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The bisazo dye Ponceau SS forms an acute oblique (V-type) dimer in dilute aqueous solution. In concentrated aqueous solution, these V-type dimers are considered to stack to form V-type blocks of chromonic liquid-crystalline (LC) columns. The weak interactions among these LC columnar V-type blocks have been spectroscopically investigated. On increasing the concentration of Ponceau SS at 25 °C, the V-type LC columnar blocks form a rhombus-type LC columnar block at 2 wt% concentration. These rhombus-type LC columnar blocks are further aligned at an acute angle at 5 and 10 wt% concentrations. The rapidly cooled 10 wt% LC sample shows an unusually sharp J-band-like peak in the electronic absorption spectrum. The emergence of this J-band-like peak has been analyzed from the viewpoint of an exciton model, suggesting that many nearest neighbor unique molecules belonging to many different rhombus-type LC columnar blocks are aligned in a head-to-tail manner to give a giant quasi-linear head-to-tail-type exciton.

Tris(8-quinolinolato)aluminum(III) (Alq3) shows electronic absorption bands at 378, 360 (in a 1:1 mixed solvent of methanol and ethanol (ME) at 77 K), 334, 316, 300, 263, 255.8, and 233 nm in ethanol at room temperature. According to the polarized fluorescence excitation spectrum together with MO calculations, for instance, the 360 nm band is assigned to an LL CT transition (an intramolecular charge transfer transition between two ligands), and the 378 nm band to an LM/ML CT one (an intramolecular charge transfer transition between ligand and metal). Alq3 shows a broad fluorescence band peaking at around 478 nm in the ME matrix at 77 K. The emission spectrum measured with a phosphoroscope has two emission bands at 567 and 478 nm. The 567 nm band accompanies vibronic bands at 578 and 605 nm, being safely assigned to a phosphorescence of Alq3. The lifetimes of the 478 and 567 nm bands are both 5.4 ms. The lifetime of the 478 nm band together with the band position and its band shape indicate that this band can be assigned to a delayed fluorescence.

It has been observed for the binary systems of oriented nematic hosts and nonmesomorphic guests (substituted anthraquinones) that the orientational orders of amino-substituted anthraquinones ascend with increasing guest concentrations. A new quantitative and experimental procedure has been proposed for obtaining the host–guest isotropic dispersion, isotropic electrostatic, anisotropic dispersion, and anisotropic electrostatic interaction energies. Among these four host–guest interaction energies, the host–guest isotropic dispersion interaction energy alone is demonstrated to be well correlated with the concentration dependence of the orientational order of the guest. A model is also proposed for the cooperative and isotropic host–guest interaction.

The dimeric complex acetato(η4-cycloocta-1,5-diene)rhodium(I), [Rh(O2CMe)(η4-cod)]2 (cod = cycloocta-1,5-diene), reacts with amino acids [HAA = L-alanine, (S)-2-amino-2-phenylacetic acid (L-phenylglycine), N-methylglycine, and N-phenylglycine] and with the amino alcohol (S)-2-amino-2-phenylethanol to afford the aminocarboxylato(η4-cycloocta-1,5-diene)rhodium(I) complexes [Rh(AA)(η4-cod)] (AA = deprotonated amino acid = aminocarboxylato ligand) and [(S)-2-amino-2-phenylethanol](η4-cycloocta-1,5-diene)rhodium(I) acetate, [Rh{(S)-HOCH2–CH(Ph)-NH2}(η4-cod)](O2CMe) (V). The complexes are characterized by IR, UV/Vis, 1H/13C NMR and mass spectroscopy. The achiral N-phenylglycine ligand gives a chiral N-phenylglycinato complex [Rh(O2C–CH2–NHPh)(η4-cod)] (IV) with the amine nitrogen atom becoming the stereogenic center upon metal coordination. Complex IV crystallizes in the tetragonal, chiral space group P43 and the crystal structure reveals twofold spontaneous resolution of a racemic mixture into homochiral helix-enantiomers. The investigated crystal contained only one type of helix, namely (left-handed or M-) 43-helical chains. This is traced first to an intermolecular N–H···O hydrogen bonding from the stereogenic amino group to a neighboring unligated carboxyl oxygen atom that connects only molecules of the same (R)-configuration into (left-handed or M-) 43-helical chains. This intrachain homochirality is supplemented, secondly, by the interlocking of adjacent chains with their corrugated van der Waals surface to allow for an interchain transmission of the sense of helicity, building the single crystal from the same homochiral helix-enantiomer. The enantiomeric amino alcohol complex V crystallizes in the monoclinic, noncentrosymmetric (Sohncke) space group P21. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

To clarify the electronic spectral properties of uranyl(V) complexes systematically, we measured absorption spectra of three types of pure uranyl(V) complexes: [UVO2(dbm)2DMSO]-, [UVO2(saloph)DMSO]-, and [UVO2(CO3)3]5- (dbm = dibenzoylmethanate, saloph = N,N‘-disalicylidene-o-phenylenediaminate, DMSO = dimethyl sulfoxide). As a result, it was found that these uranyl(V) complexes have characteristic absorption bands in the visible−near-infrared (NIR) region, i.e., at around 640, 740, 860, 1470, and 1890 nm (molar absorptivity, e = 150−900 M-1·cm-1) for [UVO2(dbm)2DMSO]-, 650, 750, 900, 1400, and 1875 nm (e = 100−300 M-1·cm-1) for [UVO2(saloph)DMSO]-, and 760, 990, 1140, 1600, and 1800 nm (e = 0.2−3.6 M-1·cm-1) for [UVO2(CO3)3]5-. These characteristic absorption bands of the uranyl(V) complexes are attributable to the electronic transitions in the UVO2+ core because the spectral features are similar to each other despite the differences in the ligands coordinated to the equatorial plane of the UVO2+ moiety...

The first shorter-molecular-axis polarized electronic absorption band of 7-methylxanthone-2-carboxylic acid octadecyl ester shows a surface pressure dependence in Langmuir films, giving rise to a s...

Fluoranthene (FA) forms a 1:1 van der Waals complex with benzene in cyclohexane. The 1H NMR spectrum of this complex shows that the FA moiety in the complex state has five kinds of hydrogen atoms and that the 1H NMR peaks assigned to the protons attached to the naphthalene skeleton are largely shifted to higher magnetic field on complex formation with benzene. These observations indicate that the complex takes the structure of CS symmetry, in which the benzene molecule mainly interacts with the π electronic system localized on the naphthalene moiety of FA. The present ab initio calculations reproduce well the 1H NMR spectral shifts mentioned above and the experimentally predicted CS structure of the complex. According to the PPP calculations for the electronic absorption spectral changes on the complex formation, the FA-benzene complex is considered to take a sandwich type structure.

The electronic absorption and polarized absorption spectra were measured at various pH conditions for ellagic acid. Comparison of these spectral data with MO calculations shows that ellagic acid exists in a 7:3 mixture of ethanol and water as free in the pH region less than 0.5, as a mixture of free and singly deprotonated species in the pH region 0.5–5.6, and as doubly deprotonated form in the pH region larger than 5.6, being deprotonated from hydroxyl group at position 8 (and/or 8′). In the pH region beyond 12.4, one lactone ring of the doubly deprotonated species opens to give a carboxyl derivative. Thermal and single crystal X-ray analyses show that ellagic acid forms a 1:4 complex with pyridine in the solid state. The endothermic energies indicate that the hydrogen bond energy between ellagic acid and pyridine is estimated to be ca. 11.4 kJ mol−1 per pyridine. Ellagic acid molecules stack almost face-to-face with the intermolecular distance of ca. 4.8 A, and take column structure along the a-axis, inclining toward the a-axis. The columns of ellagic acid molecules are stabilized through pyridine-pyridine intermolecular interactions.

Intramolecular electronic energy transfer in methylenes-linked naphthalene and anthracene (referred to as AnN, n =1, 3 and 6 denoting number of methylene units) was examined by time-correlated single-photon counting technique in n -hexane and in stretched PVA films. The energy transfer rates in A1N, A3N and A6N in solution were measured and the chain length dependence of these rate constants is discussed in terms of through-bond interaction via the connecting bridge, in addition to direct Coulombic interaction.

2,2,2-Tris(diphenylphosphinomethyl)ethane (triphos) coordinates to Co(BF4)2·6H2O to synthesis the red-violet cationic complex of [Co(triphos)(solv)2]2+ (solv: solvent) in THF/EtOH at room temperature. Addition of 2-hydroxy-2-D-carboxylic acids (L) into the cationic solution as co-ligands yields the red-brown complexes of [Co(L-2-hydroxy-2-methylacetato)(triphos)] (I), (Co(D-2-hydroxy-2-phenylacetato)(triphos)] (II), (Co(L-2-hydroxy-2-phenylacetato)(triphos)] (III) and [Co(D-2-hydroxy-2-phenyl-2-methylacetato)(triphos)] (IV). The complexes are characterized by elemental analysis, IR-, UV-vis.-, NMR- and Mass-spectroscopy. All complexes are paramagnetic. Variable temperature studies on magnetic susceptibilities (χM) measurements show the spin-crossover behaviors of the complexes with ΔHsc = −5.3 to −6.8 kJ mol−1 and ΔSsc = −31 to −36 J mol−1 K−1 in methanol.

Intramolecular excitation energy transfer has been investigated with bichromophoric compounds in which naphthalene and anthracene as donor (D) and acceptor (A), respectively, are linked through a methylene chain, i.e., 9-anthryl-(CH2)n-1-naphthyl (AnN) with n = 1, 3, and 6 methylene units as spacer. The respective compounds were dispersed in stretched PVA films with the expectation that the methylene chain takes preferred conformations elongated in the direction of stretching polymer films so that the D−A distances are determined by the methylene chain length. From analyses of picosecond time-resolved fluorescence spectra and the fluorescence decay kinetics, it has been found that the energy transfer rates show a systematic change depending on the number of the methylene chain units: 47.6 × 1010 s-1 in A1N, 1.96 × 1010 s-1 in A3N, and 0.15 × 1010 s-1 in A6N at 10 K. These changes in the energy transfer rate are basically consistent with the theoretical estimation based on the Forster's mechanism, with so...

The electronic absorption spectra of fluoranthene (abbreviated as FA) were measured in various solvents together with the polarization spectrum with the aid of the stretched polymer film technique. The electronic structure of FA is discussed in comparison with MO calculated results. The polarization directions of the electronic transitions of FA were determined. For instance, the 404 (very weak) and 360.3 nm bands are polarized along the shorter and the longer (C2-) molecular axes, respectively. A weak van der Waals type FA–benzene complex formation was recognized in cyclohexane. The equilibrium constants for this complex formation were determined at various temperatures, e.g. K = 0.147 ± 0.03 dm3·mol-1 at 298 K. The enthalpy, entropy, and free-energy changes are estimated to be ΔH° = -5.9 ± 1.2 kJ·mol-1 (-1.4 ± 0.3 kcal·mol-1), ΔS°298 = -36 ± 1.0 J·K-1 mol-1 (-8.7 ± 0.24 cal·K-1 mol-1), and ΔG°298 = 4.7 ± 0.4 kJ·mol-1 (1.1 ± 0.1 kcal·mol-1). This ΔH° value is considerably small compared with the familiar...

Temperature dependent fluorescence, excitation and absorption spectra of two spin crossover Fe(II) complexes with 2,6-bis(benzimidazole-2 ′ -yl) pyridine, Febz-H 2 (containing 2(ClO 4 − ) as counter ions) and Febz-H (uncharged), have been observed. The origin of the unexpected observed fluorescence is discussed. Polarized absorption spectra in stretched polymer films are described and aid to the interpretation as well as extended PPP–MO calculations. The observed fluorescence spectra are not only the assignment of electronic transitions but also shown to be useful for the extraction of high-spin (HS) and low-spin (LS) contents in temperature dependent spin crossover systems.

The electronic absorption and X-ray photoelectron spectra of N,N′-disalicylidenetrimethylenediaminatocopper(II) ([Cu(saltn)]) and N,N′-disalicylidene-trans-1,2-cyclohexanediaminatocopper(II) ([Cu(salchx)]) were measured. From these results and from informations derived from MO calculations the electronic structure of the complexes was clarified. Each electronic absorption band which can be assigned to the ππast; or ML/LMCT transition of [Cu(saltn)] or [Cu(salchx)] observed in the wavelength region of 450–200 nm appears at the almost same frequency as the corresponding band of N,N′-disalicylideneethylenediaminatocopper(II) ([Cu(salen)]) in solution. The LLCT bands (the intramolecular CT band between two π-electronic systems separated by saturated hydrocarbon chains such as ) also appear at nearly the same positions (ca. 245 nm) for [Cu(salchx)], [Cu(saltn)], and [Cu(salen)]. The locations of the dd transition and the intensity of the ML/LMCT transition of [Cu(saltn)] are significantly different from those of [Cu(salen)] and [Cu(salchx)]. These differences may arise from the strengths of the interaction between metal and ligand.

50数年間, 寒冷地に曝された初代十勝大橋のコンクリートの耐久性の評価を種々の手法により実施した. その結果, コアの圧縮強度は建殼時の28日恒温養生の1.8～2.0倍と著しい強度増進が認められた. この増進はセメントが粗く, ビーライトが多いことに起因する. 平均中性化速度係数から判断するとコンクリートの品質はプレキャストコンクリートの製造状態に相当し, 良好な施工が行われていたことがわかった. 構造物の部位により劣化状態が多少異なるが, 全体的に中性化等による劣化は表層のみに止まっており, 現段階での劣化は軽微であった. 凍結融解試験の結果, 凍結融解抵抗性はかなり低いことがわかったが, 耐凍害性は水はけや石張りなどによって水の供給を少なくしたことにより確保できたと考えられる.

Solid surface enhancement effects on chemiluminescence were studied using many inorganic materials as solid media. The results has been classified as follows: the first group (G-1) which has higher initial intensities and shorter lifetimes compared with the reference chemiluminescence (blank CL; medium solid used is a slide glass)—Al2O3 series including hydroxides and glass fiber filter fall under this group (G-1); the second group (G-2) which has lower initial intensities and longer lifetimes compared with the blank CL—high purity CaCO3 fall under this group (G-2); the third group (G-3) which has higher initial intensities and longer lifetimes compared with the blank CL—SiO2 powder and a silica fiber filter fall under this group (G-3); and the fourth group (G-4) which has lower initial intensities and shorter lifetimes compared with the blank CL—all remaining solid media other than group (G-1)–(G-3) fall under this group (G-4). Furthermore, from a chemiluminescent energy point of view, there exists anoth...

Electronic absorption, polarized absorption and fluorescence spectra were measured to clarify the electronic structures and the nature of electronic transitions of [Nd(acac)(terpy)(NO 3 ) 2 ] and [Pr(acac)(terpy)(NO 3 ) 2 H 2 O]. It is found for both complexes that the ππ * 1 transition is localized on the terpyridine moiety whereas the ππ * 2 transition can be assigned to the intramolecular CT transition from the terpyridine moiety (πHOMO) to the acetylacetone (πLUMO). [Nd(acac)(terpy)(NO 3 ) 2 ] (or [Pr(acac)(terpy)(NO 3 ) 2 H 2 O]) fluoresces from the upper excited state localized on the terpyridine moiety. This emission phenomenon is considered in detail because emissions from higher excited states are rarely observed.

The electronic absorption spectra of N,N′-bis(2-aminobenzylidene)ethylenediaminatocopper(II) (abbreviated to [Cu(amben)]) were measured in ethanol and in a KBr disk. From these spectral data together with the polarization spectrum in a stretched PVA film, the X-ray photoelectron spectra, and a VESCF-MO-CI calculation, the electronic structure of [Cu(amben)] has been clarified. The reduced polarization spectrum shows that [Cu(amben)] has longer-molecular axis (y) polarized bands at 438, 300, 280, 257.7 and 222 nm, and shorter ones (z) at 418, 280, 260, 242.5 and 224 nm. The 300 nm band is assigned to an overlap of the calculated ππ*3 and ππ*4 transitions, which are charge transfer transitions between the two π-electronic systems localized almost independently on the 2-aminobenzylideneimino groups. The solid-state electronic absorption bands, measured in a KBr disk, of [Cu(amben)] are red-shifted by 2-16 nm, and considerably broadened compared with those in ethanol, indicating that the [Cu(amben)] molecules...

The absorption and fluorescence spectra of 1-aminoanthracene (AA) in various solvents have been compared with those of 1-dimethylaminoanthracene (DMAA). This comparison has demonstrated that the amino group of AA in the ground electronic state acts as a proton-acceptor to form the A-type hydrogen bond with alcohol, while that of AA in the excited electronic state acts as a proton-donor to form the B-type one. In the cyclohexane-ethanol mixed solvent, the solute-solvent configuration for the fluorescing excited state of AA changes with the ethanol concentration; it keeps the same type of hydrogen bond with ethanol as that (A-type) in the ground electronic state in the lower ethanol concentrations up to 0.2% and exhibits an intramolecular-like rearrangement of the A-type hydrogen bond into the B-type one in the ethanol concentration range of 0.2—1%. This hydrogen bond rearrangement occurs in cooperation with a bulk reorientation of solvent molecules in the range of 1—100%. AA forms the hydrogen-donor-accept...

Solid surface enhancement effects on chemiluminescence were studied using several natural and synthetic polymers. The influence of surface conditions of cellulose on the chemiluminescence of powder and filter paper was also examined. Intensities for powder were relatively low compared to paper. The influence of packed powder and transparent film with the same particle size was examined for PVA, PVC and acetylcellulose. Each polymer showed similar chemiluminescent properties for film state, irrespective of their different chemical structures. Also studied were the effects of functional groups on the chemiluminescence intensity and lifetime of cellulose derivatives (cellulose, acetylcellulose, chitin and chitosan) in powder states. Finally, this paper discusses the relationship among intensities, lifetime and chemiluminescence energies for the respective samples.

The electronic structure and nature of the electronic transitions of copper(II) naphthalenediolate complexes, (2,2′-bipyridine) (2,3-naphthalenediolato) copper(II) ([Cu(ndo)(bpy)]) and (2,3-naphthalenediolato) (1,10-phenanthroline) copper(II) ([Cu(ndo)(phen)]), have been studied from the viewpoints of the polarization spectra and MO theory. The 339.0 and 296 nm bands of [Cu(ndo)(phen)] have been assigned to localized transitions of the naphthalenediolate (ndo) skeleton, and the 308, 275, and 269 nm bands on the phenanthroline (phen) skeleton. It has been clarified experimentally that the 400 nm band can be assigned to the CT transition between ndo and Cu(II). The total state wavefunctions show that the 293 and 282 nm bands are due to the intramolecular interligand CT (LL′CT) transitions from ndo to phen, thus indicating that the two π-electronic systems, separated by the central metal ion, can directly interact. The complex [Cu(ndo)(bpy)] shows the electronic transitions at 339.0, 256.0, 245, 238, and 210...

The electronic structure of bis(tropolonato)copper(II) (abbreviated to troCu(II)) has been investigated by use of a polarized electronic absorption spectrum in the stretched PVA film together with unpolarized spectra in fluid and rigid media. Comparison of the polarized absorption spectrum and MO calculations shows that troCu(II) takes a transoid structure in the PVA film. The complex troCu(II) exhibits shorter molecular axis polarized bands at 387 ( ππ 2 ∗ ), 267 ( ππ 9 ∗ ) and 220 ( ππ 13 ∗ ) nm and longer axis polarized ones at 338 ( ππ 3 ∗ ) and 252.9 ( ππ 11 ∗ ) nm. All these bands are due to ππ ∗ transitions localized on the ligand moieties. In addition to these bands, troCu(II) shows a band around 316 nm which can be assigned to ligand-to-metal (or metal-to-ligand) intramolecular charge transfer transition. A single crystal X-ray diffraction analysis shows that troCu(II) forms a sandwich type van der Waals dimer in the crystalline state. In the dimer state, a considerable charge migration occurs from the oxide ion to the carbonyl oxygen, but each monomer still maintains a transoid structure.

The polarized absorption spectrum of (2,2′-bipyridine)(catecholato)- copper(?) ([Cu(cat)(bpy)]) has been measured in the stretched poly(vinyl alcohol) (PVA) film at room temperature. It is found that the 312, 295 and 215 nm bands of [Cu(cat)(bpy)] are due to transitions localized on the bipyridine (bpy) moiety, and the 306 and 247 nm bands on the catecholate (cat) moiety. The observed 322 nm band can be regarded as an intramolecular interligand CT (LL'CT) transition from cat to bpy. The 207 nm band can be interpreted as superimposition of the two localized excitations cat and bpy, respectively, and LL'CT excitation. This implies that the two π -electronic systems of [Cu(cat)(bpy)], existing almost independently on the two ligands, can interact significantly. The complex [Cu(cat)(bpy)] shows d-d bands at 750, 625 and 550 nm, and intramolecular CT bands between the ligands and metal at 425, 335 and 245 nm.

The electronic absorption spectrum of (catecholato)(1,10-phenanthroline)copper(II) ([Cu(cat)(phen)]) measured in 1:1 methanol and water was compared with those of (catecholato)(ethylenediamine)copper(II) ([Cu(cat)(en)]) and (oxalato)(1,10-phenanthroline)copper(II) ([Cu(ox)(phen)]). From the above results together with MO calculations and polarization spectra using stretched PVA films, it is found that the 330, 295.0, 275.0, 267, 233, and 223 nm bands of [Cu(cat)(phen)] are due to transitions localized on the phen moiety, and the 292 and 210.0 nm bands on the cat moiety. The 209 nm band of [Cu(cat)(phen)] can be interpreted as arising from a mixture of two kinds of transitions localized on phen and cat. This implies that the two π-electronic systems, being usually considered to exist independently on the two moieties, can interact greatly, as newly reported here.

In ethers, such as tetrahydrofuran and 1,4-dioxane, 2,2′-pyridyl (di-2-pyridyl diketone) is photochemically reduced to the cis -enediol-type compound ( cis -1,2-di(2-pyridyl)-1,2-ethenediol), in contrast with the previously reported trans -enediol formation in alcohols, etc. This solvent dependence of the photochemical behaviour can be interpreted in terms of the difference in the reactive excited states of 2,2′-pyridyl in the two photochemical reactions. Investigations of the external heavy atom effect, triplet quenching experiments and the initial concentration dependence of the substrate indicate that cis -enediol is preferentially formed via the lowest excited singlet state of 2,2′-pyridyl in ethereal solutions, whereas the lowest excited triplet state participates in trans -enediol formation in alcohols, etc. From the isotope effects observed in deuterated tetrahydrofuran and ethanol, the initial step in the photoreactions, i.e. hydrogen atom abstraction or electron transfer, is briefly discussed.

The polarized electronic absorption spectrum of 9-cyanoanthracene has been measured in a stretched poly(vinyl alcohol) (PVA) film at 101 K, and the polarizations of the electronic transitions determined. It was found that the longer-molecular-axis polarized bands are at 364.4, 262. 1, and 229 nm, and that the shorter-molecular-axis polarized ones are at 411.2 and 223 nm. The absorption spectra of 9-cyanoanthracene were measured in MP (a 1:1 mixed solvent of methylcyclohexane and isopentane) at room and lower temperatures. It was found that additional bands appear at the lower energy sides of the corresponding monomer bands at lower temperatures. These spectral changes may be interpreted as being due to dimer formation. The dimer may be stabilized mainly through dipole-dipole interactions between the two cyano groups taking on a C2h symmetry. The 412.5, 363.5 and 281.5 nm bands of the dimer are assigned to the calculated S1←S0 (Bu←Ag), S4←S0 (Au←Ag) and S8←S0 (Au←Ag) transitions, respectively; these transi...

The electronic absorption and phosphorescence spectra of 2-acetylfuran were measured in various media at room and low temperatures. It was found that 2-acetylfuran exists as an equilibrium mixture of the O–O s-cis and O–O s-trans conformers in polyethylene (PE) film. Here, the O–O s-trans conformer was considered to be a major species, and the O–O s-cis conformer a minor species in a nonpolar medium such as PE. On the other hand, in a polar medium such as poly(vinyl alcohol), 2-acetylfuran existed almost completely as the s-cis conformer. The 0–0 phosphorescence bands of the O–O trans- and cis-species were at 447 and 427 nm in PE, respectively. The S1 states for both conformers are nπ* in character, while the T1 states are π π*.

2,2′-Furil (di-2-furyl diketone) undergoes photoreduction to give furoin on irradiation at 366 nm in triethylamine-containing benzene and ethers. On the other hand, in ethanol the photoirradiation leads to the formation of an enediol type of compound, 1,2-di(2-furan)ethene-1,2-diol. The results of quenching and sensitization both for the photoreactions and the phosphorescence demonstrate that furoin and the enediol are formed via the lowest excited singlet and the triplet states of 2,2′-furil, respectively.

The polarized electronic absorption spectrum of 9-cyanoanthracene has been measured in a stretched poly(vinyl alcohol) (PVA) film at 101 K, and the polarizations of the electronic transitions determined. It was found that the longer-molecular-axis polarized bands are at 364.4, 262. 1, and 229 nm, and that the shorter-molecular-axis polarized ones are at 411.2 and 223 nm. The absorption spectra of 9-cyanoanthracene were measured in MP (a 1:1 mixed solvent of methylcyclohexane and isopentane) at room and lower temperatures. It was found that additional bands appear at the lower energy sides of the corresponding monomer bands at lower temperatures. These spectral changes may be interpreted as being due to dimer formation. The dimer may be stabilized mainly through dipole-dipole interactions between the two cyano groups taking on a C2h symmetry. The 412.5, 363.5 and 281.5 nm bands of the dimer are assigned to the calculated S1←S0 (Bu←Ag), S4←S0 (Au←Ag) and S8←S0 (Au←Ag) transitions, respectively; these transi...

A biaxially-stretched film method has been proposed and applied for the analysis of the electronic absorption spectrum of a solute embedded in a biaxially-stretched polymer film to demonstrate its usefulness. The intrinsic absorbance change of the solute on biaxial stretching was measured by a ratio (Rbi) of the molar absorptivity (eb) of the solute in the biaxially-stretched film to that (ei) in the nonstretched isotropic film. This Rbi(= eb⁄ei) spectrum was expressed in terms of three orientation factors for three molecular axes of the solute and three absorption components (three-dimensional reduced spectra) purely polarized along the three molecular axes. Problems inherent in this method are discussed by analyzing the Rbi spectra of spherical, disk-like, and rod-like molecules. An approximate estimate of the three-dimensional reduced spectra of a rod-like molecule (pinacyanol, 1-ethyl-2-[3-(1-ethyl-2(1H)-quinolinylidene)-1-propenyl]quinolinium iodide) was obtained by an analysis of its Rbi spectrum by...

The effects of the temperature, initial concentration, and chemical quenchers on dual photoreactions of phthalazine were investigated. The results give further supporting evidence for a previously proposed reaction mechanism, i.e., phthalazine in the lowest excited singlet and triplet states affords singlet and triplet radical pairs, respectively, in the initial hydrogen abstraction process from 2-propanol. The singlet radical pair gives a reduction product in a solvent cage, whereas the radicals produced in the triplet state escape from the solvent cage, causing dimerization. On the basis of the reaction mechanism of dual photoreactions, external heavy-atom effects on the radical pairs within a solvent cage have been studied. The results indicate that heavy-atom perturbations bring about an enhancement of the intersystem crossing efficiency from the triplet-state radical pair to the singlet one, including a spin inversion of the radical pair in the solvent cage, rather than S1→T1 intersystem crossing ind...

2,2′-Pyridil (di-2-pyridyl diketone) undergoes photoreduction to afford the trans -enediol-type compound ( trans -1,2-di(2-pyridyl)-1,2-ethenediol) on irradiation with UV light in alcohols, cyclohexane, benzene—triethylamine and benzene—benzhydrol. Azulene and 1,3,5-hexatriene show quenching effects on the photoreaction at room temperature and phosphorescence at 77 K. In contrast, 1,3-cyclohexadiene and trans -stilbene sho quenching effects on the photoreaction and phosphorescence at 77 K, but do not quench the reaction at room temperature. The results indicate that trans -enediol is formed via the lowest triplet state of 2,2′-pyridil, and the conformation of triplet 2,2′-pyridil is dependent on temperature.

ピクリン酸の XPS の N1s 帯は 404.4 と 400.5eV に観測され,その強度比は 2:1 である。強度の強い 404.4eV 帯はか位とねじれた p-位のニトロ基に, 400.5eV 帯はベンゼン環とほぼ共平面にあるo-位のニトロ基に由来する。両帯のエネルギ.__.差は 3.9eV と極めて大きな値になり,これらのニトロ基が,互いにいちじるしく異なった状態におかれていることがわかる。ピクリン酸トリエチルアンモニウム塩の場合には,3個の N1s 帯が 404.3, 402.5 および 399.8eV に観測され,その強度比は 2:1:1 である。強度の強い 404.3eV 帯は p-位およびねじれた o-位のニトロ基に, 399.8eV 帯は o-位のニトロ基に由来する。また, 402.5eV 帯はトリエチルアンモニウムィオンの N1s に帰属される。幾つかのトリエチルアンモニウム塩について,カチオンの N1s イオン化エネルギーと対アニオンの大きさとの関係を検討した。対イオンがCl-からピクリン酸アニオソ,テトラシアノキノジメタソラジカルアニオソの順にイオン半径が大きくなるにつれて,アンモニウムイオンの N1s のイオソ化エネルギーは 401.5, 402.5 および 404.2eV といちじるしく高エネルギー側に移行する。この理由は次のように説明される。アニオンの半径が大きくなるにつれて両イオン間の平均距離iが増大し,カチオンからのイオン化に対するアニオンの電子によるしゃへい効果が減少し,その結果,カチオソの N1s のイオン化エネルギーが増大する。

External heavy atom effects have been studied for the photoreaction of phthalazine in 2-propanol. Addition of bromine containing compounds alters the product distribution in the dual photoreactions occurred simultaneously. The results can be interpreted in terms of enhancement of the intersystem crossing from the triplet radical pair to the singlet radical pair, including the spin inversion within the solvent cage.

To clarify the electronic spectral properties of uranyl(V) complexes systematically, we measured absorption spectra of three types of pure uranyl(V) complexes: [U(V)O2(dbm)2DMSO]-, [U(V)O2(saloph)DMSO]-, and [U(V)O2(CO3)3]5- (dbm = dibenzoylmethanate, saloph = N,N'-disalicylidene-o-phenylenediaminate, DMSO = dimethyl sulfoxide). As a result, it was found that these uranyl(V) complexes have characteristic absorption bands in the visible-near-infrared (NIR) region, i.e., at around 640, 740, 860, 1470, and 1890 nm (molar absorptivity, epsilon = 150-900 M(-1).cm(-1)) for [U(V)O2(dbm)2DMSO]-, 650, 750, 900, 1400, and 1875 nm (epsilon = 100-300 M(-1).cm(-1)) for [U(V)O2(saloph)DMSO]-, and 760, 990, 1140, 1600, and 1800 nm (epsilon = 0.2-3.6 M(-1).cm(-1)) for [U(V)O2(CO3)3]5-. These characteristic absorption bands of the uranyl(V) complexes are attributable to the electronic transitions in the U(V)O2+ core because the spectral features are similar to each other despite the differences in the ligands coordinated to the equatorial plane of the U(V)O2+ moiety. On the other hand, the epsilon values of [U(V)O2(CO3)3]5- are quite smaller than those of [U(V)O2(dbm)2DMSO]- and [U(V)O2(saloph)DMSO]-. Such differences can be explained by the different coordination geometries around the center uranium in these uranyl(V) complexes. Consequently, the absorption bands of the uranyl(V) complexes in visible-NIR region were assigned to f-f transitions in the 5f1 configuration.

To examine properties of pentavalent uranium, U(V), we have carried out electrochemical and spectroelectrochemical studies on UO(2)(saloph)L [saloph = N,N'-disalicylidene-o-phenylenediaminate, L = dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMF)]. The electrochemical reactions of UO(2)(saloph)L complexes in L were found to occur quasireversibly. The reduction processes of UO(2)(saloph)L complexes were followed spectroelectrochemically by using an optical transparent thin layer electrode cell. It was found that the absorption spectra measured at the applied potentials from 0 to -1.650 V versus ferrocene/ferrocenium ion redox couple (Fc/Fc(+)) for UO(2)(saloph)DMSO in DMSO have clear isosbestic points and that the evaluated electron stoichiometry equals 1.08. These results indicate that the reduction product of UO(2)(saloph)DMSO is [U(V)O(2)(saloph)DMSO](-), which is considerably stable in DMSO. Furthermore, it was clarified that the absorption spectrum of the [U(V)O(2)(saloph)DMSO](-) complex has a very small molar absorptivity in the visible region and characteristic absorption bands due to the 5f(1) orbital at around 750 and 900 nm. For UO(2)(saloph)DMF in DMF, the clear isosbestic points were not observed in the similar spectral changes. It is proposed that the UO(2)(saloph)DMF complex is reduced to [U(V)O(2)(saloph)DMF](-) accompanied by the dissociation of DMF as a successive reaction. The formal redox potentials of UO(2)(saloph)L in L (E(0), vs Fc/Fc(+)) for U(VI)/U(V) couple were determined to be -1.550 V for L = DMSO and -1.626 V for L = DMF.

Solid surface enhancement effects on chemiluminescence (CL) have been studied using alkaline metal salts as solid media. Effects of number of cationic species (alkali metal ions: Na+ and K+ ions) o...

Steady-state photolyses of 4-methoxy-4′-cyanoazobenzene and 4-methoxy-4′-nitroazobenzene have been studied in rigid matrices. The radical anions of these azobenzenes have been observed for the firs...

Solid surface enhancement effects on chemiluminescence (CL) have been studied using metal salicylates as solid media. Interesting CL characteristics depending on kinds of cationic species (alkaline metal ions, alkaline earth metal ions etc.) on chemiluminescence of diaryloxalate were found.

A fluorophotometric method was used to obtain equilibrium constants for the formation of a van der Waals molecular complex between fluoranthene and benzene in the ground state. The equilibrium constant for the above-mentioned complex formation is estimated to be 0.13 dm3 mol−1, which compares well with that (K = 0.15 dm3 mol−1) obtained from a traditional electronic absorption method.

TiO2-supported Cu samples were prepared by using several Cu precursors, and isolated Cu2+ ions and their behavior of thermal reduction were evaluated by means of ESR spectroscopy. Only 50% of Cu2+ ...

A procedure to measure a polarized triplet–triplet absorption spectrum using a stretched polymer film was described, and this method was applied to determine the polarizations of the triplet–triplet transitions of phenanthrene.

Electronic absorption spectra of methylene blue layers adsorbed on glass plates have been measured. Higher aggregates of this dye, up to the tetramer, are shown to exist by an analysis of the aggregate spectra on the basis of a three-dimensional PPP calculation and a diagrammatic exciton-splitting model. A shoulder, located around the monomer peak, observed in the spectrum of the adsorbed methylene blue layer is tentatively assigned to the tetramer. The observed spectral behaviour on aggregation is reproduced by the PPP calculation in which a sandwich type structure is assumed for the aggregates. The band splitting patterns in the methylene blue aggregates are explained diagrammatically in terms of the interactions of the transition moments of the monomer sub-units in an aggregate.

Measurements of a polarized triplet–triplet absorption spectrum using stretched polymer films have been attempted at liquid nitrogen temperature. The polarizations of the triplet–triplet transitions of diphenylacetylene were determined, and the molecular structure in the excited triplet state was discussed.