1
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Bedogni M, Di Maiolo F. Singlet-Triplet Inversion in Triangular Boron Carbon Nitrides. J Chem Theory Comput 2024. [PMID: 39264103 DOI: 10.1021/acs.jctc.4c00706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/13/2024]
Abstract
The discovery of singlet-triplet (ST) inversion in some π-conjugated triangle-shaped boron carbon nitrides is a remarkable breakthrough that defies Hund's first rule. Deeply rooted in strong electron-electron interactions, ST inversion has garnered significant interest due to its potential to revolutionize triplet harvesting in organic LEDs. Using the well-established Pariser-Parr-Pople model for correlated electrons in π-conjugated systems, we employ a combination of CISDT and restricted active space configuration interaction calculations to investigate the photophysics of several triangular boron carbon nitrides. Our findings reveal that ST inversion in these systems is primarily driven by a network of alternating electron-donor and electron-acceptor groups in the molecular rim, rather than by the triangular molecular structure itself.
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Affiliation(s)
- Matteo Bedogni
- Department of Chemistry, Life Science and Environmental Sustainability, Università di Parma, 43124 Parma, Italy
| | - Francesco Di Maiolo
- Department of Chemistry, Life Science and Environmental Sustainability, Università di Parma, 43124 Parma, Italy
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2
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Xu S, Zhang Y, Zang C, Liu J, Jin W, Lefkidis G, Hübner W, Li C. Unlocking Ultrafast Spin Transfer in Single-Magnetic-Center-Decorated Triangulene Systems. J Phys Chem Lett 2024; 15:3929-3937. [PMID: 38568181 DOI: 10.1021/acs.jpclett.4c00469] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/12/2024]
Abstract
Triangulene, as a typical open-shell graphene fragment, has attracted widespread attention for nanospintronics, promising to serve as building blocks in spin-logic units. Here, using ab initio calculations, we systematically study the laser-induced ultrafast spin-dynamic processes on triangulene nanoflakes, decorated with a transition-metal atom. The results reveal a competition between the induced magnetic center and the carbon edge of the triangulene, resulting in the coexistence of dual spin-density-distribution patterns on such single-magnetic-center systems, thus opening up possibilities of complex spin-dynamic scenarios beyond the spin flip. Interestingly, no matter what direction the spin points to, it is possible to achieve reversible spin-transfer processes using the same laser pulse. Increasing the pool of elementary processes to contain not only spin-direction-dependent but also spin-direction-independent scenarios allows for more versatile spin-logic operations, including classical handling of information and quantum computing. In the present work, we suggest downscaling nanospintronic devices by integrating triangulene-based nanostructures.
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Affiliation(s)
- Shuai Xu
- Department of Engineering Mechanics, Northwestern Polytechnical University, Xi'an 710072, China
- Research & Development Institute of Northwestern Polytechnical University in Shenzhen, Shenzhen 518057, China
| | - Yiming Zhang
- Department of Engineering Mechanics, Northwestern Polytechnical University, Xi'an 710072, China
- School of Science, Xi'an University of Architecture and Technology, Xi'an 710055, China
| | - Congfei Zang
- Department of Engineering Mechanics, Northwestern Polytechnical University, Xi'an 710072, China
- Research & Development Institute of Northwestern Polytechnical University in Shenzhen, Shenzhen 518057, China
| | - Jing Liu
- Institute of Theoretical Chemistry, Ulm University, 89081 Ulm, Germany
| | - Wei Jin
- School of Physics and Information Technology, Shaanxi Normal University, Xi'an 710119, China
| | - Georgios Lefkidis
- Department of Engineering Mechanics, Northwestern Polytechnical University, Xi'an 710072, China
- Department of Physics, RPTU Kaiserslautern-Landau, P.O. Box 3049, 67653 Kaiserslautern, Germany
| | - Wolfgang Hübner
- Department of Physics, RPTU Kaiserslautern-Landau, P.O. Box 3049, 67653 Kaiserslautern, Germany
| | - Chun Li
- Department of Engineering Mechanics, Northwestern Polytechnical University, Xi'an 710072, China
- Research & Development Institute of Northwestern Polytechnical University in Shenzhen, Shenzhen 518057, China
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3
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Lawrence J, He Y, Wei H, Su J, Song S, Wania Rodrigues A, Miravet D, Hawrylak P, Zhao J, Wu J, Lu J. Topological Design and Synthesis of High-Spin Aza-triangulenes without Jahn-Teller Distortions. ACS NANO 2023; 17:20237-20245. [PMID: 37791737 DOI: 10.1021/acsnano.3c05974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/05/2023]
Abstract
The atomic doping of open-shell nanographenes enables precise tuning of their electronic and magnetic states, which is crucial for their promising potential applications in optoelectronics and spintronics. Among this intriguing class of molecules, triangulenes stand out with their size-dependent electronic properties and spin states, which can also be influenced by the presence of dopant atoms and functional groups. However, the occurrence of Jahn-Teller distortions in such systems can have a crucial impact on their total spin and requires further theoretical and experimental investigation. In this study, we examine the nitrogen-doped aza-triangulene series via a combination of density functional theory and on-surface synthesis. We identify a general trend in the calculated spin states of aza-[n]triangulenes of various sizes, separating them into two symmetry classes, one of which features molecules that are predicted to undergo Jahn-Teller distortions that reduce their symmetry and thus their total spin. We link this behavior to the location of the central nitrogen atom relative to the two underlying carbon sublattices of the molecules. Consequently, our findings reveal that neutral centrally doped aza-triangulenes have one less radical than their undoped counterparts, irrespective of their predicted symmetry. We follow this by demonstrating the on-surface synthesis of π-extended aza-[5]triangulene, a large member of the higher symmetry class without Jahn-Teller distortions, via a simple one-step annealing process on Cu(111) and Au(111). Using scanning probe microscopy and spectroscopy combined with theoretical calculations, we prove that the molecule is positively charged on the Au(111) substrate, with a high-spin quintet state of S = 2, the same total spin as undoped neutral [5]triangulene. Our study uncovers the correlation between the dopant position and the radical nature of high-spin nanographenes, providing a strategy for the design and development of these nanographenes for various applications.
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Affiliation(s)
- James Lawrence
- Department of Chemistry, National University of Singapore, 117543 Singapore
| | - Yuanyuan He
- College of Material and Textile Engineering, Key Laboratory of Yarn Materials Forming and Composite Processing Technology of Zhejiang Province, Jiaxing University, Jiaxing 314001, Zhejiang, People's Republic of China
| | - Haipeng Wei
- Department of Chemistry, National University of Singapore, 117543 Singapore
| | - Jie Su
- Department of Chemistry, National University of Singapore, 117543 Singapore
| | - Shaotang Song
- Department of Chemistry, National University of Singapore, 117543 Singapore
| | | | - Daniel Miravet
- Department of Physics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - Pawel Hawrylak
- Department of Physics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
- Institute for Functional Intelligent Materials, National University of Singapore, 117544 Singapore
| | - Jianwei Zhao
- College of Material and Textile Engineering, Key Laboratory of Yarn Materials Forming and Composite Processing Technology of Zhejiang Province, Jiaxing University, Jiaxing 314001, Zhejiang, People's Republic of China
| | - Jishan Wu
- Department of Chemistry, National University of Singapore, 117543 Singapore
| | - Jiong Lu
- Department of Chemistry, National University of Singapore, 117543 Singapore
- Institute for Functional Intelligent Materials, National University of Singapore, 117544 Singapore
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4
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Nieman R, Carvalho JR, Jayee B, Hansen A, Aquino AJA, Kertesz M, Lischka H. Polyradical character assessment using multireference calculations and comparison with density-functional derived fractional occupation number weighted density analysis. Phys Chem Chem Phys 2023; 25:27380-27393. [PMID: 37792036 DOI: 10.1039/d3cp03734g] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/05/2023]
Abstract
The biradicaloid character of different types of polycyclic aromatic hydrocarbons (PAHs) based on small band gaps is an important descriptor to assess their opto-electronic properties. In this work, the unpaired electron densities and numbers of unpaired electrons (NU values) calculated at the high-level multireference averaged quadratic coupled-cluster (MR-AQCC) method are used to develop a test set to assess the capabilities of different biradical descriptors based on density functional theory. A benchmark collection of 29 different compounds has been selected. The DFT descriptors contain primarily the fractional occupation number weighted electron density (FOD) based on simplified thermally-assisted-occupation density functional theory (TAO-DFT) calculations, but the singlet-triplet energy difference and other descriptors denoted as y0 and nLUNO have been considered as well. After adjustment of the literature-recommended finite temperatures, a very good, detailed agreement between unpaired density and FOD analysis is observed which is also manifested in excellent statistical correlations. The other two descriptors also show good correlations even though the absolute scaling is not satisfactory. A new linear fit of FOD data to the MR-AQCC reference values leads to an improved regression relation for determining the recommended finite temperature value in dependence of the Hartree-Fock exchange. This provides the basis for fast and reliable assessment of the biradical character of many classes of PAHs without the need for performing computationally extended MR calculations.
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Affiliation(s)
- Reed Nieman
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA.
| | - Jhonatas R Carvalho
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA.
| | - Bhumika Jayee
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA.
| | - Andreas Hansen
- Mulliken Center for Theoretical Chemistry, Universität Bonn, D-53115, Germany
| | - Adelia J A Aquino
- Department of Mechanical Engineering, Texas Tech University, Lubbock, TX 79409-1061, USA
| | - Miklos Kertesz
- Chemistry Department and Institute of Soft Matter, Georgetown University, Washington, District of Columbia 20057-1227, USA
| | - Hans Lischka
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA.
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5
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Sandoval-Salinas ME, Ricci G, Pérez-Jiménez AJ, Casanova D, Olivier Y, Sancho-García JC. Correlation vs. exchange competition drives the singlet-triplet excited-state inversion in non-alternant hydrocarbons. Phys Chem Chem Phys 2023; 25:26417-26428. [PMID: 37522306 DOI: 10.1039/d3cp02465b] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/01/2023]
Abstract
In this work, we focus on the understanding of the driving force behind the S1-T1 excited-state energy inversion (which would thus violate Hund's rule, making the S1 state lower in energy than the T1 state) of two non-benzenoid non-alternant hydrocarbons, composed of odd-membered rings. The molecules considered here have identical chemical composition but different atomic configuration in space. The delicate interplay between structural and electronic factors that might induce inversion and its energy extension, only by a few meV, is systematically investigated here by state-of-the-art calculations. Qualitative and quantitative accurate predictions are obtained employing post-HF methods, thanks to the balanced and careful inclusion of electron correlation effects. The obtained results might guide and rationalize new searches for molecules violating Hund's rule, concomitantly demonstrating the importance of key contributions from the theoretical method of choice.
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Affiliation(s)
- M E Sandoval-Salinas
- Department of Physical Chemistry, University of Alicante, E-03080 Alicante, Spain.
- School of Physical and Chemical Science, Queen Mary University of London, London, UK
| | - G Ricci
- Unité de Chimie Physique Théorique et Structurale, & Laboratoire de Physique du Solid, Namur Institute of Structured Matter, Université de Namur, B-5000 Namur, Belgium.
| | - A J Pérez-Jiménez
- Department of Physical Chemistry, University of Alicante, E-03080 Alicante, Spain.
| | - D Casanova
- Donostia International Physics Center (DIPC), E-20018 Donostia, Euskadi, Spain.
- IKERBASQUE-Basque Foundation for Science, E-48009 Bilbao, Euskadi, Spain
| | - Y Olivier
- Unité de Chimie Physique Théorique et Structurale, & Laboratoire de Physique du Solid, Namur Institute of Structured Matter, Université de Namur, B-5000 Namur, Belgium.
| | - J C Sancho-García
- Department of Physical Chemistry, University of Alicante, E-03080 Alicante, Spain.
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6
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Vilas-Varela M, Romero-Lara F, Vegliante A, Calupitan JP, Martínez A, Meyer L, Uriarte-Amiano U, Friedrich N, Wang D, Schulz F, Koval NE, Sandoval-Salinas ME, Casanova D, Corso M, Artacho E, Peña D, Pascual JI. On-Surface Synthesis and Characterization of a High-Spin Aza-[5]-Triangulene. Angew Chem Int Ed Engl 2023; 62:e202307884. [PMID: 37604782 DOI: 10.1002/anie.202307884] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 08/11/2023] [Accepted: 08/17/2023] [Indexed: 08/23/2023]
Abstract
Triangulenes are a class of open-shell triangular graphene flakes with total spin increasing with their size. In the last years, on-surface-synthesis strategies have permitted fabricating and engineering triangulenes of various sizes and structures with atomic precision. However, direct proof of the increasing total spin with their size remains elusive. In this work, we report the combined in-solution and on-surface synthesis of a large nitrogen-doped triangulene (aza-[5]-triangulene) on a Au(111) surface, and the detection of its high-spin ground state. Bond-resolved scanning tunneling microscopy images uncovered radical states distributed along the zigzag edges, which were detected as weak zero-bias resonances in scanning tunneling spectra. These spectral features reveal the partial Kondo screening of a high-spin state. Through a combination of several simulation tools, we find that the observed distribution of radical states is explained by a quintet ground state (S=2), instead of the quartet state (S=3/2) expected for the neutral species. This confirms that electron transfer to the metal substrate raises the spin of the ground state. We further provide a qualitative description of the change of (anti)aromaticity introduced by N-substitution, and its role in the charge stabilization on a surface, resulting in an S=2 aza-triangulene on Au(111).
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Affiliation(s)
- Manuel Vilas-Varela
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15782-, Santiago de Compostela, Spain
| | | | | | - Jan Patrick Calupitan
- Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center, 20018, Donostia-San Sebastián, Spain
- Donostia International Physics Center (DIPC), 20018, Donostia-San Sebastián, Spain
| | - Adrián Martínez
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15782-, Santiago de Compostela, Spain
| | - Lorenz Meyer
- CIC nanoGUNE-BRTA, 20018, Donostia-San Sebastián, Spain
| | | | | | - Dongfei Wang
- CIC nanoGUNE-BRTA, 20018, Donostia-San Sebastián, Spain
| | - Fabian Schulz
- CIC nanoGUNE-BRTA, 20018, Donostia-San Sebastián, Spain
| | | | | | - David Casanova
- Donostia International Physics Center (DIPC), 20018, Donostia-San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, 48009, Bilbao, Spain
| | - Martina Corso
- Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center, 20018, Donostia-San Sebastián, Spain
| | - Emilio Artacho
- CIC nanoGUNE-BRTA, 20018, Donostia-San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, 48009, Bilbao, Spain
- Theory of Condensed Matter, Cavendish Laboratory, University of Cambridge, J. J. Thomson Ave., Cambridge, CB3 0HE, UK
| | - Diego Peña
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15782-, Santiago de Compostela, Spain
| | - José Ignacio Pascual
- CIC nanoGUNE-BRTA, 20018, Donostia-San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, 48009, Bilbao, Spain
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7
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Yu H, Heine T. Magnetic Coupling Control in Triangulene Dimers. J Am Chem Soc 2023; 145:19303-19311. [PMID: 37610306 PMCID: PMC10485925 DOI: 10.1021/jacs.3c05178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Indexed: 08/24/2023]
Abstract
Metal-free magnetism remains an enigmatic field, offering prospects for unconventional magnetic and electronic devices. In the pursuit of such magnetism, triangulenes, endowed with inherent spin polarization, are promising candidates to serve as monomers to construct extended structures. However, controlling and enhancing the magnetic interactions between the monomers persist as a significant challenge in molecular spintronics, as so far only weak antiferromagnetic coupling through the linkage has been realized, hindering their room temperature utilization. Herein, we investigate 24 triangulene dimers using first-principles calculations and demonstrate their tunable magnetic coupling (J), achieving unprecedented strong J values of up to -144 meV in a non-Kekulé dimer. We further establish a positive correlation between bandgap, electronic coupling, and antiferromagnetic interaction, thereby providing molecular-level insights into enhancing magnetic interactions. By twisting the molecular fragments, we demonstrate an effective and feasible approach to control both the sign and strength of J by tuning the balance between potential and kinetic exchanges. We discover that J can be substantially boosted at planar configurations up to -198 meV. We realize ferromagnetic coupling in nitrogen-doped triangulene dimers at both planar and largely twisted configurations, representing the first example of ferromagnetic triangulene dimers that cannot be predicted by the Ovchinnikov rule. This work thus provides a practical strategy for augmenting magnetic coupling and open up new avenues for metal-free ferromagnetism.
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Affiliation(s)
- Hongde Yu
- Faculty
of Chemistry and Food Chemistry, Technische
Universität Dresden, Bergstraße 66c, 01062 Dresden, Germany
| | - Thomas Heine
- Faculty
of Chemistry and Food Chemistry, Technische
Universität Dresden, Bergstraße 66c, 01062 Dresden, Germany
- Institute
of Resource Ecology, Helmholtz Zentrum Dresden-Rossendorf, Permoserstraße 15, 04318 Leipzig, Germany
- Department
of Chemistry, Yonsei University, Seodaemun-gu, Seoul 120-749, Republic of Korea
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8
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Rodríguez-Jiménez JA, Carreras A, Casanova D. Spin-Orbit Couplings of Open-Shell Systems with Restricted Active Space Configuration Interaction. J Phys Chem A 2023; 127:1206-1218. [PMID: 36719861 DOI: 10.1021/acs.jpca.2c08056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
In this work we perform electronic structure calculations to unravel the origin of spin-orbit couplings (SOCs) in open-shell molecules. For that, we select systems displaying di or polyradical character, e.g., trimethylene, and analyze the changes in the magnitude of SOC constants along molecular distortions of ethylene and in the presence of intermolecular interactions between open and closed-shell moieties in the O2-C2H4 system. Calculations were performed by using nonrelativistic wave functions obtained with the restricted active space configuration interaction (RASCI) method, in conjunction with a recent implementation for the calculation of SOC based on the spin-orbit mean field approximation. Our results demonstrate the suitability of RASCI in the calculation of SOCs of open-shell systems, while providing a deep understanding of the relationship between couplings and the nature of the electronic states. Moreover, we introduce a new definition of the SOC constant for the study of molecular aggregates.
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Affiliation(s)
- José Aarón Rodríguez-Jiménez
- Donostia International Physics Center (DIPC), 20018Donostia, Euskadi, Spain.,Kimika Fakultatea, Euskal Herriko Unibertsitatea (UPV/EHU), 20018Donostia, Euskadi, Spain
| | - Abel Carreras
- Donostia International Physics Center (DIPC), 20018Donostia, Euskadi, Spain
| | - David Casanova
- Donostia International Physics Center (DIPC), 20018Donostia, Euskadi, Spain.,IKERBASQUE, Basque Foundation for Science, 48009Bilbao, Euskadi, Spain
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9
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de Oteyza DG, Frederiksen T. Carbon-based nanostructures as a versatile platform for tunable π-magnetism. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:443001. [PMID: 35977474 DOI: 10.1088/1361-648x/ac8a7f] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 08/17/2022] [Indexed: 06/15/2023]
Abstract
Emergence ofπ-magnetism in open-shell nanographenes has been theoretically predicted decades ago but their experimental characterization was elusive due to the strong chemical reactivity that makes their synthesis and stabilization difficult. In recent years, on-surface synthesis under vacuum conditions has provided unprecedented opportunities for atomically precise engineering of nanographenes, which in combination with scanning probe techniques have led to a substantial progress in our capabilities to realize localized electron spin states and to control electron spin interactions at the atomic scale. Here we review the essential concepts and the remarkable advances in the last few years, and outline the versatility of carbon-basedπ-magnetic materials as an interesting platform for applications in spintronics and quantum technologies.
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Affiliation(s)
- Dimas G de Oteyza
- Nanomaterials and Nanotechnology Research Center (CINN), CSIC-UNIOVI-PA, E-33940 El Entrego, Spain
- Donostia International Physics Center (DIPC)-UPV/EHU, E-20018 San Sebastián, Spain
| | - Thomas Frederiksen
- Donostia International Physics Center (DIPC)-UPV/EHU, E-20018 San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, E-48013 Bilbao, Spain
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10
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Badía-Domínguez I, Canola S, Hernández Jolín V, López Navarrete JT, Sancho-García JC, Negri F, Ruiz Delgado MC. Tuning the Diradical Character of Indolocarbazoles: Impact of Structural Isomerism and Substitution Position. J Phys Chem Lett 2022; 13:6003-6010. [PMID: 35737902 PMCID: PMC9272443 DOI: 10.1021/acs.jpclett.2c01325] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
In this study, a set of 10 positional indolocarbazole (ICz) isomers substituted with dicyanomethylene groups connected via para or meta positions are computationally investigated with the aim of exploring the efficiency of structural isomerism and substitution position in controlling their optical and electronic properties. Unrestricted density functional theory (DFT), a spin-flip time-dependent DFT approach, and the multireference CASSCF/NEVPT2 method have been applied to correlate the diradical character with the energetic trends (i.e., singlet-triplet energy gaps). In addition, the nucleus-independent chemical shift together with ACID plots and Raman intensity calculations were used to strengthen the relationship between the diradical character and (anti)aromaticity. Our study reveals that the substitution pattern and structural isomerism represent a very effective way to tune the diradical properties in ICz-based systems with meta-substituted systems with a V-shaped structure displaying the largest diradical character. Thus, this work contributes to the elucidation of the challenging chemical reactivity and physical properties of diradicaloid systems, guiding experimental chemists to produce new molecules with desirable properties.
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Affiliation(s)
- Irene Badía-Domínguez
- Department
of Physical Chemistry, University of Málaga, Campus de Teatinos s/n, 29071 Málaga, Spain
| | - Sofia Canola
- Department
of Chemistry “Giacomo Ciamician”, University of Bologna, 40126 Bologna, Italy
| | - Víctor Hernández Jolín
- Department
of Physical Chemistry, University of Málaga, Campus de Teatinos s/n, 29071 Málaga, Spain
| | - Juan T. López Navarrete
- Department
of Physical Chemistry, University of Málaga, Campus de Teatinos s/n, 29071 Málaga, Spain
| | | | - Fabrizia Negri
- Department
of Chemistry “Giacomo Ciamician”, University of Bologna, 40126 Bologna, Italy
- INSTM, UdR Bologna, 40126 Bologna, Italy
| | - M. Carmen Ruiz Delgado
- Department
of Physical Chemistry, University of Málaga, Campus de Teatinos s/n, 29071 Málaga, Spain
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11
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Wang T, Berdonces-Layunta A, Friedrich N, Vilas-Varela M, Calupitan JP, Pascual JI, Peña D, Casanova D, Corso M, de Oteyza DG. Aza-Triangulene: On-Surface Synthesis and Electronic and Magnetic Properties. J Am Chem Soc 2022; 144:4522-4529. [PMID: 35254059 PMCID: PMC8931755 DOI: 10.1021/jacs.1c12618] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
![]()
Nitrogen
heteroatom doping into a triangulene molecule allows tuning
its magnetic state. However, the synthesis of the nitrogen-doped triangulene
(aza-triangulene) has been challenging. Herein, we report the successful
synthesis of aza-triangulene on the Au(111) and Ag(111) surfaces,
along with their characterizations by scanning tunneling microscopy
and spectroscopy in combination with density functional theory (DFT)
calculations. Aza-triangulenes were obtained by reducing ketone-substituted
precursors. Exposure to atomic hydrogen followed by thermal annealing
and, when necessary, manipulations with the scanning probe afforded
the target product. We demonstrate that on Au(111), aza-triangulene
donates an electron to the substrate and exhibits an open-shell triplet
ground state. This is derived from the different Kondo resonances
of the final aza-triangulene product and a series of intermediates
on Au(111). Experimentally mapped molecular orbitals match with DFT-calculated
counterparts for a positively charged aza-triangulene. In contrast,
aza-triangulene on Ag(111) receives an extra electron from the substrate
and displays a closed-shell character. Our study reveals the electronic
properties of aza-triangulene on different metal surfaces and offers
an approach for the fabrication of new hydrocarbon structures, including
reactive open-shell molecules.
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Affiliation(s)
- Tao Wang
- Donostia International Physics Center, 20018 San Sebastián, Spain
- Centro de Fisica de Materiales CFM/MPC, CSIC-UPV/EHU, 20018 San Sebastián, Spain
| | - Alejandro Berdonces-Layunta
- Donostia International Physics Center, 20018 San Sebastián, Spain
- Centro de Fisica de Materiales CFM/MPC, CSIC-UPV/EHU, 20018 San Sebastián, Spain
| | | | - Manuel Vilas-Varela
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain
| | | | - Jose Ignacio Pascual
- CIC NanoGUNE BRTA, 20018 San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, 48009 Bilbao, Spain
| | - Diego Peña
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain
| | - David Casanova
- Donostia International Physics Center, 20018 San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, 48009 Bilbao, Spain
| | - Martina Corso
- Donostia International Physics Center, 20018 San Sebastián, Spain
- Centro de Fisica de Materiales CFM/MPC, CSIC-UPV/EHU, 20018 San Sebastián, Spain
| | - Dimas G. de Oteyza
- Donostia International Physics Center, 20018 San Sebastián, Spain
- Centro de Fisica de Materiales CFM/MPC, CSIC-UPV/EHU, 20018 San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, 48009 Bilbao, Spain
- Nanomaterials and Nanotechnology Research Center (CINN), CSIC-UNIOVI-PA; 33940 El Entrego, Spain
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12
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Sancho-García JC, Brémond E, Ricci G, Pérez-Jiménez AJ, Olivier Y, Adamo C. Violation of Hund’s rule in molecules: Predicting the excited-state energy inversion by TD-DFT with double-hybrid methods. J Chem Phys 2022; 156:034105. [DOI: 10.1063/5.0076545] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- J. C. Sancho-García
- Department of Physical Chemistry, University of Alicante, E-03080 Alicante, Spain
| | - E. Brémond
- Université de Paris, ITODYS, CNRS, F-75006 Paris, France
| | - G. Ricci
- Laboratory for Computational Modeling of Functional Materials, Namur Institute of Structured Matter, Université de Namur, Rue de Bruxelles, B-5000 Namur, Belgium
| | - A. J. Pérez-Jiménez
- Department of Physical Chemistry, University of Alicante, E-03080 Alicante, Spain
| | - Y. Olivier
- Laboratory for Computational Modeling of Functional Materials, Namur Institute of Structured Matter, Université de Namur, Rue de Bruxelles, B-5000 Namur, Belgium
| | - C. Adamo
- Chimie ParisTech, PSL Research University, CNRS, Institute of Chemistry for Life and Health Sciences (i-CLeHS), FRE 2027, F-75005 Paris, France
- Institut Universitaire de France, 103 Boulevard Saint Michel, F-75005 Paris, France
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13
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Organic Emitters Showing Excited-States Energy Inversion: An Assessment of MC-PDFT and Correlation Energy Functionals Beyond TD-DFT. COMPUTATION 2022. [DOI: 10.3390/computation10020013] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The lowest-energy singlet (S1) and triplet (T1) excited states of organic conjugated chromophores are known to be accurately calculated by modern wavefunction and Time-Dependent Density Functional Theory (TD-DFT) methods, with the accuracy of the latter heavily relying on the exchange-correlation functional employed. However, there are challenging cases for which this cannot be the case, due to the fact that those excited states are not exclusively formed by single excitations and/or are affected by marked correlation effects, and thus TD-DFT might fall short. We will tackle here a set of molecules belonging to the azaphenalene family, for which research recently documented an inversion of the relative energy of S1 and T1 excited states giving rise to a negative energy difference (ΔEST) between them and, thereby, contrary to most of the systems thus far treated by TD-DFT. Since methods going beyond standard TD-DFT are not extensively applied to excited-state calculations and considering how challenging this case is for the molecules investigated, we will prospectively employ here a set of non-standard methods (Multi-Configurational Pair Density Functional Theory or MC-PDFT) and correlation functionals (i.e., Lie–Clementi and Colle–Salvetti) relying not only on the electronic density but also on some modifications considering the intricate electronic structure of these systems.
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14
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Wu Y, Zhu Y, Zhang Z, Zhao C, He J, Yan C, Meng H. Narrowband Deep-Blue Multi-Resonance Induced Thermally Activated Delayed Fluorescence: Insights from the Theoretical Molecular Design. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27020348. [PMID: 35056667 PMCID: PMC8780697 DOI: 10.3390/molecules27020348] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 01/02/2022] [Accepted: 01/06/2022] [Indexed: 11/16/2022]
Abstract
Multi-resonance thermal activated delayed fluorescence (MR-TADF) has been promising with large oscillator strength and narrow full width at half maxima of luminescence, overcoming the compromise of emission intensity and energy criteria of traditional charge transfer TADF frameworks. However, there are still limited theoretical investigations on the excitation mechanism and systematic molecular manipulation of MR-TADF structures. We systematically study the highly localized excitation (LE) characteristics based on typical blue boron-nitrogen (BN) MR-TADF emitters and prove the potential triangular core with theoretical approaches. A design strategy by extending the planar π-conjugate core structure is proposed to enhance the multiple resonance effects. Moreover, several substituted groups are introduced to the designed core, achieving color-tunable functions with relatively small energy split and strong oscillator strength simultaneously. This work provides a theoretical direction for molecular design strategy and a series of potential candidates for highly efficient BN MR-TADF emitters.
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Affiliation(s)
- Yuting Wu
- School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China; (Y.W.); (Y.Z.); (Z.Z.); (C.Z.); (J.H.); (C.Y.)
| | - Yanan Zhu
- School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China; (Y.W.); (Y.Z.); (Z.Z.); (C.Z.); (J.H.); (C.Y.)
| | - Zewei Zhang
- School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China; (Y.W.); (Y.Z.); (Z.Z.); (C.Z.); (J.H.); (C.Y.)
| | - Chongguang Zhao
- School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China; (Y.W.); (Y.Z.); (Z.Z.); (C.Z.); (J.H.); (C.Y.)
- State High-Tech Industrial Innovation Center, Shenzhen 518057, China
| | - Junpeng He
- School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China; (Y.W.); (Y.Z.); (Z.Z.); (C.Z.); (J.H.); (C.Y.)
| | - Chaoyi Yan
- School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China; (Y.W.); (Y.Z.); (Z.Z.); (C.Z.); (J.H.); (C.Y.)
| | - Hong Meng
- School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China; (Y.W.); (Y.Z.); (Z.Z.); (C.Z.); (J.H.); (C.Y.)
- Correspondence:
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15
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Kaur P, Ali ME. Influence of the Radicaloid Character of Polyaromatic Hydrocarbon Couplers on Magnetic Exchange Interactions. Phys Chem Chem Phys 2022; 24:13094-13101. [DOI: 10.1039/d1cp02044g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The molecular properties of the conjugated spacers, such as the π-conjugation, aromaticity, length of the couplers, etc., that couple two localized spin-centers influence the intramolecular magnetic exchange interactions (2J) mediated...
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16
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Omist A, Ricci G, Derradji A, Pérez-Jiménez AJ, San-Fabián E, Olivier Y, Sancho-García JC. peri-Acenoacene molecules: tuning of the singlet and triplet excitation energies by modifying their radical character. Phys Chem Chem Phys 2021; 23:24016-24028. [PMID: 34664570 DOI: 10.1039/d1cp03232a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The energy difference between singlet and triplet excitons, or ΔEST, is a key parameter for novel light-emission mechanisms (i.e., TADF or thermally activated delayed fluorescence) or other photoactivated processes. We have studied a set of conjugated molecules (peri-acenoacenes and their heteroatom-doped analogues) to observe the evolution of their excited-state properties upon increasing the system size with and without substitution with a pair of N atoms. Since these molecules exhibit a (ground-state) diradicaloid character, together with marked correlation effects influencing the excited-states formed, we have applied a variety of theoretical methods (FT-DFT, TD-DFT, SF-TD-DFT, CIS, CIS(D), SCS-CC2, SA-CASSCF, and SC-NEVPT2) to bracket the accuracy of the results while concomitantly providing insights into electronic structure. The results show how this chemical strategy (N-doping) largely modifies not only the excited-state energies but also the oscillator strengths and the ΔEST values, constituting versatile platforms for fine-tuned photophysical applications.
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Affiliation(s)
- A Omist
- Department of Physical Chemistry, University of Alicante, E-03080 Alicante, Spain.
| | - G Ricci
- Unité de Chimie Physique Théorique et Structurale & Laboratoire de Physique du Solid, Namur Institute of Structured Matter, Université de Namur, B-5000 Namur, Belgium
| | - A Derradji
- Department of Physical Chemistry, University of Alicante, E-03080 Alicante, Spain.
| | - A J Pérez-Jiménez
- Department of Physical Chemistry, University of Alicante, E-03080 Alicante, Spain.
| | - E San-Fabián
- Department of Physical Chemistry, University of Alicante, E-03080 Alicante, Spain.
| | - Y Olivier
- Unité de Chimie Physique Théorique et Structurale & Laboratoire de Physique du Solid, Namur Institute of Structured Matter, Université de Namur, B-5000 Namur, Belgium
| | - J C Sancho-García
- Department of Physical Chemistry, University of Alicante, E-03080 Alicante, Spain.
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17
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Casanova D. Restricted active space configuration interaction methods for strong correlation: Recent developments. WIRES COMPUTATIONAL MOLECULAR SCIENCE 2021. [DOI: 10.1002/wcms.1561] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- David Casanova
- Donostia International Physics Center (DIPC) Donostia Spain
- Ikerbasque Basque Foundation for Science Bilbao Spain
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18
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Rodríguez-Jiménez JA, Carreras A, Casanova D. Short-range DFT energy correction to multiconfigurational wave functions for open-shell systems. J Chem Phys 2021; 154:124116. [PMID: 33810663 DOI: 10.1063/5.0046404] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Electronic structure methods emerging from the combination of multiconfigurational wave functions and density functional theory (DFT) aim to take advantage of the strengths of the two nearly antagonistic theories. One of the common strategies employed to merge wave function theory (WFT) with DFT relies on the range separation of the Coulomb operator in which DFT functionals take care of the short-distance part, while long-range inter-electronic interactions are evaluated by using the chosen wave function method (WFT-srDFT). In this work, we uncover the limitations of WFT-srDFT in the characterization of open-shell systems. We show that spin polarization effects have a major impact on the (short-range) DFT exchange energy and are of vital importance in order to provide a balanced description between closed and open-shell configurations. We introduce different strategies to account for spin polarization in the short range based on the definition of a spin polarized electron density and with the use of short-range exact exchange. We test the performance of these approaches in the dissociation of the hydrogen molecule, the calculation of energy gaps in spin-triplet atoms and molecular diradicals, and the characterization of low-lying states of the gallium dimer. Our results indicate that the use of short-range DFT correlation in combination with a (full-range) multiconfigurational wave function might be an excellent approach for the study of open-shell molecules and largely improves the performance of WFT and WFT-srDFT.
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Affiliation(s)
| | - Abel Carreras
- Donostia International Physics Center (DIPC), 20080 Donostia, Euskadi, Spain
| | - David Casanova
- Donostia International Physics Center (DIPC), 20080 Donostia, Euskadi, Spain
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19
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Ricci G, San‐Fabián E, Olivier Y, Sancho‐García JC. Singlet‐Triplet Excited‐State Inversion in Heptazine and Related Molecules: Assessment of TD‐DFT and
ab initio
Methods. Chemphyschem 2021; 22:553-560. [DOI: 10.1002/cphc.202000926] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 12/15/2020] [Indexed: 01/31/2023]
Affiliation(s)
- G. Ricci
- Unité de Chimie Physique Théorique et Structurale & Laboratoire de Physique du Solid Namur Institute of Structured Matter Université de Namur B-5000 Namur Belgium
| | - E. San‐Fabián
- Department of Physical Chemistry University of Alicante E 03080 Alicante Spain
| | - Y. Olivier
- Unité de Chimie Physique Théorique et Structurale & Laboratoire de Physique du Solid Namur Institute of Structured Matter Université de Namur B-5000 Namur Belgium
| | - J. C. Sancho‐García
- Department of Physical Chemistry University of Alicante E 03080 Alicante Spain
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20
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Sanz-Rodrigo J, Ricci G, Olivier Y, Sancho-García JC. Negative Singlet–Triplet Excitation Energy Gap in Triangle-Shaped Molecular Emitters for Efficient Triplet Harvesting. J Phys Chem A 2021; 125:513-522. [DOI: 10.1021/acs.jpca.0c08029] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- J. Sanz-Rodrigo
- Department of Physical Chemistry, University of Alicante, E-03080 Alicante, Spain
| | - G. Ricci
- Unité de Chimie Physique Théorique et Structurale & Laboratoire de Physique du Solid, Namur Institute of Structured Matter, Université de Namur, B-5000 Namur, Belgium
| | - Y. Olivier
- Unité de Chimie Physique Théorique et Structurale & Laboratoire de Physique du Solid, Namur Institute of Structured Matter, Université de Namur, B-5000 Namur, Belgium
| | - J. C. Sancho-García
- Department of Physical Chemistry, University of Alicante, E-03080 Alicante, Spain
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21
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Carreras A, Jiang H, Pokhilko P, Krylov AI, Zimmerman PM, Casanova D. Calculation of spin–orbit couplings using RASCI spinless one-particle density matrices: Theory and applications. J Chem Phys 2020; 153:214107. [DOI: 10.1063/5.0029146] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Affiliation(s)
- Abel Carreras
- Donostia International Physics Center (DIPC), Manuel de Lardizabal Pasalekua 4, 20018 Donostia, Euskadi, Spain
| | - Hanjie Jiang
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Pavel Pokhilko
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Anna I. Krylov
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Paul M. Zimmerman
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - David Casanova
- Donostia International Physics Center (DIPC), Manuel de Lardizabal Pasalekua 4, 20018 Donostia, Euskadi, Spain
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22
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Gil-Guerrero S, Melle-Franco M, Peña-Gallego Á, Mandado M. Clar Goblet and Aromaticity Driven Multiradical Nanographenes. Chemistry 2020; 26:16138-16143. [PMID: 32893901 DOI: 10.1002/chem.202003713] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 08/26/2020] [Indexed: 11/10/2022]
Abstract
The Clar Goblet, the first radical bowtie nanographene proposed by Erich Clar nearly 50 years ago, was recently synthesized. Bowtie nanographenes present quasi-degenerate magnetic ground states, which make them so elusive as unique. A thorough analysis is presented of the spin-state energetics of Clar Goblet and bowtie nanographenes by a battery of existing and novel ab initio procedures ranging from density functional theory to complete active space Hamiltonians. With this, it was proven that π radicals of bowtie nanographenes sit on BP (Benzo[cd]Pyrene) moieties driven by their local aromaticity, a purely chemical concept, which confers global stability to the whole structure. Besides, a novel Pauli energy densities analysis provided a visual intuitive explanation for this preference. These findings allow envisioning that analogous bowtie nanographenes with arbitrary polyradical character are not only feasible at the molecular scale but will share Clar Goblet's peculiar properties.
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Affiliation(s)
- Sara Gil-Guerrero
- Department of Physical Chemistry, University of Vigo, Lagoas-Marcosende s/n, 36310, Vigo, Spain.,CICECO, Departamento de Química, Universidade de Aveiro, 3810-193, Aveiro, Portugal
| | - Manuel Melle-Franco
- CICECO, Departamento de Química, Universidade de Aveiro, 3810-193, Aveiro, Portugal
| | - Ángeles Peña-Gallego
- Department of Physical Chemistry, University of Vigo, Lagoas-Marcosende s/n, 36310, Vigo, Spain
| | - Marcos Mandado
- Department of Physical Chemistry, University of Vigo, Lagoas-Marcosende s/n, 36310, Vigo, Spain
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23
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Savarese M, Brémond É, Ciofini I, Adamo C. Electron Spin Densities and Density Functional Approximations: Open-Shell Polycyclic Aromatic Hydrocarbons as Case Study. J Chem Theory Comput 2020; 16:3567-3577. [DOI: 10.1021/acs.jctc.0c00059] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Marika Savarese
- CompuNet, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genoa, Italy
| | - Éric Brémond
- ITODYS, UMR CNRS 7086, Université de Paris, 15 rue J.-A. de Baïf, F-75013 Paris, France
| | - Ilaria Ciofini
- Chimie ParisTech, PSL Research University, CNRS, Institute of Chemistry for Health and Life Sciences, F-75005 Paris, France
| | - Carlo Adamo
- Chimie ParisTech, PSL Research University, CNRS, Institute of Chemistry for Health and Life Sciences, F-75005 Paris, France
- France and Institut Universitaire de France, 103 Boulevard Saint Michel, F-75005 Paris, France
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24
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Li J, Sanz S, Castro-Esteban J, Vilas-Varela M, Friedrich N, Frederiksen T, Peña D, Pascual JI. Uncovering the Triplet Ground State of Triangular Graphene Nanoflakes Engineered with Atomic Precision on a Metal Surface. PHYSICAL REVIEW LETTERS 2020; 124:177201. [PMID: 32412280 DOI: 10.1103/physrevlett.124.177201] [Citation(s) in RCA: 75] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 02/17/2020] [Accepted: 04/02/2020] [Indexed: 06/11/2023]
Abstract
Graphene can develop large magnetic moments in custom-crafted open-shell nanostructures such as triangulene, a triangular piece of graphene with zigzag edges. Current methods of engineering graphene nanosystems on surfaces succeeded in producing atomically precise open-shell structures, but demonstration of their net spin remains elusive to date. Here, we fabricate triangulenelike graphene systems and demonstrate that they possess a spin S=1 ground state. Scanning tunneling spectroscopy identifies the fingerprint of an underscreened S=1 Kondo state on these flakes at low temperatures, signaling the dominant ferromagnetic interactions between two spins. Combined with simulations based on the meanfield Hubbard model, we show that this S=1 π paramagnetism is robust and can be turned into an S=1/2 state by additional H atoms attached to the radical sites. Our results demonstrate that π paramagnetism of high-spin graphene flakes can survive on surfaces, opening the door to study the quantum behavior of interacting π spins in graphene systems.
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Affiliation(s)
- Jingcheng Li
- CIC Nanogune BRTA, 20018 Donostia-San Sebastián, Spain
| | - Sofia Sanz
- Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Spain
| | - Jesus Castro-Esteban
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15705 Santiago de Compostela, Spain
| | - Manuel Vilas-Varela
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15705 Santiago de Compostela, Spain
| | | | - Thomas Frederiksen
- Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, 48013 Bilbao, Spain
| | - Diego Peña
- Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), and Departamento de Química Orgánica, Universidade de Santiago de Compostela, 15705 Santiago de Compostela, Spain
| | - Jose Ignacio Pascual
- CIC Nanogune BRTA, 20018 Donostia-San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science, 48013 Bilbao, Spain
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25
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Su J, Telychko M, Song S, Lu J. Triangulenes: From Precursor Design to On‐Surface Synthesis and Characterization. Angew Chem Int Ed Engl 2020; 59:7658-7668. [DOI: 10.1002/anie.201913783] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Indexed: 11/06/2022]
Affiliation(s)
- Jie Su
- Department of Chemistry National University of Singapore 3 Science Drive 3 Singapore 117543 Singapore
- Centre for Advanced 2D Materials (CA2DM) National University of Singapore 6 Science Drive 2 Singapore 117546 Singapore
| | - Mykola Telychko
- Department of Chemistry National University of Singapore 3 Science Drive 3 Singapore 117543 Singapore
- Centre for Advanced 2D Materials (CA2DM) National University of Singapore 6 Science Drive 2 Singapore 117546 Singapore
| | - Shaotang Song
- Department of Chemistry National University of Singapore 3 Science Drive 3 Singapore 117543 Singapore
| | - Jiong Lu
- Department of Chemistry National University of Singapore 3 Science Drive 3 Singapore 117543 Singapore
- Centre for Advanced 2D Materials (CA2DM) National University of Singapore 6 Science Drive 2 Singapore 117546 Singapore
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26
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Su J, Telychko M, Song S, Lu J. Triangulenes: From Precursor Design to On‐Surface Synthesis and Characterization. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201913783] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Jie Su
- Department of Chemistry National University of Singapore 3 Science Drive 3 Singapore 117543 Singapore
- Centre for Advanced 2D Materials (CA2DM) National University of Singapore 6 Science Drive 2 Singapore 117546 Singapore
| | - Mykola Telychko
- Department of Chemistry National University of Singapore 3 Science Drive 3 Singapore 117543 Singapore
- Centre for Advanced 2D Materials (CA2DM) National University of Singapore 6 Science Drive 2 Singapore 117546 Singapore
| | - Shaotang Song
- Department of Chemistry National University of Singapore 3 Science Drive 3 Singapore 117543 Singapore
| | - Jiong Lu
- Department of Chemistry National University of Singapore 3 Science Drive 3 Singapore 117543 Singapore
- Centre for Advanced 2D Materials (CA2DM) National University of Singapore 6 Science Drive 2 Singapore 117546 Singapore
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27
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Abstract
This Perspective discusses salient features of the spin-flip approach to strong correlation and describes different methods that sprung from this idea. The spin-flip treatment exploits the different physics of low-spin and high-spin states and is based on the observation that correlation is small for same-spin electrons. By using a well-behaved high-spin state as a reference, one can access problematic low-spin states by deploying the same formal tools as in the excited-state treatments (i.e., linear response, propagator, or equation-of-motion theories). The Perspective reviews applications of this strategy within wave function and density functional theory frameworks as well as the extensions for molecular properties and spectroscopy. The utility of spin-flip methods is illustrated by examples. Limitations and proposed future directions are also discussed.
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Affiliation(s)
- David Casanova
- Donostia International Physics Center (DIPC), 20018 Donostia, Euskadi, Spain. and IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Euskadi, Spain
| | - Anna I Krylov
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
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28
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Abstract
How does edge modification affect spin distribution in open-shell graphene fragments? We investigated this effect by analyzing spin-delocalization in benzo[cd]-triangulene, a spin 1/2 graphene fragment composed of seven benzenoid rings fused in a hybrid zigzag/armchair fashion. Six rings of this system form the core of Clar's hydrocarbon triangulene, to which an additional ring is annulated in the zigzag region. The singly occupied molecular orbital (SOMO) of this hydrocarbon radical resembles both SOMOs of triangulene, but the spin density is distributed over the core in a nonuniform fashion. The uneven spin distribution is reflected in the reactivity-reaction with oxygen occurs selectively at a position with the highest spin density-and correlates nicely with relative stabilities of the corresponding Clar resonance structures. The spin distribution is different from that of a topologically similar compound composed of the same number of sp2 carbon atoms but featuring six rings only, illustrating the impact of subtle structural changes on spin-density distribution. This compound was characterized by means of UV-vis and electron paramagnetic resonance spectroscopy, cyclic voltammetry, mass spectrometry, and X-ray crystallography. The experimental results are supported by density functional theory calculations.
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Affiliation(s)
- Prince Ravat
- Institute of Organic Chemistry , University of Würzburg , Am Hubland , D-97074 Würzburg , Germany.,Department of Chemistry , University of Basel , St. Johanns-Ring 19 , CH-4056 Basel , Switzerland
| | - Olivier Blacque
- Department of Chemistry , University of Zurich , Winterthurerstrasse 190 , CH-8057 Zurich , Switzerland
| | - Michal Juríček
- Department of Chemistry , University of Basel , St. Johanns-Ring 19 , CH-4056 Basel , Switzerland.,Department of Chemistry , University of Zurich , Winterthurerstrasse 190 , CH-8057 Zurich , Switzerland
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29
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Ortiz R, Boto RA, García-Martínez N, Sancho-García JC, Melle-Franco M, Fernández-Rossier JN. Exchange Rules for Diradical π-Conjugated Hydrocarbons. NANO LETTERS 2019; 19:5991-5997. [PMID: 31365266 DOI: 10.1021/acs.nanolett.9b01773] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
A variety of planar π-conjugated hydrocarbons such as heptauthrene, Clar's goblet and, recently synthesized, triangulene have two electrons occupying two degenerate molecular orbitals. The resulting spin of the interacting ground state is often correctly anticipated as S = 1, extending the application of Hund's rules to these systems, but this is not correct in some instances. Here we provide a set of rules to correctly predict the existence of zero mode states as well as the spin multiplicity of both the ground state and the low-lying excited states, together with their open- or closed-shell nature. This is accomplished using a combination of analytical arguments and configuration interaction calculations with a Hubbard model, both backed by quantum chemistry methods with a larger Gaussian basis set. Our results go beyond the well established Lieb's theorem and Ovchinnikov's rule, as we address the multiplicity and the open-/closed-shell nature of both ground and excited states.
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Affiliation(s)
- Ricardo Ortiz
- QuantaLab , International Iberian Nanotechnology Laboratory (INL) , Av. Mestre José Veiga , 4715-330 Braga , Portugal
- Departamento de Física Aplicada , Universidad de Alicante , 03690 Sant Vicent del Raspeig , Spain
- Departamento de Química Física , Universidad de Alicante , 03690 Sant Vicent del Raspeig , Spain
| | - Roberto A Boto
- CICECO, Departamento de Química , Universidade de Aveiro , 3810-193 Aveiro , Portugal
| | - Noel García-Martínez
- QuantaLab , International Iberian Nanotechnology Laboratory (INL) , Av. Mestre José Veiga , 4715-330 Braga , Portugal
- Departamento de Física Aplicada , Universidad de Alicante , 03690 Sant Vicent del Raspeig , Spain
| | - Juan C Sancho-García
- Departamento de Química Física , Universidad de Alicante , 03690 Sant Vicent del Raspeig , Spain
| | - Manuel Melle-Franco
- CICECO, Departamento de Química , Universidade de Aveiro , 3810-193 Aveiro , Portugal
| | - Joaquı N Fernández-Rossier
- QuantaLab , International Iberian Nanotechnology Laboratory (INL) , Av. Mestre José Veiga , 4715-330 Braga , Portugal
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30
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Deng Q, Chai JD. Electronic Properties of Triangle-Shaped Graphene Nanoflakes from TAO-DFT. ACS OMEGA 2019; 4:14202-14210. [PMID: 31508542 PMCID: PMC6732987 DOI: 10.1021/acsomega.9b01259] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Accepted: 08/08/2019] [Indexed: 06/02/2023]
Abstract
Reliable prediction of the properties of nanosystems with radical nature has been tremendously challenging for common computational approaches. Aiming to overcome this, we employ thermally-assisted-occupation density functional theory (TAO-DFT) to investigate various electronic properties (e.g., singlet-triplet energy gaps, vertical ionization potentials, vertical electron affinities, fundamental gaps, symmetrized von Neumann entropy, active orbital occupation numbers, and visualization of active orbitals) associated with a series of triangle-shaped graphene nanoflakes with n fused benzene rings at each side (denoted as n-triangulenes), which can be extended from triangulene. According to our TAO-DFT results, the ground states of n-triangulenes are singlets for all the values of n studied (n = 3, 5, 7, 9, ..., and 21). Moreover, the larger the values of n, the more significant the polyradical nature of n-triangulenes. There are approximately (n - 1) unpaired electrons for the ground state of n-triangulene. The increasing polyradical nature of the larger n-triangulenes should be closely related to the fact that the active orbitals tend to be mainly concentrated at the periphery of n-triangulenes, apparently increasing with the molecular size.
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Affiliation(s)
- Qing Deng
- Department
of Physics, National Taiwan University, Taipei 10617, Taiwan
| | - Jeng-Da Chai
- Department
of Physics, National Taiwan University, Taipei 10617, Taiwan
- Center
for Theoretical Physics and Center for Quantum Science and Engineering, National Taiwan University, Taipei 10617, Taiwan
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31
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Menon A, Dreyer JAH, Martin JW, Akroyd J, Robertson J, Kraft M. Optical band gap of cross-linked, curved, and radical polyaromatic hydrocarbons. Phys Chem Chem Phys 2019; 21:16240-16251. [DOI: 10.1039/c9cp02363a] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The impact of cross-linking, curvature, and radical character on the optical band gap of polyaromatic hydrocarbons has been investigated.
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Affiliation(s)
- Angiras Menon
- Department of Chemical Engineering and Biotechnology
- University of Cambridge
- Cambridge CB3 0AS
- UK
- Cambridge Centre for Advanced Research and Education in Singapore (CARES)
| | - Jochen A. H. Dreyer
- Department of Chemical Engineering and Biotechnology
- University of Cambridge
- Cambridge CB3 0AS
- UK
| | - Jacob W. Martin
- Department of Chemical Engineering and Biotechnology
- University of Cambridge
- Cambridge CB3 0AS
- UK
- Cambridge Centre for Advanced Research and Education in Singapore (CARES)
| | - Jethro Akroyd
- Department of Chemical Engineering and Biotechnology
- University of Cambridge
- Cambridge CB3 0AS
- UK
| | - John Robertson
- Department of Engineering
- University of Cambridge
- Cambridge CB3 0FA
- UK
| | - Markus Kraft
- Department of Chemical Engineering and Biotechnology
- University of Cambridge
- Cambridge CB3 0AS
- UK
- Cambridge Centre for Advanced Research and Education in Singapore (CARES)
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