Interaction of 1-acylamino-2,2-dichloroethenyl(triphenyl)phosphonium chlorides with alkanolamines

Abstract

It is shown that the interaction of 1-acylamino-2,2-dichloroethenyl(triphenyl)-phosphonium chlorides with alkanolamines having a primary amino group results in the formation of 4-oxazolylphosphonium salts containing hydroxyalkylamine substituents at position 5 of the oxazole cycle. Under similar conditions the reaction of N-substituted alkanolamines with 1-acylamino-2,2-dichloroethenyl-(triphenyl)phosphonium chlorides leads to the formation of 1,3-oxazolidin-2-ylidene derivatives, in which the triphenylphosphonium group is located in the side chain. The structure of the new synthesized compounds has been reliably proven by elemental analysis, IR, ¹Н, ¹³С, ³¹Р NMR spectroscopy, mass spectrometry and single crystal X-ray diffraction.     

Fluorescent macrocyclic chemosensor for Zn(II) detection at alkaline pH values

ABSTRACT

The new macrocyclic ligand L (28,29-dimethoxy-27-oxa-8,11,14,17,25,26-hexaazatetracyclo[22.2.1.1(2,6).1(19,23)]nonacosa-2,4,6(28),19,21,23(29),24,26(1)-octaene) has been synthesised. It contains a tetramine chain and the 2,5-bis(2-methoxy-3-metyl-phenyl)-1,3,4-oxadiazole (PPD-OMe) chromophore, acting as coordinating and sensing units, respectively.

The fluorescent emission of L depends on the pH being highly fluorescent at pH = 2 and not emitting from pH >10. The studies highlighted that L is a PET mediated emitting chemosensor, being the PET effect regulated by the degree of the tetraamine protonation.

L coordinates metal ions (Cu(II), Zn(II) and Cd(II)) in water giving rise to an OFF-ON fluorescent response for the presence of Zn(II) ion thus signalling its presence in the medium. This response is particularly notable at pH = 9 allowing to extend the Zn(II) sensing also in the alkaline pH field.     

NMR studies on 4‐thio‐5‐furan‐modified and 4‐thio‐5‐thiophene‐modified nucleosides

Systematic NMR characterization of 4‐thio‐5‐furan‐pyrimidine nucleosides or 4‐thio‐5‐thiophene‐pyrimidine nucleosides (ribonucleosides and 2′‐deoxynucleosides) was performed. All proton and carbon signals of 4‐thio‐5‐thiophene‐ribouridine and related analogues were unambiguously assigned. The orientations of the base (4‐thiouridine or its deoxy analogue) relative to the ring (furan or thiophene) are explored by a NMR approach and further supported by X‐ray crystallographic studies. The procedures presented here would be applicable to other modified nucleosides and nucleotides. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis of 5‐substituted 1H‐tetrazoles using a recyclable heterogeneous nanonickel ferrite catalyst

An efficient method was developed for the [2 + 3] cycloaddition of sodium azide with nitriles to afford 5‐substituted 1H‐tetrazoles using nanonickel ferrite (NiFe₂O₄) as an effective heterogeneous catalyst in dimethylformamide. The main advantages of this method are high yields, simple methodology and easy work‐up. The catalyst can be recovered and reused for several cycles with predictable activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Preparation of modified MFI (ZSM-5 and silicalite-1) zeolites for potassium extraction from seawater

Modified nanosized MFI (ZSM-5 and silicalite-1) zeolites were successfully synthesized by a hydrothermal method using aluminum isopropoxide and tetraethylorthosilicate as the raw materials. The synthetic zeolites were characterized by X-ray diffraction, energy dispersion spectroscopy, and scanning electron microscopy. The ZSM-5 and silicalite-1 zeolites exhibited ellipse-like and cubic columns, respectively. The K⁺ ion-exchange equilibrium and ion-exchange capacity of the synthetic zeolites in seawater were investigated. The K⁺ ion-exchange of synthetic zeolites was rapid and reached an ion-exchange balance in approximately 20 min. The K⁺ ion-exchange capacity of ZSM-5 and silicalite-1 in seawater was 56.7 and 48.7 mg/g, respectively. The synthetic zeolites have high selectivity toward K⁺, and therefore, they can be used to selectively extract potassium from seawater.     

Biomimetic Approach for Highly Selective Artificial Water Channels Based on Tubular Pillar[5]arene Dimers

Artificial water channels mimicking natural aquaporins (AQPs) can be used for selective and fast transport of water. Here, we quantify the transport performances of peralkyl-carboxylate-pillar[5]arenes dimers in bilayer membranes. They can transport ≈10⁷ water molecules/channel/second, within one order of magnitude of the transport rates of AQPs, rejecting Na⁺ and K⁺ cations. The dimers have a tubular structure, superposing pillar[5]arene pores of 5 Å diameter with twisted carboxy-phenyl pores of 2.8 Å diameter. This biomimetic platform, with variable pore dimensions within the same structure, offers size restriction reminiscent of natural proteins. It allows water molecules to selectively transit and prevents bigger hydrated cations from passing through the 2.8 Å pore. Molecular simulations prove that dimeric or multimeric honeycomb aggregates are stable in the membrane and form water pathways through the bilayer. Over time, a significant shift of the upper vs. lower layer occurs initiating new unexpected water permeation events through toroidal pores.     

Experimental and theoretical studies of Mn(II) and Co(II) metal complexes of a tridentate Schiff's base ligand and their biological activities

We have used the condensation method to synthesize 2-acetyl-5-methylsemicarbazone ligand. Manganese(II) and Cobalt(II) complexes having formula [ML₂]X₂ were synthesized where M = Mn(II) and Co(II), L = ligand, X = Cl⁻, CH₃COO⁻, NO₃⁻, ½SO₄²⁻. The characterization data suggests the octahedral geometry for all the synthesized complexes. Tridentate nature of the 2-acetyl-5-methylsemicarbazone ligand was revealed by IR studies. Molar conductance analysis suggested the electrolytic nature of the complexes. The theoretical study includes geometrical optimization, HOMO-LUMO energy gap, energetic parameters and dipole moment. These results also confirmed the tridentate nature of the ligand and the octahedral geometry of complexes. The molecular electrostatic potential (MEP) study suggested the reactive sites for an electrophilic or nucleophilic attack in the ligand. We tested the synthesized compounds for their antifungal and antibacterial action via well diffusion method and found that parent ligand after the coordination with the metal ion showed more effective inhibition against bacteria and fungi.