Light enhanced proton conductivity in a terbium phosphonate photochromic chain complex

Crystalline complexes that exhibited light switchable proton conductivity are of great interest but still a challenge in material science. Herein, a terbium phosphonate chain complex was synthesized through assembly of electron-rich phosphonate units, electron-deficient polypyridine components and paramagnetic Tb~(3+) ions. Via light irradiation and heat treatment, the photogenerated radicals could simultaneously and reversibly tune the photochromic, luminescent and magnetic properties. Originating from the abundant hydrogen bonding networks formed between PO_3 groups and lattice water molecules, proton conductive behaviour was explored with high proton conductivity of(1.74±0.19)×10~(-3) S cm~(-1) at 80 °C and 100% relative humidity. Importantly, accompanied with the colorless sample changed to blue, the proton conductivity increased about 20% after room temperature light illumination, implying that light irradiation could act as an external stimulus to enhance the conductive properties of original material. This work innovatively realized the light responsive conductive property in the electron transfer photochromic materials, providing a novel strategy for the construction of smart materials.     

Study of non-conjugated bichromophores linked by a polyether chain. Kinetic analysis of the formation of intramolecular excimers and photocyclomerization of some bisanthracenes

Dynamic properties of polyoyethylene chains are evaluated by the determination of rate constants (k_DM) of intramolecular excimer formation for four bis(9-anthryloxy)polyoxaalkanes in benzene and ethanol. The Kinetic parameters for the photodimenzation process of these compounds have been determined.     

An infrared study of the complexing ability of manganese phthalocyanine

The complexing ability of manganese phthalocyanine (MnPhc) in the solid state has been studied in detail using i.r. spectroscopy. It has been shown that in its α modification, MnPhc readily adsorbs phenol, pyridine and formic acid. Nothing happens with the β modification. The results have been compared to previous studies and they are explained in terms of valence bond model and molecular orbital model.     

On the chichibabin amination of quinoline and some nitroquinolines

Quinoline is aminated into 2-aminoquinoline (55-60%) when treated with potassium amide/liquid ammonia/potassium permanganate at ?65°. When the amination is carried out by allowing the solution of quinoline in potassium amide/liquid ammonia to raise from ?60° to + 15° before addition of potassium permanganate, the main product is 4-aminoquinoline. Using as reagent liquid ammonia/potassium permanganate (thus without the presence of potassium amide) 3-nitroquinoline is exclusively aminated at ?40° into 4-amino-3-nitroquinoline. Using the same conditions, from 4-nitroquinoline 3-amino-4-nitroquinoline is obtained. The mechanism of these amination reactions is discussed.     

Medium effects on the ionization constants of some quinoline derivatives

Summary The deprotonation and acid ionization constants of some quinoline derivatives in aqueous organic solvents were determined. The organic solvents used include methanol and ethanol as amphiprotic solvents andDMF andDMSO as dipolar aprotic solvents. The obtainedpK ₁ andpK ₂ values are discussed with respect to the nature and the amount of the organic component. The high stabilization of the non-protonated form by dispersion forces and of the proton by its interaction with the solvent are the main factors responsible for the increase in the ionization constants of the protonated forms of the quinolines under investigation. On the other hand, H-bonding interactions (in addition to the electrostatic effect) seem to play the major role in determining the second acid-base equilibrium of 8-hydroxyquinoline. The deprotonation constants of the examined quinolines are correlated with their experimentally determined lone-pair ionization potential values.

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Lösungsmitteleffekte auf die Ionisationskonstanten einiger Chinolinderivate

Zusammenfassung Die Deprotonierungs- und Ionisationskonstanten einiger Chinolinderivate wurden in wäßrigen organischen Medien, darunter Methanol und Ethanol als amphiprotische undDMF undDMSO als dipolare aprotische Lösungsmittel, bestimmt. Die gemessenenpK ₁- undpK ₂-Werte werden im Hinblick auf die Art und Menge der organische Komponente diskutiert. Die hohe Stabilisierung der nichtprotonierten Form durch Dispersionskräfte und des Protons durch Wechselwirkungen mit dem Lösungsmittel sind die wesentlichen Faktoren, die für den Anstieg der Ionisationskonstanten der protonierten Formen der untersuchten Chinoline verantwortlich sind. Andererseits scheinen Wasserstoffbrückenbindungen — zusätzlich zum elektrostatischen Effekt — das zweite Säure-Basen-Gleichgewicht von 8-Hydroxychinolin entscheidend zu beeinflussen. Die Deprotonierungskonstanten aller untersuchten Chinoline werden mit ihren experimentell bestimmtenlone-pair-Ionisationspotentialen korreliert.

     

Influence of the alkyl chain length of some mesogenic molecules on their Langmuir film formation ability

Langmuir films of members of two homologous series, the 4‐n‐alkyl‐4′‐cyanobiphenyls (nCB) for n = 2–14 and trans‐4‐n‐alkyl(4′‐cyanophenyl)cyclohexanes (PCHn) for n = 2–12, have been studied by recording surface pressure/area isotherms and by Brewster angle microscopy. It has been found that the compounds with very short chains (n3) and very long chains (n>12 for nCB, n>10 for PCHn) are unable to form compressible monolayers at the air–water interface. Other members of both series can form stable Langmuir films, but both their rigidity and stability as well as the molecular packing vary with the alkyl chain length. The isotherms and BAM images imply that the organization of the liquid crystal molecules in the films is to some extent correlated with their ability to form corresponding mesophase in the bulk: nematogenic compounds tend to form rounded droplet‐like domains, whereas smectogenic compounds tend to form flat domains.     

Enantiomeric phosphonate analogs of the docetaxel C-13 side chain

Addition of dimethyl phosphite to racemic N-Boc-phenylglycinal led to a 75:25 mixture of syn and anti dimethyl 2-[(tert-butoxycarbonyl)amino]-1-hydroxy-2-phenylethylphosphonates. The syn-diastereoisomer was obtained in 50% yield after a single crystallization. Resolution of the syn-isomer was achieved via the (S)-O-methylmandelate esters. Racemization-free ammonolysis gave both enantiomers in high enantiomeric excess. Benzoates of both N-Boc syn-enantiomers were transformed into dimethyl (1R,2R)- and (1S,2S)-2-(benzoylamino)-1-hydroxy-2-phenylethylphosphonates in good yields.     

Enantiomeric phosphonate analogs of the paclitaxel C-13 side chain

Both enantiomers of syn diethyl 2-(benzoylamino)-1-hydroxy-2-phenylethylphosphonate have been obtained by resolution via O-methylmandelate derivatives. Removal of the resolving ester moiety was easily achieved by ammonolysis with no trace of the retro-Abramov reaction. Absolute configurations of the enantiomeric phosphonate analogs were established from ¹H (the Trost model) and ³¹P NMR data of the O-methylmandelate derivatives.     

Bromination of quinoline in the presence of some lewis acids

Data on the bromination of quinoline in acetic anhydride and in the presence of salts of p and d elements are presented. High catalytic activity of the investigated salts, particularly the salts of p elements, was demonstrated. An unexpected orientation of the bromination of quinoline in 94% sulfuric acid in the presence of copper sulfate was discovered.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 548–550, April, 1985.     

Synthetic aspects of the characterization of some silica-bound complexing agents

A number of synthetic aspects of silica-bound complexing agents are considered. Modifications of the procedure for amidization of bound amines and of the diazotizationcoupling sequence are discussed. The amidization of aminopropyl silica gel appears to be complete while that of ethylenediamine silica gel is less so. Loss of activity of the dried, bound diazonium salt appears to result from return to the Ar-NH₂ form, while a decrease in metal-ion complexation capacity for 8-quinolinol silica gel compared to the aminopropyl or ethylenediamine silica gel seems to be related to steric clogging of the matrix pores by bound organic moieties. A method of stripping the azo-coupled ligand from the appendage is examined, and some infrared and thermogravimetric characterizations are presented.     

Mechanism of thioesterase-catalyzed chain release in the biosynthesis of the polyether antibiotic nanchangmycin

The polyketide backbone of the polyether ionophore antibiotic nanchangmycin (1) is assembled by a modular polyketide synthase in Streptomyces nanchangensis NS3226. The ACP-bound polyketide is thought to undergo a cascade of oxidative cyclizations to generate the characteristic polyether. Deletion of the glycosyl transferase gene nanG5 resulted in accumulation of the corresponding nanchangmycin aglycone (6). The discrete thioesterase NanE exhibited a nearly 17-fold preference for hydrolysis of 4, the N-acetylcysteamine (SNAC) thioester of nanchangmycin, over 7, the corresponding SNAC derivative of the aglycone, consistent with NanE-catalyzed hydrolysis of ACP-bound nanchangmycin being the final step in the biosynthetic pathway. Site-directed mutagenesis established that Ser96, His261, and Asp120, the proposed components of the NanE catalytic triad, were all essential for thioesterase activity, while Trp97 was shown to influence the preference for polyether over polyketide substrates.     

Studies on the complexing behavior of a potentially tetradentate Schiff-base ligand with some transition metal ions

The Schiff base furfural-histidine with Co(II), Ni(II), Cu(II), and Zn(II) in solution gives M(AB), M(AB)B, or M(AB)₂. The Schiff base is tetradentate in M(AB)₂ and M(AB)B and tridentate in M(AB)₂; [M(AB)₂] · 2H₂O (M = Co, Ni and Zn) and [Cu(AB)]NO₃ were synthesized and characterized by elemental analysis, molecular weight determination, conductance, IR, UV–Vis, and CV. The electronic spectral measurements indicate that M(AB)₂ (M = Co(II) and Ni(II)) are octahedral and Cu(AB) is square planar geometry. The donor groups in the complexes have been identified by IR. The complexes undergo irreversible one step, two-electron reduction. Antibacterial activity of the complexes was screened for Escherichia coli and Staphylococcus aureus. Cu(II) complex was found to be more active than the Co(II), Ni(II), and Zn(II) complexes.     

Synthesis, structure, and complexing ability of hetarylhydrazones of glyoxylic acid

Benzoxazolyl-, benzthiazolyl-, 2′-quinolinyl- and 1′-phthalazinylhydrazones of glyoxylic acid (H₂L) and their complexes have been synthesized. The acid-base properties of the obtained hydrazones were studied by the methods of potentiometric titration and spectrophotometry. The hydrazones were shown to form mononuclear octahedral complexes M(HL)₂ with Ni(II) and Mn(II) acetates, whereas with Zn(II) and Cu(II) acetates binuclear complexes M₂L₂ were formed. The nature of the exchange interaction between the Cu(II) ions is discussed.     

Spectrophotometric determination of flucloxacillin in pharmaceutical preparations using some nitrophenols as a complexing agent

Some nitrophenols are proposed as chromogenic reagents for the spectrophotometric determination of flucloxacillin. The reagent forms a greenish yellow 1:1 complex with flucloxacillin at pH 9.0. This complex is stable for at least 3.0 h after its formation. The greenish yellow charge transfer complex species has an absorption maximum at 446, 435, 442, 473 and 439 nm for p-nitrophenol (I), 2,4-dinitrophenol (II), 3,5-dinitrosalycilic acid (III), picramic acid (IV) and picric acid (V), respectively, with a molar absorptivity between 1.43 x 10(4) and 2.59 x 10(4) l mol(-1) cm(-1). Beer's low is valid over the concentration range 2.0-40 microg ml(-1) of flucloxacillin. The detection and quantitation limits as well as relative standard deviation were also calculated. The reagents have been successfully used for the spectrophotometric determination of flucloxacillin in pure form and in pharmaceutical preparations.     

Identification of NanE as the thioesterase for polyether chain release in nanchangmycin biosynthesis

The polyketide synthase (PKS) for the biosynthesis of the polyether nanchangmycin lacks an apparent thioesterase comparable to the type I thioesterase domains of the modular PKSs responsible for macrolide biosynthesis. Three candidate polyether chain-releasing factors were examined. Both the putative CR domain and the NanE protein appeared to be genetically relevant. Among the three heterologously expressed soluble proteins (recombinant CR domain, the ACP-CR didomain, and NanE) tested, only NanE hydrolyzed the polyether-SNAC. By contrast, recombinant DEBS TE from the erythromycin pathway, and the recombinant MonAX, a type II TE associated with the polyether monensin biosynthesis for which a homolog has not been detected in the nanchangmycin cluster, hydrolyzed a diketide-SNAC but not the polyether-SNAC. We could thus conclude that NanE is a dedicated thioesterase mediating the specific release of the polyether chain during nanchangmycin biosynthesis.     

Electromigration of some metal ions on filter paper using sodium nitrite as a complexing electrolyte

Summary The electromigration of ten metal ions in aqueous and mixed water-alcohol media, with sodium nitrite as complexing electrolyte has been studied. Metal ions which form stable metal nitrite complexes were shown to move towards the anode as negative species, while the others moved towards the cathode. Differences in migration values in 2 and 5% sodium nitrite electrolyte at a potential gradient of 5 V/cm were large enough to make sodium nitrite a very useful complexing electrolyte for separation of these ions on filter paper strips. The effects of varying the applied potential gradient and of adding methanol, ethanol and propan-2-ol to the electrolyte system were also studied.

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Zusammenfassung Die Wanderung von 10 Metallionenarten im elektrischen Feld in wäßrigem sowie in wäßrig-alkoholischem Milieu mit Natriumnitrit als Komplexbildner wurde untersucht. Metallionen, die stabile Nitritkomplexe bilden, wandern mit negativer Ladung zur Anode, während die anderen zur Kathode wandern. Der Unterschied der Wanderungswerte in 2%iger und 5%iger Natriumnitritlösung bei 5 V/cm Ladung ist groß genug, so daß dieser komplexierende Elektrolyt sich zur Trennung auf Filterpapierstreifen sehr gut eignet. Die Wirkung der Potentialänderung sowie der Zugabe von Methanol, Äthanol bzw. Propan-2-ol zum Elektrolytgemisch wurde gleichfalls untersucht.