1,586 research outputs found
Polarity study of ionic liquids with the solvatochromic dye Nile Red: a QSPR approach using in silica VolSurf+ descriptors
No full textThe in silico VolSurfþ descriptors, accounting for both cationic and anionic structural features of ionic
liquids (ILs) were used to develop a Partial Least Squares (PLS) model able to establish a Quantitative
Structure Property Relationship (QSPR) correlation with their solvatochromic dye Nile Red polarity. The
PLS model allowed prediction of ENR values for 116 ILs providing an in silico ILs polarity database
Photoinduced ICT <i>vs.</i> excited rotamer intercoversion in two quadrupolar polyaromatic <i>N</i>-methylpyridinium cations
No full textThe excited state deactivation of two quadrupolar polyaromatic N-methylpyridinium cations is ruled by either Rotamer Interconversion (RI) in the molecule bearing two naphthyl side groups or Intramolecular Charge Transfer (ICT) by extending the aromaticity in the pyrenyl derivative.</p
Photochemistry and DNA-affinity of some pyrimidine-substituted styryl-azinium iodides
No full textThe relaxation properties of the excited states of three iodides of trans-1,2-diarylethene analogues (where one aryl group is a methylpyridinium, methylquinolinium or dimethylimidazolium group and the other one is a phenyl ring para-substituted by a pyrimidine ring) have been investigated in buffered (pH = 7) aqueous solution. As found in previous works for several analogues, these quaternized salts undergo efficient trans→cis photoisomerization while the yield of the radiative deactivation is very small at room temperature. The solvent effect on the spectral behaviour indicates the occurrence of intramolecular charge transfer which can induce interesting non-linear optical properties. The results of a study of the interactions of these salts with DNA, which might affect the cell metabolism, showed a relatively modest binding affinity for the pyridinium and imidazolium salts and a more substantial affinity for the quinolinium analogue. The formation of ligand-DNA complexes affects only slightly the radiative relaxation yield while leading to a relevant reduction of the isomerization yield. Measurements of the linear dichroism behaviour of the three compounds and comparison with three analogues bearing furan or thienyl groups, which have been found to display different affinity with DNA in previous works, gave interesting information on the nature of the ligand-DNA binding of these compounds
Synthesis and preliminary antibacterial evaluation of Linezolid-like 1,2,4-oxadiazole derivatives
No full textIn the present study the synthesis of new Linezolid-like molecules has been achieved by substitution
of the oxazolidinone central heterocyclic moiety with a 1,2,4-oxadiazole ring. Two series of
1,2,4-oxadiazoles, bearing different side-chains and containing a varying number of fluorine atoms, were
synthesized and preliminarily tested for biological activity against some Gram-positive and Gramnegative
bacteria using Linezolid and Ceftriaxone as reference drugs
Asymmetric synthesis and biological evaluation of 1,2,4-Oxadiazoles analogues of Linezolid
No full textOxazolidinones are a class of antibacterial agents which displayed activity againist a variety of gram-positive pathogens and are highly potent against multidrug-resistant bacteria. Linezolid is the first oxazolidinone antibiotic approved for clinical use but linezolid resistance began to appear. 1,2,4 – Oxadiazoles are known bioactive heterocycles whose activity has been often associated to their bioisosterism with amide or ester functionalities [1].
As results of a research project on the molecular design of heterocycle – based antibacterials to contrast Multi-Drug Resistance (MDR) [2], we report the synthesis of 1,2,4 - Oxadiazole analogues of Linezolid. The synthesis has been achieved by substitution of the morpholine ( C-ring ) with the Oxadiazole ring [3,4]. The central oxazolidinone ring was obtained through the Manninen reaction. Synthesized compounds showed good activity against Linezolid-resistant bacteria
Efficient Excited-State Symmetry Breaking in a Cationic Quadrupolar System Bearing Diphenylamino Donors
No full textWe report a joint experimental and theoretical investigation of a quadrupolar D-π-A(+) -π-D system, the electron donors being diphenylamino groups and the electron acceptor being a methylpyridinium, in comparison with the dipolar D-π-A(+) system. The emission spectra of the two compounds overlap in all the investigated solvents. This finding could be rationalized by TD-DFT calculations: the LUMO-HOMO molecular orbitals involved in the emission transition are localized on the same branch of the quadrupolar structure that becomes the fluorescent portion, corresponding to that of the single-arm compound. Excited-state symmetry breaking has been rarely observed for quadrupolar systems showing negative solvatochromism and is here surprisingly revealed, even in low polarity solvents. Femtosecond transient absorption measurements revealed that an efficient photoinduced intramolecular charge transfer takes place in the quadrupolar chromophore, more efficient than in its dipolar analogue. This result is promising in view of the application of these compounds as novel two-photon absorbing materials
Prolog+CG: A Maintainer's Perspective
No full text Prolog+CG is an implementation of Prolog with Conceptual Graphs as first-class datastructures, on a par with terms. As such, it lends itself well to applications in which reasoning with Conceptual Graphs and/or ontologies plays a role. It as originally developed by Prof. Dr. Adil Kabbaj, who in 2004 turned over maintainership of Prolog+ CG to the present author. In this paper, Prolog+CG is described in terms of its history, evolution, and maintenance. A special web-enabled version of Prolog+CG is also described. Possible interoperability with CGIF and the CharGer tool are explored. Finally, we offer some general observations about the tenets that make Prolog+CG a success.</p
Photobehaviour of methyl-pyridinium and quinolinium iodide derivatives, free and complexed with DNA. A case of bisintercalation.
No full textExcited state dynamics of four azinium salts were studied in buffered water and in the presence of salmon testes DNA. Complexation with DNA changes the photobehaviour of the free ligands lowering the photoreactivity and emission in favor of internal conversion. The interaction of these four dyes with DNA was studied with different techniques with the aim to establish the affinity and the type of binding between the ligands and DNA. The results from spectrophotometric and fluorimetric titrations provided evidence of a strong interaction between the azinium salts and the polynucleotide, with a binding constant of about 10(6) M(-1), making them interesting for therapeutical applications. Dichroic measurements allowed us to determine the possible modes of binding for each complex. Short living excited states of the free dyes were detected and characterized by ultrafast absorption spectroscopy. A further decrease of transient lifetimes was observed upon interaction with DNA. The bicationic pyridinium iodide was found to act as a bisintercalative agent, potentially increasing the cytotoxicity with low dose and less collateral effects
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