Search results for "Fluorine"

STUDIO DELLA BIODISTRIBUZIONE DI SOSTANZE BIOLOGICAMENTE ATTIVE IN ORGANISMI ACQUATICI

2022

Fluorine in Medicinal Chemistry and Chemical Biology. Edited by Iwao Ojima.

2009

Fluorinated Heterocyclic Compounds. A Photochemical Approach to a Synthesis of Fluorinated Quinazolin-4-ones

2004

An efficient and generalized photochemical methodology for the preparation of fluorinated quinazolin-4-ones is described. Depending on the starting substrate, quinazolin-4-ones bearing a perfluoroalkyl- or perfluoroaryl- substituent in position 2 or fluorine atoms on any positions of the benzo-fused moiety can easily be obtained. 5-Aryl-3-perfluoroalkylpentafluorophenyl- or 5-polyfluoroaryl-3-phenyl(methyl)-1,2,4-oxadiazoles, respectively, can be considered as ideal precursors that can be transformed into the target quinazolin-4-ones by irradiation in the presence of triethylamine (TEA) (at λ = 313 nm) or pyrene (at λ = 365 nm) in dry methanol or acetonitrile as solvent. Some mechanistic co…

A3- and A2B-fluorocorroles: synthesis, X-ray characterization and antiviral activity evaluation against human cytomegalovirus infection

2020

Twenty-nine fluorinated corroles were prepared, spectroscopically characterized, and studied for their antiviral activity against human cytomegalovirus infection. Six corroles were also fully characterized by X-ray crystallography giving insights on their geometrical features. The halogenated corroles reported herein exhibit significantly improved antiviral activity over their non-halogenated counterparts and over nitro-corrole analogs previously reported. Full activity of thirteen A3-corroles is achieved with four fluorine atoms present on the meso-phenyl ring reaching a selectivity index above 300. The maximum activity is achieved for A2B-corroles with selectivity indexes above 400. We th…

Predicting and Tuning Physicochemical Properties in Lead Optimization: Amine Basicities

2007

This review describes simple and useful concepts for predicting and tuning the pK(a) values of basic amine centers, a crucial step in the optimization of physical and ADME properties of many lead structures in drug-discovery research. The article starts with a case study of tricyclic thrombin inhibitors featuring a tertiary amine center with pK(a) values that can be tuned over a wide range, from the usual value of around 10 to below 2 by (remote) neighboring functionalities commonly encountered in medicinal chemistry. Next, the changes in pK(a) of acyclic and cyclic amines upon substitution by fluorine, oxygen, nitrogen, and sulfur functionalities, as well as carbonyl and carboxyl derivativ…

Impact of fluorine admixture, hydrogen loading, and exposure to ArF excimer laser on photoluminescence of bismuth defects in amorphous silica

2013

Abstract Photoluminescence (PL) excited by ArF (193 nm), KrF (248 nm) and N 2 (337 nm) pulsed lasers is studied in bismuth doped unfused silicon dioxide synthesized on silica substrates by surface-plasma chemical vapor deposition (SPCVD). Additive free and fluorinated (F content ~ 0.4 wt.%) amorphous silica are examined as host materials for bismuth. Three typical PL bands peaking at wavelengths of 650 nm (orange), 800 nm and 1400 nm (near infrared, NIR) were observed. It is found that fluorine additive weakly affects PL detail of as deposited samples. However, hydrogen loading completely deactivates NIR PL in the case of fluorine free sample, but only slightly suppresses the NIR band in fl…

Fluorine-free blue-green emitters for light-emitting electrochemical cells

2014

Date of Acceptance: 29/05/2014 There is presently a lack of efficient and stable blue emitters for light-emitting electrochemical cells (LEECs), which limits the development of white light emitting systems for lighting. Cyclometalated iridium complexes as blue emitters tend to show low photoluminescence efficiency due to significant ligand-centred character of the radiative transition. The most common strategy to blue-shift the emission is to use fluorine substituents on the cyclometalating ligand, such as 2,4-difluorophenylpyridine, dFppy, which has been shown to decrease the stability of the emitter in operating devices. Herein we report a series of four new charged cyclometalated iridium…

Influence of fluorine on the fiber resistance studied through the nonbridging oxygen hole center related luminescence

2013

The distribution of Non-Bridging Oxygen Hole Centers (NBOHCs) in fluorine doped optical fibers was investigated by confocal microluminescence spectroscopy, monitoring their characteristic 1.9 eV luminescence band. The results show that these defects are generated by the fiber drawing and their concentration further increases after c irradiation. The NBOHC concentration profile along the fiber provides evidence for an exponential decay with the fluorine content. This finding agrees with the role of fluorine in the fiber resistance and is discussed, from the microscopic point of view, by looking at the conversion mechanisms from strained bonds acting as precursors.

Rotational spectra of CF+and13CF+: accurate rest frequencies and spectroscopic parameters

2010

Context. The astrophysical relevance of the fluoromethylidynium ion and its importance for the interstellar chemistry of fluorine motivated the present laboratory spectroscopic investigation of both 12 CF + and the corresponding 13 C-containing isotopologue, 13 CF + . Aims. This investigation has been carried out to provide accurate rest frequencies for future (radioastronomical) observations, to improve the accuracy of the values for the spectroscopic parameters available in the literature for CF + , and to provide them for the first time for 13 CF + . Methods. Rotational spectra of CF + and 13 CF + were recorded in the millimeter- and submillimeter-wave frequency ranges. Their investigati…

Subsecond fluorine-19 MRI of the lung

2006

Minimal scan times in rapid fluorine-19 MRI using sulfur hexafluoride (SF6) have been on the order of 10 s. Because of the very short T1 relaxation time of SF6 (T1 = 1.65 ms), high receiver bandwidths are necessary to allow for a high number of excitations. Since high bandwidths cause high levels of electronic noise, SNR per acquisition has been too low to further reduce scan time. The purpose of this study was to investigate whether scan times could be reduced using hexafluoroethane (C2F6), a gas with a longer T1 (T1 = 7.9 ms) at a relatively low bandwidth of 488 Hz/pixel. Gradient-echo images were acquired during and after completion of the wash-in of a 70% C2F6- 30% O2 mixture. Peak SNR …