Bond cleavage reactions initiated by long-wavelength light are needed to extend the scope of the caged-uncaged paradigm into complex physiological settings. Axially unsymmetrical silicon phthalocyanines (SiPcs) undergo efficient release of phenol ligands in a reaction contingent on three factors - near-IR light (690 nm), hypoxia, and a thiol reductant. These studies detail efforts to define the mechanistic basis for this unique conditionally-dependent bond cleavage reaction. Spectroscopic studies provide evidence for the formation of a key phthalocyanine radical anion intermediate formed from the triplet state in a reductant-dependent manner. Computational chemistry studies indicate that phenol ligand solvolysis proceeds through a heptacoordinate silicon transition state and that this solvolytic process is favored following SiPc radical anion formation. These results provide insight regarding the central role that radical anion intermediates formed through photoinduced electron transfer with biological reductants can play in long-wavelength uncaging reactions.
An experimental study on the absorption, emission, crystal quality, and morphological characteristics of the transition metal doped zinc selenide (ZnSe) crystals is performed. This study focuses on the effect of dopant and thermal convection on crystal characteristics. Two ZnSe crystals, one doped with Fe2+ and the other with Cr2+, are grown using the physical vapor transport method. The bulk crystal samples are further divided into localized zones and overall crystallinity is evaluated using optical transparency, scanning electron microscopy, and X‐ray diffraction analyses. Gross defects, such as large precipitates, inclusions and voids, are not observed. The radial segregation and its effect on morphology and optical fluorescence and emission are studied for both doped crystals using different spots along the radius for both crystals. The absorption and emission properties are investigated and the results are discussed in terms of the energy levels from which the optical transitions occur.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.