Resolving Atomic‐Scale Defects in Conjugated Polymers On‐Surfaces

• Published in: Chemistry : a European journal 2022-08, Vol.28 (48), p.e202200944-n/a
• Main Authors: Mallada, Benjamín, Chen, Qifan, Chutora, Taras, Sánchez‐Grande, Ana, Cirera, Borja, Santos, José, Martín, Nazario, Ecija, David, Jelínek, Pavel, Torre, Bruno
• Format: Article
• Language: English
• Subjects: Anthracene; Atomic force microscopy; Chemistry; conjugated polymers; Current carriers; Defects; Density functional theory; Magnetic moments; Magnetic properties; on-surface synthesis; Optical properties; Polymers; scanning tunneling microscopy
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202200944

Atomic scale defects significantly affect the mechanical, electronic, and optical properties of π‐conjugated polymers. Here, isolated atomic‐scale defects are deliberately introduced into a prototypical anthracene‐ethynylene π‐conjugated polymer, and its local density of states is carefully examined on the atomic scale to show how individual defects modify the inherent electronic and magnetic properties of this one‐dimensional systems. Scanning tunneling and atomic force microscopy experiments, supplemented with density functional theory calculations, reveal the existence of a sharp electronic resonance at the Fermi energy around certain defects, which is associated with the formation of a local magnetic moment accompanied by substantial mitigation of the mobility of charge carriers. While defects in traditionally synthesized polymers lead to arbitrary conformations, the presented results clearly reflect the preferential formation of low dimensional defects at specific polymer sites, which may introduce the possibility of engineering macroscopic defects in surface‐synthesized conjugated polymers. On‐surface synthesis not only allows growing nanomaterials that are not achievable by traditional wet chemistry but also, combined with scanning probe techniques, enables the structure and electronic properties to be resolved with atomic resolution. Here, atomic‐scale structural defects are deliberately introduced into an anthracene‐ethynylene π‐conjugated polymer, and it is shown that such defects may give rise of π‐magnetism. These results demonstrate the potential of defect engineering strategy for fine‐tuning the optoelectronic properties of conjugated polymers.