Syntheses and Redox Chemistry of Antiaromatic Core-Modified Isophlorinoids

Synlett ◽  
2018 ◽  
Vol 29 (18) ◽  
pp. 2362-2371 ◽  
Author(s):  
Venkataramanarao Anand ◽  
Santosh Panchal ◽  
Baddigam Reddy
Keyword(s):  
Noncovalent Interactions ◽  
Chemical Properties ◽  
Structural Similarity ◽  
Redox Chemistry ◽  
Spectroscopic Techniques ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Crystallography ◽  
Stable Core

During the attempted total synthesis of chlorophyll, Woodward hypothesized the formation of tetrapyrrolic 20π isophlorin as a transient antiaromatic intermediate which provides a plausible template to synthesize stable antiaromatic molecules. Despite its structural similarity with the 18π aromatic porphyrin, it significantly differs in its electronic and chemical properties. However, due to its unstable nature under ambient conditions it immediately gets oxidized to stable 18π aromatic porphyrin. Similar macrocyclic structures with β-substituted heterocycles, such as furan/thiophene/selenophene, have been synthesized, which undergo facile oxidation to yield the 18π porphyrin dication. Attempts to synthesize stable tetrapyrrolic isophlorin and its metal complex have remained unaccomplished till date. Strategies to synthesize stable core-modified 20π isophlorin and its confused isophlorin derivative have met with considerable success. Predominantly, they are synthesized by replacing three or four pyrroles with furan/thiophene. The 20π systems either with four furan units or with a ‘pair’ of furan and thiophene units were sufficiently stable enough to resist oxidation towards the corresponding porphyrin dication. The 20π isophlorins displayed noncovalent interactions with the curved π surface of fullerene which predominantly rises due to van der Waals attraction between the dissimilar π systems. This antiaromatic isophlorin-fullerene complexes were obtained and successfully characterized by single-crystal X-ray diffraction studies. Replacing only three pyrroles by furan rings yielded the first stable pyrrole derivative of antiaromatic 20π isophlorin, which can be reversibly oxidized to 18π aromatic porphyrin without deprotonating the inner pyrrole NH. In addition, replacing all the pyrrole units of N-confused porphyrin with thiophene yielded the first derivative of confused isophlorin. Further, its two-electron oxidation led to the formation of 18π aromatic cation with enhanced aromaticity. The structure and electronic properties of the oxidized and neutral species were unambiguously determined from a combination of spectroscopic techniques, X-ray crystallography, and computational methods. These studies reveal that antiaromatic systems like isophlorin and its confused isophlorin derivative can be stabilized under ambient conditions and they offer potential to explore the chemistry of 4nπ systems. This Account focuses of recent advances in 20π antiaromatic isophlorins, confused isophlorins, and nocorroles along with their redox chemistry. 1 Introduction2 Stable 20π Isophlorins2.1 Furan-/Thiophene-Based Isophlorins2.2 Pyrrole Isophlorins3 Confused Isophlorins3.1 Isophlorin-Fullerene3.2 meso-meso-Bridged Tetraoxaisophlorin Dimer4. Norcorroles5. Conclusion and Outlook

Syntheses and crystal structures of new aurate salts of adenine or guanine nucleobases

2020 ◽  
Vol 76 (2) ◽  
pp. 139-147
Author(s):  
Anton Savchenkov ◽  
Ludmila Demina ◽  
Alexey Safonov ◽  
Mikhail Grigoriev ◽  
Roman Solovov ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Noncovalent Interactions ◽  
Spectroscopic Techniques ◽  
Stacking Interactions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ft Ir ◽  
Nitrogenous Base ◽  
Ir Spectroscopic ◽  
Chloride Monohydrate

Two new gold(III) complexes with adenine or guanine nitrogenous bases as counter-cations were synthesized. These are 6-amino-7H-purine-1,9-diium tetrachloridogold(III) chloride monohydrate, (C5H7N5)[AuCl4]Cl·H2O, 1, and 2-amino-6-oxo-6,7-dihydro-1H-purin-9-ium tetrachloridogold(III) hemihydrate, (C5H6N5O)[AuCl4]·0.5H2O, 2. Their crystal structures were studied using single-crystal X-ray diffraction and FT–IR spectroscopic techniques. The arrangement of species in the studied crystal structures implies π-stacking interactions, as well as concomitant C—H...π interactions, hydrogen bonds and other types of noncovalent interactions, which were studied qualitatively and quantitatively using the method of molecular Voronoi–Dirichlet polyhedra. The variation of the nitrogenous base from adenine to guanine results in evident differences in the packing of the species in the crystals of 1 and 2. The splitting and shifting of bands in the FT–IR spectra of the title compounds reveals several features representative of noncovalent interactions in their crystal structures.

Physicochemical characterisation of mangafodipir trisodium

1997 ◽  
Vol 38 (5) ◽  
pp. 780-789 ◽  
Author(s):  
B. Tirkkonen ◽  
A. Aukrust ◽  
E. Couture ◽  
D. Grace ◽  
Y. Haile ◽  
...  
Keyword(s):  
Water Molecules ◽  
Spectroscopic Techniques ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Crystallography ◽  
Low Viscosity ◽  
Related Substances ◽  
Organ Specific ◽  
Physicochemical Characterisation ◽  
Physicochemical Measurements

Purpose: To determine the structure and various physicochemical properties of man-gafodipir (MnDPDP) trisodium, the active ingredient of Teslascan, a new organ-specific contrast medium for MR imaging. Material and Methods: The structure of MnDPDP trisodium crystals was determined by X-ray crystallography. The possible existence of polymorphism in MnDPDP trisodium was evaluated by powder X-ray diffraction, optical microscopy, thermal analysis and IR spectroscopy. In addition, various spectroscopic techniques and physicochemical measurements were used for characterisation of MnDPDP trisodium. Results: The crystallographic data obtained for MnDPDP trisodium show that the general core structure of the MnDPDP anion is similar to that seen in related substances. The metal coordination geometry is a distorted octahedron defined by 2 phenolate oxygens, 2 carboxylate oxygens and 2 amine nitrogens. The unit cell contains 2 MnDPDP anions, 6 sodium ions and 50 water molecules. The various spectroscopic data are consistent with the structure determined by X-ray crystallography. The product (Teslascan) has low viscosity, is isotonic with blood and has a physiological pH. Conclusion: MnDPDP trisodium is a crystalline, hygroscopic solid which is readily soluble in water. No evidence of polymorphism was seen in the samples studied.

Water Promoted One-pot Three-Step Synthesis of Novel N-Saccharin Isoxazolines/Isoxazoles Using KI/Oxone Under Ultrasonic Activation

2019 ◽  
Vol 23 (11) ◽  
pp. 1270-1281 ◽  
Author(s):  
Hamza Tachallait ◽  
Mohsine Driowya ◽  
Eleuterio Álvarez ◽  
Rachid Benhida ◽  
Khalid Bougrin
Keyword(s):  
Cycloaddition Reaction ◽  
Hydroxylamine Hydrochloride ◽  
Spectroscopic Techniques ◽  
X Ray Diffraction ◽  
Ultrasonic Activation ◽  
One Pot ◽  
Ultrasonic Probe ◽  
X Ray ◽  
X Ray Crystallography ◽  
New Compounds

A green and efficient regioselective protocol was developed for the preparation of novel isoxazolines and isoxazoles of N-saccharin derivatives via the water-promoted cycloaddition reaction of nitrile oxides with alkenes and alkynes. It is noteworthy that KI/Oxone/water-promoted one-pot three-component reactions of aldehyde, hydroxylamine hydrochloride, and alkene or alkyne were observed to be very satisfactory. The synthesis of all adducts (4a-j/5a-j) has been carried out by this method with high to excellent yields (70-95%) at 25°C within 30 min, using ultrasonic probe. All the new compounds were thoroughly characterized by spectroscopic techniques and also 5b, 5c and 5f were structurally identified by single-crystal X-ray diffraction methods. X-ray crystallography structure analysis clearly supported the regioselectivity of the cycloaddition reaction.

Crystal Structure Refinements of Ge(tP12), Physical Properties and Pressure-induced Phase Transformation Ge(tP12) ↔ Ge(tI4)

2008 ◽  
Vol 63 (6) ◽  
pp. 608-614 ◽  
Author(s):  
Aron Wosylus ◽  
Yurii Prots ◽  
Walter Schnelle ◽  
Michael Hanfland ◽  
Ulrich Schwarz
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Theoretical Calculations ◽  
Structural Similarity ◽  
Phase Region ◽  
Maximum Pressure ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
Two Phase ◽  
X Ray

Single crystals of the modification Ge(tP12) are prepared by compressing semiconductor-grade germanium to pressures above 11(1) GPa and heating to temperatures between 1200(100) and 1500(150) K before a stepwise cooling precedes a complete pressure release. The tetragonal crystal structure of Ge(tP12) is refined by means of single crystal X-ray diffraction data collected at ambient conditions (a = 592.81(2), c = 698.03(3) pm, space group P43212). The atomic arrangement comprising interconnected spiral chains of fourfold symmetry bears a structural similarity to the high-pressure modification S(t I16). High-pressure ambient-temperature powder X-ray diffraction measurements reveal a significant anisotropy of the compressibility compatible with the selected crystal structure description. The determined bulk modulus of Ge(tP12) amounts to 70(1) GPa which is in good agreement with theoretical calculations and similar to experimental values of other four-coordinated germanium allotropes. Ge(tP12) is a diamagnetic semiconductor with χ0 = −3.1(3) ·10−7 emu g−1 and ρ300 K ≈ 6 Ωm at 300 K. At 10.1(3) GPa, the beginning of the formation of Ge(t I 4) indicates the onset of a structural transition. The two-phase region extends up to a maximum pressure of 13.0(5) GPa in the direction of increasing pressures. Upon stepwise decompression, the phase Ge(t P12) is reformed from Ge(t I4) at 9(1) GPa.

Structural Characterization of Gallbladder Stones Using Energy Dispersive X-ray Spectroscopy and X-ray Diffraction

2018 ◽  
Vol 21 (7) ◽  
pp. 495-500 ◽  
Author(s):  
Hassan A. Almarshad ◽  
Sayed M. Badawy ◽  
Abdalkarem F. Alsharari
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Energy Dispersive ◽  
Spectroscopic Techniques ◽  
X Ray Diffraction ◽  
Major Health Problem ◽  
X Ray ◽  
Gallbladder Stones ◽  
Pure Cholesterol ◽  
Scanning Electron

Aim and Objective: Formation of the gallbladder stones is a common disease and a major health problem. The present study aimed to identify the structures of the most common types of gallbladder stones using X-ray spectroscopic techniques, which provide information about the process of stone formation. Material and Method: Phase and elemental compositions of pure cholesterol and mixed gallstones removed from gallbladders of patients were studied using energy-dispersive X-ray spectroscopy combined with scanning electron microscopy analysis and X-ray diffraction. Results: The crystal structures of gallstones which coincide with standard patterns were confirmed by X-ray diffraction. Plate-like cholesterol crystals with laminar shaped and thin layered structures were clearly observed for gallstone of pure cholesterol by scanning electron microscopy; it also revealed different morphologies from mixed cholesterol stones. Elemental analysis of pure cholesterol and mixed gallstones using energy-dispersive X-ray spectroscopy confirmed the different formation processes of the different types of gallstones. Conclusion: The method of fast and reliable X-ray spectroscopic techniques has numerous advantages over the traditional chemical analysis and other analytical techniques. The results also revealed that the X-ray spectroscopy technique is a promising technique that can aid in understanding the pathogenesis of gallstone disease.

scholarly journals Synthesis and Characterisation of Nickel(II) Diphenylalkenylphosphine Complexes

1999 ◽  
Vol 23 (7) ◽  
pp. 418-419
Author(s):  
Simon J. Coles ◽  
Paul Faulds ◽  
Michael B. Hursthouse ◽  
David G. Kelly ◽  
Georgia C. Ranger ◽  
...  
Keyword(s):  
Single Crystal ◽  
Spectroscopic Techniques ◽  
X Ray Diffraction ◽  
X Ray ◽  
Phosphine Complexes

Nickel(II) phosphine complexes are prepared with a series of diphenylalkenylphosphine ligands and characterised by single crystal X-ray diffraction and spectroscopic techniques.

scholarly journals Deep learning for visualization and novelty detection in large X-ray diffraction datasets

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Lars Banko ◽  
Phillip M. Maffettone ◽  
Dennis Naujoks ◽  
Daniel Olds ◽  
Alfred Ludwig
Keyword(s):  
Thin Film ◽  
Crystal Structure ◽  
Artificial Intelligence ◽  
Deep Learning ◽  
Novelty Detection ◽  
Structural Similarity ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Patterns ◽  
Post Hoc

AbstractWe apply variational autoencoders (VAE) to X-ray diffraction (XRD) data analysis on both simulated and experimental thin-film data. We show that crystal structure representations learned by a VAE reveal latent information, such as the structural similarity of textured diffraction patterns. While other artificial intelligence (AI) agents are effective at classifying XRD data into known phases, a similarly conditioned VAE is uniquely effective at knowing what it doesn’t know: it can rapidly identify data outside the distribution it was trained on, such as novel phases and mixtures. These capabilities demonstrate that a VAE is a valuable AI agent for aiding materials discovery and understanding XRD measurements both ‘on-the-fly’ and during post hoc analysis.

scholarly journals 4-vinylpyridine derivatives: Protonation, methylation and silver(I) coordination chemistry

2021 ◽  
pp. 174751982198965
Author(s):  
Guoqi Zhang
Keyword(s):  
Mass Spectrometry ◽  
Schiff Base ◽  
Coordination Chemistry ◽  
Elemental Analysis ◽  
Silver Complex ◽  
Spectroscopic Techniques ◽  
X Ray ◽  
X Ray Crystallography ◽  
Pyridine Moiety ◽  
New Compounds

( E)-4-[2-(Pyridin-4-yl)vinyl]benzaldehyde, containing both a 4-vinylpyridine and an aldehyde functionality, is utilized to develop new, highly conjugated chalcone compounds and a bis-Schiff base azine compound. The chalcone-containing compounds are further explored for their protonation, methylation and silver(I) coordination chemistry using the pyridine moiety. In parallel, a cyano-containing analogue, ( E)-4-[2-(pyridin-4-yl)vinyl]benzonitrile is also synthesized and studied for its silver(I) coordination chemistry. These new compounds are fully characterized by mass spectrometry, elemental analysis and spectroscopic techniques. The methylated product of ( E)-1-(9-anthryl)-3-{4-[2-(pyridin-4-yl)vinyl]phenyl}prop-2-en-1-one and a silver complex of ( E)-4-[2-(pyridin-4-yl)vinyl]benzonitrile are structurally determined by X-ray crystallography.

scholarly journals Born out of Fire and Ice: Polymorph Studies of the Antiviral Famciclovir

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 129
Author(s):  
Liana Vella-Zarb ◽  
Ulrich Baisch
Keyword(s):  
Variable Temperature ◽  
Chemical Properties ◽  
Crystal Form ◽  
X Ray Diffraction ◽  
Crystal Forms ◽  
X Ray ◽  
Physical Chemical ◽  
Diffraction Patterns ◽  
Crystalline Forms

There is much interest and focus on solid forms of famciclovir. However, in spite of the abundance of reported differences in oral bioavailability, compressibility, and other physical–chemical properties of the various crystal forms of this drug, very little precise structural analysis is available in the literature to date. The form used in the commercial formulation is the anhydrous form I. Patents and patent applications report three different anhydrous crystalline forms on the basis of unindexed powder diffraction patterns. Single-crystal and variable-temperature X-ray diffraction experiments using the commercially available anhydrous form of famciclovir were carried out and led not only to the crystal structure determination of the anhydrous form I, but also to discovery of a new crystal form of anhydrous famciclovir from powder data.

Monitoring of Fluctuations in the Physical and Chemical Properties of a High-Calcium Fly Ash

1987 ◽  
Vol 113 ◽  
Author(s):  
Scott Schlorholtz ◽  
Ken Bergeson ◽  
Turgut Demirel
Keyword(s):  
Fly Ash ◽  
Chemical Properties ◽  
Operating Conditions ◽  
Physical And Chemical Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
Morphological Studies ◽  
High Calcium ◽  
Physical And Chemical ◽  
And Chemical Properties

ABSTRACTThe physical and chemical properties of fly ash produced at Ottumwa Generating Station have been monitored since April, 1985. The fly ash is produced from burning a low sulfur, sub-bituminous coal obtained from the Powder River Basin near Gillette, Wyoming. One-hundred and sixty samples of fly ash were obtained during the two year period. All of the samples were subjected to physical testing as specified by ASTM C 311. About one-hundred of the samples were also subjected to a series of tests designed to monitor the self-cementing properties of the fly ash. Many of the fly ash samples were subjected to x-ray diffraction and fluorescence analysis to define the mineralogical and chemical composition of the bulk fly ash as a function of sampling date. Hydration products in selected hardened fly ash pastes, were studied by x-ray diffraction and scanning electron microscopy. The studies indicated that power plant operating conditions influenced the compressive strength of the fly ash paste specimens. Mineralogical and morphological studies of the fly ash pastes indicated that stratlingite formation occurred in the highstrength specimens, while ettringite was the major hydration product evident in the low-strength specimens.

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