Investigating the change in the photophysical properties of a trio of tetraphenylcyclopentadienone derivatives with varied groups on the aromatic rings in the 3‐ and 4‐positions

Abstract

Organic compounds with electronic properties, such as a small band gap, are useful in areas ranging from organic field effect transistors to solar cells. Such organic compounds can possess conjugation and/or aromatic systems, with one example being tetraphenylcyclopentadienone and its derivatives. A trio of dramatically coloured tetraphenylcyclopentadienone derivatives with varied substituents on the aromatic rings in the 3‐ and 4‐positions were prepared. Their identities were confirmed using the usual methods, for example 1H nuclear magnetic resonance (NMR) spectroscopy, and their purity quantified using elemental analysis. The X‐ray crystal structure of compound 2 was determined. Its notable structural features involved the cyclopentadienone core with its distinct C−C and C=C bond lengths and its overall nonplanarity, both of which served to mitigate its antiaromatic nature. Chloroform solutions of compounds 2–4 exhibited absorption spectra with three absorption bands at approximately 250, 350, and 500 nm that were assigned to (π)→(π*) transitions. Computational chemistry methods assisted in assigning the observed transitions to a specific molecular orbital combination in the structures of 2–4. Emission in the red end of the visible spectrum (550–625 nm) was observed from chloroform solutions of all three of the prepared compounds.