Host–guest control on the formation of pinacyanol chloride H-aggregates in anionic polyelectrolyte solutions

The interactions of pinacyanol chloride (PIN), a cationic cyanine dye, with the anionic polyelectrolyte poly(acrylic acid, sodium salt) (PAA) towards enhancing H-aggregation were investigated by electronic absorption spectroscopy. We employed the cucurbit[7]uril (CB7) host to control the formation of these aggregates via host–guest binding interactions with the dye molecules. Absorption spectroscopic studies clearly demonstrate that PAA enhances the formation of PIN H-aggregates. Electrostatic interactions between the cyanine dye molecules and the polyelectrolyte chains assist the formation of H-aggregates at very low dye concentrations (ca. 10 μM). Furthermore, the presence of CB7 was found to effectively disrupt the interactions responsible for dye aggregation. Thus, CB7 completely disrupts the H-aggregates (as well as lower concentrations of J-aggregates) by forming inclusion complexes with PIN. A competing guest, 1-aminoadamantane (AD), was utilised to adjust the extent of aggregation of the cyanine dye. AD regulates aggregate formation by forming an extremely stable complex with CB7 and exerting a tight control on the CB7 concentration available to interact and bind with the dye. Our spectroscopic data clearly indicate that by varying the relative molar ratios of CB7 host, AD and polyelectrolyte acid groups, we can quantitatively control the extent of formation of PIN H-aggregates in these solutions.     

Host–guest system of Vitamin B10 in β-cyclodextrin: characterization of the interaction in solution and in solid state

Conventional drugs are usually formulated for the immediate release of the medicinal substances and for obtaining the desired therapeutic effect. The aim of this paper was to investigate the possible interactions between Vitamin B10 and β-cyclodextrin (β-CD), to determine the physical-chemical characteristics and the interactions present in the corresponding inclusion compound. The so-obtained compounds were characterized by X-ray diffraction, DSC and FTIR spectroscopy. ¹H NMR and UV–vis spectroscopic methods were employed to study the inclusion process in aqueous solution. The X-ray powder diffraction patterns demonstrate the inclusion compound formation, especially for the lyophilized product where the amorphous phase dominates. The existence of the inclusion compounds obtained by different methods was confirmed by comparing with DSC and FTIR data of the pure compounds and the (1:1) Vitamin B10:β-CD physical mixture (pm). ¹H NMR measurements on aqueous solutions of Vitamin B10 and β-CD in D₂O allowed us to establish the corresponding Vitamin B10’s and cyclodextrin’s protons implied in the complexation process. 2D NMR spectroscopy established the geometry of the inclusion complex. ¹H NMR, UV–Vis and fluorescence data were used to obtain the stoichiometry and the stability constant of the complex.     

An efficient electrochemical disinfection of E. coli and S. aureus in drinking water using ferrocene–PAMAM–multiwalled carbon nanotubes–chitosan nanocomposite modified pyrolytic graphite electrode

This work reported an efficient electrochemical treatment for drinking water disinfection using a pyrolytic graphite electrode modified with ferrocenyl tethered poly(amidoamine) dendrimers–multiwalled carbon nanotubes–chitosan nanocomposite. The influence parameters of electrochemical disinfection of Escherichia coli and Staphylococcus aureus, such as applied potential and sterilization time, were investigated. Further investigation indicated that almost all (99.99 %) of the initial bacteria were killed after applying a low potential of 0.4 V for 10 min. During the electrochemical disinfection process, the oxidized form of ferrocene was formed on electrode, which played a key role in the disinfection towards E. coli and S. aureus. Hence, the proposed method may provide potential application for the disinfection of drinking water.

Synthesis of 2,3-dihydroquinazolin-4(1H)-ones catalyzed by zirconium(Ⅳ) chloride as a mild and efficient catalyst

2,3-Dihydroquinazolin-4(1H)-ones have been synthesized in the high to excellent yields via condensation of 2-aminobenzamide with aldehydes and ketones in the presence of catalytic amount of ZrCl_4 in EtOH at room temperature.Mild reaction conditions, clean reaction media,simple workup and easy purification are advantages of this methodology.     

Chelating alkoxy NHC–Rh(I) complexes and their applications in the arylation of aldehydes

In this study, new rhodium(I) complexes (5 and 6) have been prepared by the reaction of [RhCl(COD)]₂ with a series of imidazolium salts (3 and 4), which were obtained from a chiral amino alcohol. The catalytic activities of these complexes were tested in the arylation of aldehydes. It was found that the synthesized rhodium complexes were highly effective catalysts for the arylation of aldehydes in short reaction times (5 min, TOF = 1193 h⁻¹). However, the obtained ee values (up to 32% ee) remained low. We have proposed a mechanism for the arylation reaction of aldehydes, which is confirmed via ¹⁹F NMR spectroscopy.     

An l-proline-based β-amino tertiary thiol: synthesis and use as a catalyst in the enantioselective addition of diethylzinc to aldehydes

Two independent routes for the synthesis of the novel β-amino tertiary thiol 1 have been developed. Utilisation of this thiol in the enantioselective addition of diethylzinc to aldehydes provided (R)-secondary alcohols in ees of up to 64%.     

Tris(hydroxymethyl)aminomethane as an efficient organobase catalyst for the synthesis of β-phosphonomalonates

Tris(hydroxymethyl)aminomethane (THAM) is a highly efficient and recyclable organobase catalyst for the nucleophilic phosphonylation of benzylidene malononitrile under solvent-free conditions. This new catalytic methodology is applicable without a solvent, eco-friendly, economically viable, avoids conventional isolation procedures, and has a facile work-up procedure and wide scope. THAM is an inexpensive, commercially available, non-toxic, and biodegradable novel organocatalyst. Furthermore, it can be reused in up to five cycles without loss in catalytic activity, and no chromatographic separation is needed to obtain the desired products.     

Progress in the study of metal–organic materials applying naphthalene diimide (NDI) ligands

1,4,5,8-naphthalenediimide (NDI) derivatives are versatile in coordination and material chemistry due to their large conjugated planar structure and special electron transfer properties. This review presents an overview of metal–organic materials derived from NDIs with their structural models, analytical techniques and potential applications outlined.     

Phase Diagram of the Benzene–Dinitratotetrapyridinecopper(II) (Guest–Host) System and Thermodynamic Parameters for the Hostβ2Guest Clathrate Dissociation

In the first part of the work, thephase diagram of the benzene -ndash;[CuPy⁴(NO³)²] system has beendetermined in the -100 to +200 °C temperaturerange using DTA and solubility techniques. The onlycompound found in the system is the[CuPy⁴(NO³)²] 2C⁶H⁶clathrate. It is stable up to a temperature of+104.2(5) °C at which it melts incongruently togive liquid and the solid [CuPy⁴(NO³)²]host phase. At 146.1(5) °C exfoliation into twoliquid phases is observed, with the composition of themonotectic point being close to that of the clathrate.In the second part of the work, thermodynamicparameters of the clathrate dissociation have beendetermined from benzene vapour pressure strainmeasurements. For the process1/2 [CuPy⁴(NO³)²]2C⁶H⁶(solid) = 1/2 [CuPy⁴(NO³)²] (solid) +C⁶H⁶ (gas) H° = 45.3(3) kJ/mole; S₂₉₈° = 126(1) J/(mole K); G₂₉₈° = 7.7(5) kJ/mole.     

An efficient,catalyst free synthesis of 3-(2′'-benzothiazolyl)-2,3-dihydroquinazolin-4(1H)-ones in aqueous medium

Abstract

An efficient and environmentally benign protocol for the synthesis of 3-(2′-benzothiazolyl)-2,3-dihydroquinazolin-4(1H)-ones has been developed. The synthesis of these pharmacologically important compounds can be achieved by the three component condensation of isatoic/5-chloroisatoic anhydride, aldehyde, and 2-aminobenzothiazole in water: ethanol (1:1, v/v) without the aid of any catalyst.

An efficient green protocol for the synthesis of chalcones by a Claisen–Schmidt reaction using bismuth(III)chloride as a catalyst under solvent-free condition

Abstract

An environmentally benign protocol for the synthesis of chalcones by the Claisen–Schmidt condensation of aldehydes with ketones using eco-friendly non-toxic bismuth(III)chloride catalyst under solvent-free condition is reported. In this protocol, the reaction time is very short, yields are high, and there are no other pollutants formed.     

Silica/A153–SO3H: An efficient catalyst for the Baeyer–Villiger oxidation of cyclic ketones with hydrogen peroxide

Silica/A153–SO₃H was prepared and characterized by FT–IR, TG and SEM. It proved to be an efficient and recyclable heterogeneous catalyst in the Baeyer–Villiger (BV) oxidation of cyclic ketones with H₂O₂ as an oxidant. Catalysts with different silica particle sizes were also made comparisons in terms of catalytic effect.     

Knölker's iron complex: an efficient in situ generated catalyst for reductive amination of alkyl aldehydes and amines

An aminated series: a well-defined iron-catalyzed reductive amination reaction of aldehydes and ketones with aliphatic amines using molecular hydrogen is presented. Under mild conditions, good yields for a broad range of alkyl ketones as well as aldehydes were achieved.     

Thiamine hydrochloride(VB1):An efficient catalyst for one-pot synthesis of α-aminophosphonates under ultrasonic irradiation

An efficient synthesis of novelα-aminophosphonates by the reaction of aldehydes and amines with triethyl phosphite in the presence of the easily available,inexpensive,and nontoxic catalyst thiamine hydrochloride(VB1).This method affords theα-aminopho-sphonates under the influence of ultrasound irradiation in aqueous medium,in short reaction times(4-6 min),high yields(85-95%), with improved purity.The process is green,mild,inexpensive and excellent yields are the main compensation of this procedure.     

Bi(NO3)3.5H2O catalyzed phosphonylation of aldehydes: An efficient route to α-hydroxyphosphonates

The Bi(NO₃)₃.5H₂O mediated synthesis of α-hydroxyphosphonates via phosphonylation of aldehydes is reported herein. Both conventional and microwave technology was efficiently applied to range of aromatic, heteroaromatic, α,β-unsaturated aldehydes under solvent-free conditions. The solvent free conditions, avoidance of toxic reagents and excellent yield are some of the remarkable features of this protocol to access the medicinally privileged structure, α-hydroxyphosphonates.     

Host–guest interactions between dapsone and β-cyclodextrin (part I): study of the inclusion compound by nuclear magnetic resonance techniques

Dapsone (4,4′diaminodiphenylsulfone) is a very effective drug to treat leprosy and a broad range of infectious conditions such as Pneumocystis carinii pneumonia, toxoplasmosis and tuberculosis. However, the oral administration of this drug generally is related to serious side effects and treatment failures. It is believed that the inclusion compound of this drug and cyclodextrins would increase the wettability and the solubility of the encapsulated drug for a supported and gradual release, maximizing its biodisponibility over time. The encapsulation of dapsone in β-cyclodextrin was investigated by five nuclear magnetic resonance spectroscopy techniques. The data obtained for the complex in aqueous solution and in solid-state revealed a strong interaction between host and guest, showing that the drug molecule is deeply inserted in the CD cavity. The diffusion experiments (diffusion ordered spectroscopy) showed a high percentage of complexation (86 %) and that the drug molecule is preferentially interacting with the large side of the β-cyclodextrin cavity.     

PEG-stabilized palladium nanoparticles： An efficient and recyclable catalyst for the selective hydrogenation of 1,5-cyclooctadiene in thermoregulated PEG biphase system

Polyethylene glycol （PEG）-stabilized palladium nanoparticles were prepared and applied to the selective hydrogenation of 1,5- cyclooctadiene （1,5-COD） in thermoregulated PEG biphase system, which allows a reaction in a single-phase at a higher temperature followed by a phase split at a lower temperature. Under the optimized reaction conditions, the conversion of 1,5-COD and the selectivity of cyclooctene （COE） were 100 and 98%, respectively. The catalyst could be easily separated from the product by phase separation and reused for 6 times without evident loss in activity and selectivity. 2007 Yan Hua Wang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.     

Structure–Properties Relations in Werner β-[Ni(NCS)2(4-MePy)4] Clathrates. Part 2. Host–Host Interactions as a Function of the Guest Molecular Size and Shape and the Amount of Absorbed Guest Compound

Careful analysis of changes in the geometry of the host lattice structure on inclusion of different guest molecules was performed for 11 -[Ni(NCS)₂(4-methylpyridine)₄] clathrates reported in the literature, and specific features were established for the geometry of the host crystal lattice structure, which are characteristic for different modes of location of the guest molecules. A new method is suggested for the analysis of the volume and shape of the empty space in clathrates. Experimental data are reported on the dependence of the a and c parameters of the unit cell of clathrate phases (with furan and dichloromethane as guest components) from the guest uptake. Consideration of these data permit us to construct a model of the changes of host–host interactions in the -[Ni(NCS)₂(4-methylpyridine)₄] clathrates with change of guest uptakes. Modeling of the process of diffusion of the guest molecule through the channel of the -[Ni(NCS)₂(4-methylpyridine)₄] clathrate allowed the nature of the rate-determining step of diffusion to be established. Part 1 of this series has been published as [3].     

Identification and measurements of strong Brønsted acid site in ultrastable Y (USY) zeolite

By using the IRMS-TPD method in which IR (infrared) and MS (mass spectroscopy) worked together, acid sites of USY (ultrastable Y) zeolite were studied. A new band of OH playing a role of Br?nsted acid was clearly detected on Na2H2-ethylenediaminetetraacetic acid (EDTA)-treated USY at 3595 cm(-1) during an elevation in temperature after the adsorption of ammonia. MS-measured TPD (temperature-programmed desorption) of NH3 and IR-measured TPD of the NH4+ cation coincided well to show that this zeolite consisted of the Br?nsted acid sites. The MS-TPD profile at higher temperatures corresponded to the IR-TPD of the 3595-cm(-1) band, and therefore, this OH was identified as a strong acid site. From comparison between IR-TPD of OH and MS-TPD, numbers of three kinds of Br?nsted OH (i.e., those in super and sodalite cages of a Y zeolite structure) and created strong Br?nsted acid site were quantified. On the other hand, strength of the Br?nsted acid site DeltaH was determined individually by a simulation method, where the corrected IR-TPD of OH was simulated based on the proposed equation. Thus, a new strong Br?nsted acid site was identified in the EDTA-treated USY, and the amount and strength was measured quantitatively.     

Ruthenium(Ⅲ) chloride as an efficient catalyst for the synthesis of perimidine derivatives under mild conditions

Various biologically important perimidine derivatives have been synthesized efficiently from various ketones and naphthalene1,8-diamine by using a catalytic amount of RuC13 (1 mol%). This method is a very simple and high yielding reaction for the synthesis of perimidine derivatives.