MODIFICATIONS OF PORPHYRINS UPON ADSORPTION ONTO POROUS VYCOR GLASS.
Item
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Title
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MODIFICATIONS OF PORPHYRINS UPON ADSORPTION ONTO POROUS VYCOR GLASS.
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Identifier
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AAI8611346
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identifier
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8611346
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Creator
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GOONATILLAKE, HAUPAGE WIMALASIRI.
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Contributor
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Thomas C. Strekas
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Date
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1986
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Inorganic
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Abstract
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Corning's code 7930 porous Vycor glass (PVG) pretreated at 550(DEGREES)C in air is used as the solid support for adsorption of tetraphenylporphyrin (TPP) and metallotetraphenylporphyrin complexes from methylene chloride solutions. Immediate color changes and absorption spectral changes of the adsorbate are observed, which suggest chemical modifications. These modifications are characterized via absorption, emission, resonance Raman and electron spin resonance spectroscopies. The acidity of the PVG surface (measured pH value between 3 and 4) plays a role in the protonation phenomena of the adsorbates. The formation of the (pi)-cation radicals on the surface of PVG, the one electron oxidation product of the porphyrin ring, is identified using esr spectroscopy in the absence of air. A hyperfine structure similar to the reported hyperfine pattern of (pi)-cation radicals of porphyrins in solution is observed. In the presence of air the cation radical is further oxidized to the dication which then reacts with nucleophilic surface silanol groups to form the isoporphyrins, the porphyrin derivatives in which the nucleophile is attached to one of the meso positions of the ring. The formation of the isoporphyrin is evidenced by absorption bands at 770 nm and 840 nm and resonance Raman bands. Presence of oxygen is found to be necessary for the formation of the isoporphyrin. Possible mechanisms for the generation of (pi)-cation radicals via interaction with Lewis and Bronsted acid sites on the surface of PVG are discussed.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Chemistry
