Abstract:Oxenium ions are important reactive intermediates in synthetic chemistry and enzymology, but little is known of the reactivity, lifetimes, spectroscopic signatures, and electronic configurations of these unstable species. Recent advances have allowed these short-lived ions to be directly detected in solution from laser flash photolysis of suitable photochemical precursors, but all of the studies to date have focused on aryloxenium ions having closed-shell singlet ground state configurations. To study alternati… Show more
“…To study alternative spin configurations for important reactive intermediates such as oxenium ions, which are not very well known regarding their reactivity, lifetimes, and electronic configurations, a photo-precursor was synthesized to the m-dimethylamino phenyloxenium ion. This method achieved direct spectroscopic detection and EPR investigation of a ground-state triplet phenyl oxenium ion possible [ 40 ].…”
Section: Detection Examples Of Reactive Oxygen and Nitrogen Speciementioning
During the last decade there has been growing interest in physical-chemical oxidation processes and the behavior of free radicals in living systems. Radicals are known as intermediate species in a variety of biochemical reactions. Numerous techniques, assays and biomarkers have been used to measure reactive oxygen and nitrogen species (ROS and RNS), and to examine oxidative stress. However, many of these assays are not entirely satisfactory or are used inappropriately. The purpose of this chapter is to review current EPR (Electron Paramagnetic Resonance) spectroscopy methods for measuring ROS, RNS, and their secondary products, and to discuss the strengths and limitations of specific methodological approaches.
“…To study alternative spin configurations for important reactive intermediates such as oxenium ions, which are not very well known regarding their reactivity, lifetimes, and electronic configurations, a photo-precursor was synthesized to the m-dimethylamino phenyloxenium ion. This method achieved direct spectroscopic detection and EPR investigation of a ground-state triplet phenyl oxenium ion possible [ 40 ].…”
Section: Detection Examples Of Reactive Oxygen and Nitrogen Speciementioning
During the last decade there has been growing interest in physical-chemical oxidation processes and the behavior of free radicals in living systems. Radicals are known as intermediate species in a variety of biochemical reactions. Numerous techniques, assays and biomarkers have been used to measure reactive oxygen and nitrogen species (ROS and RNS), and to examine oxidative stress. However, many of these assays are not entirely satisfactory or are used inappropriately. The purpose of this chapter is to review current EPR (Electron Paramagnetic Resonance) spectroscopy methods for measuring ROS, RNS, and their secondary products, and to discuss the strengths and limitations of specific methodological approaches.
“…This study may promote the advancement of the drug discovery and development process . Similar ultrafast spectroscopy measurements have been used to directly observe the photophysical and photochemical processes from femtoseconds to final products for very fast reactions …”
Section: Introductionmentioning
confidence: 99%
“…[23] Similar ultrafast spectroscopy measurements have been used to directly observe the photophysical and photochemical processes from femtoseconds to final products for very fast reactions. [24][25][26]…”
Imatinib is a synthetic tyrosinase inhibitor that is employed for the treatment of some kinds of human cancer. This drug has a low phototoxicity towards DNA, but its pyridylpyrimidine (1) fragment by itself exhibits significant phototoxicitiy. The intrinsic mechanism that leads to the enhanced photosafety of Imatinib is not yet known. Here, the properties of the excited state and interchromophoric interactions of Imatinib have been explored by using ultrafast laser flash photolysis and agarose electrophoresis studies. An intramolecular charge separation was directly observed for the irradiated Imatinib, which accounts for the relaxation of its excited state. An anionic form of pyridylpyrimidine (1) was deduced from the results of time-resolved resonance Raman spectra and by quenching experimental studies on compound 1 and diaminotoluene. In contrast, compound 1 efficiently transformed into triplet excited states with a long lifetime, which explained the phototoxicity associated with this fragment. This work provides insight into how to design drugs with lower phototoxicitiy or improved photostability by using interchromophoric interactions.
“…As a result, almost all benzylic cationic reactive intermediates are ground state singlet species, [39][40][41] with a few exceptions. 42 However, substituting the reactive intermediate can alter the energies of the frontier orbitals and lead to triplet ground states being adopted. [43][44] Here, we find that iodine atoms substituted on the aromatic rings lower the singlettriplet gaps of benzylic reactive intermediates, in some cases making the triplet state the computed ground state.…”
Manipulating frontier orbital energies of aromatic molecules with substituents is key to a variety of chemical and material applications. Here, we investigate a simple strategy for achieving high-energy inplane orbitals for aromatics simply by positioning iodine atoms next to each other. The lone pair orbitals on the iodines mix to give a high-energy in-plane σ-antibonding orbital as the highest occupied molecular orbital (HOMO). We show that this effect can be used to manipulate orbital gaps, the symmetry of the highest occupied orbital, and the adopted electronic state for reactive intermediates. This electronic effect is not limited to reactive intermediates, and we demonstrate that this iodine buttressing strategy also can be used to achieve small HOMO-lowest unoccupied molecular orbital (HOMO-LUMO) gaps in organic electronic materials. Iodinated oligomers of several of the most popular conducting polymers are computed to have smaller HOMO-LUMO gaps than the unsubstituted materials. This iodine buttressing approach for generating high-energy in-plane HOMOs is anticipated to be highly general. While the unusual properties of fluorous materials are well established, at the other extreme on the periodic table novel properties of iodous materials may await discovery. Disciplines Disciplines Organic Chemistry Comments Comments
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