Nowadays the necessity for designing and synthesizing novel imaging agents increases rapidly. The long wavelength, and thus, low energy, of excitation and emission, and the good specificity and stability are examples of essential characteristics of ideal diagnostic and therapeutic agents. In this work, the synthesis and photophysical studies of metal complexes for biological applications were performed and evaluated, and it contained the development of (a) a porphyrin probe for imaging and treatment and (b) a tripodal thermal sensor for imaging. The research and study of the two cases of complex is analyzed in the second and third chapters, respectively, which follow the introduction or literature review to the diagnostic and/ or therapeutic agents which is given with examples in the first chapter. The scope of the main project, which is analysed in the second chapter, was the development and synthesis of a porphyrin-based bio-probe capable of bacterial fluorescence imaging. The porphyrin moiety of a complex is also able to generate singlet oxygen and this effect can be used for treatment purposes (PDT, Photodynamic Therapy). Thus, the complex can act as a diagnostic and therapeutic (anti-bacterial in this case) agent simultaneously. A probe with such a dual capability is known as theranostic agent. A theranostic agent is crucial for the enhancement and expansion of personalised medicine. The studies and physical measurements of the proposed, synthesised porphyrin complex have proved its capability to be used as a theranostic probe. Furthermore, after coupling the porphyrin moiety firstly with a small protein part (ampetoid: antimicrobial peptoid) and secondly with a radionuclide (Gallium-68), the in vitro and in vivo studies have to be performed. The aim of the project analysed in the third chapter was the development of a thermal sensor. Coordination of a tripodal ligand with a mixture of two lanthanides in various ratios was achieved and the photophysical measurements of the resulted complexes were evaluated. Lanthanide metals were chosen due to their unique photophysical properties that they offer when they are connected to an organic chomophoric ligand. Additionally, the preferred final luminophore product would obey a thermostable structure over a wide temperature range and it would be capable of effectively sensing the alterations in temperature. These properties were true for the ratio 99.5:0.5 for Terbium: Europium, and thus, the complex with such a consistency clarified the final product. Furthermore, the highly promising results after repeatedly photophysical (especially emission) measurements could conclude that the complex can be served as an ideal thermal sensor. Additional emission measurements at higher temperatures have to be done in order to confirm the ability of the proposed thermal sensor to be used for bio-imaging purposes. In conclusion, two-kind of metal complexes for biological applications were synthesized and their photophysical properties were assessed. Both the bulky porphyrin complex and the smaller tripodal ligand have shown promising results for their proposed applications. Of course, a more detailed assessment is required to verify their capability.

The ability of a deprotonated aza-crown ether to allow isolation of soluble lanthanide and yttrium complexes has been investigated. A convenient route to these complexes has been demonstrated by the protonolysis reactions of Ln[(N(SiMe₃)₂]₃ with 4,13-diaza-18-crown-6. NMR spectroscopy and X-ray crystallography revealed a C₂V structure consisting of a basket shaped geometry. The successful protonolysis route has been extended to the preparation of stable alkyls, dialkyls, and alkyl cations of yttrium and zirconium stabilized by deprotonated aza- crown macrocycles. A yttrium, alkyl complex containing deprotonated diaza-18-crown-6 has been prepared by the protonolysis route. The thermal stability and reactivity of this complex were investigated. This alkyl reacts with terminal alkynes to produce a complex equilibrium between the colourless monomeric and dimeric alkynides and a purple Z-butatrienediyl (ie.RC=C=C=CR²⁻) coupling product. NMR studies demonstrate that electron poor alkynes favour coupling and that the carbon-carbon double bond forming process is readily reversible at room temperature. The flexibility of the deprotonated diaza-crown ligand is apparent from the isolation of both cis and trans-zirconium dibenzyl complexes from the protonolysis of tetrabenzyl zirconium with 4,13-diaza-18-crown-6. The structure of both isomers were investigated by NMR spectroscopy and X-ray crystallography. Both the cis and trans-isomers cleanly converted to the stable cation either by protonolysis with [n-Bu₃NH]⁺[BPh₄]⁻ or by alkyl abstraction with B(C₆F₅)₃. The reactivity of the alkyl cation derived from the reaction with B(C₆F₅)₃ was investigated. The reaction of this cation with t-BuNC gave a vinylamide complex following a 1,2-proton rearrangement of an initially formed iminoacyl. Two members of the still rare yttrium dialkyl class of compounds were isolated using monoanionic, deprotonated aza-crown ethers as supporting ligation. The dialkyl complexes were synthesized by protonolysis of Y(CH₂SiMe₃)₃(THF)₂ with either aza-18-crown-6 or aza-15-crown-5. NMR and X-ray analyses of the yttrium dialkyl supported by aza-18-crown-6 indicates a trans-dialkyl geometry while NMR analysis of the aza-15-crown-5 analog indicates a cis-dialkyl geometry. Reaction of the trans-dialkyl complex with CO afforded a trans-dienolate complex formed by the migration of SiMe₃. Alkyl abstraction from the trans-dialkyl complex using B(C₆F₅)₃ allowed generation of the first yttrium, alkyl cation. / Graduate

M.Sc. / Please refer to full text to view abstract

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Dans le cadre de cette thèse de doctorat nous nous sommes intéressés à la préparation de composés moléculaires magnétiques chiraux dont le centre métallique, siège de l'anisotropie magnétique, est également centre de chiralité. Notre étude a porté sur le contrôle de la stéréochimie du polyèdre de coordination d'un ion Ln, en particulier dans des complexes base de Schiff 3d-4f. L'approche originale que nous avons explorée consiste à induire la stéréochimie du centre Ln par un ligand-chélate anionique chiral directement lié au métal. L'anion-ligand que nous avons considéré est la forme déprotonée du trifluoroacétyl-3-camphre (abrégée Camph-). Pour des complexes de type base de Schiff 3d-4f, deux anions chiraux viennent s'ancrer sur l'ion Ln et, par transfert de chiralité, permettent de fixer la stéréochimie de la sphère de coordination de la terre-rare. Une stéréochimie Delta ou Lambda est ainsi obtenue en fonction de l'énantiomère de l'anion-chiral mis en œuvre dans la synthèse. Cette approche a permis la synthèse de plusieurs familles de composés énantiopurs (ex. [LMe2Ni(H2O)Ln(camph)2(CF3SO3)]; [LMe2Zn(Cl)Ln(camph)2(MeOH)]). Dans chaque cas une stéréochimie Lambda est associée à l'énantiomère R-(+) de l'anion chiral et une stéréochimie Delta à l'énantiomère S-(-). Cependant une telle stéréo-sélectivité n'est pas systématique, la dissymétrie de l'espace de la sphère de coordination de la terre-rare associée à son troisième anion ou à un ligand ancillaire semble jouer un rôle important.Selon la même approche, nous avons également considéré la préparation de complexes 4f mono-métalliques chiraux de formulation [Ln(Camph)4]-. L'étude des comportements magnétiques a mis en évidence des comportements de type SMM (Single Molecule Magnet) pour plusieurs composés contenant les ions Tb ou Dy. / The research work described in this thesis deals with the design, the synthesis and magnetic property investigation of magnetic low dimensional molecular materials (i.e. single Molecule Magnets, SMM), especially in 3d-4f Schiff-base complexes, involving magnetically anisotropic lanthanide (Ln) metal centers in conjunction with chirality. The aim of this investigation was to provide an efficient access to enantiopure SMMs chiral at metal (Ln). We developed an original chemical approach that consists in introducing a chiral chelating diketonate ligand directly bonded to the Ln metal center. Thus transfer of chirality from chiral ligand to the coordination polyhedron of the metal center can be achieved. Deprotonated 3-trifluoroacetyl-camphor (Camph-) has been utilized as the chiral chelating ligand to synthesize several 3d-4f Schiff-base complexes, where two chiral anions are anchored on Ln ion rendering chiral coordination sphere around the rare-earth metal center. Depending on the enantiomer of the ligand employed in the synthesis, either Delta or LAmbda stereochemistry of the Ln polyhedron is obtained. This approach allowed synthesis of several families of enantiopurs SMMs chiral at Ln such as [LMe2Ni(H2O)Ln(camph)2(CF3SO3)] or [LMe2Zn(Cl)Ln(camph)2(MeOH)], where LMe2 = bicompartmental Schiff-base ligand. In each case, reaction with the R-(+) Camph ligand results in a Lambda stereochemistry, while a Delta stereochemistry is yielded upon reaction with the S-(-) Camph ligand. However, such a stereo-selectivity is not systematic. The third anion or an ancillary ligand associated with the rare-earth metal centers appears to play an important role in controlling the stereochemistry of the coordination sphere around the rare-earth metal centers. Using the same approach, we have also successfully isolated mono-metallic chiral 4f complexes of general formulae [Ln(Camph)4]-. The study of magnetic behaviors revealed Single Molecule Magnet (SMM) behavior for several complexes containing Tb or Dy ions.

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No description available.

Galactitol and cis,cis,cis-1,3,5-cyclohexanetriol are polyols that are ideal examples of model compounds for ligands with lanthanide ions as they have their hydroxyl groups in favourable steric arrangement. Several complexes were synthesised with both lanthanide chloride and lanthanide nitrate salts with galactitol, and a variety of structures, both polymeric and monomeric, were observed. In all these complexes, galactitol acted as a bridging molecule between the lanthanide ions. A notable difference was the lanthanum chloride–galactitol complex that showed both chloride and galactitol bridging. The lanthanide nitrate salts formed only polymeric complexes with galactitol. Not all of the complexes showed nitrate ions coordinated to the metal centre, and in the neodymium nitrate– galactitol complex, which shows both monodentate and bidentate coordination of the nitrate groups. The coordination of the nitrate ions was confirmed using both XRD and IR analysis. Two complexes with lanthanide chloride salts and cis,cis,cis-1,3,5-cyclohexanetriol were synthesised and analysed. Lanthanum chloride formed a polymeric complex, which showed extensive chloride bridging between the metal centres. Praseodymium chloride formed a dimeric complex. All complexes were analysed with single-crystal X-ray diffraction, 1H NMR, 13C NMR and IR spectroscopy.

The three terminal capacitance dilatometer is the most sensitive means for measuring the thermal expansion of solid samples at low temperatures. A measuring system based around capacitance dilatometry has been automated to provide a means of routine data collection of length changes in samples in the temperature range 1.5 K to 300 K. The dilatometer has been used in conjunction with magnetisation and neutron scattering measurements to investigate members from rare earth alloys as part of a wider study of the magnetic and lattice properties of isostructural rare earth alloy series, in particular the rare earth alloy series RE2AgIn (RE = Tb, Ho and Er) and REPtIn (RE = Nd, Gd, Tb, Dy, Ho and Er). Two samples have been investigated using thermal expansion, Tb2AgIn and TbPtIn. Both order magnetically at temperatures around 50 K and phase transitions corresponding to the ordering were observed using the capacitance dilatometer for the samples. The data for the alloy series is presented and discussed with a view to describing the complex nature of these alloy systems.