Neste trabalho realizamos estudos sobre interações entre o composto 2,3,5,6-tetra(-piridil)pirazina (tppz) e Eu3+ em diferentes situações. Na primeira delas fizemos um estudo detalhado sobre as interações que ocorrem, em solução, entre o complexo tris(tenoiltrifluoroacetonato)európio(III), Eu(ttfa)3, e a tppz, em que verificamos que a tppz age como um supressor de luminescência, provavelmente através de uma segunda esfera de coordenação. Foram feitos, também, experimentos para o isolamento de cristais de complexos entre tppz e Eu3+, porém em nenhum dos métodos utilizados o complexo foi isolado, pois, quando o meio reacional voltava à temperatura ambiente a tppz precipitava. Por fim, como última tentativa de se obter complexos entre tppz e Eu3+, foram obtidos filmes por meio da técnica de Langmuir-Blodgett (LB) a partir de monocamadas mistas contendo 1-octadecanol e tppz, uma vez que a tppz sozinha não possui atividade superficial. Como resultado, foram obtidos filmes com os quais, através da espectroscopia de fotoluminescência, constatamos a formação do complexo. / In this work, we have conducted studies on the interactions of 2,3,5,6-tetra(-pyridyl)pyrazine (tppz) with Eu3+ in different situations. In the first of them, we have made a detailed study on the ongoing interactions in solution between tris(thenoiltrifluoroacetonate)europium(III), Eu(ttfa)3 and tppz, where it was verified that tppz act as a luminescence suppressor, probably through a second coordination sphere. Also, we have performed experiments with the aim of isolation crystals of complexes formed by tppz and Eu3+. However, in none of the methods used the complexes were isolated, because tppz precipitated when the reaction medium returned to the room temperature. As a last attempt to obtain the complexes between tppz and Eu3+, Langmuir-Blodgett (LB) films were formed from mixed monolayers containing 1-octadecanol and tppz, since tppz alone does not show surface activity. As a result, we have obtained films in which the complex formation was confirmed by photoluminescence spectroscopy.

Neste trabalho realizamos estudos sobre interações entre o composto 2,3,5,6-tetra(-piridil)pirazina (tppz) e Eu3+ em diferentes situações. Na primeira delas fizemos um estudo detalhado sobre as interações que ocorrem, em solução, entre o complexo tris(tenoiltrifluoroacetonato)európio(III), Eu(ttfa)3, e a tppz, em que verificamos que a tppz age como um supressor de luminescência, provavelmente através de uma segunda esfera de coordenação. Foram feitos, também, experimentos para o isolamento de cristais de complexos entre tppz e Eu3+, porém em nenhum dos métodos utilizados o complexo foi isolado, pois, quando o meio reacional voltava à temperatura ambiente a tppz precipitava. Por fim, como última tentativa de se obter complexos entre tppz e Eu3+, foram obtidos filmes por meio da técnica de Langmuir-Blodgett (LB) a partir de monocamadas mistas contendo 1-octadecanol e tppz, uma vez que a tppz sozinha não possui atividade superficial. Como resultado, foram obtidos filmes com os quais, através da espectroscopia de fotoluminescência, constatamos a formação do complexo. / In this work, we have conducted studies on the interactions of 2,3,5,6-tetra(-pyridyl)pyrazine (tppz) with Eu3+ in different situations. In the first of them, we have made a detailed study on the ongoing interactions in solution between tris(thenoiltrifluoroacetonate)europium(III), Eu(ttfa)3 and tppz, where it was verified that tppz act as a luminescence suppressor, probably through a second coordination sphere. Also, we have performed experiments with the aim of isolation crystals of complexes formed by tppz and Eu3+. However, in none of the methods used the complexes were isolated, because tppz precipitated when the reaction medium returned to the room temperature. As a last attempt to obtain the complexes between tppz and Eu3+, Langmuir-Blodgett (LB) films were formed from mixed monolayers containing 1-octadecanol and tppz, since tppz alone does not show surface activity. As a result, we have obtained films in which the complex formation was confirmed by photoluminescence spectroscopy.

The main theme of this dissertation is the study of two racemic compounds: a bimetallic complex, [(tpy)Ru(tppz)PtCl](PF₆)₃, and a trimetallic complex, [ClPt(tppz)Ru(tppz)PtCl](PF₆)₄, in solution and in the solid state, where tpy is 2,2':6',2''-terpyridine and tppz is 2,3,5,6-tetrakis(2-pyridyl)pyrazine. These two supramolecular assemblies display remarkably different stereochemistry, electrochemistry and photochemistry. The chapters in this document deal with a multidisciplinary project that is fundamental to the design and synthesis of similar entities with potential applications as antitumor agents. Chapter 1 gives an overview on the metal polyazine supramolecules. More specifically, the section is focused on the tridentate ruthenium and platinum metallic supramolecular assemblies with emphasis on their functionality and the methods used to study such systems. Chapter 2 describes the design and syntheses of the title complexes and their analogs using a building block strategy. The details of the experimental methods are included in this section. Chapter 3 presents the identification of the title complexes in solution and in the solid state by means of single crystal crystallography, mass spectrometry including FAB-MS and ESI-MS, and multiple NMR techniques including 1D ¹H-NMR, ¹⁹⁵Pt-NMR and 2D COSY, NOESY and ¹⁹⁵Pt-¹H HMQC, as well as dynamic ¹H-NMR at variable temperatures. The bi- and tri-metallic complexes are crystallized in the chiral space group of C2/c and P21/c as racemic compounds. The interconversion of the three steroisomers, M-M, P-P and M-P of trimetallic complexes are detected in the NMR timescale. The assignments of the atypical NMR resonance of the bi- and tri-metallic complexes are supported with the help of multidimensional NMR techniques and NMR spectroscopy of known systems. The process of assigning the NMR spectra is accomplished step by step with complexities presented by ring current effects. The 1D-fiber, 2D-plate and 3D-flowerlike topography of the trimetallic complex of [ClPt(tppz)Ru(tppz)PtCl](PF₆)₄ was illustrated by SEM. Chapter 4 demonstrates the electrochemical and photochemical differences between the title complexes and a comparison to known systems. Electrochemically, the Ru^II,Pt^II bimetallic and trimetallic complexes display Ru^II/III oxidations at 1.63 and 1.83 V and ligand-based reduction at -0.16 and -0.03 V versus Ag/AgCl, respectively. Spectroscopically, the Ru(dπ)⟶ tppz(π*) MLCT transitions are red-shifted relative to the monometallic synthons ([(tpy)Ru(tppz)](PF₆)₂, λ_max^abs = 472 nm and [Ru(tppz)₂](PF₆)₂, λ_max^abs = 478 nm) occurring in the visible region, centered at 530 and 538 nm in CH₃CN for [(tpy)Ru(tppz)PtCl](PF₆)₃ and [ClPt(tppz)Ru(tppz)PtCl](PF₆)₄, respectively, consistent with the bridging coordination of the tppz ligand. [ClPt(tppz)Ru(tppz)PtCl](PF₆)₄ displays an intense emission (Φ^em = 5.4×10₄) from the Ru(dπ)⟶ tppz(π*) ³MLCT state at RT with λ_max^em = 754 nm and lifetime ofτ„ = 80 ns in CH₃CN solution. The trimetallic complex, [ClPt(tppz)Ru(tppz)PtCl](PF₆)₄, exhibits a strong emission property in the solid state with λ_max^em = 764 nm, which was also studied by confocal laser induced emission scanning microscopy. By contrast, a barely detectable emission was observed for the bimetallic complex, [(tpy)Ru(tppz)PtCl](PF₆)₃. The redox and luminescence differences between bi- and tri-metallic complexes is the consequence of the nature of these supramolecular assemblies. All together the data suggest strong PtPt interactions in solution providing for assembly of these molecules into dimers or larger assemblies. Chapter 5 reports the applications of these complexes as bioactive species interacting with DNA. The prelimary data show the title complexes bind to DNA producing larger changes in DNA migration during gel electrophoreses than does the well-established anticancer drug, cisplatin. Preliminary study indicates trimetallic complex [ClPt(tppz)Ru(tppz)PtCl](PF₆)₄ can photochemically condenses DNA. This data could provide a form for development of a new class of photodynamic therapy agents in cancer treatment. Chapter 6 concludes with summaries of current research and perspective for further work. / Ph. D.