The Synthesis and Photophysical Properties of a Pyrene-Functionalized Benzophenone

Date of Award

5-1-2023

Document Type

Thesis

Degree Name

Master of Science in Chemistry

First Advisor

Erwin P. Enriquez, PhD

Abstract

Pi-conjugated molecules have been widely used as organic electronic devices, a huge portion of which are polycyclic aromatic hydrocarbons (PAH) due to their interesting optical and electronic properties. Two such molecules are pyrene and benzophenone, whose derivatives exhibit interesting photophysical properties and have been widely used in organic electronics, mainly as emissive layers in OLEDs. In this work, these two molecules were directly linked together to form a new pyrene- functionalized benzophenone derivative---abbreviated as 4-PyPhCO---via a one-step Suzuki-Miyaura coupling reaction, and its photophysical properties were studied. The compound was a yellow to yellow-green powder whose identity was confirmed with FTIR and 1H-NMR spectroscopy. It was also observed from its 1H-NMR spectrum that there is severe twisting of one of the pyrene groups in the pyrene-functionalized benzophenone, which was supported by its theoretical molecular geometry. Its UV-vis absorption spectrum in CHCl3 solvent revealed that pyrene is its main chromophore with observed bathochromic shifts in its absorption peaks. It also exhibited a sky-blue photoluminescence, with a maximum emission at 480 nm and a quantum yield comparable to that of pyrene obtained from related literature. The theoretical and electrochemical data of 4-PyPhCO also revealed that although its HOMO energy does not significantly differ from pyrene, its LUMO was significantly lower due to the electron-donation of the pyrene moieties to the benzophenone. It can therefore be inferred that there is a donor-acceptor-donor effect in 4-PyPhCO, which is the main reason for its unique photophysical properties.

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