Thermodynamic functions of Ni(II) complexes with 5-(2-hydroxyphenyl)-pyrazole derivatives. A potentiometric study

Proton-ligand dissociation constants of five biologically important pyrazole derivatives, viz. [5-(2-hydroxyphenyl)-3-(pyridin-3-yl)-4-benzoyl]-pyrazol (HPPBP), [5-(2-hydroxyphenyl)-3-(3-nitrophenyl)-4-(3-pyridinoyl)]-pyrazol (HPNPPP), [5-(2-hydroxyphenyl)-3-(3-nitrophenyl)-4-benzoyl]-pyrazol (HPNPBP), [5-(2-hydroxyphenyl)-3-phenyl-4-(3-pyridinoyl)]-pyrazol (HPPPP), and [5-(2-hydroxyphenyl)-3-(3-nitrophenyl)-4-(2-furoyl) pyrazol (HPNPFP) and metal ligand stability constants of their Ni(II) complexes in 70% (v/v) dioxane-water and 0.1 M KNO₃ were determined at 298.15, 303.15, and 308.15 K by potentiometric method. Thermodynamic functions, such as, free energy change (ΔG ^○), enthalpy change (ΔH ^○) and entropy (ΔS ^○) change for dissociation and complex formation have been estimated form temperature dependence of proton-ligand and metal-ligand stability constants and interpreted in terms of feasibility of these processes.     

Synthesis and Transformations of 4-Phosphorylated 2-Alkyl(aryl)-5-hydrazinooxazoles

Treatment of 1-phosphorylated 2,2-dichloroethenylcarboxamides with excess hydrazine hydrate gives in high yields phosphorylated derivatives of 2-alkyl(aryl)-5-hydrazinooxazoles containing the P(O)(OCH₃)₂, P(O)(OC₂H₅)₂, and P⁺(C₆H₅)₃ClO₄ ^- groups in the 4-position of the ring. The presence of the hydrazine group in these oxazole derivatives was confirmed not only by the spectral data, but also by the reactions with p-toluic aldehyde, p-toluic chloride, and phenyl isothiocyanate.     

Reaction of 2-aryl(methyl)-4-cyano-5-hydrazino-1,3-oxazoles with aryl Isothiocyanates

Accessible 2-aryl(methyl)-4-cyano-5-hydrazino-1,3-oxazoles add to aryl isothiocyanates. The resulting products undergo recyclization to form new 1,3,4-thiadiazole derivatives bearing an acylamino group on C² and an (acylamino)(cyano)methyl group on C⁵. The structure of the new compounds was proved by their IR and ¹H NMR spectra, as well as by conversion in other 1,3,4-thiadiazole derivatives.     

Reaction of cis-Ru(bpy)2Cl2 with 1-phenyl 5-(aminophenyl) 9-(2-pyridyl) benzimidazole derivatives: crystal structures of N-(4-chlorophenyl) imidazo[1,5a] pyridine and cis-[Ru(bpy)2(MeCN)2](ClO4)2

Reaction of 1-phenyl 5-(aminophenyl) 9-(2-pyridyl) benzimidazole derivatives (2) with cis-Ru(bpy)₂Cl₂ in MeCN results in the formation of N-(aryl) imidazo[1,5a] pyridine derivatives (4) and cis-[Ru(bpy)₂(MeCN)₂]²⁺ (5). Crystal structures of N-(4-chlorophenyl) imidazo[1,5a] pyridine (4b) and cis-[Ru(bpy)₂(MeCN)₂](ClO₄)₂ (5) are also reported.     

Recherches sur la formation et la transformation des esters LXXII. Aryl(ou aralcoyl ou alcoyl)amino-2-tétrahydro-m-thiazines ou aryl(ou aralcoyl ou alcoyl)amino-2-dihydro-Δ2-m-thiazines et dérivés

3-Aminopropanol reacts with aryl(or aralkyl or alkyl)isothiocyanates R? N?C?S to yield the corresponding thio-ureas R? NH? CS? NH? (CH₂)₃OH which, refluxed with hydrochloric acid, are cyclized by elimination of water. The cyclization products are identical with the hydrothiazines resulting by elimination of sulfate or phosphate from the sulfuric or phosphoric monoesters of these thio-ureas. The resulting hydrothiazines are either 2-(R-imino)-tetrahydro-m-thiazines (I) or 2-(R-amino)-dihydro-Δ²-m-thiazines (II). Their structure has been established by comparison of their spectra with those of model compounds in one of which the C?N double bond is certainly endocyclic (2-methyl-dihydro-Δ²-m-thiazine), the other presenting an exocyclic C?N double bond (3-methyl-2-phenylimino-tetrahydro-m-thiazine). When R is an aryl group, the C?N double bond is exocyclic (structure I with >C?N? Ar), and one may presume that this structure is stabilized by resonance. When R is an aralkyl or an alkyl group, the C?N double bond is endocyclic (structure II). The nmr spectra were taken with three types of solvent: CDCl₃ or CCl₄; (CD₃)₂SO; CF₃COOH. In CF₃COOH solution the benzylic protons of the hydrothiazine with R = pF? C₆H₄CH₂? couple with NH (J=5,5cps) which confirms the endocyclic position of the C?N double bond in this case.     

UV and MO study on the deprotonation of some 2-aryl-Δ2-1,3,4-oxadiazoline-5-thiones

Substituent effects on the deprotonation processes of a series of 2-aryl-Δ²-1,3,4-oxadiazoline-5-thione (1) derivatives have been studied experimentally as well as theoretically. The acid dissociation constants pK_a have been determined spectrophotometrically in ethanol-water solutions (7.5-92.5%) and vary between 3.76 and 5.80. Semiempirical molecular orbital (MO) calculations (AM1 and PM3) were used for the investigation of the existence of possible tautomeric thione and thiol forms of the studied compounds. Strong correlation between the pK_a values and the deprotonation enthalpies were evaluated.     

Preparation and characterization of symmetrical bis[4-chloro-2-pyrimidyl] dichalcogenide (S, Se, Te) and unsymmetrical 4-chloro-2-(arylchalcogenyl) pyrimidine: X-ray crystal structure of 4-chloro-2-(phenylselanyl) pyrimidine and 2-(p-tolylselanyl)-4-chloropyrimidine

Synthesis of a novel class of multinucleate pyrimidine chalcogen (S/Se/Te) derivatives has been successfully attempted for the first time by the selective substitution of chlorine at the C-2 position of 2,4-dichloropyrimidine with nucleophilic dichalcogenide anion E₂²⁻ (E = S, Se, Te) to afford bis[4-chloro-2-pyrimidyl] dichalcogenide. The highly electrophilic nature of 2,4-dichloropyrimidine compared to aryl chlorides has been further exploited to prepare a variety of 4-chloro-2-(arylchalcogenyl) pyrimidine compounds by substituting the chlorine exclusively at the C-2 position of 2,4-dichloropyrimidine with a variety of chalcogen bearing aryl anions ArE⁻ (Ar = phenyl, 1-naphthyl, p-tolyl, 4,6-dimethyl-2-pyrimidyl, 2-pyridyl, 4-methyl-2-pyridyl). All the newly prepared symmetrical and unsymmetrical pyrimidyl chalcogen compounds have been thoroughly characterized with the help of various spectroscopic techniques viz., NMR (¹H, ¹³C, ⁷⁷Se), FT-IR and mass spectrometry (in representative cases). The crystal structures of 4-chloro-2-(phenylselanyl) pyrimidine and 2-(p-tolylselanyl)-4-chloropyrimidine have been determined by X-ray crystallography.     

A study of chemiluminescence from reaction of bis(2,4,6-trichlorophenyl)oxalate, hydrogen peroxide and diethyl-2-(cyclohexylamino)-5-[(E)-2-phenyl-1-ethenyl]-3,4-furandicarboxylate as a novel fluorescer

The chemiluminescence (CL) arising from reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) with hydrogen peroxide in the presence of a diethyl-2-(cyclohexylamino)-5-[(E)-2-phenyl-1-ethenyl]-3,4-furandicarboxylate as a novel fluorescer (Flu) has been studied. The relationship between the chemiluminescence intensity and concentrations of TCPO, sodium salicylate, hydrogen peroxide and fluorescer is reported. The chemiluminescence parameters including intensity at maximum CL, time at maximum intensity, total light yield, theoretical maximum level of intensity and pseudo-first-order rate constants for the rise and fall of the CL burst (k_r and k_f) were evaluated from computer fitting of the resulting intensity-time plots. The activation parameters E_a, ΔH^Δ, ΔS^Δ and ΔG^Δ for the rise and fall steps were evaluated from the temperature dependence of k_r and k_f values.     

Synthesis and Characterization of New Schiff Bases 2-(2-(2-(Aryl)Methyleneamino)Phenylthio) Ethylthio)-N-((aryl)Methylene)Benzeneamine

A series of Schiff bases containing four to six coordination sites N₂S₂ X₂(X = O,N) 2-(2-(2-(aryl)methyleneamino)phenylthio)ethylthio)-N-((aryl)methylene)benzeneamine (2c–f) were prepared from the reaction of 1,2-di(2-aminophenylthio)ethane (1) with aromatic aldehydes. All compounds were characterized by means IR, mass, ¹H and ¹³C NMR spectroscopy, and elemental analysis, and in the case of 2b with a single crystal X-ray diffraction. The X-ray crystal structure of 2b showed that the resonance occurs between aromatic rings, through the C=N bonds of the molecule.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Synthesis of (-)-11 Hydroxy-delta8-6a, 10a-trans-tetrahydrocannabinol

When (?)-Δ⁸-6a, 10a-trans-THC (THC = Tetrahydrocannabinol), in the form of its diacetate, was irradiated in the presence of oxygen and a sensitizer, followed by reduction with NaBH₄, three allylic alcohols were formed: (?)-8α-and (?)-8β-hydroxy-Δ^9,11-THC (proportion 3:1) and (?)-9α-hydroxy-Δ^7,8-THC. Acetylation of the epimeric 8-hydroxy-compounds with Ac₂O/pyridine gave the corresponding diacetates. When (?)-Δ⁸-6a, 10a-trans-THC, in the form of its tetrahydropyranyl derivative, was heated with m-chloroperbenzoic acid, the two epimeric 8,9-epoxides were formed in equal amounts. These compounds, on treatment with butyllithium, afforded (?)-8α- and (?)-8β-hydroxy-Δ^9,11- 6a, 10a-trans-THC-tetrahydropyranylether. After removing the protecting group and treatment with Ac₂O/pyridine the same diacetates, as formed by photooxygenation of (?)-Δ⁸-THC-acetate, were obtained as a 1:1-mixture. On heating these epimeric diacetates to 290° they underwent allylic rearrangement to (?)-11-acetoxy-Δ⁸-THC-acetate. From this (?)-11-hydroxy-Δ⁸-6a, 10a-trans-THC was obtained by treatment with LiAlH₄.     

Complexes of organolead and organotin ions with 1-(2-pyridylazo)-2-naphthol

The stability constants of the complexes of 1-(2-pyridylazo)-2-naphthol with several organotin and lead ions were determined spectrophotometrically in aqueous 20% (v/v) dioxane and were shown to have very high values. The extraction of the complex of (C₂H₅)₂Pb²⁺ from water into chloroform was studied, and the formation of an extractable (C₂H₅)₂Pb(PAN)(OH) complex is postulated.     

N1-(2-furoylmethyl) and N1-(5-nitro-2- furoylmethyl) derivatives of uracil and its 5-substituted derivatives

The corresponding N₁-(2-furoylmethyl) and N₁-(5-nitro-2-furoylmethyl) derivatives of uracil and its 5-substituted derivatives were obtained by the reaction of 2-bromo- and 5-nitro-2-bromoacetylfurans with uracil, 5-fluorouracil, and thymine. The structures of these compounds as N₁-substituted uracils were proved by a study of the UV spectra at various pH values. The computational method of expanding the UV spectra into individual bands was used.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1268–1270, September, 1971.     

The preparation of some 1-(2-furyl)-2-arylethylenes

Some 1-(2-furyl)-2-arylethylenes, where the furan nucleus is substituted in position 5 with a methyl or p-chlorophenyl group and where the aryl group is phenyl, p-nitrophenyl, α-naphthyl or β-naphthyl, have been prepared by the Perkin reaction and subsequent decarboxylation of the acid. The compounds 1-12 were prepared lor of photochemistry and photoelectron spectroscopy studies. Their geometrical configurations has been established by ¹H nmr and ir spectra.     

PROTONATION CONSTANTS AND SOLVENT DEPENDENT SPIN-CROSSOVER BEHAVIOUR OF IRON(II)-2-(2′-PYRIDYL)BENZIMIDAZOLE COMPLEXES

Abstract

2-(2′-Pyridyl)benzimidazole (pybzim = LH) coordinates to iron(II) as a bidentate and forms the tris-ligated complex, [Fe(pybzim)₃]²⁺ as isolated in the solid. Titration of [Fe(pybzim)₃]²⁺ with base demonstrates the successive deprotonation of the imino hydrogens of the coordinated ligands. Protonation constants for the free ligand, pybzim (Iog₁₀ K ^H = 11.33) and the complex, [Fe(pybzim)₃]²⁺ (log₁₀ K ^H ₁ = 9.58, log₁₀ K ^H ₂ = 8.13 and log₁₀ K ^H ₃ = 6.97) were measured in 30% (v/v) H₂O/EtOH. Results show that coordination to iron(II) increases the acidity of the imino hydrogen of the ligand. Spin-crossover behaviour of the complex were studied in different solvents ME, AC, AN, NM, NB, DMF, DMSO and ANL. The complex shows strong spin-crossover behaviour which is solvent dependent. Values of the spin-equilibrium constant (K _sc) and the associated thermodynamic parameters (ΔH _sc = 18.1–21.3 kJ mol^?1 and δS _sc = 69.6–84.4JK^?1 mol^?1) were calculated. An increase of the enthalpy is observed with increasing donor number (DN) of the solvent.     

[(R)-2-Methyl-1,4,7-triazacyclononane] [1,1,1-tris(aminomethyl)ethane]-cobalt(III) and some Mono[(R)-2-methyl-1,4,7-triazacyclononane]-cobalt(III) Complexes

Summary [(R)-2-Methyl-1,4,7-triazacyclononane][1,1,1-tris(aminomethyl)ethane]cobalt(III) has been prepared and separated into two isomers which show weak Cotton effects in the¹A₁¹T₁ region (d-electron transition) compared with that of bis[(R)-2-methyl-1,4,7-triazacyclononane]cobalt(III). The effect is comparable to that of tetraammine[(R)-1,2-diamino propane]cobalt(III). The circular dichroism spectra of the mono complex change markedly upon addition of sodium sulphate. The chelate rings are more flexible in the mono than in the bis complex. Some other related mono[(R)-2-methyl 1,4,7-triazacyclononane]cobalt(III) and [(R)-2-methyl-1,4,7 triazacyclononane][1,1,1-tris(aminomethyl)ethaneI nickel (II) complexes have also been prepared and characterized.     

Synthesis and tautomerism of 2-(3,5-diaryl-1H-pyrazol-4-yl)-1-methyl-1H-benzimidazoles

The cyclocondensation of 1-methyl-2-phenacyl-1H-benzimidazole with aroylhydrazines yields 2-(3,5-diaryl-1H-pyrazol-4-yl)-1-methyl-1H-benzimidazoles. The ¹H NMR spectra indicate that these products display tautomerism. The more stable tautomers have structures containing electron-donor aryl substituents at C-5 and electron-withdrawing aryl substituents at C-3 of the pyrazole ring.     

Determination Co2+ in vitamin B12 based on enhancement of 2-(4-substituted-phenyl)-4,5-di(2-furyl) imidazole and H2O2 chemiluminescence reaction

In this paper, three kinds of imidazole derivatives, 2-(4-methylphenyl)-4,5-di(2-furyl) imidazole (MDFI), 2-(4-nitrophenyl)-4,5-di(2-furyl) imidazole (NDFI), and 2-(4-tert-butylphenyl)-4,5-di(2-furyl) imidazole (t-BDFI) were synthesized. In an alkaline medium, the chemiluminescence (CL) reaction of imidazole derivatives with H₂O₂ has been investigated. It was also found that MDFI/H₂O₂ and t-BDFI/H₂O₂ systems gave strong CL. When Co²⁺ was added into the two CL systems, the CL intensity was remarkably enhanced. In the optimum conditions, the CL intensity is linearly related to the logarithm of concentration of Co²⁺. The linear ranges are 5 × 10⁻⁹–2.5 × 10⁻⁷ mol/L for MDFI/H₂O₂ system and 5 × 10⁻⁹–2.5 × 10⁻⁷ mol/L for t-BDFI/H₂O₂ system, and the corresponding detection limits are 1.2 × 10⁻⁹ mol/L and 1.1 × 10⁻⁹ mol/L, respectively. The method was applied to the determination of Co²⁺ in vitamin B₁₂ injection. Furthermore, the CL mechanism was also discussed.     

Dibenzyltin(IV) complexes of the 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-olates: Synthesis and an investigation of structures by X-ray diffraction, solution and solid-state tin NMR, Sn Mössbauer and electrospray ionization MS

A series of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}dibenzyltin(IV) complexes have been synthesized by reacting sodium salts of 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-ol (LH) and dibenzyltin dichloride. These complexes have been characterized by ¹H, ¹³C, ¹¹⁹Sn NMR, ESI-MS in solution and by IR and ^119mSn Mössbauer, ¹¹⁷Sn CP-MAS NMR spectroscopy in solid state. In addition, the structures of three of the dibenzyltin(IV) complexes, viz., Bz₂Sn(L²)₂ (2), Bz₂Sn(L³)₂ (3), and Bz₂Sn(L⁵)₂ (5) (L = 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-ol: aryl = 4′-methylphenyl- (L²H), 4′-methoxylphenyl- (L³H) and 4′-bromophenyl- (L⁵H)) were determined by single-crystal X-ray diffraction. In general, the complexes were found to adopt a distorted cis-octahedral arrangement around the tin atom in both solution and solid state.     

Molecular structure and conformational analysis of chirai (−)-3-(4-bromobenzylidene)-1-isopropyl-2-methoxy-4-methylcyclohexene

(–)-3-(4-Bromobenzylidene)-1-isopropyl-2-methoxy-4-methylcyclohexene, capable of inducing spiral supramolecular ordering when introduced to nematic and some smectic mesophases, has been studied by an X-ray structural analysis. The crystals are orthorhombic; at 20 °Ca = 6.055(1),b = 13.282(3),c=20.734(4) Å,V=1668(1) ų,d _calc = 1.380 g cm^–3, space groupP2 ₁2₁2₁ Z=4. The cyclohexene ring has a conformation intermediate between a sofa and a half-chair. The methyl and methoxyl groups are in asyn orientation with respect to the mean plane of the cycle. The angle between the plane of the aryl substituent and the exocyclic double bond is 33°. The observed distortions of bond angles at unsaturated carbon atoms are typical of derivatives of benzylidenecyclohexene. Molecular mechanics calculations demonstrated that the conformation observed in the crystalline state is not the most favorable, and this conformation is stabilized through intermolecular interactions upon stacking in crystals. It was shown that the relative orientation of the methyl and methoxyl groups as well as the orientation of the aryl substituent substantially affect the conformation of the cyclohexene ring.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2437–2442, December, 1995.