Publication Date

Spring 2022

Advisor(s) - Committee Chair

Rui Zhang (Director), Lawrence Hill, Bangbo Yan

Degree Program

Department of Chemistry

Degree Type

Master of Science

Abstract

Chromophores are an important class of compounds in Nature and industry, with several hundred thousand tons produced annually as dyes and pigments. Alone, these compounds absorb light unto themselves; however, several of these compounds can be combined to produce a beneficial cascading transfer of energy to a core chromophore.

In this study, photophysical properties of several covalent and axially borondipyrromethene (BODIPY)-conjugated complexes of porphyrin and salphen scaffolds have been evaluated in a series of emission and catalytic studies. In the porphyrin systems, a beneficial excited energy transfer (EET) from the BODIPY moieties to the porphyrin core was observed; however, only the covalently bound BODIPY metal complexes displayed enhanced activity in the catalytic oxidation reactions in the presence of visible light. The BODIPY-porphyrin ligand displayed fluorescence quenching when excited at the porphyrin or BODIPY moieties roughly equal to 50% of the bare tetra(phenyl)porphyrin (TPP) ligand which indicated an efficient EET from the BODIPY-antennae to the porphyrin core. The axially BODIPY-porphyrin iron(III) complex displayed an intense green fluorescence corresponding to the BODIPY moiety due to an electron transfer from the phenolate ligand to the porphyrin core completely quenching the porphyrin emission. The BODIPY-salphen (L-Salphen) conjugates displayed the opposite EET compared to the porphyrin conjugates, instead transferring energy away from the salphen core to the BODIPY-moieties. A beneficial light effect was observed with the chromium L-Salphen complex; however, the effect was deemed to be the cause of visible light irradiation’s ability to destabilize the meta-stable chromium-oxo bond rather than an EET of the BODIPY-moieties to salphen core.

In addition, several iron(III) phthalocyanine complexes [FeIII(Pc)Cl] were synthesized and evaluated in the catalytic oxidation of thioanisoles to compare their viability to previous metalloporphyrin systems. The [FeIII(Pc)Cl] catalysts gave quantitative conversions of the starting sulfides with moderate to excellent selectivity towards sulfoxide over sulfone but displayed an unexpected sustainability towards oxidative degradation even with mild terminal oxidants, i.e., iodobenzene diacetate [PhI(OAc)2]. Nonetheless, efforts were made to probe the active oxospecies with PhI(OAc)2, and a putative iron(IV)-oxo radical cation was spectroscopically observed in the systems of unsubstituted phthalocyanine [H2(Pc)] and the 1,4,5,8,9,12,13,16-(a)- octabutyloxyphthalocyanine [H2(α-(OBu)8-Pc)] ligands.

Disciplines

Inorganic Chemistry | Organic Chemistry

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