Tese (doutorado)—Universidade de Brasília, Instituto de Química, Programa de Pós-Graduação em Química, 2013. / Submitted by Alaíde Gonçalves dos Santos (alaide@unb.br) on 2014-04-30T14:19:37Z No. of bitstreams: 1 2013_SergioMacedoSoares.pdf: 3457137 bytes, checksum: 4982241e41052e0306857169b637074f (MD5) / Approved for entry into archive by Guimaraes Jacqueline(jacqueline.guimaraes@bce.unb.br) on 2014-06-05T14:34:11Z (GMT) No. of bitstreams: 1 2013_SergioMacedoSoares.pdf: 3457137 bytes, checksum: 4982241e41052e0306857169b637074f (MD5) / Made available in DSpace on 2014-06-05T14:34:12Z (GMT). No. of bitstreams: 1 2013_SergioMacedoSoares.pdf: 3457137 bytes, checksum: 4982241e41052e0306857169b637074f (MD5) / Neste trabalho está retratado a síntese e a caracterização de complexos de rênio(I) com ligantes escorpionatos derivados de tiobases e bases de Schiff derivadas da condensação de beta-aminoácidos (β-alanina, ácido 2-minobutírico e β-fenilalanina) com três aldeídos (2-hidróxi-1-salicilaldeído, 2-hidróxi-1-naftaldeído e 2-hidróxi-1-piperonal). Foram sintetizadas sete bases de Schiff (três inéditas) e dois ligantes escorpionatos (inéditos), dos quais quatro foram mais eficazes na complexação do fragmento fac-{Re(CO)3}+. Os complexos foram obtidos na proporção 1:1 (metal: ligante) e as estruturas cristalinas e moleculares dos complexos [fac-{Re(bala2hnH)(CO)3}2], (H3O)[Re(fac-bphala2hn)(CO)3]?CHCl3 ?H2O, K[fac-Re(bphala2hn)(CO)3]?⅓CHCl3?2H2O e fac-[Re{κ3-HB(btz)3)}(CO)3] foram determinadas por difração de raios X em monocristal que revelou que o íon ReI está hexacoordenado conferindo aos complexos geometria octaédrica distorcida. Os complexos obtidos foram caracterizados ainda por análise do ponto de fusão (P.F.), análise elementar (C, H, N), termogravimetria, espectroscopia de absorção no infravermelho e espectroscopia de ressonância magnética nuclear de 1H, 13C e 11B. Devido a baixa solubilidade e da reatividade dos ligantes escorpionatos, as análises de espectroscopia de ressonância magnética nuclear de 11B foram fundamentais na determinação da formação dos ligantes escorpionatos bem como dos complexos de rênio(I) com esses ligantes. _______________________________________________________________________________________ ABSTRACT / This work describes the synthesis of complexes of rhenium (I) with derivatives of escorpionate tiobases ligands. It also shows the synthesis and characterization of Schiff bases derived from the condensation of beta-amino acids (β-alanine, 2-β-phenylalanine and minobutírico acid) with three aldehydes (2-hydroxy-1-salicylaldehyde, 2-hydroxy-1-naphthaldehyde and 2 -hydroxy-1-piperonal). Seven Schiff bases (three new) and two “escorpionatos” binders (unpublished) were synthesized, four of which were more effective in complexing the fragment fac-{Re(CO)3}+. The complexes were obtained in the ratio 1:1 (metal: ligand). The crystal and molecular structures of the complexes [fac-{Re(bala2hnH)(CO)3}2], (H3O)[Re(fac-bphala2hn)(CO)3]?CHCl3?H2O, K[fac-Re(bphala2hn)(CO)3]?⅓CHCl3? 2H2O e fac-[Re{κ3-HB(btz)3)}(CO)3] were determined by X-ray diffraction crystallography. Analyses revealed that the ion ReI is hexacoordenate resulting in distorted octahedral complexes. The complexes were further characterized by analysis of melting point (mp); elemental analysis (C, H, N); thermogravimetry; infrared absorption spectroscopy and proton nuclear magnetic resonance of 1H, 13C and 11B. As “escorpianatos” ligands had low solubility and reactivity, analysis of nuclear magnetic resonance spectroscopy of 11B was essential in determining the escorpionates ligands and complexes of rhenium (I) with these binders.

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Doctor of Philosophy / Department of Chemistry / Christopher J. Levy / This work examines the synthesis of novel chiral Schiff-base complexes derived from (1R,2R)-cyclohexanediamine and (R)-[1,1’-binaphthalene]-2-2’-diamine structural backbones with quinoline, isopropyl-quinoline, and benzoquinoline structural side-arms. We incorporated some degree of flexibility in the ligands and complexes so they can accommodate the sterics of different substrates during a catalytic reaction. We successfully achieved this by reducing the imine bond in the ligands to the corresponding amine bond. Therefore, the successful reduction and metallation of some of these ligands to give structures of different symmetries is reported. We had difficulty reducing ligands with the binaphthalene backbone but were able to partially reduce the ligand through a one-pot reaction with a zinc(II) salt and NaBH4. The complete 1H NMR assignments of the complexes reported in this thesis serve as a valuable tool for use in the characterization of future complexes. The complete NMR characterization of compounds reported is a complex process because they are polycyclic aromatic systems and the coupling network similarity in different parts of the molecule usually results in severe overlap of their 1H resonances. To overcome this impediment, we took advantage of various 2D-NMR techniques (COSY, NOESY, ROSEY, HSQC, and HMBC) along with other 1D-NMR experiments (1H HOMODEC, 1H, and 13C) to completely assign the desired complexes. Subsequently we also studied the coordination chemistry of several meal cations with our ligand system with the goal of obtaining single stranded monhelices. The potential use of some of the complexes in the area of NMR discrimination and kinetic resolution of racemic mixtures was examined and shown to be promising. Several NMR experiments were conducted using the racemic olefins 3-buten-2-ol and 1-penten-3-ol to demonstrate the discriminating power of our silver(I) complexes. We discovered that sterics play an important role in this resolution experiment and the bulky nature of our complexes affect the overall efficiency of the NMR discriminatory process as it diminishes the contact between the reactive metal center and the olefins involved. Temperature also plays a vital role in the chiral recognition of racemic olefins as we examined the ideal temperature needed to reduce the various dynamic processes that take place in solution at room temperature.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

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The aims of this work were first to synthesize and fully characterize compounds that may function as bleomycin analogues and, second, to test their anticancer activity in vitro. Three novel tetradentate O,N,N,O Schiff base ligands, H₃L¹, H₂L³ and H₂L³ were synthesized by condensation of three different 1,3-diaminoalkane bridging units with two equivalents of (2,4-dihydroxy–phenyl)-(phenyl)methanone. These ligands contain two neutral imine nitrogen donors and two anionic phenolate oxygen donors for the coordination of metal ions. The choice of ligand was guided by the fact that Cu(II) bleomycin analogues with ligands employing O,N,N,O donor atom sets are able to cleave double-stranded DNA via oxygen radical formation. Using these ligands, six novel metal complexes of copper(II), nickel(II) and zinc(II) were synthesized and fully characterised. Two novel ligand crystal structures and six novel metal complex crystal structures are reported in this work. The X-ray structures of the two structurally characterized nickel(II) complexes [Ni(L²)] and [Ni(L³)] adopted the same nominally square planar coordination geometry, with the metal ion bound by the pairs of imine nitrogen and ortho-phenolic oxygen atoms of the ligand’s tetradentate donor atom set. The Ni–N and Ni–O distances averaged 1.892(3) Å and 1.845(2) Å, respectively. However, when reacted with Cu(II) and Zn(II), the ligands favored the formation of multinuclear complexes as a result of metal ion bridging by ionized oxygen donor atoms (either the phenolic oxygen atoms or an alkoxide oxygen atom of the 2-hydroxy substituted alkane bridge in the case of H₃L¹) of the polyfunctional ligands. For the di- and trinuclear copper(II) complexes, the mean Cu–N and Cu–O distances averaged 1.953(3) Å and 2.082(3) Å, respectively. For the dinuclear zinc(II) complex, the mean Zn–N and Zn–O distances averaged 2.074(3) Å and 2.042(3) Å, respectively. Electron spin resonance (ESR) measurements on the paramagnetic trinuclear copper(II) complexes confirmed that the trinuclear solid state structures remain intact in fluid solution (DMF) and that two of the three copper(II) ions are antiferromagnetically coupled, leaving the third as an S = ½ center with a hyperfine coupling constant to the I = 3/2 Cu nucleus of 14.80 G. Super-hyperfine coupling (15.13 G) to two N atoms was also evident, consistent with one of the terminal copper(II) centers (O,N,N,O donor atom set) being the site of the unpaired spin density in the molecule. Density functional theory (DFT) simulations were used to determine the electronic structures of the diamagnetic mononuclear nickel(II) complexes. The simulations reproduced the structures of [Ni(L²)] and [Ni(L³)] accurately with similarity coefficients for the two complexes of 0.982 and 0.990, respectively. The simulated electronic spectra (TD-DFT) of the nickel(II) complexes showed reasonably good agreement with the experimental spectra and were useful for the assignment of the low-lying MLCT state (near 400 nm) for the complexes as well as the higher-lying π-π* transitions between 300–350 nm. All of the metal complexes and one ligand were sent to MINTEK¹ (Project AuTEK) for anticancer screening. The copper(II) complexes (bleomycin analogues capable of generating hydroxyl radicals in vivo) showed significant cytotoxicity against the human cancer cell lines A549, DU145, HT-29, and U21. The trinuclear complexes were the most cytotoxic with mean IC₅₀ values of 6(2) and 7(1) μM for [Cu₃(L²)₂Cl₂(DMF)₂] and [Cu₃(L³)₂(H₂O)₂]Cl₂, respectively. The nickel(II) complexes [Ni(L²)] and [Ni(L³)] were comparatively inactive with mean IC₅₀ values of >50 and 35(16) μM, respectively, consistent with the fact that they do not readily generate reactive oxygen species in a cellular environment. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.