bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermodynamic Stabilities and Resonance Demand of Aromatic Radical Anions in the Gas Phase
Authors: Huh Chul , Kang Chul Hyun , Lee Hai Whang , Nakamura Hirotaka , Mishima Masaaki , Tsuno Yuho , Yamataka Hiroshi 
Published: December 2003

Abstract
The electron affinities (EAs) for a series of methyl benzoates, acetophenones, benzaldehydes, and benzophenones were determined by measuring the electron-transfer equilibria in the gas phase. The effect of substituents (X) in the benzene ring on the EAs of this series as well as the nitrobenzene and benzonitrile series were correlated in terms of the Yukawa–Tsuno equation,

It has been shown that the r− value, representing the degree of π-delocalization of the negative charge into the substituent (X) at position 4, increases linearly with decreasing EA of the unsubstituted member (X = H) of the respective series, i.e., 0.65 for nitrobenzene vs. 1.05 for benzaldehyde and 1.30 for benzonitrile. This tendency of the r− value leads to the conclusion that the negative charge of a less-stable radical anion is more significantly distributed in the benzene ring than in a stable radical anion, like that of nitrobenzene. Ab initio MO calculations show that when the EA of a Y-substituted benzene decreases, the total negative charge on the substituent (Y) in the radical anion also decreases, and that the bond lengths (C2C3/C5C6) shorten. These features are consistent with the conclusion derived from the experimentally obtained r− value.
A Practical Synthesis of (1S,2R)-1-Amino-2-indanol, a Key Component of an HIV Protease Inhibitor, Indinavir
Authors: Kajiro Hiroshi , Mitamura Shuichi , Mori Atsunori , Hiyama Tamejiro 
Published: December 2003

Abstract
A synthesis of (1S,2R)-1-amino-2-indanol (1), a key component of an HIV protease inhibitor, was accomplished through (R)-2-hydroxy-1-indanone ((R)-3), which was prepared by an intramolecular Friedel–Crafts acylation of (R)-2-acetoxy-3-phenylpropanoic acid readily available from d-(R)-phenylalanine. Alternatively, (R)-3 was obtained by an enzymatic resolution of (±)-2-acetoxy-1-indanone. Ketone (R)-3 was converted into 1 through an oxime formation and diastereoselective hydrogenation.
Photochemical Reactions of 1,2-Dicyanonaphthalene with Alkenes and Dienes
Authors: Kubo Yasuo , Kiuchi Kazuyuki , Inamura Isamu 
Published: December 2003

Abstract
The photoreaction of 1,2-dicyanonaphthalene (7) with 2-methyl-1-propene (2) in acetonitrile gave a [3 + 2]adduct at the 1,8-position of the naphthalene ring of 7 with loss of hydrogen cyanide, a [2 + 2 + 2]adduct consisting of 7, 2 and acetonitrile, and a cyclobutene-fused derivative, while that in benzene afforded a [3 + 2]adduct without loss of hydrogen cyanide and the cyclobutene-fused derivative. Yields of the products largely depended on the composition of the acetonitrile–benzene mixed solvent. The results suggested a polar nature of the [2 + 2 + 2]addition and a less polar nature of the formation of the cyclobutene-fused derivative. A maximal total yield (32%) of the [3 + 2]adducts was obtained in solvents containing 20—30 volume percent of acetonitrile. [3 + 2]Photocycloadditions at the 1,8-position of the naphthalene ring of 7 were found to be general in the reactions with cyclopentene, styrene, 1,3-butadiene, and isoprene. No photoreactions with 1-hexene were observed, possibly due to the poor electron-donating ability of 1-hexene. The generality of the [3 + 2]photocycloaddition was discussed in terms of the free energy change associated with single-electron transfer from alkenes or dienes to the singlet excited state of 7.
A Chiral Bimetallic Lewis Acid as a Reaction Template. Asymmetric Reduction of Unsymmetric Ketones with LiBH4
Authors: Nozaki Kyoko , Kobori Kayo , Uemura Toshitsugi , Tsutsumi Takaharu , Takaya Hidemasa , Hiyama Tamejiro 
Published: December 2003

Abstract
A new series of chiral bimetallic Lewis acids, 5,5′-bis[(R)-2-aryl-1,3,2-dioxaborolan-4-one], have been prepared from l-(+)-tartaric acid and arylboronic acids. In the presence of these Lewis acids, unsymmetric ketones were reduced quantitatively by LiBH4, in moderate to good ee’s (up to 99% ee). The counter cation of BH4− significantly affects the ee’s of the products. The reaction is applicable to aryl alkyl ketones, dialkyl ketones, and diaryl ketones.
Silyl-Substituted Dilithium Salt of Fulvene Dianion with 6 Center/8 Electron π-System: Synthesis and Characterization
Authors: Matsuo Tsukasa , Sekiguchi Akira , Sakurai Hideki 
Published: December 2003

Abstract
Treatment of fulvene derivatives bridged by Me2Si–X–SiMe2 chains (2a : X = CH2, 2b : X = O) with lithium metal in THF yields yellow crystals of the dilithium salt of fulvene dianion (3a and 3b) with 6 center/8 electron π-system. The molecular structure of the dianion dilithium 3a has been established by X-ray crystallography. The dianion dilithium 3a has a monomeric structure and forms a contact ion pair (bis-CIP) in the crystal. One of the lithium atoms is located above the center of the five-membered ring by η5-coordination, whereas the other one is bonded to the exo-cyclic carbon atom by η2-coordination. The structural parameters of 3a are discussed in comparison to those of the neutral starting molecule 2a. The structure of 3a in solution has also been discussed on the basis of NMR spectroscopic data. The two lithium ions of 3a are not fixed to the π-skeleton in toluene-d8, but are fluxional, giving a highly symmetrical bis-CIP structure. The spectral data in THF-d8 at 298 K also suggest the bis-CIP structure of 3a. However, the lithium ion on the five-membered ring is dissociated to yield an ion pair (CIP-SSIP) at low temperature in THF-d8, and two dianion species (bis-CIP and CIP-SSIP) were found in THF-d8.
Reversible Stretching of a Polymer-Supported Cobalt-Chelate Film in Response to Oxygen
Authors: Nishide Hiroyuki , Mizuma Hiroyuki , Tsuchida Eishun , McBreen James 
Published: December 2003

Abstract
The polymer-supported N,N′-di(salicylidene)ethylenediaminatocobalt(II) [Co(salen)] took up oxygen through 2/1 Co/dioxygen adduct formation. The composite film of the polymer-supported [Co(salen)] and polymer layers reversibly bent under an oxygen and nitrogen atmosphere. The stretching was caused by a structural change in the [Co(salen)] crystal before and after the oxygen-binding, which was analyzed based on the near-IR spectral and density change as well as EXAFS.
Salt Effects on Fluorescence Spectral Shifts of DNA-Bound Hoechst 33258 and Reaction Volumes of the Minor Groove Binding
Authors: Tang Guo-Qing , Tanaka Naoki , Kunugi Shigeru 
Published: December 2003

Abstract
In this study, salt effects on the interaction of Hoechst 33258 (2′-(4-hydroxyphenyl)-5-(4-methyl-1-piperazinyl)-2,5′-bi-1H-benzimidazole trihydrochloride) with several synthetic polynucleotide duplexes were studied by fluorescence spectral shifts and reaction volumes derived from the pressure dependence of binding equilibria. Both the excitation and emission spectra of Hoechst 33258 saturated by polyd(A)·polyd(T) or poly[d(A-T)]·poly[d(A-T)] shifted to shorter wavelengths as NaCl concentrations increased. The peak intensities first increased ([NaCl] &lt; 100 mM) then started to decrease ( &gt; 100 mM NaCl). Salt dependent blue shifts were also observed in their absorption spectra. These results were in contrast to what occurred to the drug complexed with poly[d(G-C)]·poly[d(G-C)] or poly[d(A-G)]·poly[d(C-T)]. The pressure dependence of the association equilibrium constants (Kp) of the drug and two A·T polymers was examined at several salt concentrations; the results helped to derive reaction volumes. In the case of the A-T copolymer, negative volume changes were found at all ionic concentrations studied. In contrast, in the case of the homopolymer, negative volume changes were found at lower salt concentrations (10 and 50 mM) while positive ones were found at higher concentrations (100 and 200 mM NaCl). These results are discussed in terms of the local structural deformation and hydration rearrangement of DNA.
Radiation-Induced Coloration of Photochromic Dithienylethene Derivatives
Authors: Irie Setsuko , Yamaguchi Tadatsugu , Nakazumi Hiroyuki , Kobatake Seiya , Irie Masahiro 
Published: December 2003

Abstract
The radiation sensitivity of photochromic 1,2-dithienylethenes was studied with the aim to develop a new reusable color dosimeter. Upon γ-irradiation, crystalline colorless 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene turned red, and the absorption intensity increased linearly with the absorbed dose. The red color was bleached by visible-light irradiation and the crystal could be reused. On the other hand, crystalline 1,2-bis(2-methyl-1-benzothiophen-3-yl)perfluorocyclopentene did not show any radiation-induced coloration. The radiation sensitivity in solution was also examined to understand the possible applications to solution and film color dosimeters. Although radiation-induced coloration of the above two compounds was observed in benzene, no color change was detected in hexane, 2-methyltetrahydrofuran and n-butyl chloride. Excitation energy migration and transfer mechanism is considered to play a role in the coloration process in benzene.
Photodimerization of 1-Alkylthymines Crystallized from Acetonitrile Solution
Authors: Tohnai Norimitsu , Inaki Yoshiaki , Miyata Mikiji , Yasui Nobuyoshi , Mochizuki Eiko , Kai Yasushi 
Published: December 2003

Abstract
Crystallization of 1-octylthymine from acetonitrile solution gave needles and plates. The needles gave the photodimer by irradiation of UV light, but the plates did not give the photodimer. Crystal structures of needles and plates were determined by X-ray analysis. There were two pairs of thymine, which gave the photodimers in the needles of 1-octylthymine. The isomer ratio of the photodimers indicated that thymine rotated disrotatory during the photodimerization reaction to give trans-anti, cis-anti, and trans-syn isomers. The crystal structure of the plates from acetonitrile solution was identical to the structure of plates obtained from ethanol solution, which was inactive for the photodimerization as reported in the previous paper. When the alkyl group became long, the formation of trans-syn photodimer decreased because strong interaction with the alkyl group inhibited moving of molecules. The photodimerization of 1-alkylthymine was concluded to occur when the rotation of the thymine is possible in the crystal.
Synthesis of Ru- and Os-Complexes of π-Conjugated Oligomers of 2,2′-Bipyridine and 5,5′-Bipyrimidine. Optical Properties and Catalytic Activity for Photoevolution of H2 from Aqueous Media
Authors: Hayashida Naoki , Yamamoto Takakazu 
Published: December 2003

Abstract
Oligomers of 2,2′-bipyridine (Oligo-bpy) and 5,5′-bipyrimidine (Oligo-bpym) with a linear structure have been prepared by an organometallic C–C coupling reaction. The oligomeric chelating ligands have a molecular weight of about 1500 corresponding to about 10 chelating bpy or bpym units, and form soluble complexes with [M(bpy)2]2+ (M = Ru or Os). The UV-vis absorption spectra of the metal complexes of Oligo-bpy exhibit a π–π* transition band at 355 ± 6 nm and a peak at 453 ± 18 nm assigned to a MLCT absorption. The UV-vis spectra of the metal complexes of Oligo-bpym also show an absorption peak attributed to the MLCT band. The water-soluble Ru complex of Oligo-bpy catalyzes visible-light-induced H2 evolution from aqueous media in the presence of Pt cocatalyst and triethylamine.
Conversion of Ag0 into Ag2+ in γ-Irradiated Organic Solid Solutions at 77 K as Studied by ESR
Authors: Matsuura Kaoru , Hase Hirotomo , Arai Shigeyoshi , Miyatake Yoko , Hoshino Mikio 
Published: December 2003

Abstract
Ethanol and 2-methyltetrahydrofuran (MTHF) solutions of silver perchlorate were irradiated with γ-rays at 77 K. Two kinds of silver atoms (Ag0) and a small amount of dimer cations (Ag2+) were formed in both solids immediately after irradiation. On storing at 77 K, both Ag0 species reacted with Ag+ to form Ag2+ in ethanol, while in MTHF only the minor Ag0 species reacted, resulting in less growth of Ag2+ yield than in ethanol. The mechanism for the formation of Ag2+ has been discussed in terms of thermal diffusion and quantum tunneling.
Crystalline-State Racemization of Cobaloxime Complexes. 21. Racemization of a Bulky (R)-1,2-Bis(ethoxycarbonyl)ethyl Group
Authors: Sato Hiroyuki , Ohashi Yuji 
Published: December 2003

Abstract
Three cobaloxime complexes with a chiral 1,2-bis(ethoxycarbonyl)ethyl group bonded to the cobalt atom: [(R)-1,2-bis(ethoxycarbonyl)ethyl]bis(dimethylglyoximato-N,N′)[(S)-1-phenylethylamine]cobalt(III), 1, [(R)-1,2-bis(ethoxycarbonyl)ethyl]bis(dimethylglyoximato-N,N′)(pyridine)cobalt(III), 2, and [(R)-1,2-bis(ethoxycarbonyl)ethyl]bis(dimethylglyoximato-N,N′)(propylamine)cobalt(III), 3, were analyzed by X-rays. The cell dimensions of 2 were remarkably changed when the crystal was irradiated with a xenon lamp. The structure after the irradiation indicated that the chiral 1,2-bis(ethoxycarbonyl)ethyl group was changed to the disordered racemates retaining the single crystal form. The other two crystals showed no change after the irradiation in the same conditions. Comparing the reaction cavities among four crystals analyzed so far, the shape rather than size of the cavity may play an important role in the crystalline-state racemization.
Fluctuations in Multicomponent Solutions and Light Scattering Intensity Revisited
Authors: Oshiman Hiroto , Momose Takamasa , Shida Tadamasa 
Published: December 2003

Abstract
The fluctuation of physical quantities in multicomponent solutions and its relevance to the light scattering intensity are reexamined. The fluctuation of thermodynamic quantities in solutions is derived without any constraint to the system, such as the assumption of constant volume or constant mass. Based on the mean square correlation among the fluctuation of thermodynamic variables, a general expression for the light scattering intensity is obtained. The present result coincides with that derived by assuming artificial constraints to the volume or the mass of the solutions, the procedure which has been adopted customarily by previous workers. The relation between the fluctuation of density and the mass fraction is also discussed.
Three Distinct Solvated Structures of p-Nitroaniline in Acetonitrile/CCl4 Mixed Solvents: A Combined Singular Value Decomposition Analysis of Ultraviolet Absorption and Raman Spectra
Authors: Mohanalingam Kathaperumal , Yokoyama Daisuke , Kato Chihiro , Hamaguchi Hiro-o 
Published: December 2003

Abstract
Ultraviolet absorption and Raman spectra of p-nitroaniline (pNA) have been measured in acetonitrile/CCl4 mixed solvents for seventeen different fractions of acetonitrile. The observed spectral changes were interpreted with the use of a combined singular value decomposition (SVD) analysis, in which the ultraviolet absorption and Raman spectra were combined into one set of spectra. A least-squares fitting analysis was carried out for the SVD decomposed spectra and their amplitudes, using a model in which three distinct species of pNA, the 1 : 0, 1 : 1, and 1 : 2 species, exist in equilibrium. Here, the 1 : 0, 1 : 1, and 1 : 2 species have 0, 1, and 2 acetonitrile molecules associated with pNA. Three intrinsic ultraviolet absorption and Raman spectra have been obtained as a result of the fitting analyses. The three intrinsic spectra show different degrees of charge transfer in the three different solvated forms of pNA. Two equilibrium constants, K1 for the equilibrium between the 1 : 0 and 1 : 1 species and K2 for 1 : 1 and 1 : 2, have been determined. These equilibrium constants give the standard free energy changes for the association of acetonitrile with pNA. A microscopic and quantitative view on the solvation of pNA in acetonitrile/CCl4 mixed solvents has thus been established.
Study of Electrode Kinetics of Zn2+–l-Amino Acids–γ-Picoline Mixed System
Authors: Vajhallya Seema , Khan Farid 
Published: December 2003

Abstract
Polarography was used to determine the stability constants (log β) of ternary complexes of Zn2+ with l-lysine, l-ornithine, l-threonine, l-serine, l-phenylglycine, l-phenylalanine, l-glutamic acid, and l-aspartic acid as primary ligands and γ-picoline as secondary ligand at pH = 8.50 ± 0.01 and ionic strength μ = 1.0 mol dm−3 NaClO4 at 25 °C. The waves of Zn and its complexes were quasireversible. Zn formed 1 : 1 : 1, 1 : 1 : 2, and 1 : 2 : 1 complexes. The kinetic parameters viz. the standard rate constant (k), degree of irreversibility (λ), and charge transfer coefficient (α) were also determined. The trend of the stability constants of Zn2+complexes with these amino acids and γ-picoline is l-lysine &lt; l-ornithine &lt; l-threonine &lt; l-serine &lt; l-phenylglycine &lt; l-phenylalanine &lt; l-glutamic acid &lt; l-aspartic acid, which is explained on the basis of the sizes and basicities of the primary ligands.
Determination of Basicity of Core X and Terminal Y Ligands (X, Y = S and Se) of Reduced, Oxidized, and Super-Oxidized Forms of [Fe4X4(YAd)4]2− (Ad = 1-Adamantyl) in Aqueous Solutions
Authors: Nakamoto Masami , Fukaishi Kenji , Tagata Tsuyoshi , Kambayashi Hide , Tanaka Koji 
Published: December 2003

Abstract
A series of [Fe4X4(YAd)4]2− (X, Y = S, Se; Ad = 1-adamantyl) were prepared as a model of high potential iron–sulfur proteins. Hydrolysis of the clusters was effectively depressed in aqueous poly[2-(dimethylamino)hexanamide] (PDAH) solutions due to the enbedding effect in hydrophobic environment and/or inhibition of dissociation of the terminal ligand into the aqueous media. Cyclic voltammetry of those clusters in aqueous PDAH solutions showed pH-dependent redox potentials of not only the [Fe4X4]+/2+ but also the [Fe4X4]2+/3+ (X = S and Se) couples, resulting from redox-linked protonation reactions of three oxidation states of [Fe4X4(YAd)4]n− (n = 1—3). pKavalues of the reduced, oxidized, and super-oxidized forms of [Fe4X4(YAd)4]2− were determined by computer simulation of the pH dependent redox potentials. The basicity of the core X (X = S and Se) of three oxidation states of [Fe4X4(YAd)4]n− (n = 1, 2, 3) was stronger than the terminal YAd (Y = S and Se) ligands: in the case of the mono-protonated [Fe4X4(YAd)4]3−(H+) and [Fe4X4(YAd)4]2−(H+), basicity of the terminal YAd ligand of [Fe4X4(YAd)4]2−(H+) becomes stronger than that of core X, although the core X of [Fe4X4(YAd)4]3−(H+) still showed a stronger basicity than those of terminal YAd ligands.
Complex Formation and Redox Reactions in Copper–Pterin Cofactor Systems. Possible Relevance to Phenylalanine Hydroxylase
Authors: Funahashi Yasuhiro , Kato Chie , Yamauchi Osamu 
Published: December 2003

Abstract
With a view to understanding better the redox reactions between the metal center and the pterin cofactor in phenylalanine hydroxylase (PAH) and the effects of possible sulfur coordination to the metal center, we isolated model copper(II) complexes of 2,2′-bis(2-pyridylmethyl)amine (dpa), S-ethyl-N-(2-pyridylmethyl)aminoethanethiol (pat), and pterin-6-carboxylate (ptc), [Cu(dpa)(ptc)]·H2O·CH3OH (1), [Cu(pat)(Cl)]Cl·H2O (2), and [Cu(pat)(ptc)]·3H2O (3), of which 1 and 3 contained ptc as a cofactor model. These binary and ternary Cu(II) complexes were studied by X-ray diffraction, spectroscopic, and electrochemical methods. Redox reactions between Cu(II) complexes ([Cu(dpa)]2+ or 1) and tetrahydropterins (5,6,7,8-tetrahydro-6,7-dimethylpterin (h4dmp) or 5,6,7,8-tetrahydropterin-6-carboxylate (h4ptc)) were also investigated by time-resolved spectroscopic methods. The molecular structures of 1, 2, and 3 showed that dpa and pat occupy three equatorial positions and that ptc in 1 and 3 is vertically coordinated. Complexes 2 and 3 exhibited relatively high redox potentials due to thioether sulfur coordination (E1/2 = −0.06 and −0.18 V vs. Ag/AgCl, respectively) in contrast to [Cu(dpa)]2+ and 1 (E1/2 = −0.32 and −0.39 V, respectively). Coordination of h4dmp and h4ptc to the Cu(II) center of [Cu(dpa)]2+ and 2 to form ternary complexes was detected by the ESR spectra with the use of the rapid mix-freeze-quenching technique; subsequent redox reactions were concluded from the absorption spectral changes.
Selective N–N and W–N Bond Cleavage of Tungsten Pyrrolylimido Complexes Derived from Tungsten Dinitrogen Complex
Authors: Sasagawa Takao , Seino Hidetake , Ishii Youichi , Mizobe Yasushi , Hidai Masanobu 
Published: December 2003

Abstract
Treatment of the pyrrolylimido complexes cis,trans-( [WX2(NNCH=CHCH=CH)(L)(PMe2Ph)2] ) (X = Cl, Br, I; L = PMe2Ph (6), CNBut, CO, PhC≡CH, PhCHO, Br) with LiAlH4or KOH produced pyrrole, 1-aminopyrrole, and ammonia, where both the reaction conditions and the nature of the ligand L showed significant effects on the pyrrole/1-aminopyrrole selectivity. Thus, reduction of cis,trans-( [WBr2(NNCH=CHCH=CH)(CNBut)(PMe2Ph)2] ) with LiAlH4 followed by methanolysis gave pyrrole and ammonia in almost quantitative yields. On the other hand, 1-aminopyrrole was quantitatively produced from the complexes by the reaction of KOH in alcohol when L = CO, PhC≡CH, or PhCHO. While analogous treatment of 6 with KOH in ethanol afforded both pyrrole and 1-aminopyrrole with low selectivity under N2 atmosphere, 1-aminopyrrole was produced from 6 in excellent yield under 1 atm of CO. On the contrary, pyrrole and ammonia were selectively formed from the reaction of 6b (X = Br) with KOH/18-crown-6 ether in THF. Replacement of one of the PMe2Ph ligands in the diazoalkane complex cis,mer-[WBr2(NN=CMeCH2CH2COMe)(PMe2Ph)3] (12) by CO or CNBut facilitated the cyclization of the diazoalkane ligand to provide the (2,5-dimethylpyrrolyl)imido complexes cis,trans-( [WBr2(NNCMe=CHCH=CMe)(L)(PMe2Ph)2] ) (L = CO 14; L = CNBut 15), although complex 12 failed to undergo the ring closure by aqueous HBr. 2,5-Dimethylpyrrole and 1-amino-2,5-dimethylpyrrole were selectively obtained by LiAlH4 reduction of 15 and by treatment of 14 with KOH in EtOH, respectively.
Synthesis and Redox Properties of Amino Acid-Bridged Dinuclear Iron(III) Complexes
Authors: Umakoshi Keisuke , Tsuruma Yasuhiro , Oh Chang-Eon , Takasawa Akira , Yasukawa Hana , Sasaki Yoichi 
Published: December 2003

Abstract
A series of dinuclear iron(III) complexes with μ-O,O′-bridging amino acids (as zwitter ionic forms) have been prepared: [Fe2(μ-O)(μ-amino acid)(tpa)2](ClO4)4 (tpa = tris(2-pyridylmethyl)amine; amino acid = l-valine (1), l-proline (2), l-alanine (3), l-tyrosine (4), l-tryptophan (5), l-phenylalanine (6), l-alanyl-l-alanine (7)). Among them, 1, 2, and 7 were structurally characterized at 163 K. The non-equivalent ligating mode of the two tpa ligands is common to all the three complexes. The amino acid bridged complexes exhibit irreversible one electron reduction waves with splitting or accompanying shoulders. The bulk electrolysis of these complexes confirmed that the total number of electrons involved in the reduction is one; i.e. Fe2(III, III) → Fe2(II, III). Addition of acid or base leaves positive or negative components, respectively, of the splitting wave. This phenomenon was interpreted as a proton coupled electron transfer where the protonated and deprotonated amino acid bridged species are reduced at different potentials. Magnetic susceptibility measurements in the temperature range, 2—300 K, revealed antiferromagnetic coupling with J = −116, −129, −120, −120, and −129 cm−1 for 1, 2, 4, 6, and 7, respectively (H = −2JS1·S2; S1 = S2 = 5/2).