bluuebunny/crossref_metadata_2025_split huggingface dataset:
Syntheses, Structures, and Magnetic Properties of Di-μ3-Chloride-Bridged Tripalladium Compounds, [Pd3(μ3-Cl)2(HqnS)6]Cl2 (HqnS = Quinoline–2(1H)–thione) and [Pd3(μ3-Cl)2(Et2dtc)2(PPh3)2]·C6H6(Et2dtc = N, N′–Diethyldithiocarbamate)
Authors: Sugimoto Kunihisa , Kuroda-Sowa Takayoshi , Goto Tamotsu , Maekawa Masahiko , Munakata Megumu 
Published: September 2002

Abstract
Two triangular tripalladium compounds, [Pd3(μ3-Cl)2(HqnS)6]Cl2 (1) (HqnS = quinoline–2(1H)–thione), and [Pd3(μ3-Cl)2(Et2dtc)2(PPh3)2]·C6H6 (2) (Et2dtc = N, N′-diethyldithiocarbamate anion), were prepared. Their single crystal X-ray structure analyses revealed they have a similar trigonal bipyramidal framework of Pd3(μ3-Cl)2 with two chlorine atoms in apical positions. Each Pd atom in all clusters has two additional coordination sites to establish a square planar cis-PdL2(μ3-Cl)2 geometry. In compound 1, six sulfur atoms of six HqnS ligands with thion form are coordinated to the vacant sites of the Pd3(μ3-Cl)2 core. Two coordination sites of one of the three Pd atoms in 2 are occupied by two triphenylphosphines and those of the other two are coordinated by two S atoms of Et2dtc. Although both compounds have 50 valence electrons, only 1 shows paramagnetic behavior. Crystallographic data are as follows. 1: Pd3Cl4S6N6C54H42, triclinic, P1- a = 14.988(5), b = 17.328(3), c = 12.642(1) Å, α = 93.61(1), β = 96.06(2), γ = 71.79(2)°, V = 3099(1) Å3, and Z = 2. 2: Pd3Cl2P2S4N2C52H56, monoclinic, P21, a = 12.278(5), b = 17.426(6), c = 12.630(3) Å, β = 94.65(3)°, V = 2693(2) Å3, and Z = 2.
δMM*-πL Odd Electron Delocalization onto Aromatic Bridging Ligands in a Paramagnetic Dirhodium Complex and Intermolecular π-Stack Interaction in Crystal
Authors: Kawamura Takashi , Kachi Hisanori , Fujii Hiroshi , Kachi-Terajima Chihiro , Kawamura Yuzuru , Kanematsu Naohiro , Ebihara Masahiro , Sugimoto Kunihisa , Kuroda-Sowa Takayoshi , Munakata Megumu 
Published: September 2002

Abstract
The odd electron in the δRhRh* orbital of (3,1)-[Rh2(mhq)4py]+ (1+; Hmhq = 4-methyl-2-quinolinol) was estimated to be delocalized onto each π system of the four mhq bridges to the extent of ca. 9% based on its 1H NMR paramagnetic shifts. The experimental spin distribution in the mhq ligands is consistent with a model of mixing of the π HOMOs of the mhq ligands into the δRhRh* singly occupied molecular orbital (SOMO). In crystals of (3,1)-[Rh2(hq)4py] (2; Hhq = 2-quinolinol) and its cationic radical salts, 2 or 2+ molecules form intermolecular π-stack arrangements of hq ligands. Intermolecular interaction between 2+ molecules in crystal was studied by examining electronic spectra, magnetic susceptibility, ESR, and electrical conductance of its salts.
Analysis of Ion Association Reactions between Monovalent Polycyclic Aromatic Cations and Anions in Aqueous Solution as Studied by Capillary Zone Electrophoresis
Authors: Takayanagi Toshio , Ban Noriaki , Wada Eiko , Oshima Mitsuko , Motomizu Shoji 
Published: September 2002

Abstract
Ion association reactions between monovalent polycyclic aromatic cations and anions have been studied through the mobility change in capillary zone electrophoresis. When the cationic reagent possessing aromatic moieties was used, isomers of aromatic anions were well resolved. Apparent electrophoretic mobility of the anions decreased with an increase in the concentration of the cationic reagent in the migrating solution; the magnitude of the decrease was large when bulkier cations were used. The ion association constants obtained by analyzing the mobility change increased with an increase in the number of aromatic rings of either the pairing cations or the anions. The ion associates formed consist of monovalent cations and anions, and the ion association constant for an ion associate formed between 1-propylbenzo[f]quinolinium ion and pyrene-1-carboxylate ion was in the magnitude of 102.74 dm3 mol-1. Such ion associability was interpreted from the contribution of the stacking of aromatic moieties in an aqueous solution, in addition to the increase in the hydrophobicity.
Low-Temperature Heat Capacities and Ferromagnetic Phase Transition of the Organic Free Radical Ferromagnet, 4-(4-Chlorobenzylideneamino)-2,2,6,6-tetramethylpiperidin-1-oxyl (CATMP)
Authors: Miyazaki Yuji , Matsumoto Tetsuya , Ishida Takayuki , Nogami Takashi , Sorai Michio 
Published: September 2002

Abstract
Heat capacities of the organic free radical ferromagnet, 4-(4-chlorobenzylideneamino)-2,2,6,6-tetramethylpiperidin-1-oxyl (CATMP) have been measured in the temperature range between 0.1 and 311 K. A ferromagnetic phase transition was observed at 0.28 K and a heat capacity hump was found above the transition temperature. This hump is due to the short-range order characteristic of low-dimensional magnetic spin systems. The enthalpy and entropy gains due to the ferromagnetic phase transition were estimated to be 4.06 J mol-1 and 5.71 J K-1 mol-1, respectively. This entropy agrees well with the theoretical value Rln 2 ( = 5.76 J K-1 mol-1) expected for the magnetic entropy of a spin system with the spin quantum number S = 1/2, where R is the gas constant. The heat capacity hump above the transition temperature is well accounted for in terms of the S = 1/2 two-dimensional ferromagnetic Heisenberg model of square lattice with the intralayer exchange interaction J/kB = 0.42 K, where the spin Hamiltonian H = -2JSi·Sj is adopted and kB stands for the Boltzmann constant. The analysis of the magnetic heat capacities below the transition temperature on the basis of the spin wave theory clarified that the magnetic system settles down in three-dimensional ferromagnetic order below the transition temperature with the interlayer exchange interaction J′/kB = 0.024 K.
Iron(III) Trifluoroacetate as an Efficient Catalyst for Solvolytic and Nonsolvolytic Nucleophilic Ring Opening of Epoxides
Authors: Iranpoor Nasser , Adibi Hadi 
Published: September 2002

Abstract
Iron(III) trifluoroacetate was used as an efficient and nonhygroscopic catalyst for the alcoholysis, hydrolysis, and acetolysis of epoxides. The addition of chloride, bromide, iodide, and nitrate ions to epoxides to produce the corresponding 2-halo and 2-nitratoalkanols and also the conversion of epoxides to acetonides and thiiranes were also performed efficiently in the presence of this catalyst.
Bisoxazoline and Bioxazoline Chiral Ligands Bearing 4-Diphenylmethyl Shielding Substituents. Diels-Alder Reaction of Cyclopentadiene with 3-Acryloyl-2-oxazolidinone Catalyzed by the Aqua Nickel(II) Complex
Authors: Kanemasa Shuji , Adachi Kenji , Yamamoto Hidetoshi , Wada Eiji 
Published: September 2002

Abstract
Enantiopure 2-amino-3,3-diphenyl-1-propanol has been synthesized by the hidantoin route starting from diphenylacetaldehyde, followed by subsequent functional group transformations and optical resolution by a chiral HPLC. This amino alcohol can be converted into two new chiral ligands: 4,4′-bis(diphenylmethyl)-2,2′-bioxazoline and 2,2′-isopropylidenebis(4-diphenylmethyloxazoline), and further to complexes with copper(II) trifluoromethanesulfonate and nickel(II) perchlorate hexahydrate. The nickel(II) aqua complex derived from the bisoxazoline effectively catalyzes the Diels-Alder reactions of cyclopentadiene with 3-acryloyl-2-oxazolidinone in high endo-selectivities and moderate enantioselectivities through a square planar transition structure.
A Convenient One Pot Allylation of Aldehydes with Allylic Halides Prepared in Situ from Allylic Alcohols in the Presence of Metallic Bismuth
Authors: Miyoshi Norikazu , Nishio Mami , Murakami Shunsuke , Fukuma Tomohiro , Wada Makoto 
Published: September 2002

Abstract
A convenient one pot allylation of aldehydes with allylic iodides prepared in situ from allylic alcohols by using trimethylsilyl chloride and sodium iodide proceeds smoothly in the presence of metallic bismuth to afford the corresponding homoallylic alcohols in good yields.
Multi-Layer Macromonocyclic Polyamines. I. Molecular Design and Synthesis of Component Monocyclic Precursors
Authors: Iwata Masaaki 
Published: September 2002

Abstract
We designed ``multi-layer macromonocyclic polyamines'' which might be appropriate polymorphismic molecular scaffolds as host-molecules in ionic or molecular interaction with small or large guest ions or molecules. In polymorphismic molecules, several macromonocyclic polyamines with the same and/or different ring sizes and nitrogen contents are connected to each other by alkylene spacers with various length of the chain. Actual target molecules are characterized by possessing methylene chain arrays of natural polyamines, and we have synthesized from simple starting materials fourteen component macromonocycles with various sizes, 12- to 34-membered rings containing three to eight nitrogen atoms, as essential building blocks required for construction of multi-layer molecules. Our method of synthesis was shown to be very efficient. In a final step, the N-protecting benzyl group was successfully removed by hydrogenation on 10%-Pd/C under 4 kg cm-2 H2 to give the cyclic amine precursors, which could be internal and terminal components in the architecture of the multi-layer molecules. The structures of synthesized compounds were characterized and confirmed by EA, 1H NMR, SIMS, and FAB(+) mass spectrometry.
Synthesis of Optically Pure Bisphosphine Oxides and Related Compounds
Authors: Sugiya Masashi , Nohira Hiroyuki 
Published: September 2002

Abstract
Optically pure bisphosphine oxides were conveniently synthesized by Kolbe electrolytic coupling reaction of carboxylic acids possessing a chiral phosphinoyl group in 60—65% isolated yield. This synthetic approach provides a variety of accesses to P-chiral bisphosphine ligands. Their absolute configurations were intercorrelated with that of the previous reported BisP*-borane. Asymmetric hydrogenation of α-(acylamino)acrylic acids by a rhodium complex with BisP* (R = t-octyl or 1,1,3,3-tetramethylbutyl) affords N-acylamino acids in 94—96% ee.
Reaction of Various Oxiranes and Carbon Dioxide. Synthesis and Aminolysis of Five-Membered Cyclic Carbonates
Authors: Iwasaki Takeshi , Kihara Nobuhiro , Endo Takeshi 
Published: September 2002

Abstract
Various oxiranes reacted with carbon dioxide at 100 °C using lithium bromide as a catalyst under atmospheric pressure to afford the corresponding five-membered cyclic carbonates quantitatively. The rate of the reaction increased as the bulkiness of substituents on the oxirane ring was reduced or an electron-withdrawing group was introduced on the oxirane ring. The stereochemistry of the reaction of oxirane and carbon dioxide was retention without loss of optical purity. When substituted phenylethylene carbonates were reacted with benzylamine, the selectivity to afford secondary alcohol increased as the electron-withdrawing ability of the para-substituent increased.
Acid-Catalyzed Condensation of Azulenes with 9-Anthracenecarbaldehyde and the Synthesis of (9-Anthryl)di(1-azulenyl)methyl and (1-Azulenyl)[10-(1-azulenyl)-9-anthryl]methyl Hexafluorophosphates
Authors: Ito Shunji , Fujita Miwako , Morita Noboru , Asao Toyonobu 
Published: September 2002

Abstract
Acid-catalyzed condensations of 1-methyl and 1,6-di-t-butylazulenes with 9-anthracenecarbaldehyde led us to unexpected 9-(1-azulenyl)-10-[(1-azulenyl)methylidene]-9,10-dihydroanthracenes 10a and 10b as major products, together with (9-anthryl)di(1-azulenyl)methanes 7a and 7b. Hydride abstraction from 7a, 7b, and 10b with DDQ afforded substituted (9-anthryl)di(1-azulenyl)methyl and (1-azulenyl)[10-(1-azulenyl)-9-anthryl]methyl hexafluorophosphates 6a, 6b·PF6- and 11b·PF6-, respectively. Their properties were fully characterized. The reaction of the 3-methyl derivatives 10a, however, did not afford the desired (3-methyl-1-azulenyl)[10-(3-methyl-1-azulenyl)-9-anthryl]methyl hexafluorophosphate (11a·PF6-), due to the low stabilities of 11a. While cations 6a and 6b prepared from 7a and 7b showed high stabilities with large pKR+ values (10.7±0.1 and 12.4±0.1, respectively), cation 11b exhibited relatively low stabilities with the pKR+ value of 5.0±0.1.
Formation, Structure, and Thionation of 1,2,4,5-Tetrathianes [cis- and trans-3,6-Bis(1,1,3,3-tetramethyl-4-oxo-4-phenylbutyl)-1,2,4,5-tetrathianes]
Authors: Ishii Akihiko , Omata Takenori , Umezawa Kazuyo , Nakayama Juzo 
Published: September 2002

Abstract
2,2,4,4-Tetramethyl-1-phenyl-6,7-dithiabicyclo[3.1.1]heptane was treated with 2KHSO5·KHSO4·K2SO4 to yield cis- and trans-3,6-bis(1,1,3,3-tetramethyl-4-oxo-4-phenylbutyl)-1,2,4,5-tetrathianes. The formation mechanism of the tetrathianes is discussed. X-Ray crystallography disclosed that the cis- and trans-isomers take twist and chair conformations, respectively, in the solid state. Variable-temperature 1H NMR spectroscopy in solution showed that the cis-isomer takes a twist conformation exclusively in the temperature range, whereas the trans-isomer exists as an equilibrium mixture of chair and twist conformers. The cis-tetrathiane reacted with Lawesson's reagent at 50 °C to give the corresponding di-2-thianyl disulfide.
Kinetic Studies on the Autoxidation of Cysteine Catalyzed by Copper Complexes : Catecholamines Stimulate the Autoxidation
Authors: Hanaki Akira , Kinoshita Tomoyuki , Ozawa Toshihiko 
Published: September 2002

Abstract
Catecholamines including epinephrine, norepinephrine, dopamine, and dihydroxyphenylalanine accelerated copper-catalyzed oxidation of cysteine under aerobic conditions, while they had no effect under anaerobic conditions. The efficiency of the catecholamines was arranged in the decreasing order as follows; epinephrine ≈ norepinephrine ≥ dopamine &gt; dihydroxyphenylalanine. On the contrary, phenolic amines such as tyramine and tyrosine neither accelerate nor inhibit the autoxidation. The reaction can be elucidated by a ``sequentical mechanism'' which is composed of Eqs. I, II, III, IV, V, and VI :
where L is glycylglycine used as the buffer, and CyS- and Cat- denote cysteinate and catecholamine ions, respectively. The reactions (IV), (V), or both are considered to be rate-determining. The optimum pH for the autoxidation was observed at pH 7.5—7.6, and below pH 7.2 reaction (V) does not participate in the autoxidation system.
The Reaction of Nitrile Oxide-Quinone Cycloadducts. IV. Acid-Catalyzed Dealkylative Aromatization of the 1 : 1 -C=C-Adducts and Base-Induced Rearrangement Products of Aromatic Nitrile Oxides with 2,5- and 2,6-Dialkyl-p-benzoquinones
Authors: Mukawa Takashi , Muraoka Jun , Shiraishi Shinsaku 
Published: September 2002

Abstract
The 1,3-dipolar cycloadducts of aromatic nitrile oxides with 2,5- and 2,6-dialkyl-p-benzoquinones were treated with acetic anhydride/sulfuric acid to give isoxazole-fused hydroquinone diacetates in good yields. The base-induced rearrangement products from some of the 1,3-dipolar cycloadducts were treated with acetic anhydride/sulfuric acid to afford isoxazole-fused catechol diacetates and/or isoxazole-fused hydroquinone diacetates, depending on the slight difference in the substituents of the base-induced rearrangement products. The differences in the products are interpreted in terms of steric hindrance around the carbonyl and hydroxy moieties of the base-induced rearrangement products.
Electrochemical Hydrogenation of Organic Compounds on Poly[N-(5-carboxyhexyl)pyrrole] Film-Coated Electrodes Incorporating Palladium
Authors: Takano Nobuhiro , Seki Chigusa , Shimono Isao , Kobayashi Takanori , Takeuchi Takao 
Published: September 2002

Abstract
Poly[N-(5-carboxyhexyl)pyrrole] coated carbon-fiber electrodes incorporating palladium metal were prepared for the electrocatalytic hydrogenation of methyl α-oxobenzeneacetate, 2-cyclohexen-1-one, and diphenylacetylene in an ethanol-buffer solution. The reactions using these electrodes proceeded smoothly to give hydrogenated products in good yields.
An Efficient Method for the Synthesis of 4,5-Disubstituted Catechols
Authors: Ma Tingli , Kojima Takahiko , Matsuda Yoshihisa 
Published: September 2002

Abstract
4,5-Disubstituted catechols were prepared in high yields via successive Friedel-Crafts acylation in the presence of a Ti(IV) catalyst or I2 and reduction with triethylsilane of veratroles. This method provides an effective and well-regulated synthetic strategy toward catechol derivatives having a variety of substituents at the 4- and 5- positions.
Substituent Effect of 3,3,3-Trifluoropropyl Group on Organic Silanols. Palladium-Mediated Mizoroki-Heck Type and Cross-Coupling Reactions
Authors: Hirabayashi Kazunori , Kondo Tatsuhiro , Toriyama Fumihiko , Nishihara Yasushi , Mori Atsunori 
Published: September 2002

Abstract
The Mizoroki-Heck type reaction of methyl(phenyl)(3,3,3-trifluoropropyl)silanol (1a) with ethyl acrylate in the presence of Pd(OAc)2 (10 mol%) and Cu(OAc)2/LiOAc gave ethyl cinnamate in 70% yield. The palladium-catalyzed cross-coupling of 1a with 4-iodomethoxybenzene in the presence of Ag2O also afforded 4-methoxybiphenyl in 51% yield.
Catalysis of Polymer-Protected Ni/Pd Bimetallic Nano-Clusters for Hydrogenation of Nitrobenzene Derivatives
Authors: Lu Ping , Toshima Naoki 
Published: September 2002

Abstract
Poly(N-vinyl-2-pyrrolidone)-protected Ni/Pd bimetallic colloidal nanoparticles, prepared by the polyol reduction method, have been proved to have a nanometer-sized alloy structure with both metals at zerovalent state by our previous study of TEM, XRD, EXAFS, and XPS analyses. Here, dispersions of these bimetallic nanoclusters with different composition ratios are extensively examined as catalysts for the hydrogenation of various nitrobenzene derivatives: i.e., p-nitrotoluene, p-nitroanisole, 1-nitronaphthalene, p-nitrobenzonitrile, and methyl p-nitrobenzoate, at 30 °C under an atmospheric pressure of hydrogen. These bimetallic nanoclusters exhibit excellent catalytic properties for the reduction of a nitro group to an amino group with high selectivity. The catalytic activity strongly depends on the metal composition of the particles. The maximum catalytic activity can be observed at a certain intermediate composition ratio, being 3—4 times greater than that of a monometallic colloidal Pd catalyst. A bimetallic nanocluster with the mole ratio of Ni : Pd = 1/4 was the most active catalyst for the hydrogenation of para-substituted nitrobenzenes. An approximately linear relationship exists between the hydrogenation rate of the substrate with an electron-donating or electron-withdrawing group and the corresponding Hammett constant of the substituent, as well as between the hydrogenation rate and the LUMO energy level of the substrate.
Characterization of Sulfur on Pt-Alkali metal/Al2O3 Catalysts Treated with H2S by a Temperature-Programmed Reaction Using Deuterium and Its Role in the Dehydrogenation of Isobutane
Authors: Kobayashi Junya , Shimizu Takashi 
Published: September 2002

Abstract
This paper discusses the promotion of isobutane dehydrogenation due to sulfur species adsorbed on Pt-alkali metal (Li, Na, or K)/Al2O3 catalysts. A treatment with hydrogen sulfide at 833 K increased the selectivity to isobutene on all Pt-alkali metal/Al2O3 catalysts. The promotion effect of sulfurization was most significant on a Pt (1 wt%)-Na2O (3 wt%)/Al2O3 catalyst; the selectivity increased from almost 0 for a reduced catalyst to 75% for a sulfurized catalyst. The effect on the selectivity of the addition of alkali metals increased in the order sodium &gt; potassium &gt; lithium. Temperature-programmed reaction (TPR) experiments, conducted by flowing deuterium onto the sulfurized catalysts, were used to characterize the sulfur species that easily desorbed with hydrogen. The results indicated that HS- is the major species on the catalysts and that the adsorbed HS- bridges the PtSir and the Na2Sir particles. Re-reduction of the sulfurized Pt-Na2O/Al2O3 catalyst to remove the HS- decreased the selectivity from 75 to 8%, implying that HS- is effective in enhancing the selectivity.
Preparation of Microporous Silica Gel by Sol-Gel Process in the Presence of Ethylene Glycol Oligomers
Authors: Takahashi Ryoji , Sato Satoshi , Sodesawa Toshiaki , Suzuki Masanori , Ogura Katsuyuki 
Published: September 2002

Abstract
A microporous silica gel was prepared by a sol-gel process in the presence of ethylene glycol (EG) and its oligomers (oligoEG), and the pore formation process was investigated by using NMR and TG-DTA. The micropore volume changed with the polymerization degree of oligoEG, and showed a minimum at the trimer of EG. An attractive interaction between silanol and organic additives plays a key role in micropore formation: the interaction inhibits the bond formation of Si-O-Si during drying and heating, and heterogeneous domains which convert into micropore are formed after the combustion of additives. There are two kinds of interaction: one is ester (Si-OR) bond formation of a silanol with an end hydroxy group of additives; the other is hydrogen bonding between a silanol and an ether oxygen of additives. The former interaction is significant for EG. With increasing length of oligoEG, however, the former interaction rapidly disappears, while the latter becomes stronger. Because of a minimum in the combination of these interactions, the minimal volume of the micropore is observed.
Triangular Platinum(II) Cluster Complexes and Cluster Core Transformation from Square-Planar to Triangular Type
Authors: Yamaguchi Tadashi , Nishimura Nozomu , Shirakura Ken-ichi , Ito Tasuku 
Published: September 2002

Abstract
Reactions of [PtII4(μ-CH3COO)8] (1) with dioximes or with N,N′-dimethylethylenediamine induced a cluster core transformation from a square planar to a triangular type to afford PtII3 clusters.Three of these clusters have been characterized by X-ray analyses. The structure of the PtII3 cluster core is an approximate or regular isosceles triangle, two equidistant edges (2.51—2.56 Å) being somewhat shorter than the other (2.59—2.61 Å).The cluster core transformation proceeds through the substitution of the in-plane acetate ligands in 1 by incoming ligands followed by the removal of one Pt atom from the tetranuclear cluster core.An intermediate of the cluster core transformation, [{Pt4(CH3COO)4(dmgH)2(dmgH2)}2(μ-dmgH2)], was structurally characterized.It is a dimer of tetranuclear Pt(II) complex and consists of a triangular cluster unit and a mononuclear unit with square planar geometry.EHMO study and large 1JPt-Pt values of ca. 8000 Hz suggest the stability of the triangular PtII3 cluster core and the existence of strong Pt-Pt bonds.Ligands in the PtII3 cluster plane are labilized by trans effect of Pt-Pt bonds, although intramolecular hydrogen bonds reduce the lability. On the other hand, out-of-plane acetate ligands are substitution inert.
Electron-Transfer Process in Layered Photoreceptors Containing Azo Compounds
Authors: Shimada Tomoyuki , Sasaki Masaomi , Aruga Tamotsu , Umeda Minoru 
Published: September 2002

Abstract
Photoinduced electron transfer (ET) is the most essential process for carrier photogeneration in organic optoelectronic devices. In azo compound-based layered photoreceptors, carrier photogeneration is sensitized by hole transport material (HTM) incorporation. We investigated this process to elucidate the highly sensitizing mechanism. First, the photoinduced ET efficiency and overall quantum efficiency were measured and compared for the layered photoreceptor and the carrier generation layer. The result that the HTM enhances the photoinduced ET implies that the HTM works catalytically to diminish the activation energy. Although such extrinsic ET takes place independently of an electric field, the subsequent geminate pair dissociation depends on the electric field. Next, the energy-gap dependence of the ET was investigated by employing more than 50 photoreceptors to vary the energy gap over a wide range. The measured efficiency was plotted against the energy gap, in which an inverted region was not observed.