37 results on '"Felipe Medrano"'
Search Results
2. Crystal structure of 1,3-bis(1,3-dioxoisoindolin-1-yl)urea dihydrate: a urea-based anion receptor
- Author
-
Felipe Medrano, Sergio Lujano, Carolina Godoy-Alcántar, and Hugo Tlahuext
- Subjects
crystal structure ,isoindoline ,urea ,phthalimides ,protection of primary amines ,urea-based anion receptor ,Crystallography ,QD901-999 - Abstract
The whole molecule of the title compound, C17H10N4O5·2H2O, is generated by twofold rotation symmetry and it crystallized as a dihydrate. The planes of the phthalimide moieties and the urea unit are almost normal to one another, with a dihedral angle of 78.62 (9)°. In the crystal, molecules are linked by N—H...O and O—H...O hydrogen bonds, forming a three-dimensional framework structure. The crystal packing also features C—H...O hydrogen bonds and slipped parallel π–π interactions [centroid–centroid distance = 3.6746 (15) Å] involving the benzene rings of neighbouring phthalimide moieties.
- Published
- 2014
- Full Text
- View/download PDF
3. N-(2-Pyridylmethyl)phthalimide
- Author
-
Olga Garduño-Beltrán, Perla Román-Bravo, Felipe Medrano, and Hugo Tlahuext
- Subjects
Crystallography ,QD901-999 - Abstract
In the title compound, C14H10N2O2, the phtalimide and 2-pyridylmethyl units are almost perpendicular, with an interplanar angle of 85.74 (2)°. In the crystal, molecules are linked by weak C—H...O interactions, forming chains running along the b axis. The packing is further stabilized by offset π–π interactions between adjacent pyridine rings, with a centroid–centroid distance of 3.855 (2) Å.
- Published
- 2009
- Full Text
- View/download PDF
4. Synthesis and Protonation Constants of an Amide-Based Chelating Cyclophane
- Author
-
Julio Cesar Altamirano-Coronado, Carolina Godoy-Alcántar, and Felipe Medrano
- Subjects
Cyclophane ,potentiometry ,protonation ,amine ,anhydride ,condensation ,Inorganic chemistry ,QD146-197 - Abstract
n/a
- Published
- 2006
- Full Text
- View/download PDF
5. Analysis of the relative stability of trigonal and tetrahedral boronate cyclic esters in terms of boronic acid and diol acidities and the strain release effect
- Author
-
Mayte A. Martínez‐Aguirre, Felipe Medrano, Sandra Ramírez‐Rave, and Anatoly K. Yatsimirsky
- Subjects
Organic Chemistry ,Physical and Theoretical Chemistry - Published
- 2022
- Full Text
- View/download PDF
6. Examination of pinanediol–boronic acid ester formation in aqueous media: relevance to the relative stability of trigonal and tetrahedral boronate esters
- Author
-
Anatoly K. Yatsimirsky, Felipe Medrano, Marcos Flores-Alamo, and Mayte A. Martínez-Aguirre
- Subjects
Aqueous solution ,Organic Chemistry ,Potentiometric titration ,Diol ,Chromotropic acid ,Biochemistry ,Medicinal chemistry ,chemistry.chemical_compound ,chemistry ,Electronic effect ,Titration ,Physical and Theoretical Chemistry ,Acetonitrile ,Boronic acid - Abstract
The interaction of pinanediol with 2-fluorophenylboronic acid and several other substituted phenylboronic acids was studied in 40% vol. aqueous acetonitrile by 1H and 11B NMR, potentiometric and spectrophotometric titrations at variable pH values. The experimental results reveal the formation of a very stable trigonal ester (Ktrig ≈ 2 × 104 M-1) and a significantly less stable tetrahedral hydroxocomplex (Ktet ≈ 5 × 103 M-1) in contrast to the traditionally observed inverted order of stabilities KtrigKtet. Comparison of the crystal structure of the trigonal ester isolated from aqueous acetonitrile with the DFT simulated structure of the respective hydroxocomplex shows that an unusual order of stabilities KtrigKtet is observed in spite of the existence of the usual strain release effect in the O-B-O angle considered responsible for the typically observed increased stability of the tetrahedral hydroxocomplex. A complementary study of the stability of the six-membered cyclic boronate esters of chromotropic acid demonstrated the order Ktrig ≪ Ktet although the strain was absent in these esters. The results for m-, p-substituted phenylboronic acids show that the stability of both five- and six-membered trigonal esters formed with pinanediol and chromotropic acid, respectively, is insensitive to electronic effects but the electron accepting substituents stabilize the hydroxocomplexes. It follows from the whole set of results that Ktet can be much larger than Ktrig in the absence of the strain, but with a sufficiently acidic diol, and that the presence of the strain does not necessarily make Ktet larger than Ktrig for a less acidic diol with a purely saturated hydrocarbon backbone. Thus, the electronic effects manifested in the acidity of the diol appear to be more significant than the strain release effect in determining the Ktet/Ktrig ratio.
- Published
- 2020
- Full Text
- View/download PDF
7. Metallobacitracins: Affinity and structural study in aqueous solution
- Author
-
Carolina Godoy-Alcántar, Blanca Eda Domínguez-Mendoza, Nadia Alejandra Rodríguez-Uribe, Felipe Medrano, and Refugio Pérez-González
- Subjects
Isothermal microcalorimetry ,Circular dichroism ,Aqueous solution ,Chemistry ,02 engineering and technology ,Calorimetry ,Nuclear magnetic resonance spectroscopy ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,Metal ,visual_art ,Materials Chemistry ,visual_art.visual_art_medium ,Titration ,Physical and Theoretical Chemistry ,0210 nano-technology ,Stoichiometry ,Nuclear chemistry - Abstract
Metallobacitracins are complexes with an extensive antimicrobial and biological activity. In this work, we investigated the metal complexation of bacitracin with several divalent metal ions in aqueous solution. The binding constants of Zn(2+), Cd(2+), Hg(2+), Cu(2+), Ni(2+), Pd(2+), Fe(2+), Mn(2+) and Mg(2+) to bacitracin were measured by UV/Vis spectroscopy, isotermic titration calorimetry (ITC) and potentiometry while the complexes were studied by Circular Dichroism and Nuclear Magnetic Resonance (15N HSQC) for Zn(2+), Cd(2+) and Hg(2+) at different pH. By UV/Vis spectroscopy the affinity is in the range 104 to 105 M−1 at pH 6 and follows the order Ni(2+) > Cd(2+) > Hg(2+) > Zn(2+) > Fe(2+). By potentiometry, the binding constants were determined in the pH range 2–12. Microcalorimetry shows that the stoichiometry of metallobacitracins investigated is 1:1 with binding constants in the range 105–102 M−1 at pH 6 and with an order of stability of Ni(2+) > Cd(2+) > Zn(2+) > Hg(2+); ΔS, ΔH and ΔG parameters were also determined. NMR spectroscopy lets us establish the binding site of the metal ion when comparing 15N HSQC of free bacitracin and complex in natural abundance; these findings agree with calorimetric results. Chemical shift changes in complexes containing Zn(2+) and Cd(2+) exhibit a similar behavior despite pH differences. Conversely, there is not a significant change for Hg(2+) complex. The obtained data contribute to understand the mechanism of the biological activity of the metallobacitracins and give the guideline for the design of more powerful metalloantibiotics.
- Published
- 2019
- Full Text
- View/download PDF
8. Anion-assisted self-assembly of chlorodiorganotin(IV) dithiocarbamate derived from naphthylimide
- Author
-
Felipe Medrano, Karla Isabel Rivera-Márquez, Refugio Pérez-González, Nadia Alejandra Rodríguez-Uribe, Hugo Tlahuext, Carolina Godoy-Alcántar, and Miguel Ángel Claudio-Catalán
- Subjects
chemistry.chemical_classification ,010405 organic chemistry ,Chemistry ,Ligand ,Nuclear magnetic resonance spectroscopy ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,Crystallography ,Covalent bond ,Intramolecular force ,Materials Chemistry ,Titration ,Physical and Theoretical Chemistry ,Dithiocarbamate ,Anion binding ,Single crystal - Abstract
Two new chlorodiorganotin(IV) dithiocarbamate complexes with general formula {(R2SnCl)dtc} (dtc = R1R2NCS2−, R1 = Bn, R2 = naphtylimide; 3, R = n-Bu; 4, R = Ph) have been prepared from sodium N-[2-(benzylamino)ethyl]naphthalene-1,8-dicarboximide dithiocarbamate 2. The bis-dithiocarbamete 3d (R2Sn(dtc)2, R = n-Bu) was obtained as the thermodynamic product during the titration process (vide infra). All compounds were characterized by mass spectrometry, IR, 1H and 13C NMR spectroscopy. The chlorodiorganotin(IV) dithiocarbamate complexes 3–4 also were characterized by 119Sn NMR spectroscopy and single crystal X-ray diffraction analysis. The crystallographic study of these complexes showed the existence of C H…π, S…π and π…π intramolecular interactions, indicating that the naphthylimide aromatic fragment stabilized the complexes. Complexes 3 and 4 were studied as host for anions (CH3CO2−, F−, H2PO4−) in CDCl3 by UV–Vis and 119Sn NMR spectrometric titrations. The tested anions cause the displacement of the chloride ligand of the metallic centre. The excess of F− or H2PO4− induce the self-assembly of diorganotin(IV) dithiocarbamate to bis-dithiocarbamates R2Sn(dtc)2 (3d) instead of the breaking of the S Sn covalent bond. Quantum mechanical calculations at DFT level (B3LYP/def2-TZVP) were performed to obtain the thermodynamic parameters of the reactions involved in the anion addition to the complexes.
- Published
- 2018
- Full Text
- View/download PDF
9. Phase relations in the pseudobinary systems RAO3-R2Ti2O7 (R: rare earth element and Y, A: Fe, Ga, Al, Cr and Mn) and syntheses of new compounds R(A1−xTix)O3+x/2 (2/3≤x≤3/4) at elevated temperatures in air
- Author
-
V.E. Alvarez-Montaño, Shigeo Mori, Yuichi Michiue, Felipe Medrano, Noboru Kimizuka, Keiji Kurashina, Naoshi Ikeda, Yoji Matsuo, Ivan Edmundo Jacobo-Herrera, and F. Brown
- Subjects
010302 applied physics ,Quenching ,Materials science ,Metallurgy ,02 engineering and technology ,Crystal structure ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Inorganic Chemistry ,Crystal ,Crystallography ,Lattice constant ,Octahedron ,Phase (matter) ,0103 physical sciences ,Materials Chemistry ,Ceramics and Composites ,Physical and Theoretical Chemistry ,0210 nano-technology ,Powder diffraction ,Monoclinic crystal system - Abstract
Phase relations in the pseudo-binary systems RFeO 3 -R 2 Ti 2 O 7 (R: Lu, Ho and Dy), RGaO 3 -R 2 Ti 2 O 7 (R: Lu and Er), LuAlO 3 -Lu 2 Ti 2 O 7 and RAO 3 -R 2 Ti 2 O 7 (R: Lu and Yb. A: Cr and Mn) at elevated temperatures in air were determined by means of a classic quenching method. There exist Lu(Fe 1−x Ti x )O 3+x/2 , R(Ga 1−x Ti x )O 3+x/2 (R: Lu and Er) and Lu(Al 1−x Ti x )O 3+x/2 (2/3≤ x≤3/4) having the Yb(Fe 1−x Ti x )O 3+x/2 -type of crystal structure (x=0.72, space group: R 3 m , a(A)=17.9773 and c(A)=16.978 as a hexagonal setting) in these pseudo binary systems. Eighteen compounds R(A 1−x Ti x )O 3+x/2 (R: Lu-Sm and Y, A: Fe, Ga and Al) were newly synthesized and their lattice constants as a hexagonal setting were measured by means of the X-ray powder diffraction method. The R occupies the octahedral site and both A and Ti does the trigonalbipyramidal one in these compounds. Relation between lattice constants for the rhombic R(A 1−x Ti x )O 3+x/2 and the monoclinic In(A 1−x Ti x )O 3+x/2 are as follows, a h ≈5 x b m , c h ≈3 x c m x sin β and a m =3 1/2 x b m , where a h and c h are the lattice constants as a hexagonal setting for R(A 1−x Ti x )O 3+x/2 and a m , b m , c m and β are those of the monoclinic In(A 1−x Ti x )O 3+x/2 . Crystal structural relationships among α-InGaO 3 (hexagonal, high pressure form, space group: P 63/ mmc ), InGaO 3 (rhombic, hypothetical), (RAO 3 ) n (BO) m and RAO 3 (ZnO) m (R: Lu-Ho, Y and In, A: Fe, Ga, and Al, B: divalent cation element, m, n: natural number), the orthorhombic-and monoclinic In(A 1−x Ti x )O 3+x/2 (A: Fe, Ga, Al, Cr and Mn) and the hexagonal-and rhombic R(A 1−x Ti x )O 3+x/2 (R: Lu-Sm and Y, A: Fe, Ga and Al) are schematically presented. We concluded that the crystal structures of both the α-InGaO 3 (high pressure form, hexagonal, space group: P 63/ mmc ) and the hypothetical InGaO 3 (rhombic) are the key structures for constructing the crystal structures of these compounds having the cations with CN=5.
- Published
- 2017
- Full Text
- View/download PDF
10. Interaction of aromatic compounds and anions with naphthylimide-dansylamide fluorescent dyad: Experimental evidence of aryl C-H…π and aryl C-H…anion contacts and DFT calculations
- Author
-
Hugo Tlahuext, Nadia Alejandra Rodríguez-Uribe, Felipe Medrano, Miguel Ángel Claudio-Catalán, and Carolina Godoy-Alcántar
- Subjects
19f nmr spectroscopy ,Aryl ,Halide ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Medicinal chemistry ,Fluorescence ,Electron spectroscopy ,Quantum chemistry ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Analytical Chemistry ,Ion ,chemistry.chemical_compound ,chemistry ,Density functional theory ,0210 nano-technology ,Instrumentation ,Spectroscopy - Abstract
In this work the interaction of halide anions and simple aromatic compounds with a bichromophoric fluorescent dyad derived from 1,8-naphthalimide (NAPIM) and 5-(dimethylamino)naphthalene-1-sulfonyl (DANS) was studied using electronic spectroscopy, 1H, and 19F NMR spectroscopy and quantum chemistry modeling (b3lyp/def2-TZVP). The NAPIM-DANS dyad interacts with electron-rich guests with binding constants in the range of 6 × 103 to 8 × 103 M−1 in CHCl3. The formed complexes are stabilized through aryl C–H … anion and aryl C–H … π interactions.
- Published
- 2019
11. Crystal structure of N,N′-bis[2-((benzyl){[5-(dimethylamino)naphthalen-1-yl]sulfonyl}amino)ethyl]naphthalene-1,8:4,5-tetracarboximide 1,2-dichlorobenzene trisolvate
- Author
-
Hugo Tlahuext, Carolina Godoy-Alcántar, Miguel Ángel Claudio-Catalán, and Felipe Medrano
- Subjects
crystal structure ,C—H...π and π–π interactions ,Stereochemistry ,Crystal structure ,Dihedral angle ,010402 general chemistry ,Ring (chemistry) ,naphthalenediimide ,01 natural sciences ,Research Communications ,chemistry.chemical_compound ,naphthalenediimide ,Moiety ,General Materials Science ,Naphthalene ,Sulfonyl ,chemistry.chemical_classification ,Crystallography ,dansyl amide ,010405 organic chemistry ,Hydrogen bond ,General Chemistry ,Condensed Matter Physics ,C—H⋯π and π–π interactions ,0104 chemical sciences ,chemistry ,QD901-999 ,C—H⋯O ,Dansyl amide ,C—H...O - Abstract
In the structure of the title compound, cooperative C—H⋯O=C, C—H⋯π and offset π–π interactions generate supramolecular nanotubes which accommodate the 2,3-dichlorobenzene solvent molecules., The asymmetric unit of the title compound, C56H50N6O8S2·3C6H4Cl2, contains two half-molecules of the parent, A and B, which both have crystallographic inversion symmetry, together with three 2,3-dichlorobenzene molecules of solvation. Molecules A and B are conformationally similar, with dihedral angles between the central naphthalenediimide ring and the peripheral naphthalene and benzyl rings of 2.43 (7), 81.87 (7)° (A) and 3.95 (7), 84.88 (7)° (B), respectively. The conformations are stabilized by the presence of intramolecular π–π interactions between the naphthalene ring and the six-membered diimide ring of the central naphthalenediimide moiety, with ring centroid-to-centroid distances of 3.5795 (8) Å (A) and 3.5640 (8) Å (B). In the crystal, C—H⋯O hydrogen bonds link the molecules into infinite supramolecular chains along the c axis. These chains are interconnected through C—H⋯π and offset π–π interactions, generating supramolecular nanotubes which are filled by 1,2-dichlorobenzene molecules.
- Published
- 2016
12. Chlorodiphenyltin(IV) dithiocarbamate complexes as chemodosimeters and host for anions and neutral compounds in solution
- Author
-
Felipe Medrano, Hugo Tlahuext, Jorge Guerrero-Álvarez, Ámbar Yuricsi Castrejón-Antúnez, Carolina Godoy-Alcántar, Miriam Mendoza-Mendoza, Gabriela Vargas-Pineda, and Diana Iris Olea-López
- Subjects
chemistry.chemical_classification ,Chloroform ,010405 organic chemistry ,Inorganic chemistry ,Nuclear magnetic resonance spectroscopy ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences ,Inorganic Chemistry ,Solvent ,chemistry.chemical_compound ,chemistry ,Materials Chemistry ,Titration ,Physical and Theoretical Chemistry ,Methylene ,Acetonitrile ,Anion binding ,Dithiocarbamate - Abstract
The chlorodiphenyltin(IV) dithiocarbamate complexes 1–5 with general formula {(Ph2SnCl)dtc} (dtc = R1R2NCS2−; 1, R1 = Bn, R2 = 9-anthrylmethyl; 2, R1 = Bn, R2 = 9-phenanthrylmethyl; 3, R1 = Bn, R2 = 1-pyrenylmethyl; 4, R1 = 1-naphthylmethyl, R2 = 1-pyrenylmethyl; 5, R1 = R2 1-pyrenylmethyl) have been tested as host for anions and neutral amines in acetonitrile by spectrophotometric UV/Vis titrations. In addition, the titrations of the complexes 1 and 5 were studied in chloroform by 1H and 119Sn NMR spectroscopy. It was found that anions as acetate, benzoate, and dihydrogen phosphate cause a displacement of the dithiocarbamate ligands of metallic center independently of the aromatic nature of the substituents on the nitrogen atom functioning as chemodosimeters in which the indicator is displaced. However, some aliphatic amines and aromatic methylene amines and its aromatic analogs can act as guests with binding constants in the range of 103 to 106 M−1. Also, in these cases compound 5 functions as chemodosimeter without displacement of the indicator. According to 1H, 13C, 119Sn NMR data and using DFT (B3LYP) and Poisson–Boltzmann (PB) to model the solvent, structures of the complexes are proposed in which the hydrophobic and π–π interactions are suggested as the dominant interactions.
- Published
- 2016
- Full Text
- View/download PDF
13. Anion interaction with homoditopic chlorodiorganotin(IV) dithiocarbamate complexes derived from a naphthalene diimide. A pathway to obtain metallomacrocycles
- Author
-
Nadia Alejandra Rodríguez-Uribe, Georgina Pina Luis, Felipe Medrano, Miguel Ángel Claudio-Catalán, Hugo Tlahuext, and Carolina Godoy-Alcántar
- Subjects
chemistry.chemical_classification ,010405 organic chemistry ,Ligand ,chemistry.chemical_element ,Nuclear magnetic resonance spectroscopy ,Crystal structure ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,Crystallography ,chemistry ,Intramolecular force ,Materials Chemistry ,Titration ,Physical and Theoretical Chemistry ,Tin ,Dithiocarbamate ,Coordination geometry - Abstract
Four new homoditopic bis[chlorodiorganotin(IV) and triorganotin(IV) dithiocarbamate] complexes derived from naphthalene diimide (NDI) with general formula NDI-[(CH2)2-N(CH2Ph)(CS2SnR2X)]2, 3: R = n-Bu, X = Cl; 4: R = Me, X = Cl; 5: R = Ph, X = Cl; 6: R = X = Me; were prepared from triethylammonium ((1,3,6,8-tetraoxo-1,3,6,8-tetrahydrobenzo[lmn][3,8]phenanthroline-2,7-diyl)bis(ethane-2,1-diyl))bis(benzylcarbamodithioate) 2. All compounds were characterized by IR, as well as 1H and 13C NMR spectroscopy. The complexes 3–6 also were characterized by 119Sn NMR spectroscopy. In addition, complex 3 was further characterized by single-crystal X-ray diffraction analysis. The crystallographic study performed on complex 3 showed that the tin atom has a coordination geometry intermediate between square-pyramid and a trigonal-bipyramidal, with τ value of 0.69. In addition the presence of cooperative C H…π, C H…S, C H…O and S…π intramolecular interactions in the crystal structure of 3 was observed. The interaction of complexes 3–6 with anions (CH3CO2−, F−, H2PO4−) in CDCl3 was studied by UV/Vis, fluorescence and 119Sn NMR titrations. The addition of the foregoing anions to complexes 3-6 lead to the displacement of the chloride ligand at the tin(IV) atom. However, an the excess of F− or H2PO4− induced the self-assembly of complexes 3 and 5 in their corresponding binuclear metallomacrocycles.
- Published
- 2020
- Full Text
- View/download PDF
14. Kanamycin A: imine formation in aqueous solution
- Author
-
Carolina Godoy-Alcántar, Felipe Medrano, Alexander Dikiy, and Yanet Fuentes-Martínez
- Subjects
chemistry.chemical_classification ,Aqueous solution ,Organic Chemistry ,Imine ,Kanamycin ,Nuclear magnetic resonance spectroscopy ,Aldehyde ,chemistry.chemical_compound ,chemistry ,Furan ,Polymer chemistry ,medicine ,Proton NMR ,Organic chemistry ,Physical and Theoretical Chemistry ,Pyridoxal ,medicine.drug - Abstract
Imine formation in aqueous solution of kanamycin A with pyridoxal 5'-phosphate and other aldehydes was studied by potentiometry, NMR spectroscopy and computational chemistry. It was found that imines are formed with yields near 100 % at pH 7 in equimolar reactant ratio. In order to identify the kanamycin amino groups involved in the reaction, a NMR spectroscopic study was conducted. The structures of possible imines formed between kanamycin and FURAN or PLP were optimized by molecular mechanics with the OPLS-2005 force field. The 1H NMR spectra were calculated at the DFT-GIAO B3LYP/6-31G(d) level of theory for all structures and compared with the experimentally observed spectra. From these results a probable structure of the imines was proposed. The results obtained in this work show that kanamycin has the ability to form imine derivatives in high yields due to its anion recognition properties. Copyright © 2012 John Wiley & Sons, Ltd.
- Published
- 2012
- Full Text
- View/download PDF
15. Synthesis, Spectroscopic Characterization, DFT Calculations, and Dynamic Behavior of Mononuclear Macrocyclic Diorganotin(IV) Bis-Dithiocarbamate Complexes
- Author
-
JORGE ANTONIO GUERRERO ALVAREZ, Adrian Tlahuext-Aca, Viviana Reyes-Márquez, Felipe Medrano, Hugo Tlahuext, Herbert Höpfl, Karen Ochoa Lara, and Margarita Tlahuextl
- Subjects
Quantum chemical ,chemistry.chemical_classification ,Chemistry ,Stereochemistry ,chemistry.chemical_element ,Mass spectrometry ,Characterization (materials science) ,Inorganic Chemistry ,NMR spectra database ,Crystallography ,Elemental analysis ,Self-assembly ,Dithiocarbamate ,Tin - Abstract
Nine mononuclear diorganotin(IV) dithiocarbamate complexes 1–9 with 19-, 20- and 21-membered macrocyclic structures were synthesized from dimethyl, di-n-butyl, and diphenyltin(IV) dichloride and three bis-dithiocarbamate ligands derived from secondary bis-amines having aromatic spacer groups. All compounds were characterized by elemental analysis, mass spectrometry, and spectroscopic methods (IR and 1H, 13C, and 119Sn NMR). Additionally, quantum chemical DFT calculations were performed for the dimethyltin(IV) derivatives in order to model the molecular structures. For one compound series the NMR spectra showed a concentration-dependent behavior in solution, which was analyzed in detail and permitted to postulate the existence of an equilibrium with the corresponding [2+2] macrocycles.
- Published
- 2012
- Full Text
- View/download PDF
16. Effect of weak sulfur…C(π) interactions, and hydrogen bonds in supramolecular association of chlorodiphenyltin(IV) dithiocarbamate complexes: Study of their stability in solution
- Author
-
Perla Román-Bravo, Adrian Tlahuext-Aca, Carolina Godoy-Alcántar, Felipe Medrano, and Hugo Tlahuext
- Subjects
chemistry.chemical_classification ,Chemistry ,Hydrogen bond ,Inorganic chemistry ,Supramolecular chemistry ,Crystal structure ,Medicinal chemistry ,Inorganic Chemistry ,chemistry.chemical_compound ,Materials Chemistry ,Amine gas treating ,Physical and Theoretical Chemistry ,Acetonitrile ,Dithiocarbamate ,Anion binding ,Coordination geometry - Abstract
Five new chlorodiorganotin(IV) complexes derived from dithiocarbamate ligands have been prepared and structurally characterized. The complexes 1–5 with the general formula {(Ph2SnCl)dtc} (dtc = R1R2NCS2−; 1, R1 = Bn, R2 = 9-anthrylmethyl; 2, R1 = Bn, R2 = 9-phenanthrylmethyl; 3, R1 = Bn, R2 = 1-pyrenylmethyl; 4, R1 = 1-naphthylmethyl, R2 = 1-pyrenylmethyl; 5, R1 = R2 = 1-pyrenylmethyl) have been obtained from Ph2SnCl2 and the sodium dithiocarbamate salts of benzyl(9-anthrylmethyl)amine, benzyl(9-phenanthrylmethyl)amine, benzyl(1-pyrenylmethyl)amine, 1-naphthylmethyl(1-pyrenylmethyl)amine and di(1-pyrenylmethyl)amine. Compounds 1–5 have been analyzed as far as possible by elemental analysis, FAB+ mass spectrometry, IR, UV–Vis, fluorescence and NMR (1H, 13C, 119Sn) spectroscopy, and single-crystal X-ray diffraction analysis (1–3). The solid-state and solution studies showed that the dtc ligands are coordinated to the tin atoms in the anisobidentate manner. In all cases the metal centers are five-coordinate. The coordination geometry is intermediate between square-pyramidal and trigonal-bipyramidal coordination polyhedra with τ-values in the range of 0.49–0.55. The crystal structures show the presence of C–H···Cl, C–H···S, C–H···π, offset π–π and S···π contacts. The stability of the (Ph2SnCl)dtc complexes in the presence of the acetate anion has been examined in acetonitrile solutions. For all of these organotin(IV) complexes the displacement of the coordinated ligands (i.e., chloride and dtc) by the acetate anion was observed. The lability, as well as their intrinsic fluorescent properties of the polyaromatic moieties in these (Ph2SnCl)dtc compounds make them interesting candidates to detect the presence of O-donor anions at very low concentrations by displacement of the metal-coordinated dtc.
- Published
- 2012
- Full Text
- View/download PDF
17. Fluorescence and conformation in water-soluble bis(pyrenyl amide) receptors derived from polyaminopolycarboxylic acids
- Author
-
Lorena Machi, Motomichi Inoue, Felipe Medrano, Mario Sánchez, and Refugio Pérez-González
- Subjects
Hydrogen bond ,Chemistry ,General Chemical Engineering ,General Physics and Astronomy ,Protonation ,General Chemistry ,Photochemistry ,Excimer ,chemistry.chemical_compound ,Deprotonation ,Amide ,Polymer chemistry ,Proton NMR ,Pyrene ,Amine gas treating - Abstract
Fluorescent responses and conformational changes against pH were studied on four new water-soluble 1-pyrene and 1-methylpyrene bichromophores, (ttha1py)H4, (edta1mpy)H2, (dtpa1mpy)H3 and (ttha1mpy)H4, with the objective of modifying pH–fluorescence profiles and other solution properties of 1-pyrene bichromophores, (edta1py)H2 and (dtpa1py)H3, developed previously by our group; the abbreviations with acidic protons stand for pyrenyl moieties interlinked by an EDTA, DTPA (diethylenetriaminepentacetic acid) or TTHA (triethylenetetraminehexaacetic acid) chain through amide linkages. The new derivatives exhibit emission bands of monomeric pyrene and an intense structureless excimer band; the latter responds to pH sensitively. The pH dependence of the emission intensity of the DTPA and TTHA derivatives is well correlated with species distribution determined by potentiometry. In every derivative, the completely deprotonated species Ln− is the most efficient for excimer emission, followed by the corresponding monoprotonated species LH(n−1)−. In the latter, the acidic hydrogen is located on the central amine, as confirmed by 1H NMR. The resulting hydrogen bond between amino nitrogen atoms makes the aliphatic chain rigid. Further protonation stretches the interlinking chain due to electrostatic repulsion. These conformational changes with protonation result in fluorescent on–off cycles against pH window. The switching cycles of the methylpyrene derivatives are reverse to those of the corresponding pyrene derivatives, as the CH2 spacer between the amide and aromatic groups defines the orientation of pyrene rings. The sensitiveness of amide group to environment leads to a sharp change in excimer emission above pH ∼11. The combined functions of amide and amino groups lead to the novel pH-responses.
- Published
- 2011
- Full Text
- View/download PDF
18. Crystal structure of 1,3-bis(1,3-dioxoisoindolin-1-yl)urea dihydrate: a urea-based anion receptor
- Author
-
Sergio Lujano, Hugo Tlahuext, Felipe Medrano, and Carolina Godoy-Alcántar
- Subjects
crystal structure ,Crystallography ,Hydrogen bond ,isoindoline ,General Chemistry ,Isoindoline ,Crystal structure ,urea ,Dihedral angle ,protection of primary amines ,Condensed Matter Physics ,Research Communications ,Phthalimide ,Crystal ,chemistry.chemical_compound ,chemistry ,QD901-999 ,phthalimides ,Urea ,General Materials Science ,Benzene ,urea-based anion receptor - Abstract
The title compound possesses twofold rotation symmetry, with the planes of the phthalimide moieties inclined to one another by 73.53 (7)° and by 78.62 (9)° to that of the urea unit. In the crystal, molecules are linked via N—H⋯O and O—H⋯O hydrogen bonds, forming a three-dimensional framework structure., The whole molecule of the title compound, C17H10N4O5·2H2O, is generated by twofold rotation symmetry and it crystallized as a dihydrate. The planes of the phthalimide moieties and the urea unit are almost normal to one another, with a dihedral angle of 78.62 (9)°. In the crystal, molecules are linked by N—H⋯O and O—H⋯O hydrogen bonds, forming a three-dimensional framework structure. The crystal packing also features C—H⋯O hydrogen bonds and slipped parallel π–π interactions [centroid–centroid distance = 3.6746 (15) Å] involving the benzene rings of neighbouring phthalimide moieties.
- Published
- 2014
19. Nucleotide recognition by protonated aminoglycosides
- Author
-
Alexander Dikiy, Felipe Medrano, Yanet Fuentes-Martínez, Anatoly K. Yatsimirsky, and Carolina Godoy-Alcántar
- Subjects
chemistry.chemical_classification ,GTP' ,Stereochemistry ,Potentiometric titration ,Protonation ,Kanamycin ,General Chemistry ,biochemical phenomena, metabolism, and nutrition ,Binding constant ,Nucleobase ,Molecular recognition ,chemistry ,medicine ,Nucleotide ,medicine.drug - Abstract
Interactions of protonated forms of kanamycin A with nucleotides and several simple phosphate anions have been studied by potentiometric and NMR titrations. The affinity of kanamycin A to anions is comparable to that observed with other aliphatic polyammonium receptors of similar charge, but it discriminates triphosphate nucleotides with different nucleobases with binding constants following the order GTP≫CTP ≈ ATP. Kanamycin A also binds the respective uncharged nucleosides with the same selectivity. Binding of ATP is exothermic with a negative entropic contribution in contrast to what is expected for simple ion pairing. Other tested aminoglycosides, amikacin and streptomycin, bind ATP less efficiently than kanamycin A. Models of structures of kanamycin A complexes with ATP and GTP obtained by molecular mechanics (OPLS-2005) calculations based on 1H and 31P NMR data confirm the possibility of nucleotide discrimination by simultaneous ion pairing of terminal nucleotide phosphate groups with ammonium sites...
- Published
- 2010
- Full Text
- View/download PDF
20. Affinity and enantioselectivity of Rifamycin SV towards low molecular weight compounds
- Author
-
Carolina Godoy-Alcantar, Anatoly Yatsimirsky, and Felipe Medrano
- Subjects
chemistry.chemical_classification ,Stereochemistry ,Stacking ,General Chemistry ,Condensed Matter Physics ,Binding constant ,Amino acid ,Hydrophobic effect ,chemistry.chemical_compound ,chemistry ,polycyclic compounds ,Aromatic amino acids ,Proton NMR ,Molecule ,HOMO/LUMO ,Food Science - Abstract
Association of amino acids and some other low molecular weight compounds with rifamycin SV in water has been studied by 1H NMR titrations. Rifamycin binds aromatic amino acids with pronounced enantioselectivity in favor of l-enantiomers and forms complexes with heterocyclic compounds but does not interact with simple benzene derivatives. Binding constants correlate with LUMO energies and hydrophobicities (expressed as log P values) of guest molecules indicating contributions to the binding free energy from aromatic stacking interactions with the naphthohydroquinone fragment of rifamycin SV and from hydrophobic interactions. Proposed mode of binding is supported by semiempirical calculations of structures of host–guest complexes.
- Published
- 2009
- Full Text
- View/download PDF
21. Molecular Recognition of Thymine and Uracil in Water by an Amino-, Amido-, and Carboxymethyl-functionalized Pyridinophane
- Author
-
Felipe Medrano, Herbert Höpfl, Dr. David Octavio Corona-Martínez, and Carolina Godoy-Alcantar
- Subjects
chemistry.chemical_compound ,Molecular recognition ,Hydrogen bond ,Chemistry ,Amide ,Potentiometric titration ,Polymer chemistry ,Proton NMR ,Organic chemistry ,Uracil ,General Chemistry ,Nucleobase ,Thymine - Abstract
A new water soluble 26-membered macrocyclic pyridinophane functionalized by amide and carboxymethyl groups has been synthesized in a single step reaction and characterized by elemental analysis, mass spectrometry (FAB+), UV-vis, fluorescence, and 1H NMR spectroscopy as well as single-crystal X-ray diffraction analysis. Its complexation properties with the nucleobases thymine and uracil have been explored in aqueous media by performing 1H NMR titration experiments and potentiometric studies. The binding constants of the 1:1 host-guest complexes were determined as 103 M− 1 by proton NMR and 102–103 M− 1 by potentiometry. Semiempirical molecular modelling studies have shown that the nucleobases are included within the cavity of the macrocyclic receptor and that the complexes are stabilized by hydrogen bonding.
- Published
- 2007
- Full Text
- View/download PDF
22. Streptomycin hydrazone derivatives: synthesis and molecular recognition in aqueous solution
- Author
-
Juan P, Fuentes-Martineza, Diana, Gutiérrez-Rodrigueza, Edgar Rogel, Garcia, Karla I, Rivera-Mirqueza, Felipe, Medrano, Oscar, Torres-Ángeles, Evelin, Castillo-Vargas, Blanca E, Duque Montaño, and Carolina, Godoy-Alcántar
- Subjects
Magnetic Resonance Spectroscopy ,Hydrazones ,Streptomycin - Abstract
Five hydrazone derivatives of streptomycin were synthetized (D0h, D1ph, D2bt, D3dctf, D4ag) and characterized by IR, 1H and 13C NMR spectroscopy, mass spectrometry and elemental analysis. Protonation constants were determined by potentiometry for all derivatives. D1ph and D2bt derivatives were investigated as receptors of dicarboxylates and adenine nucleotides in aqueous solution by potentiometric and 1H NMR titrations. D1ph and D2bt derivatives have the highest affinity with AMP and ATP, respectively, which shows that electrostatic forces are not always the dominant factor in binding of streptomycin derivatives with nucleotides, but the conformational fit between them. Calculated structures at the DFT level of the D1ph derivative bonded with either AMP or ADP showed that the complexes are stabilized by the formation of multiple interactions with the receptors. The antibiotic activity of the derivatives was explored and compared with native streptomycin.
- Published
- 2014
23. Isolation and characterization of luminescent bicyclic boronates based on furan ring-opening reactions from 5-formyl-2-furanboronic acid
- Author
-
Victoria E. González, Felipe Medrano, Victor Barba, Mario Rodríguez, Pascal G. Lacroix, Centro de Investigaciones Químicas [Morelos] (CIQ / UAEM), Universidad Autonoma del Estado de Morelos (UAEM), Centro de Investigaciones en Optica (CIO), Consejo Nacional de Ciencia y Tecnología [Mexico] (CONACYT), Laboratoire de chimie de coordination (LCC), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Bicyclic molecule ,010405 organic chemistry ,Organic Chemistry ,Solvatochromism ,010402 general chemistry ,Ring (chemistry) ,01 natural sciences ,Biochemistry ,Combinatorial chemistry ,Fluorescence ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Furan ,Drug Discovery ,Organic chemistry ,[CHIM.COOR]Chemical Sciences/Coordination chemistry ,Luminescence ,Boronic acid - Abstract
International audience; A new family of luminescent boronates was prepared from reaction of 5-formyl-2-furanboronic acid with 2-aminophenol derivatives. The furan ring-opening was favored by the presence of the boronic acid group. Evaluation of the photophysical characteristics for all compounds showed significant solvatochromic, fluorescent, and NLO properties. (C) 2014 Elsevier Ltd. All rights reserved.
- Published
- 2014
- Full Text
- View/download PDF
24. Luminescence and non-linear optical properties of erbium-tetraphenylporphyrin complexes incorporated within a silica matrix by a sol–gel process
- Author
-
Amy Y. Clark, V. Terpugov, Felipe Medrano, M. Cervantes, and D Soto
- Subjects
Silica gel ,Organic Chemistry ,Doping ,Analytical chemistry ,chemistry.chemical_element ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Inorganic Chemistry ,Erbium ,chemistry.chemical_compound ,chemistry ,visual_art ,Tetraphenylporphyrin ,visual_art.visual_art_medium ,Molecule ,Ceramic ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,Luminescence ,Spectroscopy ,Sol-gel - Abstract
A simplified method of synthesis and purification of Erbium-Tetraphenylporphyrin (ErTpp) complexes, and their incorporation within a silica gel by the sol–gel process, is presented. On the basis of optical spectroscopic measurements in the UV–VIS range it was found that in ErTpp complexes the tetraphenylporphyrin molecule served as a protective screen for erbium ions. The half-width of the erbium ion luminescence band for the 4 S 3/2 → 4 I 15/2 transition was narrower by a factor of 5–6 in the new material than the corresponding value in erbium doped glasses or glass ceramics. It was shown that the value of the nonlinear refraction coefficient in ErTpp gels could considerably exceed that of silica glasses.
- Published
- 1999
- Full Text
- View/download PDF
25. A New Chelating Cyclophane and Its Complexation with Ni2+, Cu2+, and Zn2+: Spectroscopic Properties and Allosterism via Ring Contraction
- Author
-
Motomichi Inoue, and Arnold M. Raitsimring, Quintus Fernando, Felipe Medrano, and Michiko B. Inoue
- Subjects
Stereochemistry ,Quantum yield ,Condensation reaction ,Inorganic Chemistry ,chemistry.chemical_compound ,Electron transfer ,Crystallography ,chemistry ,Amide ,Molecule ,Carboxylate ,Physical and Theoretical Chemistry ,Cyclophane ,Coordination geometry - Abstract
A condensation reaction between ethylenediaminetetraacetic dianhydride and p-xylenediamine gave a new chelating cyclophane, 3,10,21,28-tetraoxo-5,8,23,26-tetrakis(carboxymethyl)-2,5,8,11,20,23,26,29-octaaza[12.12]paracyclophane, abbreviated as (32edtaxan)H(4), which has three types of electron-donor groups, i.e., amine, carboxylate, and amide groups. The formation of the cyclophane has been confirmed by a single-crystal X-ray analysis of its Zn(2+) complex, [Zn(2)(32edtaxan)].7.5H(2)O, which crystallized in the monoclinic space group P2(1)/c with a = 19.818(1) Å, b = 13.169(1) Å, c = 18.134(1) Å, beta = 104.491(6) degrees, and Z = 4. Each cyclophane molecule coordinates two Zn(2+) ions and results in the formation of a binuclear chelate molecule. The coordination geometry around each metal ion is distorted octahedral, the donor atoms being two carboxylate oxygen atoms, two amine nitrogen atoms, and two amide oxygen atoms. The new cyclophane exhibited a well-defined fluorescence band at 290 nm with 210 nm excitation. The emission intensity was markedly increased in the Zn(2+) complex, in which the coordination of Zn(2+) ions increases the rigidity of the cyclophane leading to a high fluorescence quantum yield. When the cyclophane was coordinated to Cu(2+) ions, the molar absorptivity of a pi-pi transition band observed at 260 nm was increased by a factor of about 10. Such a large spectral change was not observed for the Zn(2+) and Ni(2+) complexes. In the Cu(2+) complex, the two phenyl rings of the cyclophane are expected to be brought closer, as a result of the coordination of deprotonated amide nitrogens to the central metal ion. This allosterism via ring contraction is responsible for the novel behavior of the absorption spectrum. The emission band of the cyclophane was weakened by coordination of copper and nickel as a result of fluorescence quenching caused by a photo-induced electron transfer.
- Published
- 1997
- Full Text
- View/download PDF
26. Unusually high phosphodiesterolytic activity of La(<scp>iii</scp>) hydroxide complexes stabilized by glycine derivatives
- Author
-
Antonio Calderón, Anatoly K. Yatsimirsky, and Felipe Medrano
- Subjects
Molecular Structure ,Hydrolysis ,Glycine ,Metals and Alloys ,Stereoisomerism ,Cerium ,General Chemistry ,Hydrogen-Ion Concentration ,Ligands ,Organophosphates ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Kinetics ,chemistry.chemical_compound ,chemistry ,Lanthanum ,Cations ,Polymer chemistry ,Materials Chemistry ,Ceramics and Composites ,Organic chemistry ,Hydroxide - Abstract
Glycine and N,N-dimethylglycine stabilize La(III) hydroxide complexes of the type La2L2(OH)4 which possess phosphodiesterolytic activity close to that observed with most active tetravalent cations like Ce(IV).
- Published
- 2003
- Full Text
- View/download PDF
27. Recognition of anions and neutral guests by dicationic pyridine-2,6-dicarboxamide receptors
- Author
-
Felipe Medrano, Herbert Höpfl, Alejandro Dorazco González, and Anatoly Yatsimirsky
- Subjects
chemistry.chemical_compound ,Crystallography ,Deprotonation ,Pyridinium Compounds ,Chemistry ,Stereochemistry ,Hydrogen bond ,Amide ,Organic Chemistry ,Pyridine ,Pyridinium ,Anion binding ,Trifluoromethanesulfonate - Abstract
Dicationic N-methylated at pyridyl or quinolyl moieties derivatives of three isomers of N,N'-bis(pyridyl)pyridine-2,6-dicarboxamide (o-, m-, and p-1) and of N,N'-bis(3-quinolyl)pyridine-2,6-dicarboxamide (4) strongly bind anions in MeCN (log K in the range 3.5-6.5) with pronounced selectivity for Cl(-) and also bind neutral urea and amide guests with log K in the range 1.1-2.8. Crystal structures of the triflate salts of m-1, p-1, and 4 show that amide NH and pyridinium o-CH groups are directed inside the receptor cleft with their four protons forming a circle of radius ca. 2.35 A optimal for inclusion of Cl(-). The binding of anions to these protons is evident from the crystal structure of a mixed triflate/chloride salt of p-1, calculated (DFT/B3LYP 6-31G**) structures of 1:1 complexes of all receptors with Cl(-), and results of (1)H NMR titrations. In the crystal structure of o-1 pyridinium N-Me(+) groups are directed inside the receptor cleft impeding the anion complexation, but calculations demonstrate that simple rotation of pyridinium rings in opposite directions by ca. 30 degrees creates a cavity to which the Cl(-) ion can fit forming 4 hydrogen bonds to amide NH and aliphatic CH groups of N-Me(+). The results of (1)H NMR titrations confirm this type of binding in solution. Anions quench the intense fluorescence of 4, which allows their fluorescent sensing in the muM range. A new methodology for determination of anion binding constants to strongly acidic receptors by inhibitory effects of anions on the receptor deprotonation by an external base has been developed. High affinity and selectivity of anion complexation by dicationic pyridine-2,6-dicarboxamides is attributed to the rigid preorganized structure of receptors, the high acidity of NH and CH groups, and the electrostatic charge effect.
- Published
- 2010
28. Protonation of kanamycin A: detailing of thermodynamics and protonation sites assignment
- Author
-
Carolina Godoy-Alcántar, Yanet Fuentes-Martínez, Anatoly K. Yatsimirsky, Alexander Dikiy, and Felipe Medrano
- Subjects
Magnetic Resonance Spectroscopy ,Chemistry ,Chemical shift ,Organic Chemistry ,Inorganic chemistry ,Enthalpy ,Potentiometric titration ,Kanamycin ,Protonation ,Ring (chemistry) ,Biochemistry ,Crystallography ,Ionization ,Drug Discovery ,medicine ,Potentiometry ,A value ,Thermodynamics ,Protons ,Molecular Biology ,medicine.drug - Abstract
Protonation of an aminoglycoside antibiotic kanamycin A sulfate was studied by potentiometric titrations at variable ionic strength, sulfate concentration and temperature. From these results the association constants of differently protonated forms of kanamycin A with sulfate and enthalpy changes for protonation of each amino group were determined. The protonation of all amino groups of kanamycin A is exothermic, but the protonation enthalpy does not correlate with basicity as in a case of simple polyamines. The sites of stepwise protonation of kanamycin A have been assigned by analysis of 1 H– 13 C–HSQC spectra at variable pH in D 2 O. Plots of chemical shifts for each H and C atom of kanamycin A vs. pH were fitted to the theoretical equation relating them to p K a values of ionogenic groups and it was observed that changes in chemical shifts of all atoms in ring C were controlled by ionization of a single amino group with p K a 7.98, in ring B by ionization of two amino groups with p K a 6.61 and 8.54, but in ring A all atoms felt ionization of one group with p K a 9.19 and some atoms felt ionization of a second group with p K a 6.51, which therefore should belong to amino group at C3 in ring B positioned closer to the ring A while higher p K a 8.54 can be assigned to the group at C1. This resolves the previously existed uncertainty in assignment of protonation sites in rings B and C.
- Published
- 2010
29. Copolymerization of diphenylmethane andp-xylene by oxidative coupling
- Author
-
Koichi Asano, Masanobu Nakamura, Motomichi Inoue, Sergio Cantua, and Felipe Medrano
- Subjects
Condensation polymer ,Polymers and Plastics ,Chemistry ,Xylene ,Diphenylmethane ,General Chemistry ,Condensed Matter Physics ,Peroxide ,Coupling reaction ,chemistry.chemical_compound ,Polymer chemistry ,Materials Chemistry ,Copolymer ,Oxidative coupling of methane ,Polystyrene - Abstract
Diphenylmethane underwent oxidative coupling in the presence of di-t-butyl peroxide and formed 1,1,2,2-tetraphenylethane. This coupling reaction resulted in the formation of a copolymer of diphenylmethane andp-xylene. The new copolymer was soluble in common organic solvents and had a molecular weight of 32,000 (polystyrene base).
- Published
- 1992
- Full Text
- View/download PDF
30. N-(2-Pyridylmethyl)phthalimide
- Author
-
Perla Román-Bravo, Felipe Medrano, Hugo Tlahuext, and Olga Garduño-Beltrán
- Subjects
Crystal ,lcsh:Chemistry ,chemistry.chemical_compound ,Crystallography ,chemistry ,lcsh:QD1-999 ,Pyridine ,Perpendicular ,General Materials Science ,General Chemistry ,Condensed Matter Physics ,Bioinformatics ,Organic Papers - Abstract
In the title compound, C14H10N2O2, the phtalimide and 2-pyridylmethyl units are almost perpendicular, with an interplanar angle of 85.74 (2)°. In the crystal, molecules are linked by weak C—H...O interactions, forming chains running along the b axis. The packing is further stabilized by offset π–π interactions between adjacent pyridine rings, with a centroid–centroid distance of 3.855 (2) Å.
- Published
- 2009
31. Schiff base formation and recognition of amino sugars, aminoglycosides and biological polyamines by 2-formyl phenylboronic acid in aqueous solution
- Author
-
Anatoly Yatsimirsky, Felipe Medrano, and Nini Johanna Gutiérrez-Moreno
- Subjects
Models, Molecular ,Imine ,Molecular Conformation ,Protonation ,Biochemistry ,Medicinal chemistry ,chemistry.chemical_compound ,Polyamines ,Organic chemistry ,Physical and Theoretical Chemistry ,Phenylboronic acid ,Schiff Bases ,Equilibrium constant ,chemistry.chemical_classification ,Schiff base ,Aqueous solution ,Organic Chemistry ,Water ,Amino Sugars ,Boronic Acids ,Amino acid ,Solutions ,Aminoglycosides ,chemistry ,Benzaldehydes ,Titration - Abstract
Interactions of 2-, 3- and 4-formyl phenylboronic acids (FPBAs) with sugars, amino sugars, aminoglycosides and various poly- and monoamines have been studied by UV-vis, (1)H and (11)B NMR titrations in water at variable pH. Behavior of 2-FPBA was anomalous in several aspects. Transformation of the acid into its conjugate base was slow in NMR time scale and was accompanied by intramolecular cyclization affording the respective benzoboroxole. The equilibrium constants for imine formation (K(imine)) between 2-FPBA and simple monoamines including amino sugars were ca. 2 orders of magnitude larger than those with other isomers. Still one order of magnitude larger K(imine) values were observed for 2-FPBA with aminoglycosides (kanamycin, amikacin, gentamicin, neomycin) and polyamines (spermine, spermidine). The examination of UV-vis and (11)B NMR spectra of imines formed with 2-FPBA showed that formally neutral Schiff bases in fact were zwitterionic species containing a protonated imine group and an anionic B(OH)(3)(-) group. The enhanced stability of imines with monoamines can therefore be attributed to the electrostatic stabilization provided by the zwitterionic structure and further increased stability of imines with antibiotics and polyamines is explicable by additional stabilization of the borate anionic group by ion paring with ammonium groups not involved in Schiff base formation. Thanks to high molar absorptivity of protonated imines interaction of 2-FPBA with aminoglycosides allows detecting them spectrophotometrically in a μM concentration range in neutral aqueous solutions in the presence of sugars, amino sugars and amino acids.
- Published
- 2012
- Full Text
- View/download PDF
32. Comparative analysis of M–O, M–S and cation–π(arene) interactions in the alkali metal (Na+, K+, Rb+, Cs+) bis-dithiocarbamate salts of N,N′-dibenzyl-1,2-ethylenediamine
- Author
-
Reyna Reyes-Martínez, Felipe Medrano, Hugo Tlahuext, Herbert Höpfl, and Carolina Godoy-Alcantar
- Subjects
chemistry.chemical_classification ,Carbon disulfide ,Inorganic chemistry ,Ethylenediamine ,General Chemistry ,Condensed Matter Physics ,Alkali metal ,chemistry.chemical_compound ,Crystallography ,chemistry ,Hydroxide ,General Materials Science ,Qualitative inorganic analysis ,Dithiocarbamate ,Spectroscopy ,Derivative (chemistry) - Abstract
The alkali metal (Na+, K+, Rb+, Cs+) bis-dithiocarbamate (bis-dtc) salts of N,N′-dibenzyl-1,2-ethylenediamine have been prepared from the reaction of N,N′-dibenzyl-1,2-ethylenediamine with carbon disulfide in the presence of two equivalents of the corresponding alkali metal hydroxide. Additionally, the analogous triethylammonium derivative has been obtained. The resulting compounds have been analyzed as far as possible by elemental analysis, FAB+ mass spectrometry, IR, UV-Vis and NMR (1H, 13C) spectroscopy, and single-crystal X-ray diffraction, showing that the composition of the metal salts can be described by the general formula [{[(H2O)xM-µ-(H2O)yM(H2O)x][bis-dtc]}n] (1, M = Na+, x = 3, y = 2; 2, M = K+, x = 1, y = 2; 3, M = Rb+, x = 0, y = 1; 4, M = Cs+, x = 0, y = 1; 5, M = Et3HN+, x = 0, y = 0). The solid-state and solution studies showed that all alkali metal ions participate in the formation of M–O and cation-π(arene) interactions, while M–S interactions are only observed for the larger alkali metals K+, Rb+ and Cs+. As expected, within the alkali metal group there is a clear tendency for a decreasing number of M–O bonds in favor of M–S and cation–π(arene) interactions, however, only K+ forms a semi-sandwich type complex with η6-coordination.
- Published
- 2009
- Full Text
- View/download PDF
33. Rapid hydrolysis of model phosphate diesters by alkaline-earth cations in aqueous DMSO: speciation and kinetics
- Author
-
Anatoly Yatsimirsky, Felipe Medrano, and Olga Taran
- Subjects
Aqueous solution ,Chemistry ,Hydrolysis ,Metal ions in aqueous solution ,Inorganic chemistry ,Titrimetry ,Water ,Esters ,Hydrogen-Ion Concentration ,Alkaline hydrolysis (body disposal) ,Phosphate ,Catalysis ,Phosphates ,Inorganic Chemistry ,Kinetics ,chemistry.chemical_compound ,Reaction rate constant ,Metals, Alkaline Earth ,Phosphodiester bond ,Hydroxides ,Potentiometry ,Chemical Precipitation ,Hydroxide ,Dimethyl Sulfoxide - Abstract
Kinetics of the cleavage of two phosphate diesters, bis(4-nitrophenyl) phosphate and 2-hydroxypropyl 4-nitrophenyl phosphate and a triester, 4-nitrophenyl diphenyl phosphate, in the presence of Mg(II), Ca(II) and Sr(II) were studied in 90% vol. DMSO at 37 degrees C. The alkaline hydrolysis of the triester was inhibited by all cations, but with both phosphodiesters strong catalytic effects were observed. Potentiometric titrations of metal perchlorates by Bu4N(OH) revealed formation of M2(OH)3+, M(OH)+, M(OH)2 and M2(OH)5- species. Rate constants for phosphodiester cleavage by individual species were obtained from analysis of rate-concentration profiles. Observed first-order rate constants in the presence of 1-2 mM Mg(II) or Ca(II) in neutral and weakly basic solutions were 10(8)-10(11) times higher than those for background hydrolysis at the same pH while in water additions of up to 50 mM metal produced100-fold accelerations. Possible structures of DMSO solvated catalyst-substrate complexes were modeled by DFT calculations with Mg(II). The increased catalytic activity in 90% DMSO is attributed to stronger association of hydroxide ions and anionic phosphodiesters with metal ions and to preferable solvation of cations by DMSO, which creates favorable for reaction anhydrous microenvironment in the coordination sphere of the catalyst.
- Published
- 2008
- Full Text
- View/download PDF
34. Spectroscopic properties of rare-earth complexes of tetraphenyl porphyrin introduced into a silicate sol-gel matrix
- Author
-
Felipe Medrano, V. Terpugov, Amy Y. Clark, and M. Cervantes
- Subjects
Materials science ,Absorption spectroscopy ,Applied Mathematics ,Rare earth ,General Engineering ,Sol gel matrix ,Photochemistry ,Porphyrin ,Atomic and Molecular Physics, and Optics ,Silicate ,Ion ,Computational Mathematics ,chemistry.chemical_compound ,chemistry ,Visible spectrum - Published
- 2002
- Full Text
- View/download PDF
35. Rapid hydrolysis of model phosphate diesters by alkaline-earth cations in aqueous DMSO: speciation and kineticsElectronic supplementary information (ESI) available: Kinetic data for BNPP hydrolysis in aqueous alkaline solutions and TRIS buffer, 31P NMR titrations of BNPP by metal perchlorates in water and 90% DMSO, complete set of results of potentiometric titrations of alkaline-earth cations in 90% DMSO, dependence of kobsfor BNPP cleavage in 90% DMSO on concentration of Mg(ii) at constant [Mg(ii)] : [OH−] ratio. See DOI: 10.1039/b807030j
- Author
-
Olga Taran, Felipe Medrano, and Anatoly K. Yatsimirsky
- Subjects
- *
HYDROLYSIS , *ESTERS , *CHEMICAL kinetics , *CATIONS , *METAL complexes , *SOLUTION (Chemistry) , *PERCHLORATES , *DENSITY functionals - Abstract
Kinetics of the cleavage of two phosphate diesters, bis(4-nitrophenyl) phosphate and 2-hydroxypropyl 4-nitrophenyl phosphate and a triester, 4-nitrophenyl diphenyl phosphate, in the presence of Mg(ii), Ca(ii) and Sr(ii) were studied in 90% vol. DMSO at 37 °C. The alkaline hydrolysis of the triester was inhibited by all cations, but with both phosphodiesters strong catalytic effects were observed. Potentiometric titrations of metal perchlorates by Bu4N(OH) revealed formation of M2(OH)3+, M(OH)+, M(OH)2and M2(OH)5−species. Rate constants for phosphodiester cleavage by individual species were obtained from analysis of rate–concentration profiles. Observed first-order rate constants in the presence of 1–2 mM Mg(ii) or Ca(ii) in neutral and weakly basic solutions were 108–1011times higher than those for background hydrolysis at the same pH while in water additions of up to 50 mM metal produced <100-fold accelerations. Possible structures of DMSO solvated catalyst–substrate complexes were modeled by DFT calculations with Mg(ii). The increased catalytic activity in 90% DMSO is attributed to stronger association of hydroxide ions and anionic phosphodiesters with metal ions and to preferable solvation of cations by DMSO, which creates favorable for reaction anhydrous microenvironment in the coordination sphere of the catalyst. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
36. Unusually high phosphodiesterolytic activity of La(iii) hydroxide complexes stabilized by glycine derivatives.
- Author
-
Felipe Medrano, Antonio Calderón, and Anatoly K. Yatsimirsky
- Published
- 2003
37. Síntesis y reconocimiento molecular de aniones fosfatados por nuevos derivados de espiramicina
- Author
-
KARLA ISABEL RIVERA MARQUEZ and FELIPE MEDRANO VALENZUELA
- Subjects
7 [cti] ,33 [cti] - Abstract
RESUMEN En este proyecto de tesis se presenta el estudio de reconocimiento molecular de aniones por nuevos derivados aromáticos del antibiótico natural espiramicina, que es un compuesto perteneciente a la familia de los macrólidos y que presenta muchas de las características adecuadas para funcionar como un buen receptor de aniones, ya que posee dos aminoazúcares cargados positivamente en pH ácido, así como grupos hidrofóbicos e hidrofílicos y una gran cantidad de centros quirales. Sin embargo, carece de grupos aromáticos que le confieran propiedades fotofísicas de absorción y que pudieran favorecer interacciones con las unidades aromáticas de los aniones estudiados AMP, ADP y ATP. Se llevó a cabo la síntesis de cuatro nuevos derivados de espiramicina 1a-d introduciendo aminas con fragmentos aromáticos tales como: bencilo (1a), 2-metil-piridina (1b), 1-metil-natftilo (1c) y 1-metil-pirenilo (1d) mediante reacción de aminación reductiva del grupo aldehído de la espiramicina. Los derivados fueron completamente caracterizados mediante RMN (1H, 13C) y espectrometría de masas (HRMS). La adición de fragmentos aromáticos a la espiramicina se hizo con la finalidad de estudiar las propiedades fotofísicas de los nuevos derivados por la técnica espectrofotométrica UV-visible. Posteriormente, se llevaron a cabo estudios para la determinación de las constantes de protonación (pKa´s) de los derivados 1a-c por la técnica de potenciometría. Adicionalmente, las constantes de protonación calculadas para el derivado 1b fueron asignadas mediante titulación potenciométrica seguida por RMN 1H en D2O. Se realizaron estudios de reconocimiento molecular por potenciometría para la determinación de las constantes de asociación de 1a-c con huéspedes aniónicos de estructura diversa; en donde, el compuesto 1a reconoció selectivamente a los aniones fosfatados en el siguiente orden ADP > ATP > AMP > pirofosfato > fosfato, con constantes de magnitud log K = 4.82 - 3.34. Por otro lado, también se observó la asociación de 1a con dicarboxilatos, observándose una mayor afinidad por pimelato sobre adipato (log K = 4.80 v y 4.56, respectivamente). La tendencia de selectividad para los complejos formados por 1b con la misma serie de aniones fue: pirofosfato > fosfato > ATP > AMP > ADP (log K = 4.16- 2.67); mientras que con la serie de ácidos dicarboxílicos la selectividad fue: succinato > adipato > pimelato > suberato (log K = 3.27 – 3.03). Finalmente, para el receptor 1c sólo se estudió la serie de nucleótidos de adenina, cuya tendencia para la complejación fue: ATP > ADP > AMP (log K = 6.40 – 4.10). Adicionalmente, por ITC se determinaron los parámetros termodinámicos para la formación del complejo 1b-ATP. No obstante, por medio de UV-visible no fue posible determinar las constantes de asociación entre los derivados 1c-d con los nucleótidos de adenina. Se llevaron a cabo titulaciones por RMN 1H y 31P en D2O entre el derivado 1b con los aniones ATP y ADP con el fin de conocer los sitios de interacción en los complejos formados. Los valores de CIS calculados indicaron que dichos complejos se forman principalmente por interacciones de puente de hidrógeno entre los grupos amino protonados del receptor y los grupos fosfato de los nucleótidos, lo cual fue confirmado mediante estudios de química computacional a nivel de mecánica molecular. De este trabajo se concluye que el derivado bencil espiramicina 1a, mostró mayor afinidad hacia ATP y pirofosfato; mientras que el derivado 2-picolil espiramicina 1b mejoró su capacidad en el reconocimiento molecular únicamente hacia el pirofosfato y el derivado naftil espiramicina 1c potencializó su afinidad hacia ATP, todas ellas en comparación con las reportadas por espiramicina. El derivado 1a también mostró constantes de asociación más altas hacia los aniones dicarboxilato, como adipato y pimelato en comparación con las obtenidas por espiramicina. Cabe destacar que estas constantes se obtuvieron mediante la técnica de potenciometría, la cual nos permitió trabajar con mezclas acuosas para disolver mejor los derivados, arrojando valores de constantes más confiables. La técnica de ITC únicamente permitió trabajar con compuestos solubles en agua, por lo cual el derivado 1b fue el único que se estudió bajo esta técnica, determinándose los valores termodinámicos para el complejo 1b - ATP. Finalmente, por espectrofotometría con la técnica de UV-visible sólo fue posible trabajar con los derivados 1c-d, los cuales presentaron absorbancias significativas debido a la presencia de grandes grupos aromáticos. ABSTRACT In this work, the study of the anion molecular recognition by new derivatives of spiramycin is presented. Spiramycin is a natural antibiotic of the macrolide family and has many of the adequate characteristics to work as an efficient receptor for anions, including two aminosugar moieties with a positive charge at acidic pH, hydrophobic and hydrophilic groups as well as several chiral centers. However, spiramycin lacks aromatic groups that can confer photophysical properties of light emission/absorption or the ability to establish - interactions with anions such as AMP, ADP or ATP. The synthesis of four new derivatives 1a-d was carried out by reductive amination of the spiramycin aldehyde group to link aromatic moieties, such as benzyl (1a), 2-methyl-pyridyl (1b), 1-methyl-naphthyl (1c) and 1-methyl-pyrenyl (1d). The compounds 1a-d were fully characterized by 1H, and 13C NMR and mass spectrometry (HRMS). The aim of introducing aromatic fragments into the structure of spiramycin was to study the photophysical properties of the new derivatives by UV-vis spectrophotometry. Later, studies for the determination of protonation constants (pKa´s) of the derivatives by potentiometry were carried out. Additionally, the determined protonation constants for 1b were assigned unequivocally by 1H NMR titrations in D2O. Molecular recognition studies to determine the association constants between 1a-c with diverse anionic guests were carried out by potentiometry. Compound 1a selectively recognized phosphate anions in the order ADP > ATP > AMP > pyrophosphate, phosphate with association constant in the range log K = 4.82 - 3.34. In another side, the association of 1a with dicarboxylates also was observed, in this case a higher affinity for pimelate over adipate (log K = 4.80 and 4.56, respectively) was observed. The selectivity trend for the complexes formed between 1b and the same anion series was: pyrophosphate > phosphate > ATP > ADP > AMP (log K = 4.16 - 2.67); while with the studied dicarboxylates the selectivity followed the order: succinate > adipate > pimelate > suberate (log K = 3.27 – 3.03). Finally, receptor 1c was only studied with adenine nucleotides, which vii form complexes in the affinity trend: ATP > ADP > AMP (log K = 6.40 – 4.10). Besides, the thermodynamic parameters of the association between 1b-ATP were determined by ITC. The determination of association constants between the receptors 1c-d and nucleotides was not possible by UV-vis spectroscopy. In order to determine the interaction sites in the structure complexes formed between 1b derivative with ATP and ADP nucleotides, some 1H and 31P NMR titrations were performed. The calculated CIS values indicated that these complexes are formed by hydrogen bonds between the protonated amino groups of the receptor and phosphate moieties of the nucleotides, which was confirmed by molecular mechanic computational studies. In conclusion, compared with spiramycin, the benzyl spiramycin derivative 1a, has the highest affinity toward ATP and pyrophosphate; while 2-picolyl spiramycin, 1b improved its molecular recognition ability towards pyrophosphate and naphthyl spiramycin derivative 1c showed a higher affinity for ATP. Derivative 1a also showed higher association constants with dicarboxylates as pimelate and adipate in comparison with spyramycin. It´s essential to remark that constants obtained by potentiometry in aqueous solution in this study are trustworthy. Because of the ITC equipment only allows to work with substances totally dissolved in water; just the derivative 1b was studied by this technique, where the thermodynamic parameters for the 1b-ATP complex were determined. Finally, complexes with the derivatives 1c-d were analyzed by UV-Vis spectrophotometry due to the strong absorption of the aromatic groups present in the structure of the derivatives.
- Published
- 2018
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.