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Treichel M, Möller J, Meng X, Gutzeit F, Herges R, Berndt R, Weismann A. Tilted Spins in Chains of Molecular Switches on Pb(100). ACS NANO 2024. [PMID: 39276102 PMCID: PMC11440647 DOI: 10.1021/acsnano.4c07477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/16/2024]
Abstract
A complex based on a Ni(II) porphyrin exhibiting spin crossover on Ag(111) is studied on Pb(100) by scanning tunneling microscopy at 0.3 K. Strong molecular interactions between the phenyl and pentafluorophenyl moieties lead to the formation of molecular chains and cause a faceting of the substrate surface. The chains are located along double and multiple substrate steps that deviate from high-symmetry directions. Tunneling spectroscopy reveals spin-flip excitations of an S = 1 system. Measurements in high magnetic fields are used to identify a tilt of the complex and its hard anisotropy axis with respect to the surface normal. Electron injection into the substrate near the molecular rows induces a transition to a state with larger inelastic cross section, leaving the spin state unchanged.
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Affiliation(s)
- Marten Treichel
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Jenny Möller
- Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Xiangzhi Meng
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Florian Gutzeit
- Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Rainer Herges
- Otto-Diels-Institut für Organische Chemie, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Richard Berndt
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Alexander Weismann
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
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Halcrow MA. Mix and match - controlling the functionality of spin-crossover materials through solid solutions and molecular alloys. Dalton Trans 2024; 53:13694-13708. [PMID: 39119634 DOI: 10.1039/d4dt01855a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/10/2024]
Abstract
The influence of dopant molecules on the structure and functionality of spin-crossover (SCO) materials is surveyed. Two aspects of the topic are well established. Firstly, isomorphous inert metal ion dopants in SCO lattices are a useful probe of the energetics of SCO processes. Secondly, molecular alloys of iron(II)/triazole coordination polymers containing mixtures of ligands were used to tune their spin-transitions towards room temperature. More recent examples of these and related materials are discussed that reveal new insights into these questions. Complexes which are not isomorphous can also be co-crystallised, either as solid solutions of the precursor molecules or as a random distribution of homo- and hetero-leptic centres in a molecular alloy. This could be a powerful method to manipulate SCO functionality. Published molecular alloys show different SCO behaviours, which may or may not include allosteric switching of their chemically distinct metal sites.
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Affiliation(s)
- Malcolm A Halcrow
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK.
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Kuppusamy SK, Mizuno A, Kämmerer L, Salamon S, Heinrich B, Bailly C, Šalitroš I, Wende H, Ruben M. Lattice solvent- and substituent-dependent spin-crossover in isomeric iron(II) complexes. Dalton Trans 2024; 53:10851-10865. [PMID: 38826041 DOI: 10.1039/d4dt00429a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2024]
Abstract
Spin-state switching in iron(II) complexes composed of ligands featuring moderate ligand-field strength-for example, 2,6-bi(1H-pyrazol-1-yl)pyridine (BPP)-is dependent on many factors. Herein, we show that spin-state switching in isomeric iron(II) complexes composed of BPP-based ligands-ethyl 2,6-bis(1H-pyrazol-1-yl)isonicotinate (BPP-COOEt, L1) and (2,6-di(1H-pyrazol-1-yl)pyridin-4-yl)methylacetate (BPP-CH2OCOMe, L2)-is dependent on the nature of the substituent at the BPP skeleton. Bi-stable spin-state switching-with a thermal hysteresis width (ΔT1/2) of 44 K and switching temperature (T1/2) = 298 K in the first cycle-is observed for complex 1·CH3CN composed of L1 and BF4- counter anions. Conversely, the solvent-free isomeric counterpart of 1·CH3CN-complex 2a, composed of L2 and BF4- counter anions-was trapped in the high-spin (HS) state. For one of the polymorphs of complex 2b·CH3CN-2b·CH3CN-Y, Y denotes yellow colour of the crystals-composed of L2 and ClO4- counter anions, a gradual and non-hysteretic SCO is observed with T1/2 = 234 K. Complexes 1·CH3CN and 2b·CH3CN-Y also underwent light-induced spin-state switching at 5 K due to the light-induced excited spin-state trapping (LIESST) effect. Structures of the low-spin (LS) and HS forms of complex 1·CH3CN revealed that spin-state switching goes hand-in-hand with pronounced distortion of the trans-N{pyridyl}-Fe-N{pyridyl} angle (ϕ), whereas such distortion is not observed for 2b·CH3CN-Y. This observation points that distortion is one of the factors making the spin-state switching of 1·CH3CN hysteretic in the solid state. The observation of bi-stable spin-state switching with T1/2 centred at room temperature for 1·CH3CN indicates that technologically relevant spin-state switching profiles based on mononuclear iron(II) complexes can be obtained.
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Affiliation(s)
- Senthil Kumar Kuppusamy
- Institute of Quantum Materials and Technologies (IQMT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
| | - Asato Mizuno
- Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Lea Kämmerer
- University of Duisburg-Essen, Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), Lotharstraße 1, 47057 Duisburg, Germany
| | - Soma Salamon
- University of Duisburg-Essen, Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), Lotharstraße 1, 47057 Duisburg, Germany
| | - Benoît Heinrich
- Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), CNRS-Université de Strasbourg, 23, rue du Loess, BP 43, 67034 Strasbourg Cedex 2, France
| | - Corinne Bailly
- Service de Radiocristallographie, Fédération de Chimie Le Bel UAR2042 CNRS-Université de Strasbourg, 1 rue Blaise Pascal, BP 296/R8, 67008 Strasbourg cedex, France
| | - Ivan Šalitroš
- Central European Institute of Technology, Brno University of Technology, Purkyňova 123, 61200 Brno, Czech Republic
- Department of Inorganic Chemistry, Faculty of Chemical and Food Technology, Slovak University of Technology in Bratislava, Bratislava SK-81237, Slovakia
| | - Heiko Wende
- University of Duisburg-Essen, Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), Lotharstraße 1, 47057 Duisburg, Germany
| | - Mario Ruben
- Institute of Quantum Materials and Technologies (IQMT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
- Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
- Centre Européen de Sciences Quantiques (CESQ), Institut de Science et d'Ingénierie, Supramoléculaires (ISIS), 8 allée Gaspard Monge, BP 70028, 67083 Strasbourg Cedex, France
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Torres-Cavanillas R, Gavara-Edo M, Coronado E. Bistable Spin-Crossover Nanoparticles for Molecular Electronics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2307718. [PMID: 37725707 DOI: 10.1002/adma.202307718] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 08/25/2023] [Indexed: 09/21/2023]
Abstract
The field of spin-crossover complexes is rapidly evolving from the study of the spin transition phenomenon to its exploitation in molecular electronics. Such spin transition is gradual in a single-molecule, while in bulk it can be abrupt, showing sometimes thermal hysteresis and thus a memory effect. A convenient way to keep this bistability while reducing the size of the spin-crossover material is to process it as nanoparticles (NPs). Here, the most recent advances in the chemical design of these NPs and their integration into electronic devices, paying particular attention to optimizing the switching ratio are reviewed. Then, integrating spin-crossover NPs over 2D materials is focused to improve the endurance, performance, and detection of the spin state in these hybrid devices.
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Affiliation(s)
- Ramón Torres-Cavanillas
- Instituto de Ciencia Molecular, Universitat de València, Valencia, 46980, Spain
- Department of Materials, Oxford University, Oxford, OX2 6NN, UK
| | - Miguel Gavara-Edo
- Instituto de Ciencia Molecular, Universitat de València, Valencia, 46980, Spain
| | - Eugenio Coronado
- Instituto de Ciencia Molecular, Universitat de València, Valencia, 46980, Spain
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Kulmaczewski R, Halcrow MA. Iron(II) complexes of 2,6-bis(imidazo[1,2- a]pyridin-2-yl)pyridine and related ligands with annelated distal heterocyclic donors. Dalton Trans 2023; 52:14928-14940. [PMID: 37799008 DOI: 10.1039/d3dt02747c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/07/2023]
Abstract
Following a published synthesis of 2,6-bis(imidazo[1,2-a]pyridin-2-yl)pyridine (L1), treatment of α,α'-dibromo-2,6-diacetylpyridine with 2 equiv. 2-aminopyrimidine or 2-aminoquinoline in refluxing acetonitrile respectively gives 2,6-bis(imidazo[1,2-a]pyrimidin-2-yl)pyridine (L2) and 2,6-bis(imidazo[1,2-a]quinolin-2-yl)pyridine (L3). Solvated crystals of [Fe(L1)2][BF4]2 (1[BF4]2) and [Fe(L2)2][BF4]2 (2[BF4]2) are mostly high-spin, although one solvate of 1[BF4]2 undergoes thermal spin-crossover on cooling. The iron coordination geometry is consistently distorted in crystals of 2[BF4]2 which may reflect the influence of intramolecular, inter-ligand N⋯π interactions on the molecular conformation. Only 1 : 1 Fe : L3 complexes were observed in solution, or isolated in the solid state; a crystal structure of [FeBr(py)2L3]Br·0.5H2O (py = pyridine) is presented. A solvate crystal structure of high-spin [Fe(L4)2][BF4]2 (L4 = 2,6-di{quinolin-2-yl}pyridine; 4[BF4]2) is also described, which exhibits a highly distorted six-coordinate geometry with a helical ligand conformation. The iron(II) complexes are high-spin in solution at room temperature, but 1[BF4]2 and 2[BF4]2 undergo thermal spin-crossover equilibria on cooling. All the compounds exhibit a ligand-based emission in solution at room temperature. Gas phase DFT calculations mostly reproduce the spin state properties of the complexes, but show small anomalies attributed to intramolecular, inter-ligand dispersion interactions in the sterically crowded molecules.
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Affiliation(s)
- Rafal Kulmaczewski
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, UK LS2 9JT.
| | - Malcolm A Halcrow
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, UK LS2 9JT.
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Johannsen S, Gruber M, Barreteau C, Seredyuk M, Antonio Real J, Markussen T, Berndt R. Spin-Crossover and Fragmentation of Fe(neoim) 2 on Silver and Gold. J Phys Chem Lett 2023; 14:7814-7823. [PMID: 37623823 DOI: 10.1021/acs.jpclett.3c01551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/26/2023]
Abstract
The neutral spin crossover complex Fe(neoim)2, neoim being the deprotonated form of the ionogenic ligand 2-(1H-imidazol-2-yl)-9-methyl-1,10-phenanthroline (neoimH), is investigated on the (111) surfaces of Au and Ag using scanning tunneling microscopy and density functional theory calculations. The complex sublimates and adsorbs intact on Ag(111), where it exhibits an electron-induced spin crossover. However, it fragments on Au. According to density functional theory calculations, the adsorbed complex is drastically distorted by the interactions with the substrates, in particular by van der Waals forces. Dispersion interaction is also decisive for the relative stabilities of the low- and high-spin states of the adsorbed complex. The unexpected instability of the complex on the gold substrate is attributed to enhanced covalent bonding of the fragments to the substrate.
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Affiliation(s)
- Sven Johannsen
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität, 24098 Kiel, Germany
| | - Manuel Gruber
- Faculty of Physics and CENIDE, University of Duisburg-Essen, 47057 Duisburg, Germany
| | - Cyrille Barreteau
- Université Paris-Saclay CEA, CNRS SPEC, 91191 Gif-sur-Yvette, France
| | - Maksym Seredyuk
- Instituto de Ciencia Molecular (ICMol)/Departamento de Química Inorgánica, Universidad de Valencia, 46980 Paterna, Valencia, Spain
- Department of Chemistry, Taras Shevchenko National University of Kyiv, 64/13 Volodymyrska Street 01601 Kyiv, Ukraine
| | - José Antonio Real
- Instituto de Ciencia Molecular (ICMol)/Departamento de Química Inorgánica, Universidad de Valencia, 46980 Paterna, Valencia, Spain
| | | | - Richard Berndt
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität, 24098 Kiel, Germany
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Yazdani S, Phillips J, Ekanayaka TK, Cheng R, Dowben PA. The Influence of the Substrate on the Functionality of Spin Crossover Molecular Materials. Molecules 2023; 28:3735. [PMID: 37175145 PMCID: PMC10180229 DOI: 10.3390/molecules28093735] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 04/18/2023] [Accepted: 04/18/2023] [Indexed: 05/15/2023] Open
Abstract
Spin crossover complexes are a route toward designing molecular devices with a facile readout due to the change in conductance that accompanies the change in spin state. Because substrate effects are important for any molecular device, there are increased efforts to characterize the influence of the substrate on the spin state transition. Several classes of spin crossover molecules deposited on different types of surface, including metallic and non-metallic substrates, are comprehensively reviewed here. While some non-metallic substrates like graphite seem to be promising from experimental measurements, theoretical and experimental studies indicate that 2D semiconductor surfaces will have minimum interaction with spin crossover molecules. Most metallic substrates, such as Au and Cu, tend to suppress changes in spin state and affect the spin state switching process due to the interaction at the molecule-substrate interface that lock spin crossover molecules in a particular spin state or mixed spin state. Of course, the influence of the substrate on a spin crossover thin film depends on the molecular film thickness and perhaps the method used to deposit the molecular film.
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Affiliation(s)
- Saeed Yazdani
- Department of Physics, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA; (S.Y.); (J.P.)
| | - Jared Phillips
- Department of Physics, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA; (S.Y.); (J.P.)
| | - Thilini K. Ekanayaka
- Department of Physics and Astronomy, Jorgensen Hall, University of Nebraska, Lincoln, NE 68588-0299, USA;
| | - Ruihua Cheng
- Department of Physics, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA; (S.Y.); (J.P.)
| | - Peter A. Dowben
- Department of Physics and Astronomy, Jorgensen Hall, University of Nebraska, Lincoln, NE 68588-0299, USA;
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