Studying an antiaromatic polycyclic hydrocarbon adsorbed on different surfaces.

Area of Science:

• * Molecular chemistry
• * Surface science
• * Quantum chemistry

Background:

• * Antiaromatic and open-shell molecules exhibit unique electronic and magnetic properties.
• * High reactivity of these molecules poses challenges for their study.
• * Indeno[1,2-b]fluorene (IF) is a reactive antiaromatic molecule of interest.

Purpose of the Study:

• * To generate and characterize the antiaromatic molecule indeno[1,2-b]fluorene (IF).
• * To investigate the stability and properties of IF in solution and on surfaces.
• * To understand the influence of molecule-surface interactions on electronic properties.

Main Methods:

• * Generation of IF in solution via KI-induced dehalogenation.
• * On-surface generation of IF using atom manipulation at low temperatures.
• * Characterization using non-contact atomic force microscopy (nc-AFM) with CO-functionalized tips for bond-order analysis.
• * Orbital imaging using scanning tunneling microscopy (STM).

Main Results:

• * IF was generated in solution and found to be stable for minutes at ambient conditions.
• * On a bilayer NaCl film, IF preserved its predicted closed-shell configuration and antiaromatic character.
• * On a Cu(111) surface, chemisorption led to significant bond-order reorganization in the s-indacene moiety of IF.
• * Molecule-surface interactions were shown to significantly impact π-electron distribution.

Conclusions:

• * The study successfully generated and characterized the reactive antiaromatic molecule IF.
• * The electronic properties of IF are sensitive to the substrate, with preservation on insulating NaCl and modification on metallic Cu(111).
• * This work highlights the critical role of surface interactions in determining the behavior of reactive molecules.