Are there pi* shape resonances in electron scattering from phosphate groups?

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Quantum Chemistry

Background:

• Temporary anion states are crucial for understanding electron interactions with molecules.
• The P=O bond is common in biological molecules, including DNA.
• Pi* resonances are typically associated with multiple bonds and influence molecular reactivity.

Purpose of the Study:

• To investigate the nature of temporary anion states in trimethyl phosphate and related P=O compounds.
• To determine if these states exhibit pi* resonance characteristics.
• To assess the implications for the phosphate group in DNA.

Main Methods:

• Electron transmission spectroscopy (ETS) was employed to probe molecular energy levels.
• Ab initio calculations were performed to model electronic structures and interactions.
• A novel computational method was developed to analyze molecular orbital properties.

Main Results:

• No evidence of pi* resonances was found in trimethyl phosphate ((CH3O)3PO).
• Chlorophosphoryl dichloride (Cl3PO) showed characteristics attributed to sigma* orbitals, not P=O multiple bonding.
• The study presents a new computational approach for analyzing electron confinement.

Conclusions:

• Temporary anion states in trimethyl phosphate do not appear to involve pi* resonances.
• The phosphate group in DNA is unlikely to exhibit such resonances.
• The observed characteristics in Cl3PO originate from sigma* orbitals, highlighting the importance of orbital spatial properties.