1
|
Wei D, Qin Y, Xu Z, Liu H, Chen R, Yu Y, Wang D. Study of Molecular Dimer Morphology Based on Organic Spin Centers: Nitronyl Nitroxide Radicals. Molecules 2024; 29:2042. [PMID: 38731533 PMCID: PMC11085200 DOI: 10.3390/molecules29092042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Revised: 04/24/2024] [Accepted: 04/27/2024] [Indexed: 05/13/2024] Open
Abstract
In this work, in order to investigate the short-range interactions between molecules, the spin-magnetic unit nitronyl nitroxide (NN) was introduced to synthesize self-assembly single radical molecules with hydrogen bond donors and acceptors. The structures and magnetic properties were extensively investigated and characterized by UV-Vis absorption spectroscopy, electron paramagnetic resonance (EPR), and superconducting quantum interference devices (SQUIDs). Interestingly, it was observed that the single molecules can form two different dimers (ring-closed dimer and "L"-type dimer) in different solvents, due to hydrogen bonding, when using EPR to track the molecular spin interactions. Both dimers exhibit ferromagnetic properties (for ring-closed dimer, J/kB = 0.18 K and ΔES-T = 0.0071 kcal/mol; for "L"-type dimer, the values were J/kB = 9.26 K and ΔES-T = 0.037 kcal/mol). In addition, the morphologies of the fibers formed by the two dimers were characterized by transmission electron microscopy (TEM) and atomic force microscopy (AFM).
Collapse
Affiliation(s)
- Dongdong Wei
- School of Materials Science and Chemical Engineering, Anhui Jianzhu University, Hefei 230601, China
| | - Yongliang Qin
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
| | - Zhipeng Xu
- School of Materials Science and Chemical Engineering, Anhui Jianzhu University, Hefei 230601, China
| | - Hui Liu
- School of Materials Science and Chemical Engineering, Anhui Jianzhu University, Hefei 230601, China
| | - Ranran Chen
- School of Materials Science and Chemical Engineering, Anhui Jianzhu University, Hefei 230601, China
| | - Yang Yu
- School of Advanced Manufacturing Engineering, Hefei University, Hefei 230601, China
| | - Di Wang
- School of Materials Science and Chemical Engineering, Anhui Jianzhu University, Hefei 230601, China
| |
Collapse
|
2
|
Heuer MA, Reuter L, Lüchow A. Ab Initio Dot Structures Beyond the Lewis Picture. Molecules 2021; 26:911. [PMID: 33572207 DOI: 10.3390/molecules26040911] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 02/02/2021] [Accepted: 02/04/2021] [Indexed: 11/20/2022] Open
Abstract
The empirical Lewis picture of the chemical bond dominates the view chemists have of molecules, of their stability and reactivity. Within the mathematical framework of quantum mechanics, all this chemical information is hidden in the many-particle wave function Ψ. Thus, to reveal and understand it, there is great interest in enhancing the Lewis model and connecting it to computable quantities. As has previously been shown, the Lewis picture can often be recovered from the probability density |Ψ|2 with probabilities in agreement with valence bond weights: the structures appear as most likely positions in the all-electron configuration space. Here, we systematically expand this topological probability density analysis to molecules with multiple bonds and lone pairs, employing correlated Slater-Jastrow wave functions. In contrast to earlier studies, non-Lewis structures are obtained that disagree with the prevalent picture and have a potentially better predictive capability. While functional groups are still recovered with these ab initio structures, the boundary between bonds and lone pairs is mostly blurred or non-existent. In order to understand the newly found structures, the Lewis electron pairs are replaced with spin-coupled electron motifs as the fundamental electronic fragment. These electron motifs—which coincide with Lewis’ electron pairs for many single bonds—arise naturally from the generally applicable analysis presented. An attempt is made to rationalize the geometry of the newly-found structures by considering the Coulomb force and the Pauli repulsion.
Collapse
|
3
|
Kowalska JK, Henthorn JT, Van Stappen C, Trncik C, Einsle O, Keavney D, DeBeer S. X-ray Magnetic Circular Dichroism Spectroscopy Applied to Nitrogenase and Related Models: Experimental Evidence for a Spin-Coupled Molybdenum(III) Center. Angew Chem Int Ed Engl 2019; 58:9373-9377. [PMID: 31119827 PMCID: PMC6772009 DOI: 10.1002/anie.201901899] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 04/17/2019] [Indexed: 11/23/2022]
Abstract
Nitrogenase enzymes catalyze the reduction of atmospheric dinitrogen to ammonia utilizing a Mo‐7Fe‐9S‐C active site, the so‐called FeMoco cluster. FeMoco and an analogous small‐molecule (Et4N)[(Tp)MoFe3S4Cl3] cubane have both been proposed to contain unusual spin‐coupled MoIII sites with an S(Mo)=1/2 non‐Hund configuration at the Mo atom. Herein, we present Fe and Mo L3‐edge X‐ray magnetic circular dichroism (XMCD) spectroscopy of the (Et4N)[(Tp)MoFe3S4Cl3] cubane and Fe L2,3‐edge XMCD spectroscopy of the MoFe protein (containing both FeMoco and the 8Fe‐7S P‐cluster active sites). As the P‐clusters of MoFe protein have an S=0 total spin, these are effectively XMCD‐silent at low temperature and high magnetic field, allowing for FeMoco to be selectively probed by Fe L2,3‐edge XMCD within the intact MoFe protein. Further, Mo L3‐edge XMCD spectroscopy of the cubane model has provided experimental support for a local S(Mo)=1/2 configuration, demonstrating the power and selectivity of XMCD.
Collapse
Affiliation(s)
- Joanna K Kowalska
- Inorganic Spectroscopy, Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, 45470, Mülheim an der Ruhr, Germany
| | - Justin T Henthorn
- Inorganic Spectroscopy, Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, 45470, Mülheim an der Ruhr, Germany
| | - Casey Van Stappen
- Inorganic Spectroscopy, Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, 45470, Mülheim an der Ruhr, Germany
| | - Christian Trncik
- Institute for Biochemistry and BIOSS Centre for Biological Signalling Studies, Albert Ludwigs University of Freiburg, Albertstrasse 21, 79104, Freiburg, Germany
| | - Oliver Einsle
- Institute for Biochemistry and BIOSS Centre for Biological Signalling Studies, Albert Ludwigs University of Freiburg, Albertstrasse 21, 79104, Freiburg, Germany
| | - David Keavney
- Argonne National Laboratory, 9700 S. Cass Ave, Argonne, IL, 60439, USA
| | - Serena DeBeer
- Inorganic Spectroscopy, Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, 45470, Mülheim an der Ruhr, Germany
| |
Collapse
|
4
|
Steenbock T, Herrmann C. Toward an automated analysis of exchange pathways in spin-coupled systems. J Comput Chem 2018; 39:81-92. [PMID: 29044625 DOI: 10.1002/jcc.25081] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 09/22/2017] [Accepted: 09/24/2017] [Indexed: 01/25/2023]
Abstract
Understanding (super-)exchange coupling between local spins is an important task in theoretical chemistry and solid-state physics. We show that a Green's-function approach introduced earlier (Liechtenstein et al., J. Phys. F 1984, 14, L125; Steenbock et al., J. Chem. Theory Comput. 2015, 11, 5651) can be used for analyzing exchange coupling pathways in an automated fashion rather than by visual inspection of molecular orbitals. We demonstrate the capabilities of this approach by comparing it to previously published pathway analyses for hydroxy-bridged dinuclear copper complexes and an oxo-bridged dinuclear manganese complex, and employ it for discriminating between through-space and through-bond pathways in a naphthalene-bridged bisnickelocene complex. © 2017 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Torben Steenbock
- Institute of Inorganic and Applied Chemistry, Chemistry Department, University of Hamburg, Martin-Luther-King-Platz 6, Hamburg, 20146, Germany
| | - Carmen Herrmann
- Institute of Inorganic and Applied Chemistry, Chemistry Department, University of Hamburg, Martin-Luther-King-Platz 6, Hamburg, 20146, Germany
| |
Collapse
|
5
|
Molčanov K, Babić D, Kojić-Prodić B, Stare J, Maltar-Strmečki N, Androš L. Spin-coupling in dimers of 2,3-dicyano-5,6-dichlorosemiquinone radical anions in the crystalline state. Acta Crystallogr B Struct Sci Cryst Eng Mater 2014; 70:181-190. [PMID: 24441141 DOI: 10.1107/s2052520613027170] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 10/02/2013] [Indexed: 06/03/2023]
Abstract
A crystal engineering approach is used to stabilize a radical anion in the crystalline state and to modulate the separation distance within π-stacks of anion radicals. Alkali metal salts of 2,3-dicyano-5,6-dichlorosemiquinone (C8Cl2N2O2, DDQ∙- radical anions were prepared and their crystal structures determined: LiDDQ·2H2O·(CH3)2CO, RbDDQ·2H2O and CsDDQ·2H2O. In these structures, stacked dimers of radical anions are formed within π-stacked columns. Within the stacked dimers, interplanar separation distances are significantly shorter than the sum of the van der Waals radii for two C atoms; the shortest is 2.812 Å for the Li salt and the longest is 2.925 Å for the Cs salt. Diamagnetic character, observed by electron paramagnetic resonance spectroscopy, indicates spin-coupling of the unpaired electrons within the radical anion dimer. The electron-rich cyano substituents on DDQ∙- influence the electron redistribution within the ring skeleton. The crystalline compounds are also characterized by IR spectroscopy, complemented by quantum-chemical calculations based on both isolated and periodic models.
Collapse
Affiliation(s)
| | - Darko Babić
- Rudjer Bošković Institute, Bijenička 54, HR-10000 Zagreb, Croatia
| | | | - Jernej Stare
- National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia
| | | | - Lidija Androš
- Rudjer Bošković Institute, Bijenička 54, HR-10000 Zagreb, Croatia
| |
Collapse
|