This thesis describes the synthesis and magnetic characterisation of a series of polynuclear 3d and 3d/4f complexes built using phenolic oxime type ligands. Chapter two describes the reaction of salicylaldoxime and its derivatised analogues (R-saoH2) with the alkoxide containing co-ligands triethanolamine (TeaH3) and 2-(hydroxymethyl)pyridine (Hhmp), in the presence of Mn(II)/Ln(III) salts. This results in the formation of a family of sixteen [MnIII4LnIII2] clusters, which are structurally related to a previously studied [MnIII6] family of Single-Molecule Magnets (SMMs). The magnetic properties of the Ln = Y, Gd and Lu analogues can be qualitatively rationalised on the basis of a magneto-structural correlation (MSC), previously developed for MnIII alkoxide/oxime bridged dimers. Chapter three describes how the combination of two complimentary ligands, the phenolic oximes (R-SaoH2) and the diethanolamines (DeaH3), into one organic framework, creates new ligand types (H3L1 and H4L2) which can be used to construct a hexametallic MnIII wheel; [MnIII6Na(L1)6]Cl, the first example of a ferromagnetically coupled dodecametallic MnIII wheel;[MnIII 12(OMe)16(L2)4(O2CCMe3)4(MeOH)4], and the first example of a dodecametallic MnIII truncated tetrahedron; [MnIII12O4(H3L2)8(H2L2)4(TMA)4 (TMA = trianion of trimesic acid). Single crystal hysteresis measurements reveal both 3.2 and 3.3 to be SMMs at low temperature. Chapter four deals with the use of H4L2 in Cu coordination chemistry. Phenolic oximes are known to form monometallic complexes with CuII ions, as are the diethanolamines. However, the deliberate incorporation of one ligand onto the organic framework of the other permits the preparation of a family of [CuIIn] wheels (n = 4, 6, 8). In each case nearest neighbour interactions between CuII ions are shown to be strongly antiferromagnetic. DFT calculations suggest the origin of this interaction is related to the Cu-O-N-Cu dihedral angle, an observation which allows for the development of a theoretical MSC, that suggests a switch from antiferro- to ferro-magnetic exchange is possible at Cu-O-N-Cu angles > 60o.

This thesis explores the synthesis and characterisation of a range of molecular wheels containing unpaired electron spins. These molecular spin systems are of considerable interest, both for the insight they provide into the physics of such systems and for their potential as quantum bits ("qubits") in a quantum information processing device. In particular, this thesis explores using these wheels to meet criteria 1 and 5 of the DiVincenzo criteria. The synthesis of a novel homometallic and nonametallic ring of CrIII ions is introduced, along with extensive physical characterisation. Inelastic Neutron Scattering measurements suggest that the molecule has an almost degenerate S = 1/2 ground state with only 0.1 meV separation, making this ring a near perfect example of a Type I frustrated spin system. Chemical modification of the heterometallic {Cr7M} family of wheels with both hard and soft Lewis base functionality is also explored. Using a triphenylphosphine derivative, the coordination chemistry of a highly sterically hindered mono-substituted triphenylphosphine derivative with gold is explored, yielding new arrangements of the wheels. Changes in the electronic and steric properties of the system are studied by a combination of 31P NMR spectroscopy and DFT modelling, revealing dramatic changes in the phosphorus donor properties. The effect of this ligand substitution on the anisotropy tensor of CoII contained in a heterometallic {Cr7Co} ring is explored using variable temperature 1H NMR spectroscopy. Using a combination of the experimentally observed 1H NMR dipolar shifts and computational modelling, a significant change in the anisotropy tensor of the cobalt is found. Finally, as part of a g-engineering approach to qubit design the chemistry of the octametallic {Cr7Ni} ring functionalised with triphenylphosphine oxide is introduced. Initial efforts towards developing a hybrid {Cr7Ni}2Ln (Ln = Gd, Eu) qubit system, along with characterisation by EPR and luminescence spectroscopy, suggest that this may be a route to developing a qubit with the capacity for optical control of the communication.

An investigation of the electronic structure of some transition metal clusters comprising anti-ferromagnetically coupled, heterometallic arrays of eight metal ions that are wheel-shaped, is reported. The compounds were synthesized and provided by Dr. Grigore Timco of The University of Manchester and are formulated by their metal content as Cr7M, where M = a divalent 3d metal. Two families of wheels are the subject of this research, defined ‘green’ and ‘purple’ from their physical appearance. Within each family, the compounds are all isostructural. From simulation using a single Hamiltonian for Cr7M-purple compounds, where M = Zn, Mn, or Ni, it is shown that with only two exchange parameters, one JCr-Cr and one JCr-M, data from bulk magnetization, neutron scattering, Electron Paramagnetic Resonance (EPR) spectroscopy at multiple frequencies and specific heat measurements can be modelled and that there is transferability of parameters. Preliminary attempts to measure electron spin relaxation times for two of the purple wheels have shown values of T1 and T2 that are comparable with those of the more extensively studied green wheels and hence further studies in this area are warranted. Variable temperature Q- and W-band EPR spectra for a series of nine heterodimers comprising one green and one purple wheel, M=Zn, Mn or Ni in each case, are reported. For Cr7Zn-purple there is no magnetic exchange detected, whereas weak and quantifiable exchange is required to interpret the spectra from the other six dimers. EPR studies of three trimers of the form purple-green-purple are reported and the presence of magnetic exchange is identified by comparison with the spectra of the component single and double wheel compounds, although this is not quantified because of the numerical size of the simulations that are required. The process of comparing simulated to experimental spectra is a complex problem and one which is central to the work reported in this thesis. The problem of fitting has been investigated and two novel solutions, one based upon pixel mapping and the other based on wavelet transformation are proposed.

This project was focused on the synthesis and reactivity of rare-earth nbutyl complexes of the formula [CpMe2M(μ-nBu)]2 (where M = Y, Dy). Dysprosium was used as it has a large magnetic moment which is favourable for producing single molecule magnets (SMMs). Yttrium was used as a diamagnetic analogue to examine the reactivity of [CpMe2Y(μ- nBu)]2 in solution, and provide further characterisation of isolated complexes with NMR spectroscopy. Another goal of the project was to establish the reactivity of [CpMe2M(μ- nBu)]2 with respect to the commonly used alkylating reagent nbutyllithium (nBuLi). It was found that the nbutyl complexes are remarkably stable in solution and the solid state, allowing for the synthesis to be scaled up and for the nbutyl complexes to be used as starting materials. The reactivity of [CpMe2M(μ- nBu)]2 towards ferrocene was investigated. The product was a ferrocenyl-bridged dimer of the formula [CpMe2M(μ-(C5H4)FeCp)]2 resulting from a single deprotonation of ferrocene. The reactivity of [CpMe2M(μ- nBu)]2 towards N-heterocyclic carbenes (NHCs) was also investigated. No reaction occurred between [CpMe2Y(μ- nBu)]2 and 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr), a reaction did occur between [CpMe2Y(μ- nBu)]2 and 1,3-bis-(tert-butyl)imidazol-2-ylidene (ItBu) but no crystalline product could be obtained. [CpMe2M(μ- nBu)]2 reacts with 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) to form a monomeric, benzyl tethered carbene complex [CpMe2M(IMes’)]. An ortho-methyl group on one of the mesityl substituents is deprotonated generating an asymmetric functionalised carbene. A control experiment between CpMe3M (M = Dy, Y) and IMes resulted in the formation of the abnormal, rearranged carbene complexes [CpMe3M(aIMes)]. C6H6. Structural analysis revealed a very short C-H---π interaction between neighbouring molecules. The mechanism of carbene rearrangement was probed by 1H NMR spectroscopy (M = Y). Magnetic susceptibility measurements revealed that [CpMe2Dy(μ- nBu)]2, [CpMe2Dy(μ-(C5H4)FeCp)]2, [CpMe2Dy(IMes’)] and [CpMe3Dy(aIMes)]. C6H6 are not SMMs. [CpMe2M(μ- nBu)]2 activates sulfur and selenium to form hexanuclear clusters of the formula [CpMe10M((E3)2E2] (M = Dy, Y; E = S, Se). [CpMe10M((S3)2S2] is an SMM with an energy barrier to magnetisation reversal, Ueff, of 73 cm-1. The analogous selenium cluster could be characterised by single crystal X-ray diffraction however separation from unreacted selenium proved difficult without using coordinating solvent. Extraction of [CpMe10Y((Se3)2Se2] with THF resulted in the crystallisation of the ion pair [CpMe2Y(THF)3][{CpMeY(Se2)}6Se] and [{CpMe2Y(THF)}(µ-Se2)]. A trimetallic dysprosium coordination complex containing a hexaazatrinapthalene (HAN) bridging ligand is reported. Magnetic measurements on [{(thd)3Dy}3HAN] (Dy3HAN) show that it is an SMM in zero field and two magnetic relaxation mechanisms are present. An optimised DC field of 1 kOe allowed for better resolution of the two relaxation processes and an energy barrier for each process could be extracted. The Ueff barriers are 42 and 52 cm-1. Ab initio theoretical analysis revealed the magnetic anisotropy axes are nearly collinear precluding the presence of a toroidal magnetic moment. The ground state of Dy3HAN was found to be frustrated.

A central concern within the field of molecular magnetism has been the elucidation of magneto-structural correlations. This thesis describes a variety of systems and endeavours to study the relationship between structure and magnetic properties in these systems. The first body of work (chapters 2 and 3) studies CrIII dimers, with the metal centres displaying a dialkoxo bridging moiety and latterly an additional carboxylate bridge to direct the synthesis of ferromagnetic analogues. The second section of work (chapters 4‐6) moves forward to the study of larger, heterometallic 3d‐3d compounds, through the synthesis of a large family of Anderson type MIII 2MII 5 wheels and a subsequent family of (VIVO)2MII 5 wheels. Chapter 2 describes a series of di‐alkoxo bridged Cr(III) dimers, synthesised using the pyridine alcohol ligands 2‐pyridinemethanol (hmpH) and 2‐pyridineethanol (hepH) as well as 2‐picolinic acid (picH). The structures fall into four general categories and are of formula: [Cr2(OMe)2(pic)4], [Cr2(hmp)2(pic)2X2] (where X = Cl, Br), [Cr2(L)2Cl4(A)2] (where L = hmp, A = H2O; L = hmp, A = pyridine; L = hmp, A = 4‐picoline; L = hep, A = H2O), and [Cr(hmp)(hmpH)Cl2. Magnetic studies show relatively weak antiferromagnetic exchange interactions between the Cr(III) centres and DFT calculations are used to develop magneto‐structural correlations, showing that the magnitude and sign of the J value is strongly dependent upon the orientation of the dihedral angle formed between the bridging Cr2O2 plane and the O-R vector of the bridging group, and the Cr-O-Cr-O dihedral angle. Chapter 3 builds on the work from the previous chapter with discussion of a large family of chromium(III) dimers, synthesised using a combination of carboxylate and diethanolamine type ligands. The compounds have the general formula [Cr2(R1‐deaH)2(O2CR2)Cl2]Cl where R1 = Me and R2 = H, Me, CMe3, Ph, 3,5‐(Cl)2Ph, (Me)5Ph, R1 = Et and R2 = H, Ph. The compound [Cr2(Me‐deaH)2Cl4] was also synthesised in order to study the effect of removing/adding the carboxylate bridge to the observed magnetic behaviour. Magnetic studies reveal ferromagnetic exchange interactions between the Cr(III) centres in the carboxylate bridged family with coupling constants in the range +0.37 < J < +8.02 cm‐1. Removal of the carboxylate to produce the dialkoxide‐bridged compound results in antiferromagnetic exchange between the Cr(III) ions. DFT calculations to further develop the magneto-structural correlations reveal the ferromagnetic exchange is the result of an orbital counter-complementarity effect occurring upon introduction of the bridging carboxylate. Chapter 4 reports a family of heterometallic Anderson‐type 'wheels' of general formula [MIII 2MII 5(hmp)12](ClO4)4 (where MIII = Cr or Al and MII = Ni or Zn giving [Cr2Ni5], [Cr2Zn5], [Al2Ni5] and [Al2Zn5]; hmpH = 2‐pyridinemethanol) synthesised solvothermally. The metallic skeleton describes a centred hexagon with the MIII sites disordered around the outer wheel. The structural disorder is characterised via single crystal X‐ray crystallography, 1‐3D 1H and 13C solution‐state NMR spectroscopy of the diamagnetic analogue, and solid‐state 27Al MAS NMR spectroscopy of the Al containing analogues. Alongside ESI mass spectrometry, these techniques show that structure is retained in solution, and that the disorder is present in both the solution and solid‐state. Solid‐state dc susceptibility and magnetisation measurements on [Cr2Zn5] and [Al2Ni5] reveal the Cr‐Cr and Ni‐Ni exchange interactions to be JCr‐Cr = ‐1 cm‐1 and JNi‐Ni,r = ‐5 cm‐1, JNi‐Ni,c = 10 cm‐1. Fixing these values allows us to extract JCr‐Ni,r = ‐1.2 cm‐1, JCr‐Ni,c = 2.6 cm‐1, the exchange between adjacent Ni and Cr ions on the ring is antiferromagnetic and between Cr ions on the ring and the central Ni ion is ferromagnetic. Chapter 5 focusses on planar molecules, espanding the family of heterometallic Anderson‐type 'wheels' discussed in chapter 4 to include MIII = Cr, Al and MII = Co, Fe, Mn, Cu, affording five new species of formulae [Cr2Co5(hmp)12](ClO4)4, [Cr2Fe5(hmp)12](ClO4)4, [Cr2Mn5(hmp)12](ClO4)4, [Cr2Cu5(hmp)12](ClO4)2(NO3)2 and [Al2Co5(hmp)12](ClO4)4. As per previous family members, the two MIII sites are disordered around the outer wheel, with the exception of [Cr2Cu5] where the the CuII sites are localised. A structurally related, but enlarged planar disc possessing a [MIII 6MII] hexagon capped on each edge by a CuII ion is also reported, which is formed only when MIII = Al and MII = Cu. In [AlIII 6CuII 7(OH)12(hmp)12](ClO4)6(NO3)2 the Anderson moiety contains a central, (symmetry‐imposed) octahedral CuII ion surrounded by a wheel of AlIII ions. Solid‐state dc susceptibility and magnetisation measurements reveal the presence of competing exchange interactions in the Anderson wheels family, and weak antiferromagnetic exchange between the CuII ions in [Al6Cu7]. Chapter 6 describes two heterometallic wheels of formula [(VIVO)2MII 5(hmp)10Cl2](ClO4)2∙2MeOH (where MII = Ni or Co) displaying the same Anderson‐type structure as seen in chapters 4 and 5, however the use of the vanadyl moiety has the effect of removing the disorder, with the two vanadyl ions sitting on opposing sides of the ring. The magnetic properties of both show competing antiferroand ferromagnetic interactions.

High symmetry and low coordinated single-ion lanthanides have been a successful recipe to design high performance single molecule magnets (SMMs). However, enhancement of the magnetic properties of polymetallic SMMs is an important challenge. Therefore, this thesis describes the use of redox non-innocent tetrazine-based ligands and d- and f- elements in order to fine-tune the electronic structure of the resulting compounds to promote strong exchange interactions between the spin carriers. As reported in the literature, radical-bridged ligands represent a potential strategy to improve the magnetic properties of polymetallic SMMs. Thus, chapter one introduces principal concepts that govern the physical properties of metal complexes containing radical-bridged ligands. Chapter two describes the magnetic properties of a unique air-stable tetratopic radical- bridged bpymtz•− (3,6-bis(2-pyrimidyl)-1,2,4,5-tetrazine) templating four Ni(II) metal ions. The dc magnetic studies along with DFT calculations reveal strong ferromagnetic exchange coupling between the Ni− bpymtz•− of J = 98 cm-1 with a spin ground state of S = 9/2. Chapter three describes the application of another tetrazine-based ligand, bpytz (3,6- bis(3,5-dimethylpyrazolyl)-1,2,4,5-tetrazine) to probe magnetic exchange interactions in a {CoII4} supramolecular square. The modelling of dc susceptibility data shows significant Co(II) - bpytz•− magnetic coupling of J = - 118 cm-1 for a spin ground state ST = 4. While the non-reduced analog displays weak Co(II)-Co(II) exchange of J = - 0.64 cm-1 (S = 0 ground state). Additionally, the radical-radical magnetic exchange contribution was probed with an analogous {ZnII4} square, where a J = -15.9 cm-1 was found. Chapter four extends the application of reduced tetrazine ligands to lanthanide systems. Here we demonstrate that the systematic reduction of the ligand with cobaltacene (CoCp2) led to the formation of a strongly coupled bpytz•−−bpytz•− bridging ligand. Magnetic measurements combined with ab initio calculations confirm unprecedented intramolecular pi-dimerization preventing strong magnetic Dy(III)−bpytz•− communication. Chapter five describes the synthesis and characterization of {LnIII4} (Ln = Dy, Gd and Lu) where the Ln(III) ions are bridged by peripheral bpytz•−. The oxophilicity and high coordination numbers preferred by lanthanides ions lead to the formation of a cubane core made up of metal ions bridged by hydroxy ligands (M3-OH−). Experimental and computational studies were applied to verify the nature and strength of the magnetic interactions between the spin carriers.

The work presented herein focuses on the synthesis and characterization of new cyanide bridged molecular magnetic materials that form discrete molecules as well as three dimensional networks. This research is inspired by the recognition that the Prussian blue (PB) family exhibits a wide range of interesting magnetic properties such as photomagnetism, spin crossover, and high TC magnets owing to the presence of the cyanide bridge that promotes magnetic communication between adjacent metal spins. An underexplored facet of this research is the systematic development of the topic with anisotropic metal ions research that was undertaken as part of this dissertation. The resulting discoveries are materials that exhibit a wide range of bistable magnetic properties, including photomagnetism, long range magnetic ordering, SMM, and exchange-biased SMM behavior. New Prussian Blue analogs are presented in Chapter II of this thesis that are based on the nearly unexplored hexacyanoosmate(III) ion. A family of CoII PB derivatives of OsIII were found to exhibit photomagnetic and charge transfer induced spin transition (CTIST) behavior and a study of alkali metal cation dependence revealed marked differences in both the photomagnetic and CTIST properties, with the highest ordering temperature being observed for the K+ analog which exhibits a TC of 28.5 K. The phenomenon of linkage isomerism reported for PB analogs and other molecular materials that incorporate the [Cr(CN)6]3- ion wherein the CN ligand reverses its binding mode between the two metal centers was studied in detail as described in Chapter III. Small molecule models that incorporate [Cr(CN)6]3- and CoII ions were investigated by single crystal X-ray crystallography, magnetism, and solution IR studies and the data led to useful mechanistic information about the nature of the cyanide reversal process. The use of the anisotropic hexacyanoosmate(III) anion to form a trinuclear species with MnIII was undertaken in the study described in Chapter IV. The first SMM based on the hexacyanoosmate(III) ion was discovered and found to exhibit a very rare exchange biased SMM phenomena in one of its crystal forms. In Chapter V new building blocks with the pentadentate MPPA ligand are described which are ideally suited for the preparation of a range of model compounds of the dinuclear and trinuclear variety.

This thesis is concerned with the muon-spin relaxation (musr) technique and its application in the study of a number of molecular magnetic systems that may be driven through a quantum phase transition at low temperatures through the application of a magnetic field or hydrostatic pressure. Musr is a highly sensitive probe of magnetism, but its utility can be severely limited by the lack of knowledge of the muon implantation site and the extent to which the muon perturbs its host. In a system of ionic fluorides, where partial information about the muon site is experimentally available, I demonstrate systematically that these problems can be addressed accurately using electronic-structure calculations. The F--$mu$--F complex formed by muons in many fluorides can be understood as an exotic molecule-in-a-crystal defect with a zero-point energy larger than that of any naturally-occurring triatomic molecule. I demonstrate the interesting possibility of controlling the magnetic dimensionality in a molecular magnet using applied pressure. musr and high-field magnetisation experiments under applied pressure on the coordination polymer CuF$_2$(H$_2$O)$_2$(pyrazine) show a transition from a quasi-two-dimensional to a quasi-one-dimensional antiferromagnetic phase. Density-functional theory calculations and calculations of the dipolar anisotropy complement the experiments. I describe how subtle differences in chemical composition can lead to starkly different structural and magnetic properties. [Cu(pyz)(H$_2$O)(gly)$_2$](ClO$_4$)$_2$ may be considered an antiferromagnetic chain that orders below 50 mK while the related compound [Cu(pyz)(gly)](ClO$_4$) is formed from Cu$^{2+}$ dimers and remains disordered down to 30 mK in zero field, but displays a field-temperature phase diagram consistent with the Bose-Einstein condensation of triplons. I also describe musr measurements on the strong-leg spin ladder DIMPY and on the molecular nanomagnets Cr$_8$Cd and Cr$_8$Mn which highlight some of the remaining challenges for longitudinal-field musr experiments.

Submitted by Cássia Santos (cassia.bcufg@gmail.com) on 2015-04-28T13:41:06Z No. of bitstreams: 2 Dissertação - Ramon Silva Vilela - 2015.pdf: 4895993 bytes, checksum: e833ccde263d2ba04536e62344957089 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2015-04-28T13:58:37Z (GMT) No. of bitstreams: 2 Dissertação - Ramon Silva Vilela - 2015.pdf: 4895993 bytes, checksum: e833ccde263d2ba04536e62344957089 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2015-04-28T13:58:37Z (GMT). No. of bitstreams: 2 Dissertação - Ramon Silva Vilela - 2015.pdf: 4895993 bytes, checksum: e833ccde263d2ba04536e62344957089 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2014-04-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this work was obtained four new Cu(II) precursors that could be employed as building blocks in the synthesis of new molecular magnets. Using the ligand H2Et2mpyba, was obtained the compounds Na2[Na10Cu2(mpyba)2(Cl)2]·10H2O(2a), {[(CH3)4N]4[Cu2(mpyba)2(H2O)2]•H2O} (2b), {[(CH3)4N]4[K2Na2Cu4(mpyba)4]∙3H2O} (2c). Through the hydrolysis in basic medium of the ligand HEtpmo (2-pirimidil oxamato) was obtained the coordination polymer {[(CH3)4N]2[Cu(C2O4)2]·H2O}n (1a). The crystalline structures was determined by x-ray diffraction, and we could note different structural morphologies as “zig-zag” chains and bidimensional planes (complexes 1a and 2a), metallocycles bounded through potassium atoms (complex 2c) and discrete binuclear unit (complex 2b). The magnetic susceptibilities measurements was carried in the temperature range of 300 – 2 K, and the measures indicates an ferromagnetic coupling between the copper atoms for all the compounds studied, with the values of exchange constant varying between +1,14 and +7,4 cm-1. / Neste trabalho foram obtidos quatro novos precursores de Cu(II) inéditos que podem ser empregados como blocos construtores na síntese de magnetos moleculares. Partindo-se do ligante H2Et2mpyba (meta piridil bis oxamato) obteve-se quatro novos precursores, os complexos Na2[Na4Cu2(mpyba)2(Cl)2]·10H2O (2a), {(CH3)4)][Cu2(mpyba)2(H2O)2]·H2O} (2b), e {[(CH3)4N]4[K2Na2Cu4(mpyba)4]}∙3H2O} (2c). A partir da hidrólise básica do ligante HEtpmo (2-pirimidil oxamato) obteve-se o polímero de coordenação {[(CH3)4N]4[Cu(C2O4)2]·H2O}n (1a). As estruturas cristalinas dos complexos foram determinadas por difração de raios-x de monocristal, e observou-se o desenvolvimento de diferentes morfologias, como cadeias e planos bidimensionais que crescem em “zigue-zague” (complexos 1a e 2a respectivamente), o complexo 2c cristaliza na forma de metalociclos ligados por átomos de potássio e o complexo 2b se apresenta como uma unidade binuclear discreta. Foram realizadas medidas de susceptibilidade magnética em função da temperatura no intervalo de 300 a 2 K para os compostos obtidos, revelando acoplamento ferromagnético entre os átomos de cobre para todos os compostos estudados, com valores de constante de acoplamento J variando entre +1,14 e +7,4 cm-1.

Submitted by Erika Demachki (erikademachki@gmail.com) on 2017-08-09T18:18:27Z No. of bitstreams: 2 Dissertação - Renato Rabelo de Souza Filho - 2017.pdf: 3321540 bytes, checksum: 7bdb3245e17c32ea854853600a863553 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-08-10T13:29:04Z (GMT) No. of bitstreams: 2 Dissertação - Renato Rabelo de Souza Filho - 2017.pdf: 3321540 bytes, checksum: 7bdb3245e17c32ea854853600a863553 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-08-10T13:29:04Z (GMT). No. of bitstreams: 2 Dissertação - Renato Rabelo de Souza Filho - 2017.pdf: 3321540 bytes, checksum: 7bdb3245e17c32ea854853600a863553 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-07-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The synthesis, spectroscopic characterization, structural study and magnetic properties of four new compounds of formula [Co(bpcam)2]ClO4dmsoH2O (1), [Co(bpcam)2]2[Co(NCS)4]dmsoH2O (2), [Ni(bpcam)2]H2O (3) e [Cu(bpcam)Cl(H2O)] (4) [bpcam = bis(2-pyrimidylcarbonyl)amidate] are reported. The Co(II)-assisted hydrolysis of 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine (tpymt) in mild conditions leads to a mononuclear unit of [CoIII(bpcam)2]+ which is isolated as perclorate (1) and tetrakis(N-thiocianate)cobaltate(II) (2) salts. The compounds 3 and 4 are obtained by reacting Hbpcam with the metallic salts nickel(II) perchlorate hexahydrate (3) and copper(II) chloride dihydrate (4) in stoichiometric ratios. Differently from the literature data, the hydrolysis of tpymt in the presence of copper(II) chloride also results in 4, which contains bpcam-. Each bpcamgroup in 1-4 acts as a tridentate ligand being coordinated to the cobalt(III) (1 and 2)/nickel(II) (3)/ copper(II) (4) ions through three nitrogen atoms in a meridional arrangement giving rise to six-coordinate (1 and 3) or five-coordinate (4) metallic ions, whereas six-coordinate cobalto(III) and four-coordinate cobalt(II) coexist in 2. Cyclic voltammetry of 1 in acetonitrile shows the occurrence of one quasi reversible CoIII ↔ CoII process. Variable-temperature magnetic susceptibility measurements on samples of 2-4 were carried out in the temperature range 1.9-295 K. The continuous decreasing of T from 2,68 cm3mol-1K at room temperature to 1.32 cm3mol-1K at 1,9 K observed for 2 is assigned to zero-field splitting (ZFS) of pseudotetraedral complex [Co(NCS)4]2- anion. A Curie law for a magnetically isolated nickel(II) ion in the high temperatures domain is observed for 3 and the small decrease of T below 10 K being due to zerofield splitting effects. The magnetic behavior for 4 follows a Curie-Weiss law for magnetically isolated copper(II) ions with occurrence of weak antiferromagnetic intermolecular interactions. The fitting of experimental data of 2 and 3 through the spin Hamiltonian [M = Co (2) e Ni (3)] led to the following values: = 2.37 (2) e 2.12 (3) e || = 34.7 (2) e 1.72 (3). Finally, the analysis of the magnetic susceptibility data of 4 leads to a Curie-Weiss law with gCu = 2,08 e  = 0,8 K, being  the Weiss constant. / A síntese, caracterização espectroscópica, elucidação da estrutura cristalina e estudo das propriedades magnéticas de quatro novos compostos de fórmula [Co(bpcam)2]ClO4dmsoH2O (1), [Co(bpcam)2]2[Co(NCS)4]dmsoH2O (2), [Ni(bpcam)2]H2O (3) e [Cu(bpcam)Cl(H2O)] (4) [bpcam- = bis(2-pirimidilcarbonil)amidato] são descritas nesse trabalho. A hidrólise do 2,4,6-tris(2- pirimidil)-1,3,5-triazina (tpymt) assistida pelo íon cobalto(II) em condições brandas resulta na unidade mononuclear de [CoIII(bpcam)2]+ que é isolada na forma de sais de perclorato (1) e tetrakis(N-tiocianato)cobaltato(II) (2). Os compostos 3 e 4 são obtidos reagindo o pré-ligante Hbpcam com os sais metálicos perclorato de níquel(II) hexahidratado (3) e cloreto de cobre(II) dihidratado (4) em quantidades estequiométricas. Diferentemente dos dados da literatura, a hidrólise do tpymt na presença de cloreto de cobre(II) resulta em 4, o qual contém bpcam-. Cada ligante bpcam- atua como um ligante tridentado que se coordena aos íons cobalto(III) (1 e 2)/níquel(II) (3)/cobre(II) (4) através dos três átomos de nitrogênio do sítio terpiridina em um arranjo meridional dando origem a íons metálicos hexacoordenados (1 e 3), pentacoordenado (4), enquanto íons cobalto(III) hexacoordenados e cobalto(II) tetracoordenados coexistem em 2. O voltamograma cíclico de 1 em acetonitrila mostra a ocorrência de um processo CoIII ↔ CoII quase reversível. As medidas da dependência da susceptibilidade magnética em amostras de 2-4 foram realizadas na faixa de temperatura de 1,9-295 K. O decréscimo contínuo de T de 2,68 cm3 mol-1K a temperatura ambiente para 1,32 cm3 mol-1 K a 1,9 K observado para 2 decorre do desdobramento a campo zero (ZFS) do complexo aniônico pseudotetraédrico [Co(NCS)4]2-. Uma Lei de Curie para íons níquel(II) magneticamente isolados é observada a altas temperaturas para 3 e o pequeno decréscimo de T abaixo de 10 K é atribuído ao desdobramento a campo zero. O comportamento magnético de 4 segue uma Lei de Curie-Weiss para íons cobre(II) magneticamente isolados com ocorrência de interações intermoleculares antiferromagnéticas fracas. O ajuste dos dados experimentais de 2 e 3 pelo Hamiltoniano [M = Co (2) e Ni (3)] levou aos seguintes valores: = 2,37 (2) e 2,12 (3) e || = 34,7 (2) e 1,72 (3). Por fim, a análise dos dados de susceptibilidade magnética de 4 levou a uma Lei de Curie-Weiss com gCu = 2,08 e  = 0,8 K, sendo  a constante de Weiss.