence spectra and lifetimes have been measured both at 77 K and at 4.2 K. Marked doublet splittings were observed in the phosphorescence bands at 4.2 K, suggesting a large guest-host interaction.

The ESR spectra of p-benzosemiquinone radical anion included in cyclodextrins (CyDxs) in aqueous solutions were observed and analyzed. Remarkable differences in the line shape were found between the spectrum in α-CyDx aqueous solution and that in 95% ethanol. They are explained in terms of the suppressed molecular rotation of the radical included in the α-CyDx cavity. The ESR spectra of the radicals included in β- and γ-CyDx in aqueous solutions are identical with that in 95% ethanol, hence in the β- and γ-CyDx cavities the radical rotates as freely as in 95% ethanol.

Non-exponential phosphorescence decays of phenanthrene in biphenyl polycrystals have been observed. It is found that excitation with short duration quickens the decay while the decay is slower after excitation with weaker intensity. The origin of the non-exponentiality is ascribed to the distance-dependent interactions between guest molecules in the lowest excited triplet state.

The decay of the temperature-independent delayed fluorescence observed in the mixed crystals of phenanthrene in the biphenyl host has been studied at 77 K. That triplet molecules are involved in the mechanism for the emission of temperature-independent delayed fluorescence has been shown by observing the intensities at the instances of the short-pulse excitations effected with different dark periods after the steady-state excitation. It has been found that both the excitation duration and the excitation light intensity affect the decay behavior of the temperature-independent delayed fluorescence. The decay after short-pulse excitation has been observed to be more rapid than the decay after prolonged excitation with the same intensity. When the excitation light intensity is increased with a fixed duration, the delayed fluorescence is observed to decay more rapidly. It is concluded that the decay behavior of the temperature-independent delayed fluorescence can be accounted for in terms of the direct-resonan...

Two new findings are reported on the energy transfer between like molecules in rigid glass at 77 K: The depolarization of the phosphorescence is not mainly caused by the triplet-triplet energy transfer, but essentially by the singlet-singlet transfer. And the concentration where the depolarization starts to take place depends on the individual phosphor compounds.

Resonance Raman, ESR and visible absorption spectra have been observed at room temperature for the 4, 4′-bipyridine radical anion in tetrahydrofuran and for 4, 4′-bipyridine adsorbed on metallic potassium. Based on the quinoid structure of the radical anion, as predicted by the MO theory, a normal coordinate analysis has been carried out. The relative Raman intensities have also been calculated satisfactorily for the totally symmetric modes of the radical anion. Thus, the main Raman bands are interpreted in terms of the molecular structure change caused by the resonant electronic transition in the visible region. The results are compared with those of the biphenyl radical anion, 2,2′-bipyridine radical anion and the methylviolegen radical cation reported in the literature.

The delayed fluorescence observed in the mixed crystals of benzo[f]quinoline in biphenyl host has been found to be independent of temperature in the low temperature region from 90 K down to liquid helium temperature, and subtraction of this temperature-independent contribution from the observed total delayed fluorescence intensity above 90 K has given straight-line fits of the logIDF⁄IP2 vs. 1/T plots, that is, a single activation energy has been obtained over the whole temperature range studied, instead of two different ones as usually assumed. Such a correction has also been given to a new attempt of logIDF vs. 1/T plots successfully. Moreover, the decay behavior of the delayed luminescence has been studied over the wide temperature and concentration range. It has been concluded that the decay behavior of the temperature-independent delayed fluorescence may mainly be responsible for the nonexponential decay of the delayed fluorescence around 77 K.

The absorption spectrum of pyrazine has been studied at room temperature in various mixed solvents of cyclohexane and halomethanes such as carbon tetrachloride, chloroform and dichloromethane. With increasing concentration of halomethane, the singlet-singlet (S-S) and singlet-triplet (S-T) n→π* absorptions decrease in intensity and become structureless, whereas the S-S π→π* absorption remains essentially unchanged. The observations are attributed to the complex formation between pyrazine and halomethanes involving the non-bonding electrons in pyrazine. From the concentration and temperature dependences of the n→π* absorption spectra, the equilibrium constants, enthalpy and entropy changes have been obtained for the complex formation in all the systems studied. The equilibrium constants obtained from the S-S and S-T n→π* absorptions are in good agreement with each other.

The phosphorescence and phosphorescence excitation spectra of pyrazine have been studied at 77 K in various mixed solvents of cyclohexane and halomethanes such as carbon tetrachloride, chloroform, and dichloromethane. When the halomethane concentration was low (below 10−2 mol dm−3), only the cyclohexane-phase phosphorescence was observed at 77 K; the lower energy components of the well-known doublet band series in the cyclohexanephase phosphorescence were found to decrease in intensity relative to the higher energy components, with increasing concentration of halomethane. When the halomethane concentration was raised to a range higher than 10−1 mol dm−3, where the complex formation between pyrazine and the halomethanes was confirmed through absorption spectroscopy, new phosphorescence bands appeared in the 373–375 nm region for all the systems studied. With further increase of the halomethane concentration, the new bands decreased in intensity or disappeared, and the phosphorescence approached to those in...

The electronic spectrum of 4,4'-bipyridyl radical cation included in β-cyclodextrin has been studied by induced circular dichroism (ICD) spectroscopy and MO calculations. The ESR spectrum has also been observed, to identify the radical. To our knowledge this is the first report on ICD of a radical ion.

The decay of the energy‐donor phosphorescence has been observed using a N2 laser on the benzophenone–naphthalene and p‐methoxybenzaldehyde–naphthalene systems, and the results have been examined in the light of the theory developed by Inokuti and Hirayama for energy transfer by exchange interaction. Substantial discrepancies have been found between the theory and the observed phosphorescence decay curves, in particular, for the short time region after excitation. We have introduced the concept of the nonvanishing closest donor–acceptor intermolecular distance into the framework of the theory. Over the whole range of time, the experimental data have been found to agree with the theory thus amended.

Stable β-cyclodextrin inclusion complexes with radical anions of thirteen different nitrobenzenes have been generated by chemical reduction in 50% aq especially in the central portions associated with the vanishing 14 N nuclear spin component. The high resolution obtained permits the estimation of the small hyperfine coupling constants in the guest radicals due to deuterons and alkyl substituents.

A stable β-cyclodextrin inclusion complex with methyl viologen radical cation has been prepared in solution and in the form of polycrystalline powder, enabling us to study the ESR, electronic absorption, and induced circular dichroism spectra.

Within the framework of the LCAO-MO theory, a novel sign-alternation rule has been found empirically for the lowest excited ππ* triplet state in the alternant aromatic system. This rule can be applied to identify the phosphorescent state.

The absorption spectrum of benzene has been studied in carbon tetrachloride solutions of various concentrations at 77°K and in 10 per cent solution at various temperatures from 30°C to 77°K. The so-called crystalline spectrum appeared strongly at low temperature and its occurrence was ascribed to the deformation of benzene due to crystal forces of the carbon tetrachloride matrix.

The Pariser—Parr method has been used to elucidate the electronic structure and the spectrum of biphenyl. The absorptions at 300, 250, 200, and 170 mμ seem to be explained reasonably. Simple forms of linear combinations of the symmetry orbitals constructed from 2pπAO's were used as molecular orbitals. Calculations were made for three conformations, the angle between the planes of two benzene rings being 0°, 45°, or 90°. In each of the conformations 16 singlet and 16 triplet excited configurations were taken into account. An application has been made to 2,2′‐bipyridyl, and its absorption spectrum has been explained.

The SCF‐AO's expanded by Lowdin have been used for the calculation of the electron spin dipolar interactions in the triplet‐state zero‐field splittings of some aromatic molecules. Within a framework of two‐center approximation for the spin–spin interaction integrals over atomic orbitals, and adopting the Sklar‐type approximation for the exchange‐type integrals, excellent agreement with experiments has been obtained for benzene and naphthalene without invoking σ–π interactions. The wavefunctions used were obtained by means of the Pariser–Parr–Pople method, within a full single excitation configuration treatment. This approach has been extended to some aromatic nitrogen heterocycles, but the results, although promising, are poorer, possibly due to the neglect of spin–orbit coupling. Uncertainty in the choice of the C–N resonance integral and the neglect of penetration integrals in the core Hamiltonian may also be factors. Eleven molecules have been treated in all. For comparison, the single‐determinant unrestricted Hartree–Fock wavefunctions also have been employed, but these give extremely poor agreement with experiment.

The coefficients in the Pariser-Parr-type quadratic formulas for the two-center Coulomb repulsion integrals encountered in the planar as well as the non-planar conjugated systems have been expressed as linear functions of the effective nuclear charges of the 2p atomic orbitals involved. The formulas thus obtained are applicable to those conjugated systems consisting of carbon, nitrogen, and oxygen atoms, and may well be useful in variable electronegativity self-consistent field calculations on these systems. With some illustrative applications to spin densities and phosphorescent-state energies, it has been shown that the Pariser-Parr approximation gives better results than the Nishimoto-Mataga one, although the latter is successful in the prediction of electronic transitions within the singlet manifold. Incidentally, this was also the case for the phosphorescent-state zero-field splittings (Y. Gondo and Y. Kanda, This Bulletin, 43, 3943 (1970)). The electric dipole moments have also been discussed.

The induced circular dichroism (ICD) spectra of β-cyclodextrin inclusion complexes with 9,10-anthraquinone and 9,10-phenanthrenequinone have been measured, and the electronic structures and molecular orientations of the guests are discussed in terms of the ICD signs and theoretical results.

Anomalous polarization has been found for the b3g vibrations in the Raman spectrum of the protonated phenazine dication in concentrated sulphuric acid.