Structures and electron affinity energies of polycyclic quinones

Area of Science:

• Computational chemistry
• Organic chemistry
• Materials science

Background:

• Polycyclic quinones are crucial in various chemical processes.
• Understanding their electronic properties, like electron affinity energy (EAE), is key to designing new materials.
• Factors influencing EAE in quinones require detailed investigation.

Purpose of the Study:

• To calculate and analyze the quinoid structures, semiquinone radical structures, and EAEs of diverse polycyclic quinones.
• To identify the key structural and electronic factors governing EAE in these compounds.
• To computationally predict and experimentally validate the EAE of specific quinone derivatives.

Main Methods:

• Density Functional Theory (DFT) calculations were employed to determine molecular structures and electronic properties.
• Analysis of factors contributing to quinoid structural instability, including spatial repulsion and antiaromaticity.
• Assessment of stabilizing factors for semiquinone radical structures, such as inductive effects, hydrogen bonds, electrostatic interactions, and orbital interactions.
• X-ray crystallography was used to confirm calculated structural data.

Main Results:

• A strong correlation was observed between unstable quinoid structures, stable semiquinone radical structures, and high EAEs.
• Antiaromaticity and spatial repulsion were identified as primary drivers of quinoid instability.
• Inductive effects, hydrogen bonding, electrostatic, and orbital interactions significantly stabilized semiquinone radicals.
• Compound 11 exhibited the highest EAE due to combined antiaromaticity and favorable orbital interactions.
• Experimental crystal structure data for compound 8 validated the accuracy of the computational methods.

Conclusions:

• The study elucidates the critical relationship between molecular structure, electronic properties, and EAE in polycyclic quinones.
• Computational methods provide reliable predictions for EAE, guiding the design of quinones with tailored electronic characteristics.
• Compound 11 represents a promising candidate for applications requiring high electron affinity.