0000000001308421
AUTHOR
Carmen E. Castillo
Equilibrium and kinetic studies on complex formation and decomposition and the movement of Cu2+metal ions within polytopic receptors
Potentiometric studies carried out on the interaction of two tritopic double-scorpiand receptors in which two equivalent 5-(2-aminoethyl)-2,5,8-triaza[9]-(2,6)-pyridinophane moieties are linked with 2,9-dimethylphenanthroline (L1) and 2,6-dimethylpyridine (L2) establish the formation of mono-, bi- and trinuclear Cu(2+) complexes. The values of the stability constants and paramagnetic (1)H NMR studies permit one to infer the most likely coordination modes of the various complexes formed. Kinetic studies on complex formation and decomposition have also been carried out. Complex formation occurs with polyphasic kinetics for both receptors, although a significant difference is found between bot…
Equilibrium and kinetics studies on bibrachial lariat aza-crown/Cu(II) systems reveal different behavior associated with small changes in the structure
Abstract The high-yield synthesis of a new bibrachial lariat azacrown constituted by two tris(2-aminoethyl)amine (tren) units functionalized in one of its arms with a 4-methylquinoline group linked by dimethylene pyridine spacers (L2) is reported for the first time. The speciation studies show formation of mono- and binuclear Cu2+ complexes of similar stability. Comparisons are established with the complexes formed by the precursor tren-quinoline derivative (L4) and with the previously reported ligands containing naphthalene instead of quinoline as the fluorophore (L1, L3). The kinetics of formation and decomposition of Cu2+ complexes with L1 and L2 has been studied. For L1, the acid-promot…
Copper(II) complexes of quinoline polyazamacrocyclic scorpiand-type ligands: X-ray, equilibrium and kinetic studies
The formation of Cu(II) complexes with two isomeric quinoline-containing scorpiand-type ligands has been studied. The ligands have a tetraazapyridinophane core appended with an ethylamino tail including 2-quinoline (L1) or 4-quinoline (L2) functionalities. Potentiometric studies indicate the formation of stable CuL(2+) species with both ligands, the L1 complex being 3-4 log units more stable than the L2 complex. The crystal structure of [Cu(L1)](ClO(4))(2)·H(2)O shows that the coordination geometry around the Cu(2+) ions is distorted octahedral with significant axial elongation; the four Cu-N distances in the equatorial plane vary from 1.976 to 2.183 Å, while the axial distances are of 2.27…
Hydrogen and copper ion-induced molecular reorganizations in scorpionand-like ligands. A potentiometric, mechanistic, and solid-state study.
Two aza scorpionand-like macrocycles (L2 and L3) have been prepared. L2 consists of a tren amine with two of its arms cyclizized with a 2,6-bis(bromomethyl)pyridine. In L3, the remaining pendant arm has been further functionalized with a fluorophoric naphthalene group. X-ray data on the compounds [H(L3)]ClO4.H2O (1) and [H3(L3)](H2PO4)3.H2O (2) as well as solution studies (pH-metry, UV-vis, and fluorescence data) show the movement of the pendant arm as a result of the protonation degree of the macrocycles and of the formation of intramolecular hydrogen bonds. X-ray data on the complexes [Cu(L2)](ClO4)2]2.H2O (3) and [Cu(L3)](ClO4)2 (4) and solution studies on Cu2+ coordination show the impl…
Hydrogen and Copper Ion Induced Molecular Reorganizations in Two New Scorpiand-Like Ligands Appended with Pyridine Rings
The synthesis of two new ligands constituted of a tris(2-aminoethyl)amine moiety linked to the 2,6 positions of a pyridine spacer through methylene groups in which the hanging arm is further functionalized with a 2-pycolyl (L1) or 3-pycolyl (L2) group is presented. The protonation of L1 and L2 and formation of Cu(2+) complexes have been studied using potentiometric, NMR, X-ray, and kinetic experiments. The results provide new information about the relevance of molecular movements in the chemistry of this kind of so-called scorpiand ligand. The comparison between these two ligands that only differ in the position of the substituent at the arm reveals important differences in both thermodynam…
Electro- and Photo-driven Reduction of CO 2 by a trans -(Cl)-[Os(diimine)(CO) 2 Cl 2 ] Precursor Catalyst: Influence of the Diimine Substituent and Activation Mode on CO/HCOO − Selectivity
A series of [OsII(NN)(CO)2Cl2] complexes where NN is a 2,2′-bipyridine ligand substituted in the 4,4′ positions by H (C1), CH3 (C2), C(CH3)3 (C3), or C(O)OCH(CH3)2 (C4) has been studied as catalysts for the reduction of CO2. Electrocatalysis shows that the selectivity of the reaction can be switched toward the production of CO or HCOO− with an electron-donating (C2, C3) or -withdrawing (C4) substituent, respectively. The electrocatalytic process is a result of the formation of an Os0-bonded polymer, which was characterized by electrochemistry, UV/Visible and EPR spectroscopies. Photolysis of the complexes under CO2 in DMF+TEOA produces CO as a major product with a remarkably stable turnover…
Characterization of a Ferryl Flip in Electronically Tuned Nonheme Complexes. Consequences in Hydrogen Atom Transfer Reactivity
Two oxoiron(IV) isomers (R2a and R2b) of general formula [FeIV(O)(RPyNMe3)(CH3CN)]2+ are obtained by reaction of their iron(II) precursor with NBu4IO4. The two isomers differ in the position of the oxo ligand, cis and trans to the pyridine donor. The mechanism of isomerization between R2a and R2b has been determined by kinetic and computational analyses uncovering an unprecedented path for interconversion of geometrical oxoiron(IV) isomers. The activity of the two oxoiron(IV) isomers in hydrogen atom transfer (HAT) reactions shows that R2a reacts one order of magnitude faster than R2b, which is explained by a repulsive noncovalent interaction between the ligand and the substrate in R2b. Int…
Iron(II) Complexes with Scorpiand-Like Macrocyclic Polyamines: Kinetico-Mechanistic Aspects of Complex Formation and Oxidative Dehydrogenation of Coordinated Amines.
The Fe(II) coordination chemistry of a pyridinophane tren-derived scorpiand type ligand containing a pyridine ring in the pendant arm is explored by potentiometry, X-ray, NMR, and kinetics methods. Equilibrium studies in water show the formation of a stable [FeL]2+ complex that converts to monoprotonated and monohydroxylated species when the pH is changed. A [Fe(H–2L)]2+ complex containing an hexacoordinated dehydrogenated ligand has been isolated, and its crystal structure shows the formation of an imine bond involving the aliphatic nitrogen of the pendant arm. This complex is low spin Fe(II) both in the solid state and in solution, as revealed by the Fe–N bond lengths and by the NMR spect…
Structural reorganisation in polytopic receptors revealed by kinetic studies.
One of the first kinetic studies of metal ion reorganisation between the different sites of a tritopic polyaza ligand reveals well defined pathways for the movement of the metal ion.
Geometric Isomerism in Pentacoordinate Cu2+ Complexes: Equilibrium, Kinetic, and Density Functional Theory Studies Reveal the Existence of Equilibrium between Square Pyramidal and Trigonal Bipyramidal Forms for a Tren-Derived Ligand
A ligand (L1) (bis(aminoethyl)[2-(4-quinolylmethyl)aminoethyl]amine) containing a 4-quinolylmethyl group attached to one of the terminal amino groups of tris(2-aminoethyl)amine (tren) has been prepared, and its protonation constants and stability constants for the formation of Cu(2+) complexes have been determined. Kinetic studies on the formation of Cu(2+) complexes in slightly acidic solutions and on the acid-promoted complex decomposition strongly suggest that the Cu(2+)-L1 complex exists in solution as a mixture of two species, one of them showing a trigonal bipyramidal (tbp) coordination environment with an absorption maximum at 890 nm in the electronic spectrum, and the other one bein…
CCDC 1521794: Experimental Crystal Structure Determination
Related Article: M. Paz Clares, Laura Acosta-Rueda, Carmen E. Castillo, Salvador Blasco, Hermas R. Jiménez, Enrique García-España, and Manuel G. Basallote|2017|Inorg.Chem.|56|4400|doi:10.1021/acs.inorgchem.6b03070
CCDC 2192965: Experimental Crystal Structure Determination
Related Article: Valeria Dantignana, M. Carmen Pérez-Segura, Pau Besalú-Sala, Estefanía Delgado-Pinar, Álvaro Martínez-Camarena, Joan Serrano-Plana, Andrea Álvarez-Núñez, Carmen E. Castillo, Enrique García-España, Josep M. Luis, Manuel G. Basallote, Miquel Costas, Anna Company|2023|Angew.Chem.,Int.Ed.|62||doi:10.1002/anie.202211361
CCDC 2192964: Experimental Crystal Structure Determination
Related Article: Valeria Dantignana, M. Carmen Pérez-Segura, Pau Besalú-Sala, Estefanía Delgado-Pinar, Álvaro Martínez-Camarena, Joan Serrano-Plana, Andrea Álvarez-Núñez, Carmen E. Castillo, Enrique García-España, Josep M. Luis, Manuel G. Basallote, Miquel Costas, Anna Company|2023|Angew.Chem.,Int.Ed.|62||doi:10.1002/anie.202211361
CCDC 2192963: Experimental Crystal Structure Determination
Related Article: Valeria Dantignana, M. Carmen Pérez-Segura, Pau Besalú-Sala, Estefanía Delgado-Pinar, Álvaro Martínez-Camarena, Joan Serrano-Plana, Andrea Álvarez-Núñez, Carmen E. Castillo, Enrique García-España, Josep M. Luis, Manuel G. Basallote, Miquel Costas, Anna Company|2023|Angew.Chem.,Int.Ed.|62||doi:10.1002/anie.202211361
CCDC 1423684: Experimental Crystal Structure Determination
Related Article: Salvador Blasco, Begoña Verdejo, M. Paz Clares, Carmen E. Castillo, Andrés G. Algarra, Julio Latorre, M. Angeles Máñez, Manuel G. Basallote, Conxa Soriano and Enrique García-España|2010|Inorg.Chem.|49|7016|doi:10.1021/ic100609h
CCDC 2192962: Experimental Crystal Structure Determination
Related Article: Valeria Dantignana, M. Carmen Pérez-Segura, Pau Besalú-Sala, Estefanía Delgado-Pinar, Álvaro Martínez-Camarena, Joan Serrano-Plana, Andrea Álvarez-Núñez, Carmen E. Castillo, Enrique García-España, Josep M. Luis, Manuel G. Basallote, Miquel Costas, Anna Company|2023|Angew.Chem.,Int.Ed.|62||doi:10.1002/anie.202211361