Navegando por Autor "Machado, Pedro Henrique"
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Item N–H–O and weak interactions stabilizing the schiff base/picrate multicomponent salt.(2023) Niquini Junior, Fabiano Mafia; Machado, Pedro Henrique; Montilla Suárez, Jerica Margely; Moura, Ana Luiza S.; Correa, Rodrigo de SouzaHere, a new picrate salt containing a protonated Schiff base (SB) is presented. The new compound presents a high melting point (246-250 °C), compared to base free (99-101 °C), such as expected for a salt. Also, UV-Vis and infrared experiments were carried out to in order to confirm the presence of both components, a protonated SB and the picrate anion. The single-crystal X-ray diffraction reveals the formation of the new compound, containing an ion pair in the asymmetric unit. The intramolecular interactions and, mainly, the intermolecular interactions were explored in detail. The salt presents strong N–H…O hydrogen bonds and π–π stacking interactions stabilize the crystal self-assembly, differing from neutral SB which presents only weak interactions. Finally, we investigate the fluorescence properties and capability coordination with metals by Jobs method of the SB, however, no significant results were observed.Item On the experimental and theoretical calculations of rotameric conformations of a new Schiff base derived from amantadine.(2022) Niquini Junior, Fabiano Mafia; Machado, Pedro Henrique; Rodrigues, Júlia Helena Valadares; Silva, Augusto Vieira Pontes; Figueiredo, Rute Cunha; Silveira, Rafael Gomes da; Correa, Rodrigo de SouzaHerein, the condensation of amantadine with the aldehyde piperonal resulted in a new Schiff base (1). This molecule was fully characterized by elementary analysis, infrared (IR), ultraviolet-visible (UV- Vis), 13C, 1H nuclear magnetic resonance (NMR) and high-resolution mass spectroscopy, logP (logarithm of partition coefficient), as well as single-crystal X-ray diffraction (SCXRD). The crystal structure crystal- lizes in the triclinic P1 ̄ space group with only one molecule of the Schiff base in the asymmetric unit, presenting the adamantane ring disordered over two positions. The crystal self-assembly is stabilized by weak interactions, such as analyzed by Hirshfeld surface. Using the DFT calculation, an energy barrier of 9.075 kcal.mol−1 was found between the two complementary conformations observed experimentally to the adamantane group. The computed infrared spectra (in vacuum and solution) are in good agree- ment with the experimental data. The energy of the HOMO orbitals was also calculated, in which en- ergy values range -7.4030–7.6027 eV, while LUMO orbitals are in the range of -0.3610–0.5717 eV, in which the polar solvents promoted greater stabilization in the border orbitals. The chemical potential (μ) from 3.467 to 3.520 eV indicate that the structure is stable. The magnitude of the chemical hardness (η) [6.934–7.041 eV] suggests the resistance to deformation of the electronic cloud over small electrostatic disturbances, showing that the system is not very polarizable. This result can be useful to further studies to investigate the coordination ability of compound 1 with hard metal ions.Item Synthesis, infrared and molecular structure of adamantane-1-ammonium picrate monohydrate : a derivative of the antiviral symmetrel.(2020) Niquini Junior, Fabiano Mafia; Moura, Ana Luiza S.; Machado, Pedro Henrique; Oliveira, Katia Mara de; Correa, Rodrigo de SouzaThe synthesis, infrared, and crystal structure investigations of adamantane-1-ammonium picrate monohydrate, (C10H21N)(C6H2N3O7) ⋅ H2O, were performed. The title compound crystallizes in the space group P21/n with the monoclinic unit cell parameters: a = 12.7211(9) Å, b = 6.8233(4) Å, c = 21.4130(14) Å and β = 105.950(7)°, V = 1787.1(2) Å3 , Z = 4. The asymmetric unit of the studied compound consists of one Adamantane-1-ammonium cation, one water and one picrate anion with two disordered nitro groups. The molecules are connected by strong H-bonds. As can be seen, the ionic pair is linked through two bifurcate N–H⋅⋅⋅O hydrogen bonds, identified as N1–H1A⋅⋅⋅O1 and N1–H1A⋅⋅⋅O2, to form a dimer. Also, water mol ecule acts bridging two picrate molecules connected by O1w–H1w⋅⋅⋅O1 and O1w–H2w⋅⋅⋅O4. These interac tions form an infinite chain extended along the [101] direction. Finally, the main intermolecular contacts were analyzed based on Hirshfeld surfaces and their fingerprint plot.