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1. Conformational Effects on the Magnetic Properties of an Organic Diradical: A Computational Study

Author

Ivo Cacelli, Vincenzo Barone, Giacomo Prampolini, Corentin Boilleau, Alessandro Ferretti, Barone, Vincenzo, Corentin, Boilleau, Ivo, Cacelli, Alessandro, Ferretti, and Giacomo, Prampolini

Subjects
Meta, Band gap, Diradical, Chemistry, Computational chemistry, Degrees of freedom (physics and chemistry), Singlet state, Function (mathematics), Physical and Theoretical Chemistry, Ring (chemistry), Molecular physics, Computer Science Applications, Sign (mathematics)
Abstract

A theoretical study on the singlet triplet energy splitting in a m-phenylene bridged organic diradical has been performed using an original computational protocol developed in our group. The method is based on post Hatree-Fock calculations and has proven to provide accurate results with reasonable computational effort. By virtue of such efficiency, the full PES of both the singlet and triplet states as a function of the two "soft" torsional degrees of freedom at the meta position of the ring has been explored. In agreement with literature findings, we found a pronounced dependence of the sign of the energy gap from the torsional angles. Finally, exploiting the two-dimensional surface, a statistical analysis is carried out at low temperatures and a comparison with available experimental data addressed.

Published
2013

2. Ruthenium Carbon-Rich Group as a Redox-Switchable Metal Coupling Unit in Linear Trinuclear Complexes

Author

Sylvie Choua, Emmanuel Di Piazza, Thierry Roisnel, Stéphane Rigaut, Karine Costuas, Philippe Turek, Lucie Norel, Corentin Boilleau, Khalissa Merahi, Antoine Vacher, Institut des Sciences Chimiques de Rennes (ISCR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie de Strasbourg, Université de Strasbourg (UNISTRA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), ANR-12-BS07-0010-01, Agence Nationale de la Recherche, UMO-2015/17/D/ST3/00883, Narodowe Centrum Nauki, Centre National de la Recherche Scientifique, Université de Rennes 1, ANR-12-BS07-0010,RuOxLux,Modulation redox de la luminescence à l'aide de complexes organométalliques du ruthénium associés à une unité luminescente(2012), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), and Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)

Subjects
010405 organic chemistry, Chemistry, Magnetism, chemistry.chemical_element, 010402 general chemistry, Photochemistry, 01 natural sciences, Copper, Redox, 0104 chemical sciences, law.invention, Ruthenium, Inorganic Chemistry, Metal, Paramagnetism, Crystallography, law, visual_art, visual_art.visual_art_medium, [CHIM.CRIS]Chemical Sciences/Cristallography, [CHIM.COOR]Chemical Sciences/Coordination chemistry, Physical and Theoretical Chemistry, Electron paramagnetic resonance, Bimetallic strip
Abstract

International audience; The preparation and properties of novel ruthenium carbon-rich complexes [(Ph-C≡C-)Ru(dppe)(-C≡C-bipyM(hfac))] (n = 1, 2; M = Cu, Mn; bipy = 2,2'-bipyridin-5-yl) characterized by single-crystal X-ray diffraction and designed for molecular magnetism are reported. With the help of EPR spectroscopy, we show that the neutral ruthenium system sets up a magnetic coupling between two remote paramagnetic Cu units. More specifically, these copper compounds are unique examples of bimetallic and linear heterotrimetallic compounds for which a complete rationalization of the magnetic interactions could be made for exceptionally long distances between the spin carriers (8.3 Å between adjacent Cu and Ru centers, 16.6 Å between external Cu centers) and compared at two different redox states. Surprisingly, oxidation of the ruthenium redox-active metal coupling unit (MCU), which introduces an additional spin unit on the carbon-rich part, leads to weaker magnetic interactions. In contrast, in the simpler parent complexes bearing only one paramagnetic metal unit [Ph-C≡C-Ru(dppe)-C≡C-bipyCu(hfac)], one-electron oxidation of the ruthenium bis(acetylide) unit generates an interaction between the Cu and Ru spin carriers of magnitude comparable to that observed between the two far apart Cu ions in the above corresponding neutral trimetallic system. Evaluation and rationalization of this coupling with theoretical tools are in rational agreement with experiments for such complex systems.

Published
2017

3. Innenrücktitelbild: Polarized Neutron Diffraction to Probe Local Magnetic Anisotropy of a Low-Spin Fe(III) Complex (Angew. Chem. 12/2016)

Author

Karine Costuas, Rodrigue Lescouëzec, Karl Ridier, Grégory Chaboussant, Boris Le Guennic, Corentin Boilleau, Béatrice Gillon, Abhishake Mondal, Olivier Cador, Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut Parisien de Chimie Moléculaire (IPCM), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences Chimiques de Rennes (ISCR), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay, Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), and Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)

Subjects
Magnetic anisotropy, Nuclear magnetic resonance, Condensed matter physics, 010405 organic chemistry, Chemistry, Neutron diffraction, [CHIM]Chemical Sciences, General Medicine, 010402 general chemistry, Spin (physics), 01 natural sciences, ComputingMilieux_MISCELLANEOUS, 0104 chemical sciences
Abstract

International audience; no abstract

Published
2016

4. Polarized Neutron Diffraction to Probe Local Magnetic Anisotropy of a Low-Spin Fe(III) Complex

Author

Béatrice Gillon, Olivier Cador, Karine Costuas, Rodrigue Lescouëzec, Abhishake Mondal, Grégory Chaboussant, Karl Ridier, Boris Le Guennic, Corentin Boilleau, Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Equipe de Recherche en Matériaux Moléculaires et Spectroscopies (ERMMES), Institut Parisien de Chimie Moléculaire (IPCM), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Scuola Normale Superiore di Pisa (SNS), Institut des Sciences Chimiques de Rennes (ISCR), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), ANR, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay, Institut de Chimie du CNRS (INC)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), and Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)

Subjects
Coordination sphere, Neutron diffraction, molecular magnetism, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, Catalysis, law.invention, Paramagnetism, Magnetization, law, [CHIM.COOR]Chemical Sciences/Coordination chemistry, Anisotropy, Electron paramagnetic resonance, magnetic anisotropy, Condensed matter physics, Chemistry, General Medicine, General Chemistry, 021001 nanoscience & nanotechnology, Magnetic susceptibility, 0104 chemical sciences, polarized neutron diffraction, Crystallography, Magnetic anisotropy, density functional calculations, 0210 nano-technology, EPR spectroscopy
Abstract

International audience; We have determined by polarized neutron diffraction (PND) the low-temperature molecular magnetic susceptibility tensor of the anisotropic low-spin complex PPh4 [Fe(III) (Tp)(CN)3 ]⋅H2 O. We found the existence of a pronounced molecular easy magnetization axis, almost parallel to the C3 pseudo-axis of the molecule, which also corresponds to a trigonal elongation direction of the octahedral coordination sphere of the Fe(III) ion. The PND results are coherent with electron paramagnetic resonance (EPR) spectroscopy, magnetometry, and ab initio investigations. Through this particular example, we demonstrate the capabilities of PND to provide a unique, direct, and straightforward picture of the magnetic anisotropy and susceptibility tensors, offering a clear-cut way to establish magneto-structural correlations in paramagnetic molecular complexes

Published
2015

5. Structure-properties relationships in triplet ground state organic diradicals. A computational study

Author

Corentin Boilleau, Giacomo Prampolini, Ivo Cacelli, Alessandro Ferretti, Susanna Monti, Vincenzo Barone, Barone, Vincenzo, Corentin, Boilleau, Ivo, Cacelli, Alessandro, Ferretti, Susanna, Monti, and Giacomo, Prampolini

Subjects
Soundness, Chemical physics, Computational chemistry, Chemistry, Magnet, Structure (category theory), Physical and Theoretical Chemistry, Physics::Chemical Physics, Ground state, Computer Science Applications
Abstract

A fast and efficient computational protocol, devised for the accurate calculation of singlet-triplet magnetic splittings in organic diradicals, is here applied to several promising organic magnets, recently considered in the literature. The very good agreement with the measured values, obtained for all investigated compounds, suggests that the present approach could successfully flank the experiment in the design of novel magnetic materials. Indeed, some structure-magnetic properties relationships were rationalized thanks to the theoretical soundness of the adopted multireference approach. In particular the different effects of N· and NO· magnetic moieties, as well as the role of lateral aliphatic chains and phenyl pendant substituents, are discussed in detail.

Published
2013

6. Ab initio study of the influence of structural parameters on the potential energy surfaces of spin-crossover Fe(II) model compounds

Author

Nathalie Guihéry, Nicolas Suaud, Corentin Boilleau, Scuola Normale Superiore di Pisa (SNS), Systèmes étendus et magnétisme (LCPQ) (SEM), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
Spin states, Chemistry, Ab initio, General Physics and Astronomy, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, Potential energy, Molecular physics, LIESST, 0104 chemical sciences, Ab initio quantum chemistry methods, Spin crossover, Excited state, Singlet state, Physical and Theoretical Chemistry, Atomic physics, 0210 nano-technology, [CHIM.OTHE]Chemical Sciences/Other
Abstract

International audience; In spin-crossover (SCO) compounds exhibiting a light induced excited spin state trapping (LIESST) effect, the thermodynamic T(1∕2) and kinetic T(LIESST) temperature values depend on the features of the potential energy surfaces (PES) of the two lowest singlet and quintet states but also on vibrational contributions, collective effects, such as electrostatics, for instance, spin-orbit couplings to a lesser extent, etc. In this work, the question of the link between the shape of the PES of SCO compounds exhibiting a LIESST effect and their first coordination sphere structure is addressed from wave function theory based ab initio calculations. Fe(II) complexes based on model ligands suited to reproduce the main characteristics of the PES of such compounds are distorted to emphasize selectively the role played by the metal-ligand distances and the ligand-metal-ligand angles. The studied angular deformations are those usually observed in many Fe(L)(2)(NCS)(2) complexes. It is shown that the larger the deformation between the low spin and high spin equilibrium geometries, the higher the energy barrier from the high spin state and the weaker the energy difference between the bottom of the wells. These results corroborate observations made by experimentalists on a large number of complexes. While the PES features only constitutes one of the contributions to these temperatures, it is worth noticing that, relating T(1∕2) to the energy difference between the bottoms of the singlet and quintet wells and the T(LIESST) to the energy barrier from the quintet bottom well, the same slope of the empirical law T(LIESST) = -0.3T(1∕2)+T(0) is observed.

Published
2012

7. Inside Back Cover: Polarized Neutron Diffraction to Probe Local Magnetic Anisotropy of a Low-Spin Fe(III) Complex (Angew. Chem. Int. Ed. 12/2016)

Author

Karine Costuas, Rodrigue Lescouëzec, Grégory Chaboussant, Abhishake Mondal, Olivier Cador, Béatrice Gillon, Boris Le Guennic, Corentin Boilleau, and Karl Ridier

Subjects
Magnetic anisotropy, Crystallography, Condensed matter physics, law, Chemistry, Neutron diffraction, Cover (algebra), General Chemistry, Electron paramagnetic resonance, Spin (physics), Catalysis, law.invention
Published
2016

8. A bottom-up valence bond derivation of excitation energies in 1D-like delocalized systems

Author

Corentin Boilleau, Mikael Kepenekian, Jean-Paul Malrieu, Vincent Robert, Laboratoire de chimie quantique et de modélisation moléculaire (LCQMM), Centre National de la Recherche Scientifique (CNRS), Systèmes étendus et magnétisme (LCPQ) (SEM), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)

Subjects
Chemistry, General Physics and Astronomy, Charge (physics), 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, 0104 chemical sciences, Matrix (mathematics), Delocalized electron, Excited state, Quantum mechanics, Ionization, Valence bond theory, Physical and Theoretical Chemistry, Atomic physics, 0210 nano-technology, [CHIM.OTHE]Chemical Sciences/Other, Excitation, Complement (set theory)
Abstract

Using the chemically relevant parameters hopping integral t0 and on-site repulsion energy U, the charge gap (lowest dipolarly allowed transition energy) in 1D systems is examined through a bottom-up strategy. The method is based on the locally ionized states, the energies of which are corrected using short-range delocalization effects. In a valence bond framework, these states interact to produce an excitonic matrix which accounts for the delocalized character of excited states. The treatment, which gives access to the correlated spectrum of ionization potentials, is entirely analytical and valid whatever the U/t0 ratio for such systems ruled by Peierls-Hubbard Hamiltonians. This second-order analytical derivation is finally confronted to numerical results of a renormalized excitonic treatment using larger blocks as functions of the U/t0 ratio. The method is applied to dimerized chains and to fused polybenzenic 1D lattices. Such approaches complement the traditional Bloch-function based picture and deliver a conceptual understanding of the charge gap opening process based on a chemical intuitive picture. © 2012 the Owner Societies.

Published
2011

9. Possible use of DFT approaches for the determination of double exchange interactions

Author

Corentin Boilleau, Nathalie Guihéry, Jean-Paul Malrieu, Roland Bastardis, Nicolas Suaud, Systèmes étendus et magnétisme (LCPQ) (SEM), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), LAboratoire de Mathématiques et PhySique (LAMPS), Université de Perpignan Via Domitia (UPVD), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)

Subjects
010304 chemical physics, Condensed matter physics, Spin states, Spin polarization, Chemistry, Non symmetric, 010402 general chemistry, 01 natural sciences, 0104 chemical sciences, symbols.namesake, Quantum mechanics, 0103 physical sciences, symbols, Physical and Theoretical Chemistry, Hamiltonian (quantum mechanics)
Abstract

International audience; DFT calculations are performed on a model mixed-valence system presenting a double exchange phenomenon. Due to the intrinsic multireference character of the lowest Ms components of the spin states, it is shown that the interactions involved in the double-exchange model cannot be simply extracted from the DFT energies as it is sometimes done. It is, however, possible to extract from different DFT single determinant energies the interactions of a generalized Hubbard Hamiltonian, from which, in a second step, the double-exchange spectrum may be evaluated. The problems generated by the charge and spin polarization are discussed in both symmetric and non symmetric geometries, and the sensitivity of the results to the choice of the density functional is illustrated.

Published
2010

10. Light-induced excited spin state trapping: ab initio study of the physics at the molecular level

Author

Nathalie Guihéry, Marie-Laure Bonnet, Pierre Labéguerie, Corentin Boilleau, Nicolas Suaud, Systèmes étendus et magnétisme (LCPQ) (SEM), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Laboratoire de Chimie - UMR5182 (LC), Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon)-Institut de Chimie du CNRS (INC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse)

Subjects
Physics, Spin states, 010405 organic chemistry, Spin transition, General Chemistry, 010402 general chemistry, 01 natural sciences, Biochemistry, Potential energy, Catalysis, LIESST, 0104 chemical sciences, Colloid and Surface Chemistry, Excited state, Singlet fission, Atomic physics, Triplet state, Wave function, [CHIM.OTHE]Chemical Sciences/Other
Abstract

International audience; This paper provides a qualitative analysis of the physical content of the low-energy states of a spin-transition compound presenting a light-induced excited spin state trapping (LIESST) phenomenon, namely, [Fe(dipyrazolpyridine)2](BF4)2, which has been studied using the wave function-based CASPT2 method. Both the nature of the low-energy states and the relative position of their potential energy wells as a function of the geometry are rationalized from the analysis of the different wave functions. It is shown that the light-induced spin transition occurring in such systems could follow several pathways involving different excited spin states. In an ideal octahedral geometry, the interconversion from the excited singlet state to the triplet of lower energy, which is usually seen as an intermediate state in the LIESST mechanism, is quite unlikely since there is no crossing between the potential energy curves of these two states. On the contrary, in lower-symmetry complexes, the geometrical distortion of the coordination sphere due to ligand constraints is responsible for the occurrence of a crossing between these two states in the Franck-Condon region, leading to a possible participation of this triplet state in the LIESST mechanism. In the reverse LIESST process, a crossing between the potential energy curves of another triplet state and the excited quintet state occurs in the Franck-Condon region as well.

Published
2009

11. Is it possible to determine rigorous magnetic Hamiltonians in spin s = 1 systems from density functional theory calculations?

Author

Corentin Boilleau, Jean-Paul Malrieu, Nathalie Guihéry, Roland Bastardis, Nicolas Suaud, Pierre Labèguerie, Systèmes étendus et magnétisme (LCPQ) (SEM), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), LAboratoire de Mathématiques et PhySique (LAMPS), Université de Perpignan Via Domitia (UPVD), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse)

Subjects
010304 chemical physics, Magnetic moment, Chemistry, Orbital-free density functional theory, General Physics and Astronomy, 010402 general chemistry, 01 natural sciences, 0104 chemical sciences, Spin magnetic moment, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, symbols.namesake, Amplitude, Quantum mechanics, 0103 physical sciences, symbols, Density functional theory, Ising model, Physical and Theoretical Chemistry, Hamiltonian (quantum mechanics), Eigenvalues and eigenvectors
Abstract

International audience; The variational energies of broken-symmetry single determinants are frequently used (especially in the Kohn-Sham density functional theory) to determine the magnetic coupling between open-shell metal ions in molecular complexes or periodic lattices. Most applications extract the information from the solutions of m(s)(max) and m(s)(min) eigenvalues of S(z) magnetic spin momentum, assuming that a mapping of these energies on the energies of an Ising Hamiltonian is grounded. This approach is unable to predict the possible importance of deviations from the simplest form of the Heisenberg Hamiltonians. For systems involving s=1 magnetic centers, it cannot provide an estimate of neither the biquadratic exchange integral nor the three-body operator interaction that has recently been proven to be of the same order of magnitude [Phys. Rev. B 70, 132412 (2007)]. The present work shows that one may use other broken-symmetry solutions of intermediate values of m(s) to evaluate the amplitude of these additional terms. The here-derived equations rely on the assumption that an extended Hubbard-type Hamiltonian rules the interactions between the magnetic electrons. Numerical illustrations on a model problem of two O(2) molecules and a fragment of the La(2)NiO(4) lattice are reported. The results obtained using a variable percentage of Fock exchange in the BLYP functional are compared to those provided by elaborate wave function calculations. The relevant percentage of Fock exchange is system dependent but a mean value of 30% leads to acceptable amplitudes of the effective exchange interaction.

Published
2008

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