5 results on '"Carlos Platas-Iglesias"'
Search Results
2. Ditopic binuclear copper(II) complexes for DNA cleavage
- Author
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Jesús Mosquera, M. Eugenio Vázquez, Israel Carreira-Barral, Andrés de Blas, Carlos Platas-Iglesias, Miguel Riopedre-Fernández, David Esteban-Gómez, and Macro-Organic Chemistry
- Subjects
Circular dichroism ,Ditopic receptors ,010402 general chemistry ,DFT calculations ,01 natural sciences ,Biochemistry ,Pyrophosphate ,Inorganic Chemistry ,Hydrolysis ,chemistry.chemical_compound ,Coordination Complexes ,DNA cleavage ,010405 organic chemistry ,Ligand ,Hydrogen bond ,DNA ,Anion recognition ,0104 chemical sciences ,Binuclear copper complexes ,Crystallography ,chemistry ,Intramolecular force ,Amine gas treating ,pUC19 ,Copper ,Plasmids - Abstract
Herein we present the synthesis of two ligands containing two di(2-picolyl)amine (DPA) units linked by either a 1,1′-(pyridine-2,6-diyl)bis(3-ethylurea) (L1) or a 1,1′-(1,3-phenylene)bis(3-ethylurea) (L2) spacer. The corresponding binuclear CuII and ZnII complexes were prepared and isolated. The X-ray structures of the L1 ligand and the [Cu2L1Cl2]2+ complex evidence an unusual cis/trans conformation of one of the urea groups stabilized by an intramolecular hydrogen bond with the nitrogen atom of the pyridyl spacer. The CuII complexes form rather strong ternary complexes with phosphorylated anions. The [Cu2L1]4+ complex presents a rather high affinity for pyrophosphate (logK11 = 8.19 at pH 7, 25 °C), while [Cu2L2]4+ stands out because of its strong binding to AMP2− (logK11 = 9.3 at pH 7, 25 °C). The interaction of the CuII complexes with deoxyribonucleic acid from calf thymus (ct-DNA) was monitored using circular dichroism (CD) and luminescence spectroscopies. These studies revealed a quite strong interaction of the complexes with ct-DNA (Kb = (6.4 ± 0.7) × 103 for [Cu2L1]4+ and Kb = (6.3 ± 1.0) × 103 for [Cu2L2]4+). Competition experiments carried out in the presence of methyl green and BAPPA (N1,N3-Bis(4-amidinophenyl)propane-1,3-diamine) as major and minor groove competitors, respectively, confirm that the interaction of both complexes with DNA takes place through the minor groove, in agreement with docking studies. The [Cu2L2]4+ complex is quite efficient in promoting the cleavage of the double-stranded pUC19 plasmid DNA, by favoring the conversion of the supercoiled form to the nicked form following a hydrolytic mechanism.
- Published
- 2020
3. The chemical consequences of the gradual decrease of the ionic radius along the Ln-series
- Author
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Kristina Djanashvili, J. A. Peters, Carlos F. G. C. Geraldes, and Carlos Platas-Iglesias
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Lanthanide ,Lanthanide contraction ,Steric effects ,Aqueous solution ,Ionic radius ,010405 organic chemistry ,Chemistry ,Solution structures ,010402 general chemistry ,01 natural sciences ,NMR ,0104 chemical sciences ,Ion ,Inorganic Chemistry ,Chemical physics ,Materials Chemistry ,Computational methods ,Atomic number ,Physical and Theoretical Chemistry ,Valence electron ,X-ray crystallography - Abstract
[Abstract] In the periodical system, the lanthanides (the 15 elements in the periodic table between barium and hafnium) are unique in the sense that their trivalent cations have their valence electrons hidden behind the 5s and 5p electrons. They show a gradual decrease in ionic radius with increasing atomic number (also known as the lanthanide contraction). The resulting steric effects determine to a large extent the geometries of complexes of these ions. Here, we discuss these effects, particularly upon the properties of the complexes in aqueous solution, for selected families of Ln3+-complexes of oxycarboxylate and aminocarboxylate ligands. The physical properties of the cations are very different, which is very useful for the elucidation of the configuration, conformation and the dynamics of the complexes by X-ray techniques, NMR spectroscopy, and optical techniques. Often the structural analysis is assisted by computational methods.
- Published
- 2019
4. Cinderella Elements: Strategies to Increase the Stability of Group 1 Complexes by Tailoring Crown Macrocycles
- Author
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Andrés de Blas, Teresa Rodríguez-Blas, Aurora Rodríguez-Rodríguez, David Esteban-Gómez, Israel Carreira-Barral, and Carlos Platas-Iglesias
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Benzimidazole ,Stereochemistry ,Sodium ,Cryptand ,X-ray crystal structures ,chemistry.chemical_element ,Ether ,Lariat ether ,Alkaline metal complexes ,Inorganic Chemistry ,chemistry.chemical_compound ,Macrocyclic ligands ,Aniline ,chemistry ,Group (periodic table) ,Polymer chemistry ,Materials Chemistry ,Crown ethers ,Physical and Theoretical Chemistry ,Acetonitrile - Abstract
[Abstract] The synthesis and structural characterization of six sodium complexes with bibracchial lariatethers containing aniline or benzimidazole side arms, and derived from 1,7 diaza-12-crown-4, 1,10-diaza-15-crown-5 or 4,13-diaza-18-crown-6, are reported. The X-ray structures of four of these compounds have been obtained. Additionally, the X-ray structures of a sodium macrobicyclic complex derived from 1,10-diaza-15-crown-5, and a potassium complex with a bibracchial lariat ether containing aniline side arms are also reported. Bonding distances as well as the stability constants in acetonitrile solution confirm that the coordination of the pendant arms provides an important contribution to the overall stability of the complexes, particularly when benzimidazole pendants are present rending more stable complexes, even more than cryptand complexes of the same size. Compared with the parent crown ethers, the stability increases when the side arms contain benzimidazole moieties but remains about the same order when aniline side arms are present. Xunta de Galicia; CN2012/011
- Published
- 2014
5. Conformational study of lanthanide(III) complexes of N-(2-salicylaldiminatobenzyl)-1-aza-18-crown-6 by using X-ray and ab initio methods
- Author
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Marta Mato-Iglesias, Teresa Rodríguez-Blas, Marina González-Lorenzo, Andrés de Blas, David Esteban-Gómez, and Carlos Platas-Iglesias
- Subjects
Lanthanide ,Ligand ,Chemistry ,Coordination number ,18-Crown-6 ,Ab initio ,Inorganic Chemistry ,Bond length ,chemistry.chemical_compound ,Crystallography ,Macrocyclic ligands ,Ab initio quantum chemistry methods ,Lanthanides ,Materials Chemistry ,Molecule ,Ab initio calculations ,Physical and Theoretical Chemistry ,Crown compounds - Abstract
[Abstract] A structural study of lanthanide complexes with the deprotonated form of the monobracchial lariat ether N-2-salicylaldiminatobenzyl-aza-18-crown-6 (L4) (Ln = La(III)–Tb(III)) is presented. Attempts to isolate complexes of the heaviest members of the lanthanide series were unsuccessful. The X-ray crystal structures of [Pr(L4)(H2O)](ClO4)2 · H2O · C3H8O and [Sm(L4)(H2O)](ClO4)2 · C3H8O show the metal ion being bound to the eight donor atoms of the ligand backbone. Coordination number nine is completed by the oxygen atom of an inner-sphere water molecule. Two different conformations of the crown moiety (labelled as A and B) are observed in the solid state structure of the Pr(III) complex, while for the Sm(III) complex only conformation A is observed. The complexes were also characterized by means of theoretical calculations performed in vacuo at the HF level, by using the 3-21G∗ basis set for the ligand atoms and a 46 + 4fn effective core potential for lanthanides. The optimized geometries of the Pr(III) and Sm(III) complexes show an excellent agreement with the experimental structures obtained from X-ray diffraction studies. The calculated relative energies of the A and B conformations for the different [Ln(L4)(H2O)]2+ complexes (Ln = La, Pr, Sm, Ho or Lu) indicate a progressive stabilization of the A conformation with respect to the B one upon decreasing the ionic radius of the Ln(III) ion. For the [Ln(L4)(H2O)]2+ systems, most of the calculated bond distances between the metal ion and the coordinated donor atoms decrease along the lanthanide series, as usually observed for Ln(III) complexes. However, our ab initio calculations provide geometries in which the Ln–O(5) bond distance [O(5) is an oxygen atom of the crown moiety] increases across the lanthanide series from Sm(III) to Lu(III). Ministerio de Educación y Ciencia; CTQ2006-07875
- Published
- 2008
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