Structure and behavior of organic analytical reagents : Chelates of 2-(o-hydroxyphenyl)-benzoxazole, 2-(o-hydroxyphenyl)-benzothiazole and 2-(o-hydroxyphenyl)-benzothiazoline.

The reactions of the chelating reagents named in the title, with a number of metal ions, have been studied in order to evaluate the behavior of reagents containing reactive groupings analogous to those of 8-hydroxyquinoline, but so arranged as to form six-membered ring chelates with metal ions. All three reagents have been found to give less stable chelates than 8-hydroxyquinoline, indicating that for this type of reagent, six-membered ring chelates are less stable than five. 2-(o-Hydroxy-phenyl)-benzoxazole and 2-(o-hydroxyphenyl)-benzothiazole have been found to be potentially useful as organic precipitating agents for metal ions, being more selective than 8-hydroxyquinoline, which they somewhat resemble in behavior. In contrast to the oxazole and thiazole, 2-(o-hydroxyphenyl)-benzothiazoline was found to react with most of the metal ions tried. Because of the solubility of its chelates in organic solvents, 2-(o-hydroxyphenyl)-benzothiazoline may be a useful solvent extraction agent for metal ions.     

Structure and behavior of organic analytical reagents : Heats and entropies of formation of several divalent metal chelates of 2- and 4-methyl-8-hydroxyquinoline1

The Calvin-Bjerrum titration technique for the determination of chelate formation constants has been applied to the Cu(II), Ni(II), Co(II), Zn(II) and Mn(II) chelates of 2- and 4-methyl-8-hydroxyquinoline. Measurements were made at several temperatures in order to evaluate ΔH and ΔS values of chelation. The results obtained were interpreted in terms of steric hindrance of the 2-methyl group. In all cases the heats of formation of the chelates of 2-methyl-8-hydroxyquinoline were remarkably morepositive than those for the corresponding chelates of 4-methyl-8-hydroxyquinoline. This large difference in the strengths of the metal-chelate bonds is apparently due to the hindrance of the methyl groups which prevent the close grouping of the two reagent molecules around the metal in chelates of 2-methyl-8-hydroxyquinoline. The lower bond strength in chelates of 2-methyl-8-hydroxy-quinoline is partially compensated by a relatively larger entropy of formation. This is attributed to decreased solvent chelate interaction caused by the shielding of the polar O, N, and metal atoms by the 2-methyl groups. The determination of chelate fortmation constants of 2-phenyl-8-hydroxyqumoline has been carried out to further extend our study of steric effects in metal chelates.     

Structure and behavior of organic analytical reagents : Dimethylglyoxime and its oxygen monomethyl ether

The titration procedure described in previous papers of this series has been applied to a study of some metallic chelates of dimethylglyoxime and of its O-monomethyl ether. Evidence is presented for the existence of dimethylglyoxime chelates with Zn (II), Pb (II), Cd (II), and La (III) in addition to the known Cu (II), Ni (II), and Co (II) complexes. Formation constants are calculated for these complexes, and for those of dimethylglyoxime O-monomethyl ether, on the basis of their most probable structures. The results indicate that the famed specificity of dimethylglyoxime fur nickel does not lie in any special stability of this chclate. but in some other factor, possibly solubility. A comparison of the chelates of dimethylglyoxime with those of its O-ether is discussed in terms of such structural factors as hydrogen bonding and steric hindrance. Heat content and entropy changes have been calculated for the chelation of dimethylglyoxime with Cu (II) and Ni (II) ions.     

Tautomerism of 2-(o-hydroxyphenyl)-azines

The tautomeric properties ofo-hydroxyphenylazines have been investigated by¹⁷O NMR and UV spectroscopy. 2-(o-Hydroxyphenyl)-pyridine and itsp-nitrophenole analog II exist in chloroform or ethanol as a phenol A. In the case of 2-(2-hydroxy-5-nitrophenyl)-quinoline the NH-tautomer is realized, the content of which increases when going to the dinitro-analog IV.

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Die Tautomerie von 2-(o-Hydroxyphenyl)-azinen (Kurze Mitteilung)

Zusammenfassung Es wurden die tautomeren Eigenschaften vono-Hydroxyphenylazinen mittels¹⁷O-NMR und UV-Spektroskopie untersucht. 2-(o-Hydroxyphenyl)-pyridin und seinp-Nitrophenol-Analog II existieren in Chloroform und Ethanol als Phenol A. Das 2-(2-Hydroxy-5-nitrophenyl)-chinolin liegt als NH-Tautomer vor, dessen Anteil im Dinitro-Analog IV noch steigt.

     

Structure of 3-(o-hydroxyphenyl) derivatives of 2-quinoxalone and 2-benzoxazinone

It is shown by IR and UV spectroscopy that the products of the reaction of o-hydroxybenzoylformic acid with o-phenylenediamine and o-aminophenol have the 3-(cyclohexa-3,5-dien-2-onylidene)quinoxalone structure rather than the 3-(o-hydroxyphenyl)-2-quinoxalone structure. 3-(o-Methoxyphenyl)-2-quinoxalone and 3-(o-methoxyphenyl)-3,4-dihydro-2H-benzo-1,4-oxazin-2-one were synthesized as model compounds.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1126–1128, August, 1977.     

Spectrophotometric studies and analytical application of Ce(III) chelates with 1-(2-pyridylazo)-2-naphthol (PAN)

A sensitive procedure for spectrophotometric determination of cerium(III) has been developed. AtpH 10.2 cerium reacts with 1-(2-pyridylazo)-2-naphthol in 40% ethanol to form a red complex which has an absorption maximum at 545 nm. The molar absorptivity at 545 is 3.95·10³ mol^–1. Maximum stability of the complex was attained in pure ethanol. The stoichiometries and structures of the chelates were studied applying conductometric titration, visible spectrophotometry and IR spectrophotometry. The IR spectra revealed that coordination takes place through the N=N, C-OH and pyridyl group.

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Spektrophotometrische Untersuchungen und analytische Anwendung von Ce(III)-Chelaten mit 1-(2-Pyridylazo)-2-naphthol (PAN)

Zusammenfassung Es wurde eine empfindliche Methode zur spektrophotometrischen Bestimmung von Cer(III) entwickelt. Bei einempH von 10,2 reagiert Cer mit 1-(2-Pyridylazo)-2-naphthol in 40% Ethanol unter Bildung eines roten Komplexes mit einem Absorptionsmaximum bei 545 nm (=3 950). Der Komplex besitzt in reinem Ethanol ein Maximum an Stabilität. Die Stöchiometrien und Strukturen der gebildeten 1:1- und 1:2-Chelate wurden mittels konduktometrischer Titration, Elektronen- und IR-Spektrometrie untersucht. Die IR-Daten zeigen, daß die Koordination über N=N, C-OH und Pyridyl erfolgt.

     

Synthesis of 1-(benzothiazol-2-yl)-5-(o-hydroxyphenyl)-1H-1,2,4-triazoles

Recyclization of 4-oxo-1,3-benzoxazinium perchlorates by the action of benzothiazolylhydrazine gave previously unknown benzothiazolyl-substituted 1,2,4-triazoles that attract interest as potential biologically active substances. The structure of the isolated compounds was determined on the basis of their IR and ¹H and ¹³C NMR spectra.     

Structure of 2H-3,4-dihydro-3-(o-hydroxyphenyl)-3-oxo-1,5,3-benzodioxaphosphepine

An x-ray diffraction structural analysis on 2H-3,4-dihydro-3-(o-hydroxyphenyl)-3-oxo-1,5,3-benzodioxaphosphepine was studied. The seven-membered heterocycle in this compound has an almost symmetrical twist conformation with a strong intramolecular 0-H... O=P hydrogen bond.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2648–2650, November, 1990.     

Syntheses and spectrophotometric studies of 2-(2-thiazolylazo)- and 2-(2-benzothiazolylazo)-5-dimethylaminobenzoic acids as analytical reagents: Determination of nickel

2-(2-ThiazolyIazo)-5-dimethylaminobenzoic acid (TAMB) and 2-(2-benzothiazolylazo)-5-dimethylaminobenzoic acid (BTAMB) have been synthesized, and their potential for determinations of metals has been studied spectrophotometrically. Both are extremely sensitive chromogenic reagents for the determination of nickel. Molar absorptivities in aqueous methanol are 0.95 × 10⁵ (TAMB) and 1.2 × 10⁵ (BTAMB). In aqueous methanol, at apparent pH 5–9.5, the system conforms to Beer's law for 0.05–0.5 ppm nickel; Cu, Cr, Co, Pd and Fe interfere, but they can easily be masked.     

2-(2-氨基-3-吡啶基)-苯并咪唑的合成、晶体结构和荧光特性研究

在合成2-(2-氨基-3-吡啶基)-苯并咪唑的基础上,利用NMR(1H、13C、COSY、HSQC和HMBC)、MS、IR和UV进行了详细表征;通过X-ray单晶衍射仪测定了该化合物的晶体结构,实验结果表明该晶体属于三方晶系(空间群R3,a=1.833 7(3)nm,b=1.833 7(2)nm,c=1.777 7(4)nm,V=5.176 4(15)nm3,Z=18),很好地支持了波谱表征的结果。同时,结合密度泛函计算,研究了2-(2-氨基-3-吡啶基)-苯并咪唑的荧光光谱。结果表明,化合物的双荧光不是由同一种异构体发射的,而是来源于不同异构体:长波区500~600 nm的荧光由K构型发射,短波区350~450 nm的发射由异构体E1和E2共同产生,理论预测的光谱与实验一致。     

Sulfonated 1-(2-pyridylazo)-2-naphthols and 2-(2-pyridylazo)-1-naphthols as spectrophotometric reagents: Determination of nickel

Three sulfonated 1-(2-pyridylazo)-2-naphthols and six sulfonated 2-(2-pyridylazo)-1-naphthols were synthesized, and their application to the spectrophotometric determination of metals was studied. The acidity constants of the reagents and the stability constants of the nickel chelates are reported, and the relationship between their properties and the position of the sulfonic acid group is discussed. 1-(2-Pyridylazo)-2-naphthol-6-sulfonic acid (PAN-6S) and 1-(2-pyridylazo)-2-naphthol-7-sulfonic acid (PAN-7S) are sensitive and selective reagents for nickel. The determination of nickel in the presence of cobalt with PAN-6S is described. Extraction of the chelate as the ion-pair with tetraphenylarsonium ions into chloroform is suitable for the determination of 1–10 μg Ni at 570 nm; the molar absorptivity is 56 000 l mol^-1 cm^-1, and interferences are easily avoided.     

Micro-gravimetric determination of cadmium with 2-(o-hydroxyphenyl)-benzoxazole

Summary The authors have developed an exact micro-gravimetric method for the determination of cadmium with 2-(o-hydroxyphenyl)-benzoxazole.

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Zusammenfassung Beschreibung einer exakten mikro-gravimetrischen Methode zur Bestimmung des Cadmiums mit 2-(o-Hydroxyphenyl)-benzoxazol.

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Résumé Les auteurs ont élaboré une micro-méthode gravimétrique exacte pour la détermination du cadmium au moyen de 2-(o-hydroxyphenyl)-benzoxazole.

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Dedicated to Prof. Dr.Hans Lieb on the occasion of his 70th birthday.     

2-(3-羟基-2-吡啶基)-苯并咪唑的合成、晶体结构及光谱研究

在合成2-(3-羟基-2-吡啶基)-苯并咪唑的基础上, 利用NMR (1H, 13C, COSY, HSQC 和HMBC), MS, IR 和UV 进
行了详细表征; 通过X-ray 单晶衍射测定该化合物的晶体结构, 实验结果表明该晶体属于单斜晶系{空间群为P21/c,
a＝14.289(3) Å, b＝10.618(2) Å, c＝12.783(3) Å, β＝93.51(3)°, V＝1935.8(7) Å3, Z＝8}, 很好支持了波谱表征的结果.
2-(3-羟基-2-吡啶基)-苯并咪唑的荧光光谱表明, 该化合物在激发态下存在双质子转移现象, 密度泛函计算结果合理解
释了实验现象.     

1,2- And 1,3-cyclohexanedione bis(2-hydroxybenzoylhydrazone)s as analytical reagents

The synthesis, characteristics and analytical properties of 1,2- and 1,3-cyclohexanedione bis(2-hydroxybenzoylhydrazone)s are described. Spectral characteristics, pK values, hydrolysis resistance, reactions with common cations and their potential use in kinetic analysis are reported.     

1-（4-硝基苯基）-3-（2-苯并咪唑）-三氮烯的合成及与铜（Ⅱ）的显色反应

报道了1-（4-硝基苯基）-3-（2-苯并咪唑）-三氮烯（NPBMT）的合成及其与铜（Ⅱ）的显色反应。在非离子表面活性剂OP存在下,于pH11．5的Na2B4O7-NaOH缓冲介质中,NPBMT与铜（Ⅱ）形成2：1的桔红色络合物,络合物的最大吸收峰为417nm,表观摩尔吸光系数为2．62×10^4 L·mol^-1·cm^-1,10mL溶液中,铜（Ⅱ）量在0—15μg／mL范围内符合比尔定律。该法用于人发和食品中微量铜的测定,测定结果与AAS法相符。     

1,1,1-三[3-（2-苯并咪唑基）-2-氧杂丙基]丙烷镍配合物合成以及结构测定

合成了一个新的三脚架结构配体及其镍配合物的晶体。该晶体属单斜晶系, P2_l/n空间群,a = 1.2151(4) nm, b = 1.5535(5) nm, c = 2.1740(7) nm, β = 90.551(18)°, V = 4.103(2) nm~3, Z = 4, M_r = 834.03, R = 0.0556, wR = 0.1256, μ = 0.541 mm~(-1), F(000) = 1758。配合物中Ni与配体的三个N和 三个O构成六配位变形八面体结构。晶体中存在着分子间氢键,晶体结构依靠库仑 力和氢键作用而稳定。