Theoretical and experimental study of the vibrational spectra of 1.5-dimethylcytosine

The Raman spectra of the solid 1,5-dimethylcytosine and the FTIR spectra at room and low temperatures respectively have been registered. Quantum mechanical calculations of energies, geometries and vibrational wavenumbers were carried out by using ab initio (HF) and Density Functional Theory (DFT/BLYP and B3LYP) methods with different basis sets. The best level of theory in order to reproduce the experimental wavenumbers is the BLYP method with the 6-31G* basis set. The theoretical calculations indicate the presence of four stable tautomers of 1,5-dimethylcytosine: amino-oxo; imino-oxo (a and b) and imino-hidroxy. Their geometries were optimised by using the BLYP/6-31G* method, being the amino-oxo tautomer the most stable, followed by the imino-oxo tautomer, while the imino-hidroxy one is the most unstable. The complete assignment of the observed bands in the vibrational spectra of the amino-oxo tautomer is proposed in this work. © 2007 Elsevier B.V. All rights reserved.Fil: Brandán, S.A.. Universidad Nacional de Tucumán; ArgentinaFil: Benzal, María Graciela. Universidad Nacional de Tucumán; ArgentinaFil: García Ramos, J.V.. Csic - Instituto de Estructura de la Materia (iem);Fil: Otero, J.C.. Universidad de Málaga; EspañaFil: Ben Altabef, Aida. Universidad Nacional de Tucumán; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentin

Synthesis, molecular structure, vibrational and theoretical studies of a new non-centrosymmetric organic sulphate with promising NLO properties

International audienceThe new non-centrosymmetric inorganic-organic hybrid material tetrakis(2,6-dimethylpiperazine-1,4-diium) tetrakis(sulfate) dihydrate (DMPS) has been prepared and crystallized in the non-centrosymmetric space group Cc of the monoclinic system with the crystallographic parameters a = 25.044 (4) Å, b = 12.1046 (18) Å, c = 14.075 (2) Å, β = 107.289 (5) °, V = 4074.0 (10) Å3 and Z = 4. The tetrahedron (S(1)O4 2−) and (S(4)O4 2−) anions are connected to water molecules forming as infinite chains type C4 4(12) along the c-axis in y = ¼ and ¾. The 2,6-dimethylpiperazine-1,4-diium cations are correlated to the inorganic part by means of N–H⋯O and C–H⋯O hydrogen bonds. The diprotonated piperazine ring endorses a chair conformation, with the methyl groups placing in an equatorial site. Intermolecular contacts in the crystal structure were computed by Hirshfeld surface examination. Infrared spectrum proves the presence of the functional groups in the synthesised salt and different coordination modes are observed in the sulfate groups. Optical propriety affirms a noteworthy band gap energy signifying steadiness of the title compound. Furthermore, the polarizability and first order hyperpolarizability of the title molecule were calculated and interpreted. Subsequently, theoretical calculations indicate that first order hyperpolarizability is 13 times greater than urea. Moreover, the thermodynamic properties (heat capacity, entropy, and enthalpy) of the title compound at different temperatures were calculated in gas phase. Additionally, two neutral, one anionic and the hydrated species experimentally observed by X-ray diffraction were identified in the vibrational infrared spectrum of DMPS combining the experimental spectrum with the corresponding predicted by using DFT calculations and the scaled quantum mechanical force field (SQMFF) procedure. © 2018 Elsevier B.V

Synthesis and physic-chemical properties of a novel chromate compound with potential biological applications, bis(2-phenylethylammonium) chromate(VI)

International audienceThe structure of bis(2-phenylethylammonium) chromate (VI) (2phCr) was determined from X-ray diffraction data. The compound crystallizes in the monoclinic system (space group C2/c) with the lattice parameters a = 38.136 (2) Å b = 11.2334 (6) Å c = 8.1643 (4) Å; β = 98.480 (2) V = 3459.3 (3) Å 3 and Z = 8. The structure was solved from 3358 independent reflections with R = 0.034 and Rw = 0.1089. The structure consists of discrete anions (CrO 4 2− ) stacked in layers parallel to (b, c) plane at x = 1/4 and 3/4. These anions are connected to the 2-phenylethylammonium cations through N–H⋯O and C–H⋯O hydrogen bonds, forming a two-dimensional arrangement. Crystal structure and spectroscopic studies are reported for the 2phCr. In addition, Hirshfeld surfaces and two-dimensional fingerprint plots estimate the intermolecular interactions accountable for the generation of crystal packing. Furthermore, the title compound was screened for antibacterial activities against five pathogenic strains namely Escherichia coli ATCC 8739, Salmonella typhimurium ATCC 14028, Staphylococus aureus ATCC 6538, Enterococcus feacium ATCC 19434 and Streptocoque B (Sreptococcus agalactiae) and antifungal activities against a clinical strain called Candida albicans ATCC 10231, corroborating significant activity. In silico investigation of bioactivity of 2phCr was performed via molecular docking analysis with four types of secreted aspartic proteinases (SAP, SAP1, SAP3, and SAP5) from Candida albicans to explore the antifungal properties in comparison to behavior of known antifungals used to treat Candida albicans, and with three types of β-ketoacyl acyl carrier protein synthase enzymes (KAS I (FabB), KAS II (FabF) and KAS III (FabH)) from Escherichia coli in comparison with that of aminothiazole, thilactomycin, and cerulerin antimicrobials. In addition, the complete assignments for 2phCr are reported considering monodentate coordination for the chromate group