Papers by Michel verdaguer
In everyday life, the word “magnetism” most often refers to solid materials, metals, alloys, oxid... more In everyday life, the word “magnetism” most often refers to solid materials, metals, alloys, oxides. As for molecules, they are considered to be isolated, non-magnetic objects. Nevertheless, to be or not to be (magnetic) is not the appropriate question: everything is magnetic; the true problem lies in determining how. The purpose of this lecture is to illustrate the magnetism of molecules through some experiments.
Journal de physique. Colloque, Dec 1, 1988
Le Journal de Physique Colloques, 1986
Lea porphyrines d e fer h anses d e p a n i e r presentent des genes s t e r i q u e s a u r l e ... more Lea porphyrines d e fer h anses d e p a n i e r presentent des genes s t e r i q u e s a u r l e a d e w faces d u cycle porphyrinique e t une grande stabilite par rapport h l'oxydation par l e dioxygene . Nous pr&sentons une etude d ' absorption X d ' une serie d e cee composes We( I1 ) , plan car*; Im-Fe( I1 )-Q2, o c t e d r i q u e ; Fe( 1 1 1 )-OH, p y r d d e h base c a r r e e l , e n s o l u t i o n ou h l ' B t a t s o l i d e , pour mieux c o n n a i t r e s t r u c t u r e moleculaire e t fonction d e ces analogues d'hemee f i x a n t l'[email protected] presentons egalement les ~~8 u l t a t S pnSliminaires d e 1'Btude c i n e t i q u e par EXAPS rBeolu dans l e tempa,de l'oxydation p a r lloxyg@ne moleculaire d'une porphyrine d e F e ( I 1 ) h anse de p a n i e r (B H P ) , e n d e r i v e BHP-Fe( I11 )-OH.
Electrons in Molecules, 2013
Physical Review B, 1997
The magnetic susceptibility of high-spin molecules CrNi 6 (Sϭ15/2) and CrMn 6 (Sϭ27/2) has been m... more The magnetic susceptibility of high-spin molecules CrNi 6 (Sϭ15/2) and CrMn 6 (Sϭ27/2) has been measured at high frequency ͑680 MHz͒, in a magnetic field ͑up to 5 T͒, and at low temperature ͑down to 18 mK͒. A large decrease of the imaginary part of the susceptibility with increasing electromagnetic power is observed. This nonlinear effect is attributed to tunneling of the high-spin molecules between the two states ͉ϮS͘ of the ground doublet across the anisotropy-energy barrier.
Le Journal de Physique Colloques, 1986
Nous etudions par spectroscopic d'absorption d e s rayons X les t r a n s i t i o n s de s p i n ... more Nous etudions par spectroscopic d'absorption d e s rayons X les t r a n s i t i o n s de s p i n d e complexes du c o b a l t ( I 1 ) . du f e r ( 1 1 ) e t du f e r ( I I 1 ) . La c o n t r a c t i o n d e la premigre sphgre d e coordination l o r s du passage haut-spin -> bas-spin e s t mesur6e par ExApS pour t o u s les complexes. Le XANES d e s complexes du f e r m e t e n evidence les v a r i a t i o n s de s t r u c t u r e electronique l o r s d e la t r a n s i t i o n . L a v a r i a t i o n d ' o r d r e l o c a l e s t confronthe aux r 6 s u l t a t s d ' a u t r e s techniques pour d i s c u t e r l e caractTre c o o g r a t i f du p h e n M n e . ABSTRACT W e study by X-Ray absorption spectroscopy t h e s p i n crwssover f o r Co(II), Fe( I1 ) and Fe( I11 ) complexes. EXAFS allows t o measure t h e f i r s t coordination sphere c o n t r a c t i o n through t h e thermally induced high-spin ->
ChemInform, 2006
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
European Review, 2014
When I received this pocket-sized book, with its elegant blue-green cover illustrated by an impre... more When I received this pocket-sized book, with its elegant blue-green cover illustrated by an impressive picture of a magnolia acuminata tree, I was anxious to discover why Peter Day, an internationally recognised materials scientist, was leaving the scientific field that we had had in common for 30 years (molecular magnetism) to explore new frontiers in botany ‘On the Cucumber Tree’. The subtitle provides a quick answer: ‘scenes from the life of an itinerant jobbing scientist’. But it is not before reading the title page with a quotation from ‘Memoirs of a New Man’, a novel by William Cooper (alias Harry S. Hoff), that I began to understand that something other than botany was involved:
Polyhedron, 2001
This tutorial is a tribute to Olivier Kahn, a smart scientist who was the man of the transition f... more This tutorial is a tribute to Olivier Kahn, a smart scientist who was the man of the transition from magnetochemistry to molecular magnetism. The text presents in a simple way the models used by the late Olivier Kahn to obtain new molecular magnetic systems with unusual but predictable properties. The step starts from the quantum model, followed by the synthesis of systems of increasing complexity (spin cross over mononuclear complexes, binuclear antiferro-, ferro-, and ferri-complexes, one dimensional ferrimagnetic chains and molecule-based magnets) and ends with pratical applications. The tutorial then shows how Kahn's model can be applied to three-dimensional Prussian Blue analogues to get room-temperature magnets and associated devices in a rational way.
Journal of the American Chemical Society, 1988
Acknowledgment. This work was supported by Grant HL-20350 from the National Institutes of Health.... more Acknowledgment. This work was supported by Grant HL-20350 from the National Institutes of Health. We are grateful to Joan Klinger for technical assistance. ... Registry No. Imidazole, 288-32-4; 9-methyladenine, 700-00-5; cytosine monohydrate, 6020-40-2; urea, 57-1 3-6; ...
Journal of the American Chemical Society, 1981
In summary, a strongly electron-deficient and sterically hindered TPP Mn-O intermediate was produ... more In summary, a strongly electron-deficient and sterically hindered TPP Mn-O intermediate was produced in the present reductive dioxygen activation system which is most probably identical with that obtained from the 0-transfer reaction in TPP.Mn"'-PhIO system. Further studies directed to the clarification of the reductive oxygen activation mechanism and the identification of active oxidizing species are in progress.
Inorganic Chemistry, 1984
contribution is the largest one. It decreases when the two unpaired electrons delocalize in wide ... more contribution is the largest one. It decreases when the two unpaired electrons delocalize in wide or different regions of space. For "similar" bridges, the substitution of sulfur and nitrogen to oxygen shows that the less electronegative character of an atom and/or the more diffuse character of its AO's
![Research paper thumbnail of [Fe(Phen)(CN)4]-: A Versatile Building Block for the Design of Heterometallic Systems. Crystal Structures and Magnetic Properties of PPh4[Fe(Phen)(CN)4]·2H2O and [{Fe(Phen)(CN)4}2M(H2O)2]·4H2O [Phen = 1,10-Phenanthroline; M = Mn(II) and Zn(II)]](https://a.academia-assets.com/images/blank-paper.jpg)
Inorganic Chemistry, 2001
The mononuclear PPh4[Fe(phen)(CN)4]*2H2O (1) complex and the cyanide-bridged bimetallic [[Fe(phen... more The mononuclear PPh4[Fe(phen)(CN)4]*2H2O (1) complex and the cyanide-bridged bimetallic [[Fe(phen)(CN)4]2M(H2O)2]*4H2O compounds [M = Mn(II) (2) and Zn(II) (3); phen = 1,10-phenanthroline; PPh4 = tetraphenylphosphonium cation] have been synthesized and structurally and magnetically characterized. Complex 1 crystallizes in the monoclinic system, space group P2(1)/c, with a = 9.364(4) A, b = 27.472(5) A, c = 14.301(3) A, beta = 97.68(2) degrees, and Z = 4. Complexes 2 and 3 are isostructural and they crystallize in the monoclinic system, space group P2(1)/n, with a = 7.5292(4) A, b = 15.6000(10) A, c = 15.4081(9) A, beta = 93.552(2) degrees, and Z = 2 for 2 and a = 7.440(1) A, b = 15.569(3) A, c = 15.344(6) A, beta = 93.63(2) degrees, and Z = 2 for 3. The structure of complex 1 is made up of mononuclear [Fe(phen)(CN)4]- anions, tetraphenyphosphonium cations, and water molecules of crystallization. The iron(III) is hexacoordinate with two nitrogen atoms of a chelating phen (2.018(6) and 2.021(6) A for Fe-N) and four carbon atoms of four terminal cyanide groups (Fe-C bond lengths varying in the range 1.906(8)-1.95(1) A) building a distorted octahedron around the metal atom. The structure of complexes 2 and 3 consists of neutral double zigzag chains of formula [[Fe(phen)(CN)4]2M(H2O)2] and crystallization water molecules. The [Fe(phen)(CN)4]- entity of 1 is present in 2 and 3 acting as a bridging ligand toward M(H2O)2 units [M = Mn(II) (2) and Zn(II) (3)] through two cyanide groups in cis positions, the other two cyanide remaining terminal. Two water molecules in trans positions and four cyanide-nitrogen atoms from four [Fe(phen)(CN)4]- units build a distorted octahedral surrounding Mn(II) (2) and Zn(II) (3). The M-O bond lengths are 2.185(3) (2) and 2.105(3) A (3), whereas the M-N bond distances vary in the ranges 2.210(3)-2.258(3) A (2) and 2.112(3)-2.186(3) A (3). The structure of the [Fe(phen)(CN)4]- complex ligand in 2 and 3 is as in 1. The shorter intrachain Fe-M distances through bridging cyano are 5.245(5) and 5.208(5) A in 2 and 5.187(1) and 5.132(1) A in 3. The magnetic properties of 1-3 have been investigated in the temperature range 2.0-300 K. Complex 1 is a low-spin iron(III) complex with an appreciable orbital contribution. The magnetic properties of 3 correspond to the sum of two magnetically isolated spin triplets, the magnetic coupling between the low-spin iron(III) centers through the -CN-Zn-NC- bridging skeleton (iron-iron separation larger than 10.2 A) being negligible. More interestingly, 2 exhibits one-dimensional ferrimagnetic behavior due to the noncompensation of the local interacting spins (S(Mn) = 5/2 and S(Fe) = 1/2) which interact antiferromagnetically through bridging cyano groups. A comparison between the magnetic properties of the isostructural compounds 2 and 3 allow us to check the antiferromagnetic coupling in 2.
Inorganic Chemistry, 1988
ray absorption studies (XANES-EXAFS) have been performed on four titanium alkoxides Ti(OR)4 (OR =... more ray absorption studies (XANES-EXAFS) have been performed on four titanium alkoxides Ti(OR)4 (OR = OAm', OPr', OEt, OBu")). Only one kind of Ti-0 distance of about 1.80 A has been found for Ti(OAm*)4 and Ti(OPri)4 from EXAFS experiments, while two kinds of Ti-0 distances of about 1.80 and 2.05 A, respectively, attributed to terminal and bridging alkoxy groups, have been found for both Ti(OEt), and T~(OBU")~. Moreover, for these latter compounds Ti-Ti correlations have been observed for the first time (about 3.1 A), giving direct evidence of the oligomeric structure of such compounds. A model is proposed for the molecular structure of each alkoxide, based on Ti-0 and Ti-Ti distances (EXAFS) together with the coordination number of titanium (XANES). Ti(OAm'), and Ti(OPri)4 are monomeric species in which the titanium atom is 4-fold coordinated (tetrahedron). Ti(OEt), and Ti(OBu"), are oligomers (most probably trimers) in which each titanium atom is in 5-fold coordination. *To whom correspondence should be addressed the molecular structure of each alkoxide, based on T i 4 and Ti-Ti distance together with the coordination number of titanium. Samples. Ti(OPri)4, Ti(OEt),, and T~(OBU")~ were purchased from Fluka and used as received. Ti(OAm')4 was prepared from Ti(OPri), by alcohol exchange according to a previously published procedure." X-ray Absorption Study. (a) Experimental Procedure. The titanium K-edge spectra were recorded at room temperature at LURE,'the French synchrotron radiation facility, by using an EXAFS 111 spectrometer. The operating conditions in the storage ring DCI were the following: positions at energies of 1.85 GeV and intensities of about 150 mA. The two-crystal Si 31 1 monochromator was detuned by about 30% from its maximum flux position to discard harmonics from the beam. The photon flux was measured by two ionization chambers flushed by a helium-neon gas mixture. The entrance slit was 0.5 mm. A 6-pm titanium metallic foil was used to check the energy calibration just before or just after each XANES spectrum. This ensures an experimental accuracy in energy better than 0.25 eV. For the study of the Ti K-edge structure, the energy was scanned by 0.25-eV steps over the energy range 4950-5050 eV, while, for EXAFS data acquisition, the energy was scanned by 2-eV steps over the energy range 4850-5600 eV. The accumulation time was 1.6 or 2.4 s per point. The pure alkoxides were sealed into cells in order to avoid hydrolysis. The thickness of the cells was 0.15 mm, and the windows were made of X-ray-transparent Kapton. (b) Data Analysis. Near-edge spectra were processed by subtracting a linear background computed by least-square fitting from the preedge region and normalized by using the beginning of EXAFS oscillation as a unit. Energy calibration was made by taking the position of the first max-(a) Laboratoire de Spectrochimie du Solide. (b) Laboratoire de Spectrochimie des BlBments de Transition. (c) LURE.
Inorganic Chemistry, 1988
... 420, and Laboratoire de Chimie Physique des Materiaux Amorphes, UA No. ... Jorunn Sletten,*la... more ... 420, and Laboratoire de Chimie Physique des Materiaux Amorphes, UA No. ... Jorunn Sletten,*la Hakon Hope,laVe Miguel Julve,lb Olivier Kahn,*lc Michel Verdaguer,lc and Ary Dworkinld Received August 6, 1987 The title compound, [(Cu(petdien)),(CO,)] (C10.J2, has been ...
Le Journal de Physique IV, 1997
X-ray absorption spectroscopy at the L2 3 edges of 3d transition metals has been used to study th... more X-ray absorption spectroscopy at the L2 3 edges of 3d transition metals has been used to study the electronic structure of molecule based magnets with Curie temperatures ranging from 66 K to 315 K. These magnets are bimetallic cyanides of the Prussian blue family, constructed by a three dimensional assembling of -NC-Cr m -CN-A u -units. Using Ligand Field Multiplet calculations, where hybridization is mainly taken into account through configuration interaction, we have been able to reproduce nicely the spectra and to determine the exact ground state of the transition metals. We have separated covalence and charge transfer effects occurring in the bond between the 3d ions and the cyano ligand. We have also recorded X-ray Magnetic Circular Dichroism (XMCD) at nickel L23 edges in the ferromagnet Cs I [Ni II Cr In (CN)6]-2H20 (Tc = 90 K). With Ligand Field Multiplet calculations the shape of the experimental XMCD signal can be reproduced. The application of the orbital and spin sum rules gives a too small magnetic moment on nickel. A complete calculation taking covalence into account showed that hybridization cannot be responsible for the experimental low nickel magnetic moment. L 2,3 edges and then the Cr m L2>3 edges. The Cr m -CN bond is expected to have a much stronger covalent character than the A "-NC bond. Ni L2 3 edges were recorded on the soft X-ray SU22 beam line of the storage ring Super-ACO at LURE (°r say) [11,20,21,22]'. Co, Fe, Mn and Cr L2 3 edges were recorded on the U4B beam line (Dragon beam line) at the fcookhaven National Laboratory [11,23,24].
Chemistry – A European Journal, 2003
Following a bottom‐up approach to nanomaterials, we present a rational synthetic route from hexac... more Following a bottom‐up approach to nanomaterials, we present a rational synthetic route from hexacyanometalates [M(CN)6]3− (M=CrIII, CoIII) cores to well‐defined heptanuclear complexes. By changing the nature of the metallic cations and using a localised orbital model it is possible to control and to tune the ground state spin value. Thus, with M=CrIII, d3, S=3/2, three heptanuclear species were built and characterised by mass spectrometry in solution, by single‐crystal X‐ray diffraction and by powder magnetic susceptibility measurements, [CrIII(CNM′Ln)6]9+ (M′=CuII, NiII, MnII, Ln=polydentate ligand), showing spin ground states SG=9/2 [CuII], with ferromagnetic interactions JCr,Cu=+45 cm−1, SG=15/2 [NiII] and JCr,Ni=+17.3 cm−1, SG=27/2 [MnII], with an antiferromagnetic interaction JCr,Mn=−9 cm−1, (interaction Hamiltonian ℋ︁=−JCr,M [SCrΣiSM(i)], i=1–6). With M=CoIII, d6, S=0, the heptanuclear analogues [CoIII(CN−M′Ln)6]9+ (M′=CuII, NiII, MnII) were similarly synthesised and studied....
Chemistry of Materials, 1992
... Francesc Lloret,*vt Rafael Ruiz,+ Miguel Julve Juan Faus: Yves Journaux,*tt Isabel Castro:i( ... more ... Francesc Lloret,*vt Rafael Ruiz,+ Miguel Julve Juan Faus: Yves Journaux,*tt Isabel Castro:i( and Michel Verdaguers ... Inorganique, UA 420 Universits de Paris-Sud, 91405 Orsay, France Laboratorie de Chime des Metaux de Transition URA CNRS 419, UniversitZ Pierre et Marie ...
Dalton Transactions, 2012
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Papers by Michel verdaguer