Experimental investigation for stability and surface properties of TiO2 and Al2O3 water-based nanofluids

Journal of Thermal Analysis and Calorimetry - Nanofluids have gained recent attention because of their potential applications in diverse engineering fields like enhancing thermal transport,...     

An efficient electrophilic N-amination utilizing in situ generated chloramine under phase transfer conditions

An efficient, one-pot, phase transfer N-amination technology was developed. The protocol utilizes chloramine, an inexpensive and safe electrophilic aminating agent potentially viable for commercial manufacturing.     

Surfactant-mediated solvent-free dealkylative cleavage of ethers and esters and trans-alkylation under neutral conditions

A simple, surfactant-mediated, one-pot, solvent-free dealkylative cleavage of aryl ethers and esters followed by subsequent optional trans-alkylation under essentially neutral conditions has been developed.     

Effect of the three-body force on triton asymptotic normalization constants by the hyperspherical harmonics expansion method

We investigate the change in the calculated value of asymptotic normalization constant (ANC) by the hyperspherical harmonics expansion method with the inclusion of three nucleon force (3BF) in addition to two nucleon force. We see that ANC does not change very much with the inclusion of 3BF indicating that the 3BF does not alter the asymptotic behaviours of HHE wavefunction significantly.     

Studies on thermal properties of bismuth vanadate catalysts

Physicochemical properties of bismuth vanadate catalysts with varying compositions, e.g., Bi₄V₆O₂₁-6 1/2H₂O·1 ₂ ¹ NH₃; Bi₆V₂O₁₄·3 H₂O; Bi₆V₄O₁₉·6 H₂O have been studied by chemical analysis, differential thermal analysis, thermogravimetry, infrared, X-ray diffraction, surface area and magnetic susceptibility techniques.The endotherms, in all the cases, prior to exo ones are due to stepwise dehydration and those following exochanges are due to decomposition of adsorbed impurities, sintering and melting, etc. The last endopeak, in all the cases, however is due to melting. The exochanges are attributed to stepwise phase transitions. The V-0 stretching in all the compounds is characteristic of polyvanadates. Two types of vanadium-oxygen bonds e.g., V=O and V-O -V are characterized by IR analysis. The fresh first and third vanadates are amorphous whereas the second one is crystalline. The exochanges (presumably due to disorder-order transitions) are suggested to be related to displacement of oxygen anions. The precipitated vanadates are similar with their corresponding solid state reaction products of Bi₂O₃ and V₂O₅ when they are heated at elevated temperature. The fresh as well as treated vanadates are diamagnetic. These systems display maximum surface area at the temperature corresponding to complete dehydration. The composition of the precipitated vanadates is not ultimately defined by Bi/V ratio and the binary compound consequently formed.

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Zusammenfassung Die physikalisch-chemischen Eigenschaften von Bismuthvanadat-Katalysatoren verschiedener Zusammensetzung, z.B. Bi₄V₆O₂₁·6 ₂ ¹ H₂O·1 ₂ ¹ NH₃; Bi₆V₂O₁₄·3 H₂O; Bi₆V₄O₁₉·6 H₂O wurden durch chemische Analyse, Differentialthermoanalyse, Thermogravimetrie, Infrarot, Röntgendiffraktion, Oberflächenmessung und magnetische Susceptibilitätsmessung untersucht. In jedem Fall werden die den Exo-Änderungen vorangehenden Endo-Änderungen durch stufenweise Dehydratisierung verursacht und diejenigen, welche den Exo-Änderungen folgen, durch Zersetzung adsorbierter Verunreinigungen, Sinterung und Schmelzen. Der letzte Endopeak ist jedoch in jedem Falle dem Schmelzen zuzuschreiben. Die Exo-Änderungen werden stufenweisen Phasenübergängen zugeschrieben. In allen Verbindungen ist die V-O Dehnung für die Polyvanadate charakteristisch. Zwei Typen von Vanadium-Sauerstoff Bindungen, z. B. V=O und V-O-V wurden durch IR-Analyse charakterisiert. Die frisch synthetisierten ersten und dritten Vanadate sind amorph, während das zweite kristallin ist. Die (vermutlich durch Unordnung-Ordnungs Übergänge verursachten) Exo-Änderungen sind wahrscheinlich mit der Bewegung der Sauerstoff-Anionen verbunden. Die gefällten Vanadate sind — wenn sie auf hohe Temperaturen erhitzt werden — ihren entsprechenden Festphasen-Reaktionsprodukten Bi₂O₃ und V₂O₅ ähnlich. Die ursprünglichen wie die behandelten Vanadate sind diamagnetisch. Diese Systeme weisen die maximale Oberfläche bei der ihrer vollständigen Dehydratisierung entsprechenden Temperature auf. Die Zusammensetzung der gefällten Vanadate wird letzten Endes nicht durch. ihr Bi-V-Verhältnis und die in der Folge entstandene Binärverbindung bestimmt.

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Résumé Les propriétés physico-chimiques des catalyseurs au vanadate de bismuth, de diverses compositions, par ex. Bi₄V₆O₂₁ · 6 ₂ ¹ H₂O · 1 ₂ ¹ NH₃,Bi₆V₂Oi₁₄ · 3H₂O, Bi₆V₄O₁₉ · 6H₂O, ont été étudiées par analyse chimique, analyse thermique différentielle, thermogravimétrie, spectroscopie infrarouge, diffraction des rayons X, mesures de surfaces spécifiques et de susceptibilité magnétique.Dans tous les cas, les phénomènes endothermiques qui précèdent ceux de nature exothermique sont dus à la déshydratation par étapes; les phénomènes endothermiques qui suivent ceux de nature exothermique sont dus aux impuretés adsorbées, au frittage, à la fusion, etc ... Cependant, le dernier pic endothermique est toujours dû à la fusion. Les changements exothermiques sont attribués à des transitions de phases par étapes. La déformation V-0 dans tous les composés est caractéristique des polyvanadates. Deux types de liaisons vanadium-oxygène, par ex. V=O et V-O-V ont été caractérisés par analyse infrarouge. Le premier et le troisième vanadate, fraîchement préparés, sont amorphes alors que le second est cristallisé. Les. phénomènes exothermiques (probablement dus à des transitions désordre-ordre) sont sans doute en rapport avec le déplacement des anions oxygène. Les vanadates précipités — si on les. chauffe jusqu'à une température élevée — sont similaires aux produits correspondants, obtenus par réaction à l'état solide entre Bi₂O₃ et V₂O₅. Les vanadates fraîchement préparés ainsi que ceux qui ont subi un traitement thermique, sont diamagnétiques. Ces systèmesmontrent une surface spécifique maximalé à la température correspondant à la déshydratation complète. La composition des vanadates précipités n'est pas finalement définie par le rapport Bi/V et le composé binaire formé par la suite.

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- - , , Bi₄V₆O₂₁ · 6.5 ₂ ·1.5 NH₃; Bi₆V₂O₁₄ · ₂; Bi₆V₄O₁₉· 6H₂O , , , , - , . , , , , , . . . . V- . - : V= V--V. , — . , (-, -) . , Bi₂O₃ V₂O₅ . , . , . Bi/V, a, , .

     

Spherical shape complementarity as an overriding motif in the molecular recognition of noncharged organic guests by p-sulfonatocalix[4]arene: complexation of bicyclic azoalkanes

[reaction: see text] The complexation of p-sulfonatocalix[4]arene (CX4) with 2,3-diazabicyclo[2.2.1]hept-2-ene (1), 2,3-diazabicyclo[2.2.2]oct-2-ene (2), 2,3-diazabicyclo[3.2.2]non-2-ene (3), 1-methyl-4-isopropyl-2,3-diazabicyclo[2.2.2]oct-2-ene (4), and 1-phenyl-2,3-diazabicyclo[2.2.2]oct-2-ene (5) was studied in D2O at pD 7.4 by 1H NMR spectroscopy. The formation of deep inclusion complexes was indicated by large upfield 1H NMR shifts of the guest protons (up to 2.6 ppm), which were also used to assign, in combination with 2D ROESY spectra, a preferential inclusion of the isopropyl group of 4 and a dominant inclusion of the azo bicyclic residue for 5. The bicyclic azoalkanes 1-3 showed exceptionally high binding constants on the order of 1000 M(-1), 1-2 orders of magnitude larger than for previously investigated noncharged organic guest molecules. The strong binding was attributed to the spherical shape complementarity between the guest and the conical cavity offered by CX4. Interestingly, although the derivatives 4 and 5 are more hydrophobic, they showed a 2-3 times weaker binding, which was again attributed to the deviation from spherical shape in these bridgehead-substituted derivatives. The preferential inclusion of the hydrophilic but spherical bicyclic residue of 5 rather than the hydrophobic aromatic phenyl group provides a unique observation in aqueous host-guest chemistry and corroborates the pronounced spherical shape affinity of CX4.     

Substituent electronic effects on the persistence and absorption spectra of (Z)-o-xylylenols. A nanosecond laser flash photolysis study

[reaction: see text] A systematic investigation on a broad set of aldehydes reveals that the lifetimes of (Z)-photoenols can be modulated by variation of the substituents. We have found that the lifetimes of (Z)-enols (in benzene) can be varied by more than 1 order of magnitude with a judicious choice of the substituents that exert mesomeric and inductive effects as, for example, in the case of pentamethylbenzaldehyde (tau = 35 ns) and dicyanomesitaldehyde (tau = 760 ns). This study thus points to the fact that the electronic factors in conjunction with hydrogen bonding stabilization can considerably broaden the uni- as well as bimolecular chemistry based on photoenolization. Further, we have shown that the photoenols exhibit dramatic shifts in their absorption properties with variation of the substituents; although the photoenols have long been considered to be colored, their absorption properties have not been heretofore comprehensively examined.     

Physico-chemical properties of catalysts: Thermal analysis,infrared spectroscopy,X-ray diffraction and magnetic susceptibility of the vanadates of zinc,manganese and silver

Thermal characteristics of the vanadates of zinc, manganese and silver have been studied by DTA and TG techniques and the different transition products thus obtained have been characterised by IR, X-ray diffraction and magnetic susceptibility data. Chemical analyses indicate the following compositions of these vanadates: (1) Zn₂V₂O₇.5H₂O, (2) Zn₃(VO₄)₂.3H₂O, (3) Mn(VO₃)₂.2H₂O and (4) Ag₃VO₄. The DTA curves indicate that zinc pyrovanadate undergoes endothermic changes at 110–195, 265, 365, 440, 660° and one exothermic change at 485°. This system is diamagnetic which becomes completely paramagnetic after 660°. Zinc orthovanadate exhibits a number of endothermic peaks at 300, 470, 700, 815 and 930° respectively. This system is feebly paramagnetic and retains this property up to 930°. Manganese metavanadate undergoes endothermic changes at 240, 280–590, 830 and 880° respectively. This vanadate is paramagnetic and paramagnetism increases appreciably at 590° and remains constant up 830°. Silver orthovanadate exhibits three endothermic changes at 180, 455 and 640°, respectively.

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Zusammenfassung Die thermischen Charakteristika der Vanadate von Zink, Mangan und Silber wurden durch DTA- und TG-Methoden untersucht und die auf diese Weise erhaltenen verschiedenen Übergangsprodukte durch Daten aus IR-, Röntgen- und magnetischer Susceptibilität charakterisiert. Die chemische Analyse deutet auf folgende Zusammensetzung dieser Vanadate: 1) Zn₂V₂O₇.5H₂O, 2) Zn₃(VO₄)₂.3H₂O, 3) Mn(VO₃)₂.2H₂O und 4) Ag₃VO₄. Die DTA-Kurven zeigen endotherme Veränderungen des Zink-pyrovanadats bei 110–195, 265, 365, 440 und 660° und eine exotherme Veränderung bei 485°. Dieses System ist diamagnetisch und wird nach 660° vollständig paramagnetisch. Zink-orthovanadat zeigt eine Anzahl exothermer Peaks bei 300, 470, 700, 815, bzw. 930°. Dieses System ist schwach paramagnetisch und behält diese Eigenschaft bis zu 930°. Im Manganmetavanadat vollziehen sich endotherme Veränderungen bei 240, 280–590, 830 und 880°. Dieses Vanadat is paramagnetisch, der Pararnagnetismus steigt zusehends bei 590° und bleibt bis zu 830° konstant. Silberorthovanadat zeigt drei endotherme Veränderungen bei 180, 455 bzw. 640°.

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Résumé On a étudié par ATD et TG les caractéristiques thermiques des vanadates de zinc, de manganèse et d'argent. La caractérisation des divers produits de transition ainsi obtenus a été effectuée à partir des données fournies par IR, rayons X et susceptibilité magnétique. Les analyses chimiques indiquent les compositions suivantes de ces vanadates: (1) Zn₂V₂O₇.5H₂O, (2) Zn₃(VO₄)₂.3H₂O, (3) Mn(VO₃)₂.2H₂O et (4) Ag₃VO₄. Les courbes ATD du pyrovanadate de zinc montrent des effets endothermiques à 110–195, 265, 365, 440 et 660° ainsi qu'un phénomène exothermique à 485°. Ce corps est diamagnétique; il devient complètement paramagnétique au-dessus de 660°. L'orthovanadate de zinc donne des pics endothermiques à 300, 470, 700, 815 et 930°. Il est faiblement paramagnétique jusqu'à 930°. Le métavanadate de manganèse est le siège de phénomènes endothermiques à 240, 280–590, 830 et 880°. Il est paramagnétique et son paramagnétisme augmente de manière appréciable à 590° pour rester constant jusqu'à 830°. L'orthovanadate d'argent montre trois effets endothermiques à 180, 455 et 640°.

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, . - , . : Zn₂V₂O₇·5H₂O, Zn₃(VO₄)₂ · 3H₂O, Mn(VO₃)₂· 2H₂O Ag₃VO₄. , 110–195°, 265, 365,440 660° 485°. , 660° . 300, 470, 700, 815 930°. 930°. 240, 280–590, 830 880°. , 590° 830°. 180, 455 640°.

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The authors are grateful to the Physical Research Wing and Catalyst Research and Development Section, F. C. I., Sindri and also the Analytical Physics Division and Catalyst Section, I.I.P., Dehradun (India) for their help in getting TG and X-ray patterns of the catalysts studied.     

Syntheses, structures, and reactivities of (Fe-NO)6 nitrosyls derived from polypyridine-carboxamide ligands: photoactive NO-donors and reagents for S-nitrosylation of alkyl thiols

Two new iron nitrosyls derived from two designed pentadentate ligands N,N-bis(2-pyridylmethyl)-amine-N'-(2-pyridylmethyl)acetamide and N,N-bis(2-pyridylmethyl)-amine-N'-[1-(2-pyridinyl)ethyl]acetamide (PcPy(3)H and MePcPy(3)H, respectively, where H is the dissociable amide proton) have been structurally characterized. These complexes are similar to a previously reported (Fe-NO)6 complex, [(PaPy(3))Fe(NO)](ClO(4))(2) (1) that releases NO under mild conditions. The present nitrosyls, namely [(PcPy(3))Fe(NO)](ClO(4))(2) (2) and [(MePcPy(3))Fe(NO)](ClO(4))(2) (3), belong to the same (Fe-NO)6 family and exhibit (a) clean (1)H NMR spectra in CD(3)CN indicating S = 0 ground state, (b) almost linear Fe-N-O angles (177.3(5) degrees and 177.6(4) degrees for 2 and 3, respectively), and (c) N-O stretching frequencies (nu(NO)) in the range 1900-1925 cm(-)(1). The binding of NO at the non-heme iron centers of 1-3 is completely reversible and all three nitrosyls rapidly release NO when exposed to light (50 W tungsten bulb). In addition to acting as photoactive NO-donors, these complexes also nitrosylate thiols such as N-acetylpenicillamine, 3-mercaptopropionic acid, and N-acetyl-cysteine-methyl-ester in yields that range from 30 to 90% in the absence of light. The addition of alkyl or aryl thiolate (RS(-)) to the (Fe-NO)6 complexes in the absence of dioxygen results in the reduction of the iron metal center to afford the corresponding (Fe-NO)7 species.