The last two decades have seen extensive growth in interest in metal-ion assemblies, especially for building new polynuclear exchange-coupled magnetic systems. However, the concept of designing polynuclear extended structures has still not matured to the level of retro-synthetic approach developed for the organic and pharmacological molecules. Although some progress has been made with secondary building units (SBUs) in metal-organic-frameworks (MOFs), the control seems to be just an illusion when it comes to bridging ligands such as the azide ion. When it is asserted that the azido ligand is versatile in its bridging capabilities, what is actually meant is that it would be difficult to predict or control its bridging properties, or in other words, the azido based polynuclear complexes are difficult to pre-design. However, this kind of serendipity is not always bad news for the chemists. For example, the azido ligand has been shown to mediate magnetic exchanges between paramagnetic metals in a predictable fashion (usually depending upon the bonding geometries). Therefore, it is a well-respected ligand in polynuclear assemblies of paramagnetic ions. Serendipitous assemblies offer new magnetic structures that we may not otherwise even think about synthesizing. Similarly, there are other ligands, such as alkoxido, oximato, carboxylato etc. which also behave like azide. These ligands are very important in the study of magnetic exchanges to develop an understanding of the underlying mechanisms in molecular magnetism. Serendipitous assemblies have also led to systems like single molecule magnets (SMMs), which have enriched the field with potential applications in computing and have also been used for the confirmation of the quantum magnetic properties like tunneling phenomenon, spin decoherence etc. Investigations incorporated in this thesis work led to several novel strategies for using serendipity as an advantage and build unprecedented structural topologies with interesting new molecular-magnetic properties. All the reported complexes were thoroughly analyzed through elemental analysis, spectroscopy, X-ray structure determination (both single crystal & powder diffractions) and variable temperature magnetic susceptibility measurements. In a few suitable cases, model structures obtained from the X-ray structures were also employed to study the magnetic exchange mechanisms through density functional theory (DFT) calculations and simulations. CHAPTER 1 of the thesis presents a general review on the ever-growing field of metal-ion assembly. In particular, the importance of the ‘serendipitous approach’ to build new and interesting metal-ion clusters and polyclusters is highlighted. This chapter also describes the basic concepts of exchange-based molecular magnetism as applied to the metal-ion assemblies. CHAPTER 2 describes the concept of using lower molar proportions of blocking bidentate chelating ligands in the neutral copper(II)-azido systems, which increases the number of coordination sites for the versatile azido bridges to assemble the metal-ions in higher dimensions, based on smaller cluster units. Syntheses, structures and magnetic properties of ten novel complexes are described in this chapter: [Cu3(tmen)2(N3)6]n (1), [Cu4(Me-hmpz)2(N3)8]n (2), [Cu4(men)2(N3)8]n (3), [Cu6(deen)2(N3)12]n (4), [Cu6(aem)2(N3)12]n (5), [Cu6(dmeen)2(H2O)2(N3)12]n (6), [Cu6(N,N'-dmen)2(N3)12]n (7), [Cu6(hmpz)2(N3)12]n (8), Cu5(N,N-dmen)2(N3)10]n (9), and [Cu5(N,N'-dmen)5(N3)10]n (10) [tmen = N,N,N',N'-tetramethylethylenediamine, Me-hmpz = 1-methylhomopiperazine, men = N-methylethylenediamine, deen = N,N'-diethylethylenediamine, aem = 4-(2-aminoethyl)morpholine, dmeen = N,N-dimethyl-N'-ethylethylenediamine, N,N'-dmen = N,N'-dimethylethylenediamine, hmpz = homopiperazine, N,N-dmen = N,N-dimethylethylenediamine]. Most of these complexes have simple oligonuclear basic building units (Scheme 1), such as trinuclear (1), tetranuclear (2, 3) and hexanuclear (4-8), but the overall arrangements of these cluster units in higher dimensions vary widely and serendipitously. For example, the hexanuclear complexes 4-7, although having almost identical basic structures, assemble in three- (4, 5) or two- (6, 7) dimensions with different connectivity among the basic structures. However, complex 9 is made from two different building units (Cu2 and Cu3). Complex 10, although having metal to blocking molar ratio 1:1, presents an unprecedented 1D structure for such complexes. Analysis of the magnetic susceptibility data for complexes 1-9 using theoretical exchange models for fitting is also described. Density functional theory (DFT, B3LYP) was employed to further analyze the experimental magnetic data for complexes 1, 2, 3 and 9 to better understand the magnetic exchange mechanisms in such systems. CHAPTER 3 continues with the same concepts developed in the previous chapter using multidentate neutral and anionic co-ligands. Using lower molar proportions of these multidentate ligands, seven novel complexes have been synthesized (keeping the initial metal to ligand ratio as 2:1): [Cu4(L1)2(N3)8]n (11), [Cu4(L2)2(N3)8]n (12), [Cu4(L3)2(N3)8]n (13), [Cu4(L4)2(N3)8]n (14), [Cu9(L5)4(N3)18]n (15), [Cu4(L6)2(H2O)2(N3)6] (16) and [Cu4(L7)2(N3)6]n (17) [where L1-5 are the condensation products of 2-pyridinecarboxaldehyde and 2-{2-(methylamino)ethyl}pyridine (L1), N,N-diethylethylenediamine (L2), N,N-dimethylethylenediamine (L3), N-methylethylenediamine (L4), N,N,2,2-tetramethylpropanediamine (L5); HL6 and HL7 are the condensation products of 2-hydroxy-3-methoxybenzaldehyde with N,N-diethylethylenediamine (HL6), and N-ethylethylenediamine (HL7)]. The ligand L1 is particularly interesting, as it is a hemiaminal ether (usually considered to be unstable intermediates in the reactions of aldehydes and secondary amines in alcoholic solvents), and was found to be trapped in 11. Although 11-13 have identical tetranuclear basic structures (with the rare simultaneous end-on and end-to-end bridges between two neighbouring metal-ions, Scheme 2) and extend in one-dimension. However, 13 is differently organized from the other two complexes. For 14, the bridging structure among the peripheral copper(II) ions changes to double end-on (Scheme 2), and the resulting structure extends in two dimensions. However, with L5, metal to ligand ratio is 9:4 (under similar conditions and initial molar proportions of the components) in 15, which can be seen as two different fragments: [Cu4(L5)4(N3)6]2+ and [Cu5(N3)12]2- linked alternately to give an overall 1D structure. HL6 and HL7 have one ionisable phenolic group that replaces one azido anion and generates two pockets for the metal atoms. These monoanionic ligands give tetranuclear complexes (16 and 17) with basic structures resembling (Scheme 2) to 11-14. While 17 is 1D in nature, two coordinated water molecules prevent the structure of 16 to grow and results in a discrete cluster. The variable temperature magnetic properties of these complexes were thoroughly analyzed through experimental and theoretical (DFT) studies. CHAPTER 4 reports the use of a pyridyl substituted propanediolate ligand in the assembly of two novel 1D heterometallic complexes: [Mn3Na(L)4(CH3CO2)(MeOH)2](ClO4)2∙3H2O (18) and [Mn3Na(L)4(CH3CH2CO2)(MeOH)2](ClO4)2∙2MeOH∙H2O (19) [LH2 = 2-methyl-2-(2-pyridyl)propane-1,3-diol, Scheme 3]; both featuring octahedral MnIV ions linked alternately to one trigonal prismatic MnII ion and even more interestingly to one trigonal prismatic NaI ion (Scheme 3). The complexes are essentially identical in structure and magnetic behavior, showing a weak ferromagnetic interaction among the neighboring manganese ions. DFT studies on a model complex supports the S = 11/2 ground spin state, deduced from dc and ac susceptibility measurements. CHAPTER 5 illustrates the use of a few dicarboxylates as potential bridging ligands to assemble tri- and hexanuclear MnIII-clusters. With the salicylaldoximate (salox) as the [MnIII3O(salox)3]+, triangle-generating moiety and keeping the reaction conditions (solvent, base, reaction time and crystallization process) identical, four new extended complexes that differ both in their basic and higher dimensional organizations are reported. When 1,3-phenylenediacetate (phda) is used (in EtOH), in the resulting complex [MnIII6O2(salox)6(EtOH)4(phda)]n∙(saloxH2)n∙(2H2O)n (20), a single type of MnIII6 clusters are linked by the dicarboxylate (interestingly the complex crystallizes with uncoordinated saloxH2 molecules). However, when two differently substituted isophthalate linkers (5-iodoisophthalate and 5-azidoisophthalate) are used, two almost identical complexes [MnIII6O2(salox)6(MeOH)5(5-I-isoph)]n∙(3MeOH)n (21) and [MnIII6O2(salox)6(MeOH)4(H2O)(5-N3-isoph)]n∙(4MeOH)n (22) are isolated, with two different types of Mn6 clusters (Scheme 4) linked alternately in one dimension. More interestingly, use of another substituted isophthalate (5-nitroisophthalate) produced a heteronuclear complex [MnIII3NaO(salox)3(MeOH)4(5-NO2-isoph)]n∙(MeOH)n(H2O)n (23) with only MnIII3 triangles as the basic cluster assembled in two dimensions. Temperature and field dependent dc and ac susceptibility measurements show that the complexes 20-22 behave as non-interacting single molecule magnets with ground spin state S = 4. Complex 23 is dominantly antiferromagnetic with a ground spin state S = 2. The magnetic behaviours of these complexes are also supported by theoretical calculations (DFT) on models generated from the crystal structures.

Submitted by Biblioteca do Instituto de Física (bif@ndc.uff.br) on 2017-07-06T19:06:18Z No. of bitstreams: 1 tese.pdf: 4548404 bytes, checksum: f3c3be1c9d5bbc0d098d37be6674bd4b (MD5) / Made available in DSpace on 2017-07-06T19:06:18Z (GMT). No. of bitstreams: 1 tese.pdf: 4548404 bytes, checksum: f3c3be1c9d5bbc0d098d37be6674bd4b (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Universidade Estadual de Feira de Santana / Neste trabalho, utilizamos cálculos de primeiros princípios baseados na Teoria do Funcional da Densidade (DFT - Density Functional Theory) para investigar a estabilidade energética e as propriedades magnéticas de compostos químicos. Foram estudados os complexos com metais de transição contendo radicais do tipo nitronilnitróxido [M(II)(Phtfac)2(NITpPy)2] [M = Co, Mn] e [M(II)(NITmPy)2(DMSO)2] [M = Cu, Ni, Co], bem como o silicato de cobre Na2Cu5(Si2O7)2. A partir do cálculo da energia total, determinamos a configuração de equilíbrio para os cinco complexos metálicos e os valores das constantes de acoplamento. Além disso, foram obtidas também as respectivas distribuições de densidade de magnetização, fundamentais para entender os mecanismos de acoplamento magnético nesse tipo de sistema. Para o silicato de cobre, cujos responsáveis pelas propriedades magnéticas são cadeias alternadas de trímeros e dímeros, calculamos a energia total das 32 configurações possíveis; determinamos o estado fundamental e as constantes de acoplamento magnético. / In this work we use first principles calculations based on density functional theory (DFT) to investigate the energy stability and the magnetic of chemical compounds. We studied the transition metal complexes with nitronyl nitroxide radical M(II)(P[htfac)2(NITpPy)2] [M = Co, Mn] and [M(NITmPy)2(DMSO)2] [M = Cu, Ni, Co], as well as the copper silicate Na2Cu5(Si2O7)2. By calculating the total energy, we determine the equilibrium configuration for the five metal complexes and the values of coupling constants. Moreover, we obtained their magnetization density distributions, fundamental for understanding the mechanisms of magnetic coupling in this type of system. For the copper silicate, whose magnetic properties are responsible for alternate chains of dimers and trimers, we calculate the total energy of the 32 possible configurations and determine the ground state and magnetic coupling constants.

Dans le domaine du stockage de l'information, la miniaturisation de l'unité magnétique portant l'information est un enjeu capital. Ainsi, la découverte de molécules possédant des propriétés de relaxation lente de leur aimantation, comparables à celles des aimants classiques, constitue une avancée majeure suscitant l'espoir de pouvoir un jour stocker l'information à l'échelle moléculaire.Cette thèse a pour but d'étudier les propriétés magnétiques des chaînes aimants. Ces chaînes sont constituées d'unités magnétiques liées par des interactions magnétiques au sein d'un réseau unidimensionnel. Au delà de leurs potentielles applications, les chaînes aimants sont parfaitement adaptées à l'étude fondamentale des chaînes de spins. Le premier chapitre de ce manuscrit constitue un rappel des propriétés statiques et dynamiques des chaînes aimants connues à ce jour. Le deuxième chapitre décrit les propriétés statiques des parois séparant les différents domaines d'aimantation dans des chaînes de spins de topologies magnétiques variées. Le troisième chapitre de ce manuscrit décrit les propriétés dynamiques des chaînes de spins d'Ising. Bien que seul le modèle de Glauber soit utilisé dans la littérature associée aux chaînes aimants, il existe une infinité de modèles dynamiques d'Ising.Grâce à l'étude détaillée de trois modèles, il est montré dans ce chapitre que l'application d'un champ magnétique permet de révéler différentes dynamiques de relaxation de l'aimantation pour chacun des modèles considérés. Ces résultats permettent enfin de proposer deux protocoles expérimentaux à même de déterminer le modèle dynamique le plus adapté à l'étude des chaînes aimants. / The size reduction of magnetic units able to store information is an important issue for the design of high-density data storage devices. The discovery of molecules that show slow relaxation of their magnetization, similar to classical magnets, is a great breakthrough in terms of molecular scale information storage. The work presented in this thesis is devoted to the study of the magnetic properties of Single Chain Magnets. Single Chain Magnets can be viewed as a one-dimensional assembly of anisotropic magnetic units linked by magnetic interactions. Beyond their potential applications, Single Chain Magnets are interesting prototypes for the fundamental study of spin chains. The first chapter of this manuscript summarizes some known static and dynamic properties of Single Chain Magnets. Chapter II is devoted to the static properties of domain walls, which link the magnetic domains in spin chains, considering various magnetic topologies. Chapter III is dedicated to the dynamic properties of Ising spin chains. In the Single Chain Magnet literature, the Glauber model is used to describe the dynamic properties of such spin chains. However, there exists an infinite number of dynamic Ising models. In this chapter, three dynamic models are studied in detail. We show that the presence of a magnetic field allows us to discern different magnetization relaxation behaviors associated with each dynamic model. These results allow us to establish two experimental protocols in order to determine the most suitable dynamic model to describe the properties of Single Chain Magnets.

No description available.

Η σύνθεση και ο χαρακτηρισμός πλειάδων των μετάλλων μετάπτωσης σε ενδιάμεσες οξειδωτικές βαθμίδες αποτελεί σήμερα έναν από τους κύριους ερευνητικούς στόχους πολλών επιστημονικών ομάδων παγκοσμίως εξαιτίας των εφαρμογών που βρίσκουν σε διάφορα επιστημονικά πεδία, όπως στη βιοανόργανη χημεία, στην επιστήμη των υλικών, στη μοριακή φυσική και στη θεωρητική χημεία. Οι πλειάδες αυτές περιέχουν πολλές φορές έναν ασυνήθιστα μεγάλο αριθμό ασυζεύκτων ηλεκτρονίων στη θεμελιώδη κατάσταση και παρουσιάζουν εξαιρετικό ενδιαφέρον από μαγνητικής απόψεως. Αυτό συμβαίνει γιατί μια υψηλή τιμή spin στη θεμελιώδη κατάσταση είναι αναγκαία (άλλα όχι ικανή) συνθήκη ώστε αυτού του είδους οι σύμπλοκες ενώσεις να εμφανίζουν το φαινόμενο του μονομοριακού μαγνητισμού (single-molecule magnetism). Στην παρούσα Εργασία μελετήθηκε το σύστημα αντίδρασης μαγγάνιο/α-βενζοΐνη οξίμη (α-benzoin oxime, bzoxH2) κάτω από βασικές συνθήκες, το οποίο οδήγησε στην απομόνωση και το δομικό (μέσω κρυσταλλογραφίας ακτίνων-Χ σε μονοκρυστάλλους) και μαγνητοχημικό χαρακτηρισμό των μοριακών πλειάδων [Mn8O4(bzox)8(MeOH)4] (1), [Mn9O2(bzox)11(bzoxH)(MeOH)4(H2O)2] (2) και [Mn9O2(bzox)11(bzoxH)(H2O)6] (3). Τα σύμπλοκα 1-3 αποτελούν τις πρώτες δομικά χαρακτηρισμένες πλειάδες τρισθενών μεταλλοϊόντων με υποκαταστάτη την α-βενζοΐνη οξίμη. Το σύμπλοκο 1 αποτελείται από οκτώ ιόντα MnIII, με το δομικό του πυρήνα να παρουσιάζει μία πρωτότυπη τοπολογική διευθέτηση τεσσάρων τριγωνικών Mn3 υπομονάδων, ανά δύο κάθετων μεταξύ τους, η οποία οδηγεί σε μια ενδιάμεση τιμή spin στη θεμελιώδη κατάσταση, SΤ = 2. Τα ισοδομικά σύμπλοκα 2 και 3 αποτελούνται από εννέα ιόντα MnIII, με το δομικό τους πυρήνα να παρουσιάζει μία επίσης πρωτότυπη τοπολογική διευθέτηση εναλλασσσόμενων τριγωνικών και γραμμικών Mn3 υπομονάδων, η οποία οδηγεί σε μια ενδιάμεση τιμή spin στη θεμελιώδη κατάσταση, SΤ = 3. / The synthesis and characterization of polynuclear metal complexes (clusters) containing paramagnetic 3d-metal ions in intermediate oxidation states have gained intense interest due to the applications of these compounds in several fields of science, such as bioinorganic chemistry, materials science, molecular physics and theoretical chemistry. Such high nuclearity transition metal clusters are one of the growing research subjects in Molecular Magnetism, given the fact that they often possess a fairly large ground-state spin value, which is one of the necessary requirements for a molecule to be able to exhibit the phenomenon of single-molecule magnetism. In the present work, we studied the reaction scheme manganese/α-benzoin oxime (bzoxH2) under basic conditions, which has led to the isolation, and structural (through single-crystal X-ray crystallography) and magnetochemical characterization of the molecular complexes [Mn8O4(bzox)8(MeOH)4] (1), [Mn9O2(bzox)11(bzoxH)(MeOH)4(H2O)2] (2) and [Mn9O2(bzox)11(bzoxH)(H2O)6] (3). Complexes 1-3 are the first structurally characterized trivalent metal clusters with the ligand α-benzoin oxime. Compound 1 consists of eight MnIII atoms and its irregular metal core presents an unprecedented topology based on four triangular Mn3 units, which are vertical to each other, thus leading to an ST = 2 ground state. The isostructural compounds 2 and 3 comprise nine MnIII atoms arranged in a unusual topology based on linear and triangular Mn3 units, thus leading to an ST = 3 ground state.

Η σύνθεση και ο χαρακτηρισμός πλειάδων των μετάλλων μετάπτωσης σε ενδιάμεσες οξειδωτικές βαθμίδες αποτελεί σήμερα έναν από τους κύριους ερευνητικούς στόχους πολλών επιστημονικών ομάδων παγκοσμίως εξαιτίας των εφαρμογών που βρίσκουν σε διάφορα επιστημονικά πεδία, όπως στη βιοανόργανη χημεία, στην επιστήμη των υλικών, στη μοριακή φυσική και ηλεκτρονική, και στη θεωρητική χημεία. Οι πλειάδες αυτές περιέχουν πολλές φορές έναν ασυνήθιστα μεγάλο αριθμό ασυζεύκτων ηλεκτρονίων στη θεμελιώδη κατάσταση και παρουσιάζουν εξαιρετικό ενδιαφέρον από μαγνητικής απόψεως. Αυτό συμβαίνει γιατί μια υψηλή τιμή spin στη θεμελιώδη κατάσταση είναι αναγκαία (άλλα όχι ικανή) συνθήκη ώστε αυτού του είδους οι σύμπλοκες ενώσεις να εμφανίζουν το φαινόμενο του μονομοριακού μαγνητισμού (single-molecule magnetism). Στην παρούσα Εργασία μελετήθηκε το σύστημα αντίδρασης μαγγάνιο/2-πυριδυλομεθανόλη (hmpH), παρουσία ή απουσία κυανικών ιόντων (OCN-) και κάτω από βασικές συνθήκες, το οποίο οδήγησε στην απομόνωση και το δομικό (μέσω κρυσταλλογραφίας ακτίνων-Χ σε μονοκρυστάλλους) και μαγνητοχημικό χαρακτηρισμό των πλειάδων [Mn7(OH)3(OCN)3(hmp)9](ClO4)2 (1), [Mn16O8(OMe)4(OCN)4(O2CMe)12(hmp)6(MeOH)2] (2), [Mn18O14(O2CMe)18(hmp)4(hmpH)2(H2O)2] (3) και [Mn18O14(O2CEt)18(hmp)4(hmpH)2(H2O)2] (4). Οι πλειάδες 1-4 είναι μικτού-σθένους (ΙΙ/ΙΙΙ). Το σύμπλοκο 1 αποτελεί ένα νέο μέλος μιας μεγάλης οικογένειας επταπυρηνικών συμπλόκων με το δομικό πυρήνα τους να περιλαμβάνει έξι ιόντα Mn διευθετημένα κυκλικά γύρω από ένα έβδομο κεντρικό ιόν Mn2+. Τα σύμπλοκα 2, 3 και 4 αποτελούν παραδείγματα υψηλής πυρηνικότητας και συμμετρίας πλειάδων του Mn, με αισθητικά όμορφες δομές και ενδιαφέρουσες μαγνητικές ιδιότητες. / The synthesis and characterization of polynuclear metal complexes (clusters) containing paramagnetic 3d-metal ions in intermediate oxidation states have gained intense interest due to the applications of these compounds in several fields of science, such as bioinorganic chemistry, materials science, molecular physics and electronics, and theoretical chemistry. Such high nuclearity transition metal clusters are one of the growing research subjects in Molecular Magnetism, given the fact that they often possess a fairly large ground-state spin value, which is one of the necessary requirements for a molecule to be able to exhibit the phenomenon of single-molecule magnetism. In the present work, we studied the general reaction system manganese/2-(hydroxymethyl)pyridine (hmpH), in the presence or absence of cyanate ions (OCN-), under basic conditions, which has led to the isolation, and structural (through single-crystal X-ray crystallography) and magnetochemical characterization of the compounds [Mn7(OH)3(OCN)3(hmp)9](ClO4)2 (1), [Mn16O8(OMe)4(OCN)4(O2CMe)12(hmp)6(MeOH)2] (2), [Mn18O14(O2CMe)18(hmp)4(hmpH)2(H2O)2] (3) and [Mn18O14(O2CEt)18(hmp)4(hmpH)2(H2O)2] (4). All complexes 1-4 are mixed-valent (II/III). Complex 1 is a new member of a growing family of heptanuclear clusters with a core consisting of six Mn ions arranged in a ring around a seventh central Mn2+ ion. Complexes 2, 3 and 4 are examples of high-nuclearity and high-symmetry Mn clusters with aesthetically pleasing structures and interesting magnetic properties.

Cette thèse porte sur la synthèse de nouveaux complexes binucléaires à ponts cyanures de type {Fe(μ-CN)Co}, qui reproduisent au sein d'une seule molécule les propriétés originales du réseau de coordination d'analogue de bleu de Prusse AxCo[Fe(CN)6]y•nH2O (A=ions alcalins), i.e. un transfert d'électron intramoléculaire thermo- et photo-induit à l'état solide. Au sein de ce travail, nous nous sommes intéressés à l'étude des propriétés physiques des paires moléculaires Fe/Co, avec l’objectif de comprendre les mécanismes du phénomène de transfert d'électrons. Le chapitre I contient les exemples les plus représentatifs des réseaux de coordination d'analogues de bleu de Prusse et de leurs analogues moléculaires Fe/Co, en se concentrant sur les techniques utilisées pour comprendre leurs propriétés photomagnétiques et les stratégies synthétiques employées pour contrôller leur dimensionnalité et obtenir ces analogues moléculaires. Les bases théoriques du transfert d'électron ainsi que la motivation de ce travail sont décrites à la fin du chapitre. Après une introduction sur l’utilisation des briques moléculaires employées au cours de ce travail à travers l’étude de leurs potentiels redox, le chapitre II est consacré à la synthèse et la caractérisation de nouveaux composés dinucléaires à ponts cyanures Fe/Co. Des études structurales, spectroscopiques, magnétiques, photomagnétiques, diélectriques et d’absorption des rayons-X révèlent qu'un transfert d’électron métal-métal peut être déclenché à l'état solide en faisant varier la température et par application de la lumière. Dans le chapitre III est présenté l'influence de l'environnement des complexes binucléaires Fe/Co, à savoir les contre-ions, sur le transfert d’électron thermo- et / ou photo-induit à l'état solide. Enfin le chapitre IV porte sur la possibilité de transférer le phénomène de transfert d'électron des paires Fe/Co étudiées de l'état solide à la solution / This thesis is dedicated to the synthesis of new dinuclear cyanido-bridged Co/Fe complexes, which mimics on a single molecule the original properties of the coordination network of Prussian Blue Analogues AxCo[Fe(CN)6]y•nH2O (A= alkaline ions), i.e. intramolecular thermal and photo-induced electron transfer in the solid state. We focus on the study of the physical properties of the simplest Fe/Co PBA, a dinuclear complex, with the hope to understand the fundamental concepts of this fascinating phenomenon. Chapter I contains the most representative examples of Fe/Co PBAs, focusing on the synthetic strategies employed in order to obtain Fe/Co PBAs of different dimensionalities and the techniques used to understand their photomagnetic properties. The theoretical background of the electron transfer phenomenon and the motivation of our work are described in the end of the chapter. After introducing the choice of the building blocks used in this work through the study of their redox potential properties, chapter II is devoted to the synthesis and the characterization of a novel dinuclear Fe/Co cyanido-bridged complex, which exhibits metal-to-metal electron transfer properties in solid state triggered by temperature and light. The ET phenomenon has been also studied by X-ray absorption spectroscopy and dielectric measurements. In Chapter III is illustrated the influence of the environment content of the dinuclear Fe/Co complexes, such as the counter ions, on the occurrence of the thermally and/or photo-induced electron transfer in solid state, thus highlighting the versatility of these molecular materials. Finally in chapter IV, the possibility of transferring the electron transfer phenomenon of the studied Fe/Co pairs from solid state to solution is investigated.

L’objectif de cette thèse est la synthèse de composés de manganèse et de matériaux hybrides qui soient intéressants du point de vue bioinorganique et magnétique. Pour accomplir ce but, nous avons découpé la stratégie en trois étapes constituant les différents chapitres de ce manuscrit :(a) Synthèse et caractérisation des composés moléculaires de manganèse et l’étude de leurs propriétés magnétiques.Nous avons réussi à obtenir la structure cristalline des vingt-trois nouveaux composés de Mn de différentes nucléarités, d’état d’oxydation II, III ou IV. Nous avons étudié les propriétés magnétiques de ces composés et nous avons établi des corrélations magnéto-structurales. Les composés de MnII ont été aussi étudiés par spectroscopie RPE.(b) Synthèse et caractérisation des matériaux hybrides basés sur des composés moléculaires de manganèse insérés dans de la silice mésoporeuse. Les composés moléculaires sélectionnés ont été insérés dans de la silice mésoporeuse (du type MCM-41). Les complexes de Mn dans les supports ont été caractérisés par ATG, XPS, ICP-OES, spectroscopie IR et mesures magnétiques. (c) Étude des propriétés catalytiques des composés moléculaires et des matériaux hybrides.Une famille de composés moléculaires obtenus dans cette thèse sont des modèles structuraux et fonctionnels de la catalase à Mn, une enzyme présente dans certaines bactéries, ayant des propriétés antioxydantes (H2O2 « scavenger »). L’activité catalase pour ces composés et les matériaux hybrides dérivés a été étudiée dans l’acétonitrile et dans l’eau. / The main objective of this work is the synthesis of manganese compounds and hybrid materials that may be relevant from a bioinorganic and magnetic point of view. The developed strategy comprises three main steps that form different sections in this thesis:(a) Synthesis and characterization of molecular manganese compounds and study of the magnetic propertiesThe crystal structure of twenty-three new Mn compounds of different nucleartities were obtained in which the Mn oxidation state is II, III, or IV. The magnetic properties of all these compounds were profoundly studied and they have been rationalized with their structural and electronic parameters. The MnII compounds were also studied with EPR spectroscopy. (b) Synthesis and characterization of hybrid materials based on molecular manganese compounds inside mesoporous silica.Selected molecular compounds were inserted inside mesoporous silica (MCM-41 type). The Mn complexes inside the supports were characterized with TGA, XPS, ICP-OES, IR spectroscopy, and magnetic measurements.(c) Study of the catalytic properties of both molecular compounds and hybrid materials.A family of the molecular compounds obtained in this work are structural and functional models of the Mn catalase, an enzyme found in some bacteria with antioxidant properties (H2O2 scavenger). The catalase activity for these compounds and the hybrid materials was studied in acetonitrile and water.

La chimie de coordination de l’ion manganèse(II), à partir de radicaux nitronyl nitroxyde et de macrocycles thiacalix[4]arènes, a mis en évidence des propriétés magnétiques et optiques remarquables au sein de ses complexes. Ces matériaux moléculaires ont la particularité de manifester leurs propriétés sous l’application de stimuli externes. Ainsi, un composé lamellaire à base de polymères de coordination bidimensionnels d’ions Mn(II) et de radicaux nitronyl nitroxyde, a révélé une conversion de tautomérisme de valence induite thermiquement, et des complexes polynucléaires d’ions Mn(II)−sulfonylcalix[4]arènes ont montré une luminescence intense centrée sur l’ion métallique sous éclairement. Nos travaux de thèse s’insèrent dans la continuité de ces résultats développés antérieurement dans notre équipe. Notre objectif a été de comprendre l’origine des perturbations électroniques subies par l’ion Mn(II) dans ces complexes de coordination. Pour cela, l’étude approfondie des relations entre les structures cristallines des composés Mn(II)−radicaux et Mn(II)−thiacalix[4]arènes et leurs propriétés physiques, a été au cœur de notre recherche. Ce manuscrit présente les synthèses, les structures cristallines et la caractérisation des propriétés magnétiques et optiques de composés obtenus par des processus d’ingénierie moléculaire. La modification des ligands nitronyl nitroxyde et thiacalix[4]arènes par synthèse organique, et la substitution des contre-ions au sein de ces complexes ioniques lors de leur synthèse, ont été le fil conducteur de nos travaux. Ces modifications chimiques ont permis d’élaborer de nouveaux complexes qui présentent à leur tour une conversion de tautomérisme de valence thermo-induite ou une forte luminescence centrée sur l’ion Mn(II). La comparaison des structures et des propriétés des nouveaux complexes obtenus et antérieurs, a permis une interprétation et une rationalisation des relations structures-propriétés. Ces résultats permettront par la suite d’améliorer et de moduler, de façon maitrisée et selon la nécessité, les structures moléculaires et à l’état solide des composés suivant les propriétés visées / Manganese(II) coordination chemistry, with nitronyl nitroxide radicals and thiacalix[4]arene macrocycles, revealed remarkable magnetic and optical properties. These molecular compounds show their properties under external stimuli. Recently, a lamellar compound, made of Mn(II) – nitronyl nitroxyde 2D coordination polymers, presented a thermo-induced valence tautomeric conversion, and Mn(II) – thiacalix[4]arene polynuclear complexes shown an intense luminescence centered on the metallic ion. Our PhD work takes part in the continuity of these previous results. Our goal was to understand the origin of the electronic perturbations inside these compounds. The depth study of the relationships between the structures and the physical properties was the central point of our research. This thesis will present the synthesis, the crystalline structures and the magnetic and optical characterizations of new compounds obtained by different molecular engineering processes. Organic modifications of the ligands and substitution of the counter-ion during the synthesis were the central thread of our work. Thanks to these chemical modifications, new compounds has been synthesized which are presenting also a thermo-induced valence tautomeric conversion or an intense luminescence. The comparison of all compounds made possible an interpretation and a rationalization of the structure-property relationships. Next step will be to improve or to modulate, in function of the need, the molecular or solid state structures regarding the expected properties

In this work we studied magnetic properties of molecular magnets of the new heteropolyanion {Cu20}, dodecanuclear cluster {Ni12}, and the heterometallic {Cr7M} wheels, in which one of the CrIII ions of Cr8 has been replaced by a Fe, Cu, Zn, Ni, ion with this extra-spin acts as local probe for the spin dynamics.Such systems have been synthesized recently and they are well described using the Heisenberg spin Hamiltonian with a Zeeman term of an applied magnetic field along the z-axis. Using the numerical exact diagonalization method, we have calculated the energy spectrum and the eigenstates for different compounds,and we have used them for reexamining the available experimental susceptibility data to determine the values of exchange parameters.We have studied the thermodynamic properties such magnetization, susceptibility, heat-capacity. At low temperature regions molecular magnets act as individual quantum nanomagnets and can display super-paramagnetic phenomena like macroscopic quantum tunneling, ground state degeneracy, level-crossing. A crucial issue for understanding these phenomena is the coupling between magnetic molecular levels and the environment such as nuclear spins. We have modeled the behavior of the proton spin lattice relaxation rate as a function of applied magnetic field for low temperatures as it is measured in Nuclear Magnetic Resonance (NMR) experiments.