Ring Currents in the Clar Goblet Calculated Using Configurational State Averaging.

Area of Science:

• Theoretical Chemistry
• Quantum Chemistry
• Materials Science

Background:

• The Hückel-London-Pople-McWeeny formalism is a standard for calculating ring currents in closed-shell systems.
• Understanding electronic properties of open-shell molecules, like the Clar goblet, is crucial for novel materials.
• The Clar goblet presents a challenge due to conflicting ground state multiplicity rules (Hund's vs. Ovchinnikov's).

Purpose of the Study:

• To extend the Hückel-London-Pople-McWeeny formalism to handle open-shell configurations using configurational averages.
• To investigate the electronic ring currents in the non-Kekulean benzenoid Clar goblet.
• To analyze the impact of different charge states (neutral, dication, dianion) on the Clar goblet's ring currents.

Main Methods:

• Extension of the Hückel-London-Pople-McWeeny formalism to configurational averages for open shells.
• Application of Hückel-London and Hubbard-London models to calculate ring-current maps.
• Comparison with ipsocentric pseudo-π and ab initio π-current maps for validation.

Main Results:

• The extended formalism successfully calculates ring currents for open-shell systems.
• The Clar goblet exhibits twin diatropic perimeter currents on distinct molecular halves across its dication, dianion, and neutral states.
• Disagreement in ground state multiplicity rules (triplet vs. singlet) had minimal impact on predicted ring currents.

Conclusions:

• Configurationally averaged Hückel-London calculations accurately describe the diatropic ring currents in the Clar goblet.
• The study provides valuable insights into the electronic behavior of open-shell polycyclic aromatic hydrocarbons.
• The findings support the application of this extended formalism for studying complex molecular systems.