X-ray Quality Geometries of Geodesic Polyarenes from Theoretical Calculations:  What Levels of Theory Are Reliable?

2005 ◽  
Vol 70 (14) ◽  
pp. 5713-5716 ◽  
Author(s):  
Marina A. Petrukhina ◽  
Kristian W. Andreini ◽  
James Mack ◽  
Lawrence T. Scott
Keyword(s):  
Theoretical Calculations ◽  
X Ray ◽  
Geodesic Polyarenes

The X-Ray Molecular Structure of 1-(2′,4′-Dinitrophenyl)-1,2,3-triazole and the Problem of the Orthogonal Interaction Between a 'Pyridine-Like' Nitrogen and a Nitro Group

2005 ◽  
Vol 58 (11) ◽  
pp. 817 ◽  
Author(s):  
Glenn P. A. Yap ◽  
Fernando A. Jové ◽  
Rosa M. Claramunt ◽  
Dionisia Sanz ◽  
Ibon Alkorta ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Nitro Group ◽  
Title Compound ◽  
Theoretical Calculations ◽  
X Ray

The structure of the title compound serves for a discussion about the topic of orthogonal interactions. This interaction, although weak, is important due to its peculiar geometry. Other examples from the Cambridge Crystallographic Database, together with theoretical calculations are reported.

scholarly journals Synthesis, Cytotoxic Activity, Crystal Structure, DFT Studies and Molecular Docking of 3-Amino-1-(2,5-dichlorophenyl)-8-methoxy-1H-benzo[f]chromene-2-carbonitrile

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 184
Author(s):  
Menna El Gaafary ◽  
Tatiana Syrovets ◽  
Hany M. Mohamed ◽  
Ahmed A. Elhenawy ◽  
Ahmed M. El-Agrody ◽  
...  
Keyword(s):  
Cytotoxic Activity ◽  
Cell Lines ◽  
Cancer Cell ◽  
Dna Methyltransferase ◽  
Human Cancer ◽  
Theoretical Calculations ◽  
Cancer Cell Lines ◽  
Molecular Structures ◽  
Cytotoxic Activities ◽  
X Ray

The target compound 3-amino-1-(2,5-d ichlorophenyl)-8-methoxy-1H-benzo[f]-chromene-2-carbonitrile (4) was synthesized via a reaction of 6-methoxynaphthalen-2-ol (1), 2,5-dichlorobenzaldehyde (2), and malononitrile (3) in ethanolic piperidine solution under microwave irradiation. The newly synthesized β-enaminonitrile was characterized by FT-IR, 1H NMR, 13C NMR, mass spectroscopy, elemental analysis and X-ray diffraction data. Its cytotoxic activity was evaluated against three different human cancer cell lines MDA-MB-231, A549, and MIA PaCa-2 in comparison to the positive controls etoposide and camptothecin employing the XTT cell viability assay. The analysis of the Hirshfeld surface was utilized to visualize the reliability of the crystal package. The obtained results confirmed that the tested molecule revealed promising cytotoxic activities against the three cancer cell lines. Furthermore, theoretical calculations (DFT) were carried out with the Becke3-Lee-Yang-parr (B3LYP) level using 6-311++G(d,p) basis. The optimization geometry for molecular structures was in agreement with the X-ray structure data. The HOMO-LUMO energy gap of the studied system was discussed. The intermolecular-interactions were studied through analysis of the topological-electron-density(r) using the QTAIM and NCI methods. The novel compound exhibited favorable ADMET properties and its molecular modeling analysis showed strong interaction with DNA methyltransferase 1.

Mixed Metal Oxide Interfaces: An Experimental and Theoretical Assessment of Secondary Metal Influences in Metal Impregnated Aluminas

1994 ◽  
Vol 368 ◽  
Author(s):  
M. Malaty ◽  
D. Singh ◽  
R. Schaeffer ◽  
S. Jansen ◽  
S. Lawrence
Keyword(s):  
Photoelectron Spectroscopy ◽  
Theoretical Calculations ◽  
Mixed Metal Oxide ◽  
X Ray Diffraction ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Mixed Metal ◽  
Metal Interactions ◽  
Metal Metal ◽  
Bimetallic System

ABSTRACTStudies of the mixed-metal interface in metal impregnated alumina have indicated the possibility of much metal-metal and metal-substrate interaction. Studies were carried out on NiCu/Al2O3 system which was evaluated to develop a better understanding of the forces that drive modification of the catalytic selectivity of Ni in the presence of Cu. Electron Paramagnetic Resonance (EPR), Powder X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD) and theoretical calculations were carried out on this bimetallic system, using Ni,Ag/Al2O3 as a reference as Ni shows negligible electron perturbation on co-adsorbance with Ag onto alumina. XRD results indicate that gross modification of the electronic fields of Ni and Cu are due to direct coupling and intercalation into the alumina matrix. As a result of this phenomena, these materials may form a good base for the development of novel ceramics based on mixed-metal interactions where the intermetallic perturbations are driven by the substrate effects.

Salts of purine alkaloids caffeine and theobromine with 2,6-dihydroxybenzoic acid as coformer: structural, theoretical, thermal and spectroscopic studies

2021 ◽  
Vol 77 (11) ◽  
Author(s):  
Mateusz Gołdyn ◽  
Anna Komasa ◽  
Mateusz Pawlaczyk ◽  
Aneta Lewandowska ◽  
Elżbieta Bartoszak-Adamska
Keyword(s):  
Hydrogen Bonds ◽  
Water Solubility ◽  
Theoretical Calculations ◽  
Spectroscopic Studies ◽  
X Ray Diffraction ◽  
Dihydroxybenzoic Acid ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Purine Alkaloids ◽  
Vis Spectroscopy

The study of various forms of pharmaceutical substances with specific physicochemical properties suitable for putting them on the market is one of the elements of research in the pharmaceutical industry. A large proportion of active pharmaceutical ingredients (APIs) occur in the salt form. The use of an acidic coformer with a given structure and a suitable pK a value towards purine alkaloids containing a basic imidazole N atom can lead to salt formation. In this work, 2,6-dihydroxybenzoic acid (26DHBA) was used for cocrystallization of theobromine (TBR) and caffeine (CAF). Two novel salts, namely, theobrominium 2,6-dihydroxybenzoate, C7H9N4O2 +·C7H5O4 − (I), and caffeinium 2,6-dihydroxybenzoate, C8H11N4O2 +·C7H5O4 − (II), were synthesized. Both salts were obtained independently by slow evaporation from solution, by neat grinding and also by microwave-assisted slurry cocrystallization. Powder X-ray diffraction measurements proved the formation of the new substances. Single-crystal X-ray diffraction studies confirmed proton transfer between the given alkaloid and 26DHBA, and the formation of N—H...O hydrogen bonds in both I and II. Unlike the caffeine cations in II, the theobromine cations in I are paired by noncovalent N—H...O=C interactions and a cyclic array is observed. As expected, the two hydroxy groups in the 26DHBA anion in both salts are involved in two intramolecular O—H...O hydrogen bonds. C—H...O and π–π interactions further stabilize the crystal structures of both compounds. Steady-state UV–Vis spectroscopy showed changes in the water solubility of xanthines after ionizable complex formation. The obtained salts I and II were also characterized by theoretical calculations, Fourier-transform IR spectroscopy (FT–IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and elemental analysis.

ChemInform Abstract: Synthesis of cis-1-((2-Hydroxymethyl)cyclopentyl)uracil and Determination of Its Conformation by X-Ray Crystallography and AM1 Theoretical Calculations.

ChemInform ◽  
2010 ◽  
Vol 27 (43) ◽  
pp. no-no
Author(s):  
L. SANTANA ◽  
M. TEIJEIRA ◽  
E. URIARTE ◽  
C. TERAN ◽  
U. CASELLATO ◽  
...  
Keyword(s):  
Theoretical Calculations ◽  
X Ray ◽  
X Ray Crystallography

scholarly journals Detecting quadrupole: a hidden source of magnetic anisotropy for Manganese alloys

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Jun Okabayashi ◽  
Yoshio Miura ◽  
Yohei Kota ◽  
Kazuya Z. Suzuki ◽  
Akimasa Sakuma ◽  
...  
Keyword(s):  
Magnetic Anisotropy ◽  
Quantum Physics ◽  
Theoretical Calculations ◽  
Magnetic Moments ◽  
Perpendicular Magnetic Anisotropy ◽  
Linear Dichroism ◽  
First Principles Calculation ◽  
X Ray ◽  
Manganese Alloys ◽  
Ordered Alloys

Abstract Mn-based alloys exhibit unique properties in the spintronics materials possessing perpendicular magnetic anisotropy (PMA) beyond the Fe and Co-based alloys. It is desired to figure out the quantum physics of PMA inherent to Mn-based alloys, which have never been reported. Here, the origin of PMA in ferrimagnetic Mn3− δ Ga ordered alloys is investigated to resolve antiparallel-coupled Mn sites using x-ray magnetic circular and linear dichroism (XMCD/XMLD) and a first-principles calculation. We found that the contribution of orbital magnetic moments in PMA is small from XMCD and that the finite quadrupole-like orbital distortion through spin-flipped electron hopping is dominant from XMLD and theoretical calculations. These findings suggest that the spin-flipped orbital quadrupole formations originate from the PMA in Mn3− δ Ga and bring the paradigm shift in the researches of PMA materials using x-ray magnetic spectroscopies.

scholarly journals Alternatives to the Existence of Large Cooling Flows

1990 ◽  
Vol 115 ◽  
pp. 232-239
Author(s):  
Wallace Tucker
Keyword(s):  
Surface Brightness ◽  
Large Scale ◽  
Theoretical Calculations ◽  
Central Peak ◽  
High Energy ◽  
Cooling Time ◽  
Radiative Cooling ◽  
Massive Black Hole ◽  
X Ray ◽  
Cooling Flows

AbstractArguments against the existence of large scale cooling flows in clusters of galaxies are presented. The evidence for cooling flows is all circumstantial, consisting of observations of cool gas or hot gas with a radiative cooling time less than the Hubble time, or a central peak in the x-ray surface brightness profile. There is no evidence for large quantities (several tens to several hundreds of solar masses per year) of matter actually flowing anywhere. On the contrary, several lines of evidence — stellar dynamics, observations of the amount of star formation, x-ray surface brightness observations, theoretical calculations of the growth of thermal instabilities, the amount of cold gas — suggest that cooling flows, if they exist, must be suppressed by one to two orders of magnitude from the values implied by simple estimates based on the radiative cooling time of the x-ray emitting gas. Two heat sources which might accomplish this — thermal conduction and relativistic particles, are considered and an alternative to the standard model for cooling flows is presented: an accretion flow with feedback wherein the accretion of gas into a massive black hole in the central galaxy generates high energy particles that heat the gas and act to limit the accretion.

scholarly journals Size Matters: New Zintl Phase Hydrides of REGa (RE = Y, La, Tm) and RESi (RE = Y, Er, Tm) with Large and Small Cations

Crystals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 600
Author(s):  
Werwein ◽  
Hansen ◽  
Kohlmann
Keyword(s):  
Density Functional ◽  
Theoretical Calculations ◽  
Structural Diversity ◽  
Type Structure ◽  
Zintl Phases ◽  
Structure Form ◽  
Functional Theory ◽  
X Ray ◽  
Hydrogenation Reactions ◽  
Tetrahedral Voids

Many Zintl phases exhibiting a CrB type structure form hydrides. Systematic studies of AeTtHx (Ae = Ca, Sr, Ba; Tt = Si, Ge, Sn), LnTtHx (Ln = La, Nd; Tt = Si, Ge, Sn), and LnGaHx (Ln = Nd, Gd) showed the vast structural diversity of these systems. Hydrogenation reactions on REGa (RE = Y, La, Tm) and RESi (RE = Y, Er, Tm) were performed in steel autoclaves under hydrogen pressure up to 5 MPa and temperatures up to 773 K. The products were analyzed by X-ray and neutron powder diffraction. RESi (RE = Y, Er, Tm) form hydrides in the C-LaGeD type. LaGaD1.66 is isostructural to NdGaD1.66 and shows similar electronic features. Ga-D distances (1.987(13) Å and 2.396(9) Å) are considerably longer than in polyanionic hydrides and not indicative of covalent bonding. In TmGaD0.93(2) with a distorted CrB type structure deuterium atoms exclusively occupy tetrahedral voids. Theoretical calculations on density functional theory (DFT) level confirm experimental results and suggest metallic properties for the hydrides.

Synthesis and Structure of Bis-Urea Phenazines

2002 ◽  
Vol 57 (8) ◽  
pp. 937-945 ◽  
Author(s):  
Tom Fricke ◽  
Anton Dickmans ◽  
Umasish Jana ◽  
Manfred Zabel ◽  
Peter G. Jones ◽  
...  
Keyword(s):  
Weak Interaction ◽  
Theoretical Calculations ◽  
Nmr Titration ◽  
X Ray ◽  
Nitrate Ions

Substituted phenazines 7 and 15 with two urea units have been prepared and characterized. X-ray structure analyses are reported for intermediates 5, 9, 11b and 12. According to theoretical calculations the geometry of the two urea moieties in phenazines 7 and 15 should be well suited for the binding of trigonal planar anions, such as nitrate. NMR titration revealed that compound 15 indeed shows a weak interaction with nitrate ions in DMSO.

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