Browsing by Autor "Daniela Fonseca"

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Crystal Structure and Characterization of Coordination Complexes with 2-(Tert-Butoxy)-6-(1h-Imidazol-1-Yl)Pyridine
(RELX Group (Netherlands), 2025) David Ezenarro-Salcedo; Daniela Fonseca; Sergio Alexander Patiño-Cubides; Mario A. Macías; John Hurtado
Electrochemical Characterization of Cobalt Complexes with Benzoate and Azole-Pyridine Ligands As Potential Electrolytes in Batteries
(Institute of Physics, 2025) Lina Katherine La Rotta; Daniela Fonseca; John Hurtado; María I. Montañez
The study of electroactive species with multiple redox events is of interest due to their applications as electrolytes in Redox Flow Batteries (RFBs). This multi-electron behavior can be observed in organic molecules and coordination compounds containing ligands with heteroatoms such as O and N in π-extended systems. In this context, a study of 3,5-dinitrobenzoic acid, its respective cobalt complexes (1), and azole-pyridine co-ligands (2) was conducted. Electrochemical characterization of the cobalt complexes was performed using cyclic voltammetry. Measurements were conducted in a three-electrode cell, using glassy carbon as the working electrode, Ag/AgCl as the reference electrode, and a Pt wire as the counter electrode. 1 mM solutions of the benzoate ligand, 0.6 mM of complex 1, and 0.7 mM of complex 2 were prepared in acetonitrile with 0.1 M TBAPF 6 as the supporting electrolyte. The 3,5-dinitrobenzoic acid ligand was studied in a potential window of -1.7 to 0 V. Two redox events were observed at potentials of -1.21 V and -0.79 V. Both events were quasi-reversible, with ΔE values of 88 mV and 53 mV, respectively. For complex 1, an exploratory window from -1.7 to 0 V was studied, and two quasi-reversible redox events were observed that appeared to coincide with those of the benzoate ligand. These events occurred at -1.24 V and -0.93 V. It is proposed that all these events are due to redox processes of the nitro groups present in the ligand, suggesting that cobalt may not be exhibiting redox activity. In contrast, complex 2 was studied in the potential window of 1 to 2.2 V, showing two irreversible oxidation events at around 1.73 V and 1.96 V. A decrease in peak current was observed over successive cycles, indicating a potential chemical process involving the oxidized species. To evaluate the stability of the species of interest, cyclic voltammetry over 20 cycles was performed It was observed that the 3,5-dinitrobenzoic acid ligand and its complex 1 presented more stable profiles, without significant changes in the peak currents or potentials. However, complex 2 exhibited instability because as the cycles pass, the current potentials decrease and the oxidation peaks disappear. Additionally, for the benzoate ligand and complex 1, cyclic voltammetries were carried out at different scanning speeds in order to obtain the diffusion coefficients of each species. In this order of ideas, both the 3,5-dinitrobenzoic acid ligand and complex 1 are the most suitable molecules to study their application in redox flow batteries. The benzoate ligand has the advantage of having a lower molecular weight, an important factor in energy density, but it has lower stability, while complex 1 has a higher molecular weight but provides greater stability. On the other hand, complex 2 does not present reversible redox events, which is why it is not applicable as an electrolyte in BFR. Figure 1
Influence of the Lewis basicity hardness of recrystallization solvents on the coordination sphere of the complex [Co(3,5-dinitrobenzoate-O,O′)2]
(2021) Andrés Felipe Pérez; Daniela Fonseca; John Jady Hurtado; Mario A. Macías
Coordination compounds are obtained by the reaction between Lewis acids (metal) and Lewis bases (ligand).According to Pearson's acid-base theory, also known as HSAB theory, the stability of the compound depends on the hardness of the acid and the base and their affinity.Hard bases tend to react with hard acids and soft bases prefer to react with soft acids.By just varying the hardness of the metal, the ligand or the solvent it is possible to substantially change the structure of the complex, giving a plethora of possibilities for the synthesis of different coordination compounds.This phenomenon was evidenced in coordination compounds of Cu (II) and Zn (II), where changing the ligand from 3,5-dinitrobenzoate to pyrazole derivatives affects the number of metallic centers present after crystallization 1 .Interested in these results we decided to study the effect of the recrystallization solvent on the coordination sphere of the complex [Co(3,5-dinitrobenzoate-O,O')2].Depending on the donor capabilities of the solvent, the complex undergoes a change on its coordination sphere, changing from a trinuclear Co (II) complex when the solvent is a soft base to mononuclear Co (II) complex when the solvent is a hard base.These structural changes are of great interest because materials and molecules that include cobalt in their structure have several spin states, which gives it interesting magnetic properties 2 .Figure 1.Effect of the solvent Lewis basicity on the chemical structure of the complex.
Syntheses, Characterization and Photophysical Properties of Phthalimide-Pyrazole Compounds: Effect of the Substituent in the Pirazole Ring on the Crystal Structures
(RELX Group (Netherlands), 2024) David Ezenarro-Salcedo; Daniela Fonseca; Paulo C. Piquini; Bernardo A. Iglesias; Mario A. Macías; John Hurtado