Browsing by Author "Chaur, Manuel N."
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Item Determination of the binding constants of propeller-like metal complexes of picolinaldehyde-2-pyridylhydrazone(Elsevier S.A., 2018-12-13) Carmona Vargas, Christian C.; AristizĂĄbal, Sandra L.; BelalcĂĄzar, MarĂa I.; D'Vries, Richard F.; Chaur, Manuel N.Herein, we determined the binding constants for transition metal complexes of Cu2+, Co2+, Fe2+, Ni2+, and Zn2+ ions formed with the ligand picolinaldehyde-2-pyridylhydrazone (PapyH) using the Benesi-Hildebrand method. Stoichiometry 2:1 (ligand: metal) was previously determined by the Jobâs method and confirmed by single-crystal X-ray diffraction finding a propeller-like structure of the [Fe(Papy)2] compound. PapyH and the metal complexes were characterized by 1H NMR and UV-Vis spectroscopy, respectively. The Cu2+ complex exhibited the highest stability constant, which was confirmed by competitive reaction of different metal ions with the ligand PapyH.Item (E)-5-[1-Hydroxy-3-(3,4,5-trimethoxyphenyl)allylidene]-1,3-dimethylpyrimidine-2,4,6-trione: Crystal structure and Hirshfeld surface analysis(International Union of Crystallography, 2017-07-13) Soto-Monsalve, MĂłnica; Romero, Elkin L.; Zuluaga, Fabio; Chaur, Manuel N.; D'Vries, Richard F.In the title compound, C18H20N2O7, the dihedral angle between the aromatic rings is 7.28 (7)° and the almost planar conformation of the molecule is supported by an intramolecular O - HâŻO hydrogen bond, which closes an S(6) ring. In the crystal, weak C - HâŻO hydrogen bonds and aromatic Ï-Ï stacking link the molecules into a three-dimensional network. A Hirshfeld surface analysis showed that the major contribution to the intermolecular interactions are van der Waals interactions (HâŻH contacts), accounting for 48.4% of the surface. © Soto-Monsalve et al. 2017.Item (E)-5-[1-Hydroxy-3-(3,4,5-trimethoxyphenyl)allylidene]-1,3-dimethylpyrimidine-2,4,6-trione: crystal structure and Hirshfeld surface analysis(Acta Crystallographica Section E: Structure Reports Online, 2017) Soto-Monsalve, MĂłnica; Romero, Elkin L.; Zuluaga, Fabio; Chaur, Manuel N.; DâVries, Richard F.In the title compound, C 18 H 20 N 2 O 7 , the dihedral angle between the aromatic rings is 7.28 (7)° and the almost planar conformation of the molecule is supported by an intramolecular OâH...O hydrogen bond, which closes an S (6) ring. In the crystal, weak CâH...O hydrogen bonds and aromatic ÏâÏ stacking link the molecules into a three-dimensional network. A Hirshfeld surface analysis showed that the major contribution to the intermolecular interactions are van der Waals interactions (H...H contacts), accounting for 48.4% of the surface.Item Multiple Reversible Dynamics of Pyrimidine Based Acylhydrazones(Wiley-VCH Verlag, 2020-05-08) Arango, Alejandra M.; Wist, Julien; Ellena, Javier Alcides; D'Vries, Richard Fernando; Chaur, Manuel N.We employed (Z)âN'â[phenyl(pyrimidinâ2âyl)methylene]nicotinohydrazide (2) and (Z)â4â(dimethylamino)âN'â[phenyl(pyrimidinâ2âyl)methylene]benzohydrazide (3) as cores of dynamic chemical systems whose different states are modulated, in a reversible fashion, through specific physical and chemical stimuli. The structure of the compounds was determined by Nuclear Magnetic Resonance (NMR) techniques (1D and 2D) and confirmed by singleâcrystal Xâray diffraction. By Variable temperature (VT) 1H NMR experiments and DFT calculations, the conformational isomerism of 2 was studied and added as an additional input for the dynamic system. Additionally, 2 exhibits configurational E/Z isomerization mediated by pH variations and UV light. On the other hand, configurational isomerism locks an unlocks a tridentate pocket for metal cation coordination in both 2 and 3. All the different dynamic states configurational/conformational isomerism and locked and unlocked coordination constitute a development in the field of systems of multiple dynamics suitable for molecular machines.Item New pyrazolino and pyrrolidino[60]fullerenes: the introduction of the hydrazone moiety for the formation of metal complexes(Journal of Physical Organic Chemistry, 2016) Romero, Elkin L.; Cabrera-Espinoza, Andrea; Ortiz-Peña, Nathaly; Soto-Monsalve, MĂłnica; Zuluaga, Fabio; DâVries, Richard F.; Chaur, Manuel N.The [3 + 2] cycloaddition reaction of C60 with pyridine-derived hydrazones (acting as dipolar reagents) was successfully conducted resulting in fullerene derivatives 5a, 5b. The compounds were characterized by means of NMR, UVâVis spectroscopy, and X-ray crystallography. The electrochemical behavior was also investigated. The fulleropyrazoline 5a exhibits anodically shifted reduction potentials of about 100 mV when compared with those for C60, whereas 5b exhibits cathodic shifts relative to pristine C60. The complexation reaction of 5b with metallic ions (Zn2+, Cd2+, and Fe2+) was achieved. Job and BenesiâHildebrand analysis confirmed the formation of complexes with a molar ratio of 1:1 and binding constants between 2.26 Ă 105 and 1.59 Ă 105 Mâ1. Electrochemistry of these complexes showed a marked influence of the metal ion on the reduction potentials.Item A Photochemical and Electrochemical Triggered Bis(hydrazone) Switch(Chemistry - A European Journal, 2017) Gordillo, MĂłnica A.; Soto-Monsalve, MĂłnica; Carmona-Vargas, Christian C.; Gutierrez, Gustavo; D'vries, Richard F.; Lehn, Jean-Marie; Chaur, Manuel N.Herein, we report the synthesis of a double hydrazone capable of undergoing photochemical E/Z isomerization through the imine double bonds. The bis(hydrazone) 1-E,E can be considered as a ""two-arm"" system in which the controlled movement of each arm is obtained by photo-modulation, making possible the appearance of two isolable metastable isomeric states 1-E,Z and 1-Z,Z. Such states are characterized by very specific structural, optical and electrochemical properties. The latter, allows the reversible return from either 1-E,Z or 1-Z,Z to the 1-E,E state. Our results are of great importance in the further development of molecular machines and photochemically controlled reactions by introducing for the first time double hydrazones as tunable photochemical switches.Item Structural characterization of a fluorescein hydrazone molecular switch with application towards logic gates(New Journal of Chemistry, 2018) Villada, Juan D.; DâVries, Richard F.; MacĂas, Mario; Zuluaga, Fabio; Chaur, Manuel N.A fluorescein acylhydrazone (2) as well as its metal complexes with Zn2+, Ni2+ and Cu2+ ions were synthesized and characterized by means of NMR (1H, 13C and 2D experiments), UV-Vis, fluorescence spectroscopy, FT-IR and single crystal X-Ray diffraction. The compound crystallizes in PÄ« triclinic space group, with two fluorescein acylhydrazone (2) conformers and one water molecule per symmetric unit. The fluorescein acylhydrazone (2) and metal derivates were analysed by cyclic voltammetry, finding a relation between the shifting in their redox potential with the quenching of fluorescence. Emission and UV-Vis absorption logic gates were fabricated based on the metal ion binding of 2 and its behaviour at different pH values. Compound 2 exhibited âon-offâ behaviour in the fluorescence emission with the addition of triethylamine (TEA) this effect is highly enhanced by the joint addition of Zn2+. Conversely, the fluorescence is highly quenched by the addition of trifluoroacetic acid (TFA) or Ni2+ ions allowing to fabricate a AND gate using TEA and Zn2+ as inputs, and a INHIBIT gate with the addition of TFA or Ni2+, both using the fluorescence emission as outputs. The addition of Cu2+ resulted in a fluorescence emission at 525 nm that is red shifted with the addition of TEA. This behaviour allowed us to construct a XOR gate with the fluorescence emission at 525 nm as output, and the addition of Cu2+ and TEA as inputs. The absorption in the visible region was used to create AND gates with the addition of Cu2+ ions and TEA, or Ni2+and TEA as inputs. The INH, AND, XOR gates were manipulated by the controlled addition of different metal cations, TEA and TFA as inputs, and fluorescence emission and visible absorption as outputs allowing us to create three different combinatorial circuits in which we want to highlight a new molecular âHALF-ADDERâ.Item Structural, spectroscopic, and theoretical analysis of a molecular system based on 2-((2-(4- chlorophenylhydrazone)methyl)quinolone(Universidad Nacional de Colombia, 2018-12-02) Romero, Elkin L.; Soto-Monsalve, MĂłnica; GutiĂ©rrez, Gustavo; Zuluaga, Fabio; D'Vries, Richard F.; Chaur, Manuel N.A novel molecular system based on 2-((2-(4-chlorophenylhydrazone)methyl)quinoline (1-E) was synthesized. Interconversion of 1-E to its configurational isomer 1-Z was achieved using UV radiation (250 W Hg lamp). Such isomerization was monitored by1H-NMR. The results suggest that the hydrazone derivative can act as a chemical brake in solution. This molecular system was structurally (Single Crystal X-Ray diffraction and DFT calculations) and spectroscopically (NMR, UV, and IR) characterized. Electrochemical measurements showed that configurational changes induce differential redox behavior. In this regard, the reported quinoline system exhibits different dynamic absorption and electrochemical properties that are modulated by UV-light. Therefore, 1-E can be regarded as a potential photo-electrochemical switch. © 2018, Universidad Nacional de Colombia. All rights reserved.Item Synthesis, characterization, and redox potential properties of a new double-stranded Ni-bis(hydrazone)-based helicate(Academic Press Inc., 2020-08-25) Villada, Juan D.; Carmona Vargas, Christian C.; Alcides Ellena, Javier; Ayala, Alejandro P.; RamĂrez Pradilla, Juan S.; Combariza, M. Y.; Galarza, Esperanza; D'Vries, Richard Fernando; Chaur, Manuel N.Herein we report the synthesis and structural characterization of a new Ni-bis(hydrazone) complex with the chemical formula [Ni2(L)2(Cl)2](Cl)2·2H2O (L â= â2-(heptylthio)-4,6-bis(2-((E)-pyridin-2-ylmethylene)hydrazineyl)pyrimidine). Suitable crystals for X-ray diffraction showed the supramolecular interactions of this complex to exhibit a helical structure coordinating two Ni2+ metal ions bounded by two 2-(heptylthio)-4,6-bis(2-((E)-pyridin-2-ylmethylene)hydrazineyl)pyrimidine ligands. In addition, exploitation of the electrochemical properties by cyclic voltammetry, for this helicate, showed catalyzing ability for the reduction of H+ to H2.Item When serendipity knocks on the door: Synthesis and Physicochemical Characterization of 7-Chloro-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidin-5-one(Sociedade Brasileira de Quimica, 2019-03-19) Carmona-Vargas, Christian C.; Ellena, Javier; DâVries, Richard F.; Chaur, Manuel N.Herein, we present the serendipitous obtaining of 7-chloro-2,3-dihydro-5H-thiazolo [3,2-a]pyrimidin-5-one in 40% yield by using POCl3 and a thiobarbituric acid derivative. The thiazolopyrimidine derivative was characterized by 1H nuclear magnetic resonance (NMR), UV-Vis, and Fourier transform infrared (FTIR) spectroscopy. Additionally, the structure was confirmed by single crystal X-ray diffraction, where it was found that the compound crystallizes in the P-1 triclinic space group with two conformeric molecules of 7-chloro-2,3-dihydro-5H-thiazolo [3,2-a]pyrimidin-5-one by asymmetric unit. Also, from the structural data was studied the supramolecular interactions using Hirshfeld surface analysis and 2D fingerprint plots. © 2019 Sociedade Brasileira de QuĂmicaItem When Serendipity Knocks on the Door: Synthesis and Physicochemical Characterization of 7-Chloro-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidin-5-one(Journal of the Brazilian Chemical Society, 2019) Carmona-Vargas, Christian C.; Ellena, Javier; DâVries, Richard F.; Chaur, Manuel N.Herein, we present the serendipitous obtaining of 7-chloro-2,3-dihydro-5H-thiazolo [3,2-a]pyrimidin-5-one in 40% yield by using POCl3 and a thiobarbituric acid derivative. The thiazolopyrimidine derivative was characterized by 1H nuclear magnetic resonance (NMR), UV-Vis, and Fourier transform infrared (FTIR) spectroscopy. Additionally, the structure was conïŹrmed by single crystal X-ray diffraction, where it was found that the compound crystallizes in the P-1 triclinic space group with two conformeric molecules of 7-chloro-2,3-dihydro-5H-thiazolo [3,2-a]pyrimidin-5-one by asymmetric unit. Also, from the structural data was studied the supramolecular interactions using Hirshfeld surface analysis and 2D ïŹngerprint plots.