Tuning the Spin Interaction in Non-planar Organic Diradicals Through Mechanical Manipulation
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2024
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| author | Vegliante, Alessio Fernandez, Saleta Ortiz, Ricardo Vilas-Varela, Manuel Baum, Thomas Friedrich, Niklas Romero-Lara, Francisco Aguirre, Andrea Vaxevani, Katerina Wang, Dongfei Garcia, Carlos van der Zant, Herre S. J. Frederiksen, Thomas Peña, Diego Pascual, Jose Ignacio |
| author_facet | Vegliante, Alessio Fernandez, Saleta Ortiz, Ricardo Vilas-Varela, Manuel Baum, Thomas Friedrich, Niklas Romero-Lara, Francisco Aguirre, Andrea Vaxevani, Katerina Wang, Dongfei Garcia, Carlos van der Zant, Herre S. J. Frederiksen, Thomas Peña, Diego Pascual, Jose Ignacio |
| contents | Open-shell polycyclic aromatic hydrocarbons (PAHs) represent promising building blocks for carbon-based functional magnetic materials. Their magnetic properties stem from the presence of unpaired electrons localized in radical states of $π$ character. Consequently, these materials are inclined to exhibit spin delocalization, form extended collective states, and respond to the flexibility of the molecular backbones. However, they are also highly reactive, requiring structural strategies to protect the radical states from reacting with the environment. Here, we demonstrate that the open-shell ground state of the diradical 2-OS survives on a Au(111) substrate as a global singlet formed by two unpaired electrons with anti-parallel spins coupled through a conformational dependent interaction. The 2-OS molecule is a protected derivative of the Chichibabin's diradical, featuring a non-planar geometry that destabilizes the closed-shell quinoidal structure. Using scanning tunneling microscopy (STM), we localized the two interacting spins at the molecular edges, and detected an excited triplet state a few millielectronvolts above the singlet ground state. Mean-field Hubbard simulations reveal that the exchange coupling between the two spins strongly depends on the torsional angles between the different molecular moieties, suggesting the possibility of influencing the molecule's magnetic state through structural changes. This was demonstrated here using the STM tip to manipulate the molecular conformation, while simultaneously detecting changes in the spin excitation spectrum. Our work suggests the potential of these PAHs for a new class of all-carbon spin-crossover materials. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2402_08641 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Tuning the Spin Interaction in Non-planar Organic Diradicals Through Mechanical Manipulation Vegliante, Alessio Fernandez, Saleta Ortiz, Ricardo Vilas-Varela, Manuel Baum, Thomas Friedrich, Niklas Romero-Lara, Francisco Aguirre, Andrea Vaxevani, Katerina Wang, Dongfei Garcia, Carlos van der Zant, Herre S. J. Frederiksen, Thomas Peña, Diego Pascual, Jose Ignacio Mesoscale and Nanoscale Physics Chemical Physics Open-shell polycyclic aromatic hydrocarbons (PAHs) represent promising building blocks for carbon-based functional magnetic materials. Their magnetic properties stem from the presence of unpaired electrons localized in radical states of $π$ character. Consequently, these materials are inclined to exhibit spin delocalization, form extended collective states, and respond to the flexibility of the molecular backbones. However, they are also highly reactive, requiring structural strategies to protect the radical states from reacting with the environment. Here, we demonstrate that the open-shell ground state of the diradical 2-OS survives on a Au(111) substrate as a global singlet formed by two unpaired electrons with anti-parallel spins coupled through a conformational dependent interaction. The 2-OS molecule is a protected derivative of the Chichibabin's diradical, featuring a non-planar geometry that destabilizes the closed-shell quinoidal structure. Using scanning tunneling microscopy (STM), we localized the two interacting spins at the molecular edges, and detected an excited triplet state a few millielectronvolts above the singlet ground state. Mean-field Hubbard simulations reveal that the exchange coupling between the two spins strongly depends on the torsional angles between the different molecular moieties, suggesting the possibility of influencing the molecule's magnetic state through structural changes. This was demonstrated here using the STM tip to manipulate the molecular conformation, while simultaneously detecting changes in the spin excitation spectrum. Our work suggests the potential of these PAHs for a new class of all-carbon spin-crossover materials. |
| title | Tuning the Spin Interaction in Non-planar Organic Diradicals Through Mechanical Manipulation |
| topic | Mesoscale and Nanoscale Physics Chemical Physics |
| url | https://arxiv.org/abs/2402.08641 |