Noncovalent paramagnetic complexes: detection of halogen bonding in solution by ESR spectroscopy

Mugnaini, Verónica; Punta, Carlo; Liantonio, Rosalba; Metrangolo, Pierangelo; Recupero, Francesco; Resnati, Giuseppe; Pedulli, Gian Franco; Lucarini, Marco

doi:10.1016/j.tetlet.2006.03.033

Cited by 65 publications

(75 citation statements)

References 32 publications

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“…13 C spectra, recorded with broadband proton decoupling in the range 0−200 ppm and 32K data points, were processed using Lorenzian filtering, resulting in 15 Hz resonance broadening followed by a π/2-shifted squared sinebell. The DMSO signal ( 1 H quintuplet at 2.50 ppm, 13 C septuplet at 29.43 ppm) was used as the internal reference. Assignments for 1 H resonances were done on the basis of line splitting patterns caused by homonuclear scalar coupling, while 13 C resonance assignments were supported by GIAO-derived NMR shielding parameters (cf.…”

Section: Methodsmentioning

confidence: 99%

Synthesis and Physico-Chemical Properties in Aqueous Medium of All Possible Isomeric Bromo Analogues of Benzo-1H-Triazole, Potential Inhibitors of Protein Kinases

et al. 2012

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In ongoing studies on the role of the individual bromine atoms of 4,5,6,7-tetrabromobenzotriazole (TBBt) in its relatively selective inhibition of protein kinase CK2α, we have prepared all the possible two mono-, four di-, and two tri-bromobenzotriazoles and determined their physicochemical properties in aqueous medium. They exhibited a general trend of a decrease in solubility with an increase in the number of bromines on the benzene ring, significantly modulated by the pattern of substitution. For a given number of attached bromines, this was directly related to the electronic effects resulting from different sites of substitution, leading to marked variations of pK(a) values for dissociation of the triazole proton. Experimental data (pK(a), solubility) and ab initio calculations demonstrated that hydration of halogenated benzotriazoles is driven by a subtle balance of hydrophobic and polar interactions. The combination of QM-derived free energies for solvation and proton dissociations was found to be a reasonably good predictor of inhibitory activity of halogenated benzotriazoles vs CK2α. Since the pattern of halogenation of the benzene ring of benzotriazole has also been shown to be one of the determinants of inhibitory potency vs some viruses and viral enzymes, the present comprehensive description of their physicochemical properties should prove helpful in efforts to elucidate reaction mechanisms, including possible halogen bonding, and the search for more selective and potent inhibitors.

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Section: Methodsmentioning

confidence: 99%

Synthesis and Physico-Chemical Properties in Aqueous Medium of All Possible Isomeric Bromo Analogues of Benzo-1H-Triazole, Potential Inhibitors of Protein Kinases

et al. 2012

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“…Depending on the hybridization (sp 3 = 2 ), nor its coupling to other nuclei observed. In the electron paramagnetic resonance (EPR, or electron spin resonance, ESR) spectra of an I-appended nitroxide radical, [26] and the halogen-bonded complex of a nitroxide radical with a iodofluorocarbon molecule [27] the expected coupling to the iodine nuclear spin is not observed either, presumably because the nuclear relaxation is too rapid. However, in some cases, where radicals are centered on iodine or near iodine, characteristic sextets resulting from the hyperfine coupling structure caused by the nuclear spin of 127 I (I = 5 = 2 ) can be observed, as exemplified by the s* and iodine radicals formed from RÀI by electron capture in solution [28] and those formed by irradiation of KIO 4 crystals in the presence of O 2À .…”

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confidence: 99%

Commemorating Two Centuries of Iodine Research: An Interdisciplinary Overview of Current Research

et al. 2011

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Iodine was discovered as a novel element in 1811 during the Napoleonic Wars. To celebrate the bicentennial anniversary of this event we reflect on the history and highlight the many facets of iodine research that have evolved since its discovery. Iodine has an impact on many aspects of life on Earth as well as on human civilization. It is accumulated in high concentrations by marine algae, which are the origin of strong iodine fluxes into the coastal atmosphere which influence climatic processes, and dissolved iodine is considered a biophilic element in marine sediments. Iodine is central to thyroid function in vertebrates, with paramount implications for human health. Iodine can exist in a wide range of oxidation states and it features a diverse supramolecular chemistry. Iodine is amenable to several analytical techniques, and iodine compounds have found widespread use in organic synthesis. Elemental iodine is produced on an industrial scale and has found a wide range of applications in innovative materials, including semiconductors--in particular, in solar cells.

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“…As shown from theoretical [56,57] and temperature-dependent EPR studies [58], nitronyl radicals act as very good halogen bond donors and their co-crystallization with 1,4-diiodotetrafluorobenzene provided the very first example of a halogen bonded TEMPO radical, namely, a trimeric entity obtained with 4-amino-TEMPO (Fig. 15a) [59].…”

Section: Nitronyl Radicalsmentioning

confidence: 95%

Organizing Radical Species in the Solid State with Halogen Bonding

Fourmigué

Lieffrig

2014

Topics in Current Chemistry

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The electronic properties (conductivity, magnetism) of radical systems in the solid state essentially depend on (1) the extent of delocalization of the spin density in the molecule and (2) the intermolecular interactions between radicals. The halogen bond has proven very efficient in engineering such magnetic or conducting structures and recent advances along these lines are reviewed here. Three situations are considered: (1) halogenated radical species acting as halogen bond donors, as found in iodotetrathiafulvalene-based chiral conductors or bilayer systems, and in spin crossover (SCO) complexes with halogenated ligands, (2) radical species acting as halogen bond acceptors, such as neutral nitronyl species or anionic, mixed-valence dithiolene complexes, interacting with closed-shell halogen bond donors (iodoperfluoro alkanes and arenes, iodo- or bromo-pyridinium cations), and, finally, (3) charge transfer salts where both halogen bond donor and acceptor are radical species.

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Noncovalent paramagnetic complexes: detection of halogen bonding in solution by ESR spectroscopy

Cited by 65 publications

References 32 publications

Synthesis and Physico-Chemical Properties in Aqueous Medium of All Possible Isomeric Bromo Analogues of Benzo-1H-Triazole, Potential Inhibitors of Protein Kinases

Synthesis and Physico-Chemical Properties in Aqueous Medium of All Possible Isomeric Bromo Analogues of Benzo-1H-Triazole, Potential Inhibitors of Protein Kinases

Commemorating Two Centuries of Iodine Research: An Interdisciplinary Overview of Current Research

Organizing Radical Species in the Solid State with Halogen Bonding

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