bluuebunny/crossref_metadata_2025_split huggingface dataset:
A New Synthetic Method of Alkyl Carbonocyanidate N-Oxides
Authors: Shimizu Tomio , Hayashi Yoshiyuki , Teramura Kazuhiro 
Published: July 2006

Abstract
A thermal decomposition of dimethyl nitromalonate to bis(carbomethoxy)furoxan was observed at about 170 °C. In the presence of dipolarophiles, an intermediate, methyl carbonocyanidate N-oxide MeOCOC≡N→O, could be trapped as cycloadducts in good yields by the 1,3-dipolar cycloaddition. Treatment of dimethyl nitromalonate in mesitylene at the refluxing temperature resulted in a formation of methyl 2-(hydroxyimino)-2-(2,4,6-trimethylphenyl)acetate.
Hydroxylation of Cedrol by m-Chloroperbenzoic Acid. Synthesis of an Epimer of the Alleged “Senoxydene”
Authors: Tori Motoo , Matsuda Reiko , Asakawa Yoshinori 
Published: July 2006

Abstract
Cedrol was hydroxylated by m-chloroperbenzoic acid to give four tertiary alcohols and two secondary alcohols, one of which was converted into an epimer of “senoxydene” in four steps.
Ring-cleavage Reactions of Aromatic Hydrocarbons Studied by FT–IR Spectroscopy. I. Photooxidation of Toluene and Benzene in the NOx–Air System
Authors: Bandow Hiroshi , Washida Nobuaki , Akimoto Hajime 
Published: July 2006

Abstract
The products of the atmospheric photooxidation reactions of toluene and benzene were analyzed quantitatively using long-path FT–IR spectroscopy. Methylglyoxal (only in the case of toluene), glyoxal and maleic anhydride were observed as aromatic ring-cleavage products. In the toluene photooxidation, yields of methylglyoxal, glyoxal, and maleic anhydride were 14±4, 15±4, and 4.0±0.4% (mole/mole), respectively. The formation of small molecules, formaldehyde and formic acid, was observed. It is suggested that the precursor of the ring-cleavage reaction is OH–aromatics–O2 adducts, and that the α-dicarbonyls and unsaturated γ-dicarbonyls are produced by ring cleavage after cyclization of the OH–aromatics–O2 adduct. The observation of maleic anhydride is considered as an evidence of the aromatic ring cleavage into C2 and C4 fragments. The fraction of the ring cleavage process in the total reaction is 29 and 15–20% in the cases of toluene and benzene, respectively.
Effect of Methyl Substitution in 1,2-Ethanediaminenickel(II) Complexes upon Their Thermal Stabilities
Authors: Tsuchiya Ryokichi , Uehara Akira , Suzuki Masatatsu , Matsuda Akira 
Published: July 2006

Abstract
The enthalpy changes (ΔH) in the reaction of three types of the nickel(II) complexes, [Ni(AA)2(H2O)2]X2·nH2O, [NiX2(AA)2], and [Ni(AA)2]X2, with aqueous potassium cyanide solution were calorimetrically measured at 25 °C, where AA denotes a diamine selected from 1,2-ethanediamine (en), N-methyl-1,2-ethanediamine (N-men), N,N-dimethyl-1,2-ethanediamine (NN-dmen), N,N′-dimethyl-1,2-ethanediamine (NN′-dmen), and N,N,N′-trimethyl-1,2-ethanediamine (NNN′-tmen); X is Cl, Br, I, NO3, or ClO4; n=0, 2, or 3. The thermal stabilities of the complexes in the solid state defined by the enthalpy changes (not by the free energy changes) were compared with one another, so that the thermal stabilities of the complexes are highly dependent on numbers and/or positions of N-methyl groups on diamines. In the series of [NiX2(AA)2] and [Ni(AA)2]X2 type complexes, the NN′-dmen complexes are the most stable. Except for the NN′-dmen complexes, as the numbers of N-methyl group(s) contained in the diamines increase, the complexes have the tendency to become less stable. The relative thermal stabilities of the present complexes were discussed in terms of the basicities of diamines and steric effect of N-methyl groups.
Class Separation of Higher Hydrocarbons by Thin-Layer Chromatography with Flame Ionization Detection
Authors: Yamamoto Yojiro 
Published: July 2006

Abstract
3-Aminopropyl or 3-cyanopropyl-bonded silica-gel thin-layer rods (Chromarod NH2–SII or CN–SII) were prepared and a hydrocarbon class separation of higher hydrocarbons has been investigated by flame ionization detection–thin-layer chromatography (FID–TLC) with those rods as the stationary phase. The resolutions (Rs) of the class separation with Chromarod NH2–SII and CN–SII were compared with those with conventional rods on the market, which were silica-gel-sintered (Chromarod S and SII) and alumina-gel-sintered (Chromarod A) thin-layer rods. An adequate class separation of higher hydrocarbons into Saturates (Sa), Monoaromatics (M-Ar), Diaromatics (D-Ar) and Triaromatics (T-Ar) could be performed by FID–TLC with Chromarod NH2–SII or CN–SII.
Kinetic Studies of Fast Equilibrium by Means of High-performance Liquid Chromatography. X. Separation of Rotamers of Acetanilides
Authors: Moriyasu Masataka , Kawanishi Kazuko , Kato Atsushi , Hashimoto Yohei , Sugiura Makiko 
Published: July 2006

Abstract
The restricted rotation about the carbonyl–nitrogen bonds of acetanilides has been investigated by means of high-performance liquid chromatography. The separation of two rotamers (E- and Z-forms) of acetanilides has been achieved at low temperatures. The presence of a very small amount of the E-form has been confirmed for 3-, 4-, and non-substituted acetanilides. The ratios of the E- and Z-forms in different solvents have also been determined. By combining the HPLC and NMR results, it has been elucidated that the molecular structure of acetanilide in solution can be described in terms of an equilibrium between a large amount of the nearly planar Z-form and a small amount of the twisted E-form.
Kinetic Studies of Solvent and Pressure Effects on Thermochromic Behavior of 6-Nitrospiropyran
Authors: Sueishi Yoshimi , Ohcho Masanobu , Nishimura Norio 
Published: July 2006

Abstract
The thermal conversion of 6-nitrospiropyran from a merocyanine form to a spiro form was studied in various solvents and under high pressures. The rates of the thermal conversions were remarkably retarded in polar solvents, and a Kirkwood plot of the rate constants showed a large downward deviation as the solvent polarity increased. The rate constants (on a logarithmic scale) were linearly related to Kosower’s Z-values. The values of the activation volumes were positive and divided into two groups: ΔV≠≈10 cm3 mol−1 (in nonpolar solvents) and ΔV≠≈20 cm3 mol−1 (in polar solvents). These findings suggest that for the reaction in polar solvents, specific interactions are operating and that the thermal conversion proceeds via a transition state which is much less polar than the initial state.
NQR Study of Phase Transitions in SbCl3·(C6H5)2NH2+Cl− and 2SbCl3·C6H5OCH3
Authors: Ishihara Hideta , Okuda Tsutomu , Yamada Koji , Negita Hisao 
Published: July 2006

Abstract
The temperature dependence of 35Cl and 121,123Sb NQR frequencies was measured in SbCl3·(C6H5)2NH2+Cl− between 77 and 300 K. A phase transition takes place at 108 K and 35Cl NQR lines disappeared above about 275 K. Possible mechanisms of the phase transition and of the disappearance of 35Cl NQR lines were suggested. The phase transition in 2SbCl3·C6H5OCH3 was investigated by the NQR technique. The temperature dependence of the splitting of the 121Sb(ν1) NQR lines in the low-temperature phase gave a critical exponent of β=1⁄2 near the transition point Tc. A Zeeman-effect experiment revealed that the crystals in both low- and high-temperature phases were monoclinic.
Electrochemical Behavior of Dibutyltin(IV) Compounds and Their Determination at ppb Levels by Differential Pulse Anodic Stripping Voltammetry
Authors: Kitamura Hideki , Sugimae Akiyoshi , Nakamoto Masao 
Published: July 2006

Abstract
The electrochemical behavior of dibutyltin(IV) compounds (Bu2SnX2) (X=chloride, laurate (L), and 6-methylheptyl maleate (MHM)) in 50% (v/v) and 80% (v/v) ethanol–water media (apparent pH 7.3) containing 0.002% Triton X-100 has been investigated by polarography and cyclic voltammetry. It has been found that Bu2SnX2 gives a two-electron transfer step at about −0.8 V vs. SCE, which consists of very close two one-electron steps, and a two-electron step at about −1.4 V in both media. Over the potential range of either side of the first reduction wave, both Bu2SnX2 and their reduction products are significantly adsorbed on the surface of a mercury electrode in 50% (v/v) ethanol, but not in 80% (v/v) ethanol. The adsorbed reduction products are readily re-oxidized at the mercury electrode in 50% ethanol. The re-oxidation peak was successfully utilized for the determination of traces of Bu2SnCl2 by means of the differential pulse anodic stripping voltammetry (DPASV) over the concentration range of 3–50 ppb (μg dm−3) at the deposition time of 60 s. The DPASV behavior of Bu2SnX2 (X=chloride, L, MHM, and 1-dodecanethiolate) has been investigated in a 50% ethanol medium in detail. Further, a procedure has been developed for determining Bu2SnX2 in natural water down to ppb levels.
Hydroxylation of Aliphatic Compounds with m-Chloroperbenzoic Acid. Synthesis of Hydroxylated Vitamin K1 Analogues
Authors: Tori Motoo , Sono Masakazu , Asakawa Yoshinori 
Published: July 2006

Abstract
Pristane and 1,5,9,13-tetramethyltetradecyl acetate were treated with m-chloroperbenzoic acid in chloroform under reflux to afford hydroxylated derivatives, respectively. The products, 13- and 9-hydroxy-1,5,9,13-tetramethyltetradecyl acetates, were converted to hydroxylated vitamin K1 analogues via the corresponding hydroxyphytols.
Boron Trifluoride Etherate-catalyzed Backbone Rearrangement of 13β,18β-Epoxybaccharan-3β-yl Acetate. A Sequential Migration of Two Methyl Groups and a Hydride in Biogenetic Direction
Authors: Ohta Shinya , Tori Motoo , Suemura Koji , Irokawa Tomomi , Moriyama Yoshihiko , Tsuyuki Takahiko , Takahashi Takeyoshi , Itai Akiko , Iitaka Yoichi 
Published: July 2006

Abstract
13β,18β-Epoxybaccharan-3β-yl acetate was treated with boron trifluoride etherate in acetic anhydride to afford a complex mixture, in which a formation of backbone rearrangement products, D:C-friedobacchar-9(11)-en- and -7-en-3β-yl acetates together with 3β-acetoxy-D-friedo-13,18-secobacchar-13-en-18-ylidene diacetate was observed. The D:C-friedobacchar-9(11)-ene derivative is the first example of the backbone rearrangement product formed by a sequential migration of two methyl groups and a hydride towards the biogenetic direction in baccharene-shionene series.
Isomers of the (2,4-Pentanedionato)bis(N-phenylethylenediamine)cobalt(III) Ion
Authors: Ouyang Yue , Kojima Masaaki , Fujita Junnosuke 
Published: July 2006

Abstract
By reaction of [Co(acac)2(Ph-en)]+ (acac=2,4-pentanedionate ion, Ph-en=N-phenylethylenediamine) with Ph-en in methanol in the presence of active charcoal, three racemic pairs of diastereomers, Δ(SS) Λ(RR)-, Δ(SR)Λ(RS)-, and Δ(RR)Λ(SS)-trans(N-Ph,N-Ph)-[Co(acac)(Ph-en)2]2+ were obtained. The isomers epimerize in water, methanol, and ethanol to give an equilibrium mixture of the isomers.
Electron Transfer Initiated Replacement of Bromo and Methoxyl Groups with Aryliminodi-, Arylamino-, and Arylthiomagnesium Reagents
Authors: Okubo Masao , Nakagawa Yasuhiro , Yoshida Masatoshi , Yanase Hidenobu 
Published: July 2006

Abstract
The replacement of bromo and methoxyl groups of fluorenone, N-(9-fluorenylidene)aniline, and α-benzylideneacetophenone with ArSMgBr(S), ArNHMgBr(NH), and ArN(MgBr)2(N) were examined. The distribution of products obtained in the reactions with the reagents including ArMgBr(C) and ArOMgBr(O) were explained in terms of relative electron-donating abilities of reagents: C&gt;S&gt;NH&gt;N&gt;O.
Ultrasounds in Synthetic Reactions. III. Reduction of Organic Halides with Nickel(II) Chloride–Zinc–Water
Authors: Yamashita Junzo , Inoue Yoshio , Kondo Takashi , Hashimoto Harukichi 
Published: July 2006

Abstract
The reductive dehalogenation of aryl chlorides as well as other organic halides was facilitated with nickel(II) chloride–zinc–water in hexamethylphosphoric triamide irradiated with ultrasound.
Decarboxylative Photoaddition of 3-Butenoate Anion to 1-Methyl-2-phenyl-1-pyrrolinium Perchlorate via Electron-transfer Reaction
Authors: Kurauchi Yoshiaki , Ohga Kazuya , Nobuhara Hideo , Morita Shigeru 
Published: July 2006

Abstract
The photolysis of 1-methyl-2-phenyl-1-pyrrolinium perchlorate (1) with a 3-butenoate anion in an aqueous solution efficiently gives a 2-allylpyrrolidine adduct. Mechanistic studies demonstrate that the photo-reaction is induced by a one-electron transfer from 3-butenoate to the singlet excited-state of 1.
Preferred Conformation of 1-Phenyl-2-propanol. Ab initio and Molecular Mechanics Calculations with Geometry Optimization
Authors: Abe Kazuhisa , Hirota Minoru , Morokuma Keiji 
Published: July 2006

Abstract
The most stable conformation of 1-phenyl-2-propanol, optimized by ab initio and molecular mechanics (MM2) calculations, is a phenyl-methyl anti and phenyl-OH gauche conformation with an intramolecular OH-π hydrogen bond.
Synthesis of Ketazines from Dinitrogen Coordinated to Tungsten
Authors: Hidai Masanobu , Kurano Masa-aki , Mizobe Yasushi 
Published: July 2006

Abstract
When treated with a methanol/acetone mixture at 50 °C, the complex trans-[W(N2)2(PPh2Me)4] gives acetone azine in moderate yield, although the yield is slightly lower than that from cis-[W(N2)2(PMe2Ph)4]. Under UV irradiation, these dinitrogen complexes produce acetone azine even at room temperature.
Direct N-Allylation of Amides with 2-Allylisourea Catalyzed by Palladium(0)
Authors: Inoue Yoshio , Taguchi Masaaki , Hashimoto Harukichi 
Published: July 2006

Abstract
Direct N-allylation of amides catalyzed by palladium(0) complexes took place under neutral conditions by the use of 2-allylisourea as the allylating agent.
Gas Chromatography–Mass Spectrometry of N-Trifluoroacetyl Trimethylsilyl Esters of Some Iminodicarboxylic Acids
Authors: Kawashiro Katsuhiro , Morimoto Shiro , Yoshida Hideyuki 
Published: July 2006

Abstract
The simultaneous N-trifluoroacetylation and O-trimethylsilylation of some iminodicarboxylic acids were studied by the use of a mixture of α,α,α,α′,α′,α′-hexafluoro-N-methyldiacetamide and N,O-bis(trimethylsilyl)trifluoroacetamide, as a derivatizing reagent. The resulting N-trifluoroacetyl trimethylsilyl ester derivatives gave rather complicated mass spectra with molecular (M+) and M–15 (loss of CH3) ions upon electron impact at 20 eV.
Synthesis of Guanidino-1,3,5-triazines Using DMF
Authors: Iio Kokoro , Ichikawa Eiichi 
Published: July 2006

Abstract
2,4,6-Triguanidino-1,3,5-triazine and 2,4,6-tris(3-methylguanidino)-1,3,5-triazine were synthesized in 42 and 52% yields, respectively, by the cyclotrimerization of cyanoguanidine and 1-methyl-3-cyanoguanidine using DMF as a solvent in the presence of hydrogen chloride. 1-Phenyl-3-cyanoguanidine, 1,2-dimethyl-3-cyanoguanidine, and 2-imidazolidinylidenecyanamide, however, were cyclodimerized to the corresponding guanidino-1,3,5-triazines in a similar manner.
Electronic Structure and Lattice Distortion of Benzene Anion
Authors: Kimura Minoru , Kawabe Hiroyuki , Nishikawa Kiyoshi , Aono Shigeyuki 
Published: July 2006

Abstract
Electronic structure, especially the charge density or the spin density of the benzene anion (exactly dihydrophenylide ion) is investigated by the Hubbard Hamiltonian with vibronic interaction. Two limiting cases, i.e., I⁄β&lt;&lt;1 and I⁄β&gt;&gt;1 (I is the electron repulsion on site, β the absolute value of transfer integral.) are analytically examined. For whole range of this ratio, the numerical calculation has been performed. The actual system falls into the latter case, where the electron correlation produces a strong effect on the spin density distribution.
ESR Spectra of Benzene Anion
Authors: Kimura Minoru , Kawabe Hiroyuki , Nishikawa Kiyoshi , Aono Shigeyuki 
Published: July 2006

Abstract
Based on the spin density calculated in our previous paper, the ESR spectra of the benzene anion (exactly the dihydrophenylide ion) are analyzed by the Bloch equation. A hyperfine spectrum broader than those of usual aromatic radicals attributes to the chemical exchange process that the ion in question surrounded by solvent molecules undergoes a rotational motion characterized by the time τ which is the life time of chemical exchange. The line shape for each hyperfine spectrum is given in terms of 1⁄T2 and τ under the condition of τ⁄T2&lt;&lt;1.
Structure of Ni(II)– and Zn(II)–Glycinato Complexes in Aqueous Solution Determined by EXAFS Spectroscopy
Authors: Ozutsumi Kazuhiko , Yamaguchi Toshio , Ohtaki Hitoshi , Tohji Kazuyuki , Udagawa Yasuo 
Published: July 2006

Abstract
The EXAFS spectroscopy has been used to determine the structure of the bis(glycinato) complexes of nickel(II) and zinc(II) ions of low solubility (0.1–0.3 mol dm−3) in aqueous solution. The structural parameters were evaluated by the least-squares analysis both in the reciprocal and in the real spaces on the basis of various standard samples of known structures. Analysis of the EXAFS spectra of aqueous solutions containing the bis(glycinato) complexes of nickel(II) and zinc(II) ions has revealed that both complexes have two additional water molecules bound to the central metal ions to complete the octahedral structure. The structure of the nickel(II) complex is similar both in crystals and in solution, whereas the bis(glycinato)zinc(II) in solution is coordinated with two water molecules instead of two neighboring glycinato carbonyl oxygen atoms in the solid state.
Preparation and Stereochemistry of Cobalt(III) Complexes Containing 1,1,10,10-Tetraphenyl-4,7-diaza-1,10-diphosphadecane or 2,11-Dimethyl-5,8-diaza-2,11-diphosphadodecane, R2PCH2CH2NHCH2CH2NHCH2CH2PR2 (R=C6H5 or CH3)
Authors: Atoh Masamichi , Kashiwabara Kazuo , Fujita Junnosuke 
Published: July 2006

Abstract
New quadridentate phosphine ligands, 1,1,10,10-tetraphenyl-4,7-diaza-1,10-diphosphadecane (pp-PNNP) and 2,11-dimethyl-5,8-diaza-2,11-diphosphadodecane (mm-PNNP), were prepared from (ClCH2CH2NHCH2)· 2HCl and NaPR2 (R=C6H3, CH3) and purified through their Ni(II) complexes. Seven new cobalt(III) complexes containing the phosphine ligand were prepared: [CoX2(pp- or mm-PNNP)]n+(X2=(Cl)2, (NCS2), C5H7O2−(2,4-pentanedionate ion), and CO32−). Four complexes of [CoX2(pp- or mm-PNNP)]+ (X=Cl, NCS) afforded only a trans(X,X) isomer, and [Co(acac)(pp- or mm-PNNP)]2+ and [Co(CO3)(pp-PNNP)]+ complexes yielded a cisβ isomer. The geometrical structures were assigned on the basis of the NMR and visible-ultraviolet absorption spectra.
Reduction of Aryl Halides and N-Hydroxy Nitrogen Compounds in Fast Atom Bombardment Mass Spectrometry
Authors: Nakamura Takemichi , Nagaki Hidemi , Kinoshita Takeshi 
Published: July 2006

Abstract
Aromatic halogenated compounds and N-hydroxy nitrogen compounds were reduced to dehalogenated and deoxy analogs, respectively, in the fast atom bombardment ion source of a mass spectrometer. The reaction was found to occur in the liquid phase on exposure to a neutral fast atom beam.
Chemical Synthesis of a Heat-stable Enterotoxin of Yersinia enterocolitica
Authors: Yoshimura Shoko , Shimonishi Yasutsugu 
Published: July 2006

Abstract
A peptide with the amino acid sequence Ser–Ser–Asp–Trp–Asp–Cys–Cys–Asp–Val–Cys–Cys–Asn–Pro–Ala–Cys–Ala–Gly–Cys of heat-stable enterotoxin (ST) produced by Yersinia enterocolitica was synthesized by a conventional method. The synthetic peptide was found to be identical with the corresponding natural peptide by chemical and physicochemical criteria, thus establishing the amino acid sequence of an ST of Yersinia enterocolitica.
A Convenient Synthesis of 6-Hydroxy-7,9-bis(p-methoxybenzyl)-5-methylene-2-oxa-7,9-diazabicyclo[4.2.2]decane-8,10-dione
Authors: Yamaura Masanori , Suzuki Tsuneji , Hashimoto Hironobu , Yoshimura Juji , Shin Chung-gi 
Published: July 2006

Abstract
The title compound, the key intermediate for a total synthesis of bicyclomycin, was synthesized from N,N′-diacetyl anhydroglycine through twelve steps. The three-carbon branch for the construction of the bicyclic skeleton was introduced to the 2,5-piperazinedione ring as an alkylidene substituent, and then the olefinic function was converted into a diol function. The formation of bicyclic ring was achieved by treatment with N-bromosuccinimide followed by the intramoleculer substitution of the primary hydroxyl group in the side chain, and finally the secondary hydroxyl group was converted to the methylene function by an improved Peterson reaction.
The Carbon-13 NMR Spectra and Electronic Structure of 3H-Phenoxazin-3-ones
Authors: Hasegawa Kan-ichi , Ueno Yoshio 
Published: July 2006

Abstract
The 13C NMR chemical shifts of 3H-phenoxazin-3-one (1) and eighteen of its derivatives are reported. The chemical shifts of 1 can be explained in terms of a successive polarization of the π-conjugated framework by an electron-withdrawing carbonyl group and a π-donating ether oxygen. The principal factor solution for the chemical shifts of the 2-substituted 3H-phenoxazin-3-ones suggests that the first and the second factors collectively controlling the 2-substituent effect are electronic and steric effects, respectively. A dual substituent parameter analysis elucidated the transmission modes of the polar and resonance effects of the 2-substituents, and that the first and the fourth factor loadings multiplied by the corresponding standard deviation of the chemical shifts correlate with the CNDO/2 substituent-induced σ and π charge densities.
Intermolecular Bromine Transfer of 2-Amino-7-bromotropone Derivatives Catalyzed by Strong Acid
Authors: Wakabayashi Hidetsugu , Ishikawa Sumio , Okai Harue , Nozoe Tetsuo 
Published: July 2006

Abstract
Upon heating acetic acid containg a trace amount of coned sulfuric acid at 120 °C under nitrogen, 2-bromo-7-(2-hydroxyanilino)tropone (1a) gave 6-bromocyclohepta[b][1,4]benzoxazine (2a) as the main product and cyclohepta[b][1,4]benzoxazine, its 6,8-dibromo derivative and trace amounts of other mono-, di-, and tribromo compounds. This reaction became much more complex in the presence of oxygen. A similar bromine transfer was observed for 2-bromo-7-(dimethylamino)-, 7-(2-hydroxy-5-methylanilino)-, and 7-(2-methoxyanilino)tropone although the cite of the intermolecular bromine transfer depended upon the structures of the substrates and the reaction conditions. In contrast, 2a and 2-amino-5-bromotropone derivatives were completely stable towards the strong acid. Possible reaction pathways for this bromine transfer reaction are discussed.
Interaction of Hydrophobic Cyclic Dipeptides and Acylbenzenes as Studied by Fluorescent Quenching
Authors: Ootubo Toshiro , Kimura Shunsaku , Imanishi Yukio 
Published: July 2006

Abstract
The effect of the hydrophobic interaction on the association in aqueous media of tyrosine-containing cyclic dipeptides and 1-acyl-4-bromobenzenes having various lengths of acyl chain was investigated by quenching of the fluorescence of the former compounds by the latters. In ethanol, the change of fluorescence intensity (I0⁄I) was linearly related to the quencher concentration according to the Stern-Volmer’s plot, which was attributed to a dynamic quenching. In this case, structures of fluorophores and quenchers did not affect the quenching constant. However, in a buffer solution, I0⁄I was linearly related to the quencher concentration according to the Perrin’s plot, which was attributed to a static quenching. Perrin’s quenching constants depended on the structure of fluorophores and quenchers. In some cases, a quencher molecule was bound to a fluorophore by hydrophobic interaction in a favorable arrangement for fluorescent quenching. In aqueous solution, fluorophores and quenchers formed comparatively large aggregates with nonspecific arrangement for fluorescent quenching. In this case, Perrin’s quenching constants were independent of the nature of quenchers and related with the size of formed aggregates.