scholarly journals Cyclodextrin-Driven Formation of Double Six-Ring (D6R) Silicate Cage: NMR Spectroscopic Characterization from Solution to Crystals

Crystals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 457 ◽  
Author(s):  
Mohamed Haouas ◽  
Clément Falaise ◽  
Charlotte Martineau-Corcos ◽  
Emmanuel Cadot
Keyword(s):  
Spectroscopic Characterization ◽  
Xrd Analysis ◽  
Group Symmetry ◽  
Cage Structure ◽  
Counter Ions ◽  
Supramolecular Adduct ◽  
Hybrid Complex ◽  
Secondary Building Units ◽  
Perfect Symmetry ◽  
Donor Acceptor

Identification and isolation of secondary building units (SBUs) from synthesis media of zeolites still represent a challenging task for chemists. The cage structure anion Si12O3012− known as the double six-ring (D6R) was synthesized from α-cyclodextrin (α-CD) mediated alkaline silicate solutions and conditions of its stability and reactivity in aqueous solution were studied by using nuclear magnetic resonance (NMR) spectroscopy. A single crystal X-ray diffraction (XRD) analysis revealed a novel polymorph of the hybrid complex K12Si12O30·2α-CD·nD2O (n ≈ 30–40), which crystallizes in the orthorhombic C2221 space group symmetry with a = 14.841(4) Å, b = 25.855(6) Å, and c = 41.91(1) Å. The supramolecular adduct of the silicate anion sandwiched by two α-CDs forms a perfect symmetry matching the H-bonding donor-acceptor system between the organic macrocycle and the D6R unit. The driving force of such a hybrid assembly has found to be strongly dependent on the nature of the cation present as large alkali counter ions (K+, Rb+ and Cs+), which stabilize the D6R structure acting as templates. Lastly, we provided the first 29Si MAS NMR measurement of 3Q Si in an isolated D6R unit that allows the verification of the linear correlation between the chemical shift and <SiOSi> bond angle for 3Q Si species in DnR cages (n = 3, 4, 6).

Neutral 4-phenyl-1-[phenyl(pyridin-2-yl)methylidene]semicarbazide and its salt forms with inorganic anions

2019 ◽  
Vol 75 (1) ◽  
pp. 1-7
Author(s):  
Vinicius Oliveira Araujo ◽  
Bárbara Tirloni ◽  
Lívia Streit ◽  
Vânia Denise Schwade
Keyword(s):  
Solid State ◽  
Spectroscopic Characterization ◽  
Water Molecules ◽  
Keto Form ◽  
Chloride Dihydrate ◽  
Ir And Nmr Spectroscopy ◽  
Tautomeric Forms ◽  
Counter Ions ◽  
Salt Forms ◽  
Good Agreement

Semicarbazones can exist in two tautomeric forms. In the solid state, they are found in the keto form. This work presents the synthesis, structures and spectroscopic characterization (IR and NMR spectroscopy) of four such compounds, namely the neutral molecule 4-phenyl-1-[phenyl(pyridin-2-yl)methylidene]semicarbazide, C19H16N4O, (I), abbreviated as HBzPyS, and three different hydrated salts, namely the chloride dihydrate, C19H17N4O+·Cl−·2H2O, (II), the nitrate dihydrate, C19H17N4O+·NO3 −·2H2O, (III), and the thiocyanate 2.5-hydrate, C19H17N4O+·SCN−·2.5H2O, (IV), of 2-[phenyl({[(phenylcarbamoyl)amino]imino})methyl]pyridinium, abbreviated as [H2BzPyS]+·X −·nH2O, with X = Cl− and n = 2 for (II), X = NO3 − and n = 2 for (III), and X = SCN− and n = 2.5 for (IV), showing the influence of the anionic form in the intermolecular interactions. Water molecules and counter-ions (chloride or nitrate) are involved in the formation of a two-dimensional arrangement by the establishment of hydrogen bonds with the N—H groups of the cation, stabilizing the E isomers in the solid state. The neutral HBzPyS molecule crystallized as the E isomer due to the existence of weak π–π interactions between pairs of molecules. The calculated IR spectrum of the hydrated [H2BzPyS]+ cation is in good agreement with the experimental results.

Direct Spectroscopic Characterization of a Transitory Dirhodium Donor-Acceptor Carbene Complex

Science ◽  
2013 ◽  
Vol 342 (6156) ◽  
pp. 351-354 ◽  
Author(s):  
K. P. Kornecki ◽  
J. F. Briones ◽  
V. Boyarskikh ◽  
F. Fullilove ◽  
J. Autschbach ◽  
...  
Keyword(s):  
Spectroscopic Characterization ◽  
Carbene Complex ◽  
Donor Acceptor

Poly(bisthiophene-carbazole-fullerene) Double-Cable Polymer As New Donor−acceptor Material: Preparation and Electrochemical and Spectroscopic Characterization

2009 ◽  
Vol 113 (43) ◽  
pp. 14087-14093 ◽  
Author(s):  
Nicolas Berton ◽  
Isabelle Fabre-Francke ◽  
David Bourrat ◽  
Frédéric Chandezon ◽  
Saïd Sadki
Keyword(s):  
Spectroscopic Characterization ◽  
Donor Acceptor ◽  
Material Preparation

Avoiding problems with hydrogen misplacement in reporting crystal structures

2013 ◽  
Vol 69 (8) ◽  
pp. 808-810 ◽  
Author(s):  
Ivan Bernal ◽  
Steven F. Watkins
Keyword(s):  
Hydrogen Bonding ◽  
Crystal Structures ◽  
Three Dimensional ◽  
Group Symmetry ◽  
Quality Data ◽  
Computing Systems ◽  
High Quality Data ◽  
Positional Disorder ◽  
Donor Acceptor ◽  
Close Contacts

Intermolecular hydrogen bonding is an integral part of many crystal structures. Hydrogen bonding sometimes results in one-, two- or three-dimensional supramolecular assemblies, a common feature of which is positional disorder of H atoms related to space-group symmetry. Yet some reported structures fail to include all possible donor–acceptor close contacts, or to seek H-atom electron densities associated with apparentD—H...Atrios, while some H-atom positions violate principles of chemistry or crystal physics. Modern diffraction equipment and sophisticated computing systems provide high-quality data; thus, failure to characterize and report fully an accurate, complete and physically correct hydrogen-bonding model should not be acceptable. We illustrate the relevant issues with three published examples in the hope of slowing the proliferation of these problems, with the scientifically desirable goal of improving the accuracy of crystallographic models while also providing improved search keys for information retrieval.

scholarly journals Crystallographic and spectroscopic characterization of (R)-O-acetylmandelic acid

2016 ◽  
Vol 72 (7) ◽  
pp. 901-903
Author(s):  
Cady Cirbes ◽  
Joseph M. Tanski
Keyword(s):  
Hydrogen Bonding ◽  
Carboxylic Acid ◽  
Mandelic Acid ◽  
Phenylacetic Acid ◽  
Spectroscopic Characterization ◽  
Acid Group ◽  
Intermolecular Hydrogen Bonding ◽  
Carboxylic Acid Group ◽  
Donor Acceptor

The title compound [systematic name: (R)-(−)-2-acetoxy-2-phenylacetic acid], C10H10O4, is a resolved chiral ester derivative of mandelic acid. The compound contains an acetate group and a carboxylic acid group, which engage in intermolecular hydrogen bonding, forming chains extending parallel to [001] with a short donor–acceptor hydrogen-bonding distance of 2.676 (2) Å.

scholarly journals Crystallographic and spectroscopic characterization of 4-nitro-2-(trifluoromethyl)benzoic acid and 4-nitro-3-(trifluoromethyl)benzoic acid

2019 ◽  
Vol 75 (4) ◽  
pp. 524-528
Author(s):  
George L. Diehl III ◽  
Lisa Je ◽  
Joseph M. Tanski
Keyword(s):  
Hydrogen Bonding ◽  
Carboxylic Acid ◽  
Benzoic Acid ◽  
Nitro Group ◽  
Spectroscopic Characterization ◽  
Acid Group ◽  
Carboxylic Acid Group ◽  
Donor Acceptor ◽  
Graph Set

The title compounds, both C8H4F3NO4, represent two isomers of nitro trifluoromethyl benzoic acid. The compounds each contain a nitro functionality para to the carboxylic acid group, with the trifluoromethyl substituent ortho to the acid group in the 2-isomer and ortho to the nitro group in the 3-isomer. The regiochemistry with respect to the trifluoromethyl group results in steric interactions that rotate the carboxylic acid group or the nitro group out of the aromatic plane in the 2- and 3-isomer, respectively. Each molecule engages in intermolecular hydrogen bonding, forming head-to-tail dimers with graph-set notation R 2 2(8) and donor–acceptor hydrogen-bonding distances of 2.7042 (14) Å in the 2-isomer and 2.6337 (16) in the 3-isomer. Recrystallization attempts did not yield untwinned crystals.

Spectroscopic Characterization of Ion-Implanted GaN

2002 ◽  
Vol 743 ◽  
Author(s):  
L. Chen ◽  
B. J. Skromme
Keyword(s):  
Low Temperature ◽  
High Purity ◽  
Spectroscopic Characterization ◽  
Acceptor Pair ◽  
Donor Acceptor ◽  
Optical Activation ◽  
Donor Acceptor Pair ◽  
Low Temperature Photoluminescence ◽  
Do So

ABSTRACTWe investigate implantation of high purity HVPE GaN with Mg, Be, C, Zn, Cd, Ca, N, O, P, As, Ne, and Ar. After annealing at 1300 °C, the material is characterized using low temperature photoluminescence (PL). The Mg acceptors exhibit much better optical activation than Be, C, Zn, Cd, or Ca acceptors implanted and annealed under the same conditions. Acceptor-bound exciton peaks and well-resolved donor-acceptor pair bands are observed for both Mg and Zn. A broad peak centered near 2.78 eV is obtained for Cd, confirming that it is deeper than Zn. Isoelectronic As or P exhibit sharp no-phonon bound exciton lines at 2.952 and 3.200 eV, respectively. Defect-related bands centered at 2.2 and 2.35 eV are studied. Both Be and C strongly enhance the yellow (2.2 eV) PL band, but no other impurities do so, including O.

Zweikernige μ-Nitridokom plexe von Molybdän / Binuclear μ-Nitrido Complexes of Molybdenum

1986 ◽  
Vol 41 (6) ◽  
pp. 793-795 ◽  
Author(s):  
Josef Schmitte ◽  
Kurt Dehnicke
Keyword(s):  
Ir Spectra ◽  
Acceptor Complex ◽  
Nitrido Complexes ◽  
Counter Ions ◽  
Donor Acceptor ◽  
Molybdenum Pentachloride

The μ-nitrido complexes [Mo2NC19]2⊖ and [Mo2NCl9]⊖, with PPh3Me⊕ as the counter ions, are prepared by reactions of [MoNC14]2⊖ and [MoNCl4]⊖, respectively, with molybdenum pentachloride in CH2Cl2. With POCl3 [Mo2NC19]2⊖ forms the donor-acceptor complex [Mo2NCl9(POCl3)]2⊖, whereas with acetonitrile disproportionation occurs, [MONCI4]⊖ and [MoCl5(CH3CN)]⊖ being formed, respectively. The IR spectra are discussed.

scholarly journals Synthesis and Spectroscopic Characterization of Thienopyrazine-Based Fluorophores for Application in Luminescent Solar Concentrators (LSCs)

Molecules ◽  
2021 ◽  
Vol 26 (18) ◽  
pp. 5428
Author(s):  
Xheila Yzeiri ◽  
Massimo Calamante ◽  
Alessio Dessì ◽  
Daniele Franchi ◽  
Andrea Pucci ◽  
...  
Keyword(s):  
Stokes Shift ◽  
Spectroscopic Characterization ◽  
Spectroscopic Studies ◽  
Solar Concentrators ◽  
Luminescent Solar Concentrators ◽  
Silicon Photovoltaics ◽  
Donor Acceptor ◽  
Intense Light ◽  
Stokes Shifts

Organic fluorophores have found broad application as emitters in luminescent solar concentrators (LSCs) for silicon photovoltaics. In particular, the preparation of organic conjugated systems with intense light-harvesting ability, emissions in the deep-red and NIR regions, and large Stokes shift values represent a very challenging undertaking. Here, we report a simple and easy way to prepare three symmetrical donor–acceptor–donor (DAD) organic-emitting materials based on a thienopyrazine core. The central core in the three dyes was modified with the introduction of aromatic substituents, aiming to affect their optical properties. The fluorophores were characterized by spectroscopic studies. In all cases, visible-NIR emissions with large Stokes shifts were found, highlighting these molecules as promising materials for the application in LSCs.

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