Leonor Maria
Instituto Superior Técnico
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Featured researches published by Leonor Maria.
Dalton Transactions | 2009
Leonor Maria; Célia Fernandes; Raquel Garcia; Lurdes Gano; António Paulo; Isabel Santos
Novel ether-containing tris(pyrazolyl)methane chelators stabilize thefac-[99mTc(CO)3]+ moiety providing complexes with significant, fast and stable heart uptake, together with a extremely fast liver clearance.
Dalton Transactions | 2007
Leonor Maria; Susana Cunha; Margarida Videira; Lurdes Gano; António Paulo; Isabel Santos
This report describes the synthesis and biological evaluation of cationic (99m)Tc-tricarbonyl complexes anchored by ether-containing tris(pyrazolyl)methane or bis(pyrazolyl)ethanamine ligands to be applied in the design of radiopharmaceuticals for myocardial imaging: fac-[(99m)Tc(CO)(3){RC(pz)(3)}](+) (R = H (1a), MeOCH(2) (2a), EtOCH(2) (3a), (n)PrOCH(2) (4a)) and fac-[(99m)Tc(CO)(3){RNHCH(2)CH(pz)(2)}](+) (R = H (5a), MeO(CH(2))(2) (6a)) (pz = pyrazolyl). At the no carrier added level, complexes 1a-6a were obtained in high radiochemical yield (> 98%) by reaction of fac-[(99m)Tc(CO)(3)(H(2)O)(3)](+) with the corresponding tripod chelator in aqueous medium. All these complexes display a high in vitro and in vivo stability, except 6a which metabolizes in vivo yielding fac-[(99m)Tc(CO)(3){HO(CH(2))(2)NHCH(2)CH(pz)(2)}](+) (7a). Biological studies in mice have shown that among the radiotracers evaluated in this work, 3a, anchored by a tris(pyrazolyl)methane chelator bearing an ethyl methyl ether substituent, has the highest heart uptake (3.6 +/- 0.5%ID g(-1) at 60 min p.i.). Complex 3a presents also the best heart: blood, heart: liver and heart: lung ratios, appearing as the most promising as a potential myocardial imaging agent. The chemical identity of 1a-7a was ascertained by HPLC comparison with the previously reported fac-[Re(CO)(3){HC(pz)(3)}]Br (1) and with the novel fac-[Re(CO)(3){RC(pz)(3)}]Br (R = MeOCH(2) (2), EtOCH(2) (3), (n)PrOCH(2)(4)) and fac-[Re(CO)(3){RNHCH(2)CH(pz)(2)}]Br (R = H (5), MeO(CH(2))(2) (6) HO(CH(2))(2) (7)). The novel Re(I) tricarbonyl complexes, 2-7, were characterized by the common analytical techniques, including single crystal X-ray diffraction analysis. The solid state structure confirmed the presence of facial and tridentate (kappa(3)-N(3)) anchor ligands. Solution NMR studies have also shown that this kappa(3)-N(3) coordination mode is retained in solution for all complexes (2-7).
Journal of Organometallic Chemistry | 2001
Jacqueline Collin; Nicolas Giuseppone; Nada Jaber; Angela Domingos; Leonor Maria; Isabel Santos
Abstract Reactions of lanthanide triiodides with potassium bistrimethylsilyl amide have been investigated. For lanthanum, recrystallisation from THF–toluene led to monocrystals of the dimeric bisamide [La(μ-I){N(TMS) 2 } 2 (THF)] 2 . We have shown that samarium diiodide and lanthanide triiodides are efficient for lanthanum and samarium reactions, a mixture of tris amides and iodo bisamides is obtained, while only the latter compound is obtained for ytterbium.
Inorganic Chemistry | 2015
Leonor Maria; Isabel Santos; Vânia R. Sousa; Joaquim Marçalo
A new monoiodide U(III) complex anchored on a hexadentate dianionic 1,4,8,11-tetraazacyclotetradecane-based bis(phenolate) ligand, [U(κ(6)-{((tBu2)ArO)2Me2-cyclam})I] (1), was synthesized from the reaction of [UI3(THF)4] (THF = tetrahydrofuran) and the respective potassium salt K2((tBu2)ArO)2Me2-cyclam and structurally characterized. Reactivity of 1 toward one-, two-, and four-electron oxidants was studied to explore the reductive chemistry of this new U(III) complex. Complex 1 reacts with one-electron oxidizers, such as iodine and TlBPh4, to form the seven-coordinate cationic uranium(IV) complexes [U(κ(6)-{((tBu2)ArO)2Me2-cyclam})I][X] (X = I (2-I), BPh4 (2-BPh4)). The new uranium(III) complex reacts with inorganic azides to yield the pseudohalide uranium(IV) complex [U(κ(6)-{((tBu2)ArO)2Me2-cyclam})(N3)2] (4) and the nitride-bridged diuranium(IV/IV) complex [(κ(4)-{((tBu2)ArO)2Me2-cyclam})(N3)U(μ-N)U(κ(5)-{((tBu2)ArO)2Me2-cyclam})] (5). Two equivalents of [U(κ(6)-{((tBu2)ArO)2Me2-cyclam})I] (1) effect the four-electron reduction of 1 equiv of PhN═NPh to form the bis(imido) complex [U(κ(4)-{((tBu2)ArO)2Me2-cyclam})(NPh)2] (6) and the U(IV) species 2-I. Moreover, the hemilability of the hexadentate ancillary ligand ((tBu2)ArO)2Me2-cyclam(2-) allows to perform the reductive cleavage of azobenzene with an unprecedented formation of a trans-bis(imido) complex. The complexes were characterized by NMR spectroscopy, and all the new uranium complexes were structurally authenticated by single-crystal X-ray diffraction.
Dalton Transactions | 2006
Carolina Moura; Rute F. Vitor; Leonor Maria; António Paulo; Isabel Santos
The novel pyrazolyl-based ligands 3,5-Me2pz(CH2)2NH(CH2)2NH(CH2)2NH2 and pz*(CH2)2NH-Gly-CH2STrit (pz*=pz, 3,5-Me2pz, 4-(EtOOC)CH(2)-3,5-Me2pz) were synthesized, and their suitability to stabilize Re(V) oxocomplexes was evaluated using different starting materials, namely (NBu4)[ReOCl4], [ReOCl3(PPh3)2] and trans-[ReO2(py)4]Cl. Compound reacts with trans-[ReO2(py)4]Cl yielding the cationic compound [ReO(OMe){3,5-Me2pz(CH2)2N(CH2)2NH(CH2)2NH2}](BPh4) in a low isolated yield. In contrast, the neutral complexes [ReO{pz*(CH2)2NH-Gly-CH2S}] (pz*=pz, 3,5-Me2pz, 4-(EtOOCCH2)-3,5-Me2pz) were synthesized almost quantitatively by reacting [ReOCl3(PPh3)2] or (NBu4)[ReOCl4] with the trityl-protected chelators. The X-ray diffraction analysis of and confirmed the tetradentate coordination mode of the respective ancillary ligands. In the monoanionic chelator coordinates to the metal through four nitrogen atoms, while in the chelator is trianionic, coordinating to the metal through three nitrogens and one sulfur atom. Solution NMR studies of , including two-dimensional NMR techniques (1H COSY and 1H/13C HSQC), confirmed that the N3S coordination mode of the chelators is retained in solution. Unlike , complexes may be considered relevant in the development of radiopharmaceuticals, as further corroborated by the synthesis of the congener [99mTcO{pz(CH2)2-NH-Gly-CH2S}]. This radioactive compound was obtained from 99mTcO4- in aqueous medium, in almost quantitative yield and with high specific activity and radiochemical purity.
Journal of Molecular Catalysis A-chemical | 2000
Jacqueline Collin; Leonor Maria; Isabel Santos
Abstract Uranium triiodide is found to be an efficient Lewis acid catalyst for various Diels–Alder reactions which are performed in mild conditions and with low amounts of catalysts. The replacement of an iodide by a dihydrobis(pyrazolyl)borate ligand does not increase activity or selectivity.
Inorganic Chemistry Communications | 2003
Leonor Maria; Ângela Domingos; Isabel Santos
Abstract The novel KBp i Pr2 and the previously described KTp i Pr2 react with [UI3(THF)4], in THF, yielding the new compounds [ U { κ 3 -Bp i Pr2 )} 3 ] (1) and [ UI 2 ( κ 3 -Tp i Pr2 )( THF ) x ] (x=2–3) (2), respectively. Compound 1 is remarkably stable, while 2 decomposes in solution, being the main decomposition product [ UI 2 ( κ 3 -Tp i Pr2 )( κ 1 -pz i Pr2 H ) ] (3). The formation of 3 is prevented when [UI3(THF)4] reacts with KTp i Pr2 in toluene, in the presence of strong neutral coordinating ligands.
Journal of Biological Inorganic Chemistry | 2007
Elisa Palma; Bruno L. Oliveira; João D. G. Correia; Lurdes Gano; Leonor Maria; Isabel Santos
Journal of Organometallic Chemistry | 2006
Leonor Maria; Carolina Moura; António Paulo; Isabel Santos
Journal of the American Chemical Society | 2006
Leonor Maria; António Paulo; Isabel Santos; Philipp Kurz; Bernhard Spingler; Roger Alberto