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1.
Inorg Chem ; 59(5): 2646-2650, 2020 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-32049514

RESUMO

Ditopic helicate ligands 1 and 2 were synthesized for the formation of dinuclear EuIII luminescent chiral helical assemblies (Eu2·L3) in competitive organic and protic solvent media. Spectroscopic analysis revealed formation of the 2:3 (Eu2·L3) and 2:2 (Eu2·L2) species in methanolic solutions. Circular dichroism and circularly polarized luminescence (CPL) spectroscopy confirmed the chiral purity of the helical systems, while scanning electron microscopy imaging demonstrated the formation of hierarchical self-assemblies with spherical morphologies.

2.
ACS Appl Bio Mater ; 3(5): 3413-3422, 2020 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-35025383

RESUMO

Assembly and co-assemblies of peptide amphiphiles through specific noncovalent forces expand the space of molecular architectonics-driven construction of diverse nanoarchitectures with potential biological applications. In this work, cyclic dipeptide amphiphiles (CDPAs) of cyclo(Gly-Asp) with varying lengths of alkyl chains (C8-C18) were synthesized, and their molecular organization was studied. The noncovalent interactions of the components, CDP and alkyl chain, drive the molecular self-assembly of CDPAs into well-defined and diverse nanoarchitectures such as nanotubes, nanospheres, nano/microsheets, and flowers. The co-assembly of CDPAs with biological molecules such as nucleosides was studied to ascertain their utility as potential drug delivery vehicles. Mechanical properties of these nanoarchitectures in nanoindentation study established them as robust in nature. A temperature-dependent NMR study confirmed the formation of stable co-assembly of CDPAs, primarily driven by the intermolecular hydrogen bonding interactions. Computational modeling of oligomers of CDPAs and their co-assembly with nucleosides/nucleotides reveal the molecular level interactions and driving force behind such assemblies. CDPAs exhibit good biocompatibility and cytocompatibility, as revealed by the cellular studies which substantiated their suitability for drug delivery applications. The co-assembly of CDPA with an anticancer drug 5-bromo-2'-deoxyuridine (BrdU) was studied as a drug delivery platform and cytotoxicity was successfully assessed in HeLa cells. Computational modeling of the oligomers of CDPAs and their co-assembly with the drug molecule was performed to understand the molecular level interactions and driving force behind the assemblies. Our findings reveal the design strategy to construct diverse structural architectures using CDP as the modular building unit and specific molecular interactions driven co-assembly for potential application as drug delivery carrier.

3.
Dalton Trans ; 47(35): 12308-12317, 2018 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-30113616

RESUMO

Chiral lanthanide-based supramolecular structures have gained significant importance in view of their application in imaging, sensing and other functional purposes. We have designed chiral C2-symmetrical ligands (L) based on the use of two 2,6-pyridine-dicarboxylic-amide moieties (pda), that differ from one another by the nature of the diamine spacer groups (from 1,3-phenylenedimethanamine (1(S,S), 2(R,R)) and benzene-1,3-diamine (3(S,S), 4(R,R)) to much bulkier 4,4'-(cyclohexane-1,1-diyl)bis(2,6-dimethylaniline) (5(S,S), 6(R,R))) between these two pda units. The self-assembly between L and Eu(iii) ions were investigated in CH3CN solution at low concentration whereby the changes in the absorbance, fluorescence and Eu(iii)-centred emission spectra allowed us to model the binding equilibria occurring in the solution to the presence of [Eu:L2], [Eu2:L2], [Eu2:L3] assemblies and reveal their high binding constant values. The self-assembly in solution were also studied at higher concentration by following the changes in the 1H NMR spectra of the ligands upon Eu(iii) addition, as well as by using MALDI-MS of the isolated solid state complexes. The chiroptical properties of the ligands were used in order to study the structural changes upon self-assembly between the ligands and Eu(iii) ions using circular dichroism (CD) and circularly polarised luminescence (CPL) spectroscopies. The photophysical properties of [Eu2:L3] complexes were evaluated in solution and showed a decrease of luminescence quantum yield when going from the ligand with smaller (1(S,S)) to bulkier (5(S,S)) linker from ∼5.8% to ∼2.6%. While mass-spectrometry revealed the possible formation of trinucler assemblies such as [Eu3:L3] and [Eu3:L2].

4.
Org Lett ; 19(5): 1068-1071, 2017 03 03.
Artigo em Inglês | MEDLINE | ID: mdl-28221046

RESUMO

A facile one-pot synthesis of 3-amino-[1,2,4]-triazolo[4,3-a]pyridines from thiosemicarbazides through anion mediated synthesis is reported. Thiosemicarbazides derived from 2-hydrazino pyridine, 5-chloro 2-hydrazino pyridine, and 2-hydrazine quinoline were formed in situ as anion receptors in the presence of TBAF. Under microwave heating, thiosemicarbazides furnished the triazolo pyridines in good to moderate yields. The formation of the thiosemicarbazides hydrogen bonding anion receptors was critical in cascading the reaction toward the formation of the triazolo pyridines.

5.
Angew Chem Int Ed Engl ; 54(15): 4566-70, 2015 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-25693755

RESUMO

The design and synthesis of tripodal ligands 1-3 based upon the N-methyl-1,3,5-benzenetricarboxamide platform appended with three aryl urea arms is reported. This ligand platform gives rise to highly preorganized structures and is ideally suited for binding SO4 (2-) and H2 PO4 (-) ions through multiple hydrogen-bonding interactions. The solid-state crystal structures of 1-3 with SO4 (2-) show the encapsulation of a single anion within a cage structure, whereas the crystal structure of 1 with H2 PO4 (-) showed that two anions are encapsulated. We further demonstrate that ligand 4, based on the same platform but consisting of two bis-urea moieties and a single ammonium moiety, also recognizes SO4 (2-) to form a self-assembled capsule with [4:4] SO4 (2-) :4 stoichiometry in which the anions are clustered within a cavity formed by the four ligands. This is the first example of a self-sorting self-assembled capsule where four tetrahedrally arranged SO4 (2-) ions are embedded within a hydrophobic cavity.


Assuntos
Benzamidas/química , Fosfatos/química , Sulfatos/química , Ureia/análogos & derivados , Sítios de Ligação , Ligação de Hidrogênio , Ligantes , Metilação , Modelos Moleculares
6.
Chem Commun (Camb) ; 50(74): 10819-22, 2014 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-25089301

RESUMO

The synthesis and characterisation of novel aryl-pyridyl ureas are described, which form self-assembly structures via extended hydrogen bonding and π-π interactions in the solid state, and in selected cases, form supramolecular gels with antimicrobial properties against Staphylococcus aureus and/or Escherichia coli.


Assuntos
Escherichia coli/efeitos dos fármacos , Géis/química , Géis/farmacologia , Staphylococcus aureus Resistente à Meticilina/efeitos dos fármacos , Piridinas/química , Ureia/química , Ureia/farmacologia , Antibacterianos/química , Antibacterianos/farmacologia , Testes de Sensibilidade a Antimicrobianos por Disco-Difusão , Ligação de Hidrogênio
7.
Chemistry ; 18(7): 2021-9, 2012 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-22250048

RESUMO

Six solvated salts of a mononuclear manganese(III) complex with a chelating hexadentate Schiff base ligand are reported. One member of the series, [MnL]PF(6)⋅0.5 CH(3)OH (1), shows a rare low-spin (LS) electronic configuration between 10-300 K. The remaining five salts, [MnL]NO(3)⋅C(2)H(5)OH(2), [MnL]BF(4)⋅C(2)H(5)OH(3), [MnL]CF(3)SO(3)⋅C(2)H(5)OH (4), [MnL]ClO(4)⋅C(2)H(5)OH (5) and [MnL]ClO(4)⋅0.5 CH(3)CN (6), all show gradual incomplete spin-crossover (SCO) behaviour. The structures of all were determined at 100 K, and also at 293 K in the case of 3-6. The LS salt [MnL]PF(6)⋅0.5 CH(3)OH is the only member of the series that does not exhibit strong hydrogen bonding. At 100 K two of the four SCO complexes (2 and 4) assemble into 1D hydrogen-bonded chains, which weaken or rupture on warming. The remaining SCO complexes 3, 5 and 6 do not form 1D hydrogen-bonded chains, but instead exhibit discrete hydrogen bonding between cation/counterion, cation/solvent or counterion/solvent and show no significant change on warming.

8.
Chem Biol Drug Des ; 78(5): 787-99, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21756289

RESUMO

Eight new para-quinones and one known analogue have been synthesized from p-chloranil. Five have been structurally characterized by single crystal diffraction, and a range of ligand folding is observed. All nine have been tested for their potency towards Gram(+) S. aureus and Gram(-) E. coli. Quinones 3, 6, 7 and 8 have shown activity towards S. aureus and quinones 3 and 8 also show good activity towards E. coli.


Assuntos
Antibacterianos , Desenho de Fármacos , Escherichia coli/efeitos dos fármacos , Modelos Químicos , Quinonas , Staphylococcus aureus/efeitos dos fármacos , Antibacterianos/síntese química , Antibacterianos/química , Antibacterianos/farmacologia , Cristalografia por Raios X , Testes de Sensibilidade Microbiana , Conformação Molecular , Quinonas/síntese química , Quinonas/química , Quinonas/farmacologia
9.
Metallomics ; 2(8): 530-4, 2010 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-21072337

RESUMO

The crystal structure and antibacterial activity of the first metal complex of 2-aminophenoxazine-3-one is reported. We describe the silver(i) complex of this important biological molecule and show that the binding mode is through the phenoxazine ring nitrogen. A new synthetic route to 2-aminophenoxazine-3-one is also reported.


Assuntos
Oxazinas/química , Prata/química , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos dos fármacos , Testes de Sensibilidade Microbiana , Modelos Moleculares , Estrutura Molecular , Oxazinas/farmacologia
10.
Org Lett ; 9(15): 2767-70, 2007 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-17580882

RESUMO

The first Cu-catalyzed cross-coupling of aromatic oximes and haloarenes is reported. This one-step formation of the =N-O-Ar linkage gives access to a range of oxime ethers in good to moderate yields.


Assuntos
Cobre/química , Halogênios/química , Iodetos/química , Oximas/química , Modelos Moleculares
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