Multiconfigurational Ground State of a Diradicaloid Characterized at the Atomic Scale

Area of Science:

• Molecular physics
• Surface science
• Quantum chemistry

Background:

• Understanding molecular behavior at the nanoscale is crucial for developing new materials and electronic devices.
• Investigating molecules with unusual electronic structures, like diradicaloids, can reveal fundamental quantum mechanical phenomena.

Purpose of the Study:

• To experimentally generate and characterize a singlet diradicaloid molecule composed of two phenalenyl units linked by a C4 chain.
• To investigate the electronic correlations and many-body ground state of the diradicaloid using advanced scanning probe techniques.
• To correlate experimental findings with theoretical multiconfigurational calculations.

Main Methods:

• Tip-induced molecular synthesis on an ultrathin insulating sodium chloride (NaCl) surface.
• Atomic force microscopy (AFM) for measuring bond-order contrast.
• Scanning tunneling microscopy (STM) for mapping charge-state transitions.
• Multiconfigurational quantum chemical calculations for theoretical analysis.

Main Results:

• Successful generation and characterization of a singlet diradicaloid molecule.
• Experimental evidence of significant bond-order variations along the C4 chain, indicative of delocalized electrons.
• Observation of distinct charge-state transitions, confirming a complex many-body ground state.
• Demonstration of strong electronic correlations affecting the molecule's geometry and electronic properties.

Conclusions:

• The study provides experimental validation for the manifestation of strong electronic correlations in a single molecule.
• The findings highlight the capability of scanning probe microscopy in probing intricate electronic phenomena at the molecular level.
• This work contributes to the fundamental understanding of molecular magnetism and correlated electron systems.