Molecular motion of guests trapped in N-methyl-1,3-diaminopropanecadmium(II) tetracyanonickelate(II) host lattices

1993 ◽  
Vol 71 (11) ◽  
pp. 1810-1815 ◽  
Author(s):  
Shinichi Nishikiori ◽  
Christopher I. Ratcliffe ◽  
John A. Ripmeester
Keyword(s):  
Molecular Motion ◽  
Time Averaging ◽  
Axially Symmetric ◽  
Guest Molecules ◽  
H Nmr ◽  
Nmr Techniques ◽  
Temperature Application ◽  
Host Lattices ◽  
Cp Mas Nmr ◽  
Reorientation Process

The molecular motion of guest molecules in Cd(mtn)Ni(CN)4•0.5G clathrates (mtn = N-methyl-1,3-diaminopropane, G = toluene, nitrobenzene, dichloromethane, and chloroform) were studied by using CP/MAS 13C and 2H NMR techniques. At room temperature, application of 13C CP/MAS NMR with dipolar dephasing showed the presence of large amplitude molecular motion in all cases. Temperature dependent 2H NMR spectra for the toluene-d8 clathrate shows that the methyl group rotated at all temperatures down to 77 K. Also, a 2-site in-plane reorientation process of the entire molecule is activated above 180 K, which goes over into axially symmetric in-plane rotation around 450 K. Severely restricted motions were also observed for the nitrobenzene and haloalkane guests. The rather complicated dynamic behaviour of the guest molecules at low and room temperatures can be attributed to the presence of static disorders which disappear at higher temperatures due to time averaging.

Six-Sided Heptaporphyrin Array: Towards a Nano-Sized Cube

2004 ◽  
Vol 69 (5) ◽  
pp. 996-1008 ◽  
Author(s):  
Steven J. Langford ◽  
Clint P. Woodward
Keyword(s):  
Single Step ◽  
One Pot ◽  
H Nmr ◽  
The Core ◽  
Nmr Techniques ◽  
Axial Vertex

A strategy in preparing a family of hexameric porphyrin cubes based on the interplay of Sn(IV)-O and Ru(II)-N interactions is described. In this first iteration, we have prepared the heptamer [SnIV(TPyP)·(4)2][Ru(CO)(TPP)]6 (4 = (E)-(3-(4-pyridyl)acrylate)) constituting a 5,10,15,20-tetra(4-pyridyl)porphyrin (TPyP) core and 5,10,15,20-tetraphenylporphyrin (TPP) faces and compared its formation by stepwise and "one-pot" strategies where up to nine components are assembled in a single step in a regiospecific manner. In one example, the heptamer is formed around the template [SnIV(TPyP)·(4)2] bearing pyridine groups in which the nitrogens radiate octahedrally along each vertex. The ability to modulate the axial vertex through choice of pyridine is also demonstrated. 1H NMR measurements on [SnIV(TPyP)·(4)2][Ru(CO)(TPP)]6 indicate that the protons on the core template are extremely shielded as a result of the anisotropy of the peripheral porphyrin units. Various NMR techniques, including NOESY experiments, have been used to characterise the heptamer in solution.

E-Homolupane Derivatives Substituted in Position 17 and 22a. 1H NMR, 13C NMR and IR Spectra

1995 ◽  
Vol 60 (4) ◽  
pp. 619-635 ◽  
Author(s):  
Václav Křeček ◽  
Stanislav Hilgard ◽  
Miloš Buděšínský ◽  
Alois Vystrčil
Keyword(s):  
Nmr Spectra ◽  
2D Nmr ◽  
Coupling Constants ◽  
Side Chain ◽  
Oxidation Reactions ◽  
H Nmr ◽  
Complete Assignment ◽  
Nmr Techniques ◽  
Intramolecular Association ◽  
C Nmr

A series of derivatives with various oxygen functionalities in positions 17,22a or 19,20 was prepared from diene I and olefin XVI by addition and oxidation reactions. The structure of the obtained compounds was confirmed by 1H NMR, 13C NMR and IR spectroscopy. The kind of intramolecular association of the 17α-hydroxy group was studied in connection with modification of the side chain and substitution in position 22a. Complete assignment of the hydrogen signals and most of the coupling constants was accomplished using a combination of 1D and 2D NMR techniques. The 1H and 13C NMR spectra are discussed.

scholarly journals Interactions between 4-thiothymidine and water-soluble cyclodextrins: Evidence for supramolecular structures in aqueous solutions

2016 ◽  
Vol 12 ◽  
pp. 549-563 ◽  
Author(s):  
Vito Rizzi ◽  
Sergio Matera ◽  
Paola Semeraro ◽  
Paola Fini ◽  
Pinalysa Cosma
Keyword(s):  
Inclusion Complexes ◽  
Pyrimidine Ring ◽  
Protective Role ◽  
Supramolecular Structures ◽  
Water Soluble ◽  
Aqueous Environment ◽  
Spectroscopic Techniques ◽  
Guest Molecules ◽  
H Nmr ◽  
Cv Measurements

Since several years the inclusion of organic compounds (guests) within the hydrophobic cavity (host) of cyclodextrins (CDs) has been the subject of many investigations. Interestingly, the formation of inclusion complexes could affect the properties of the guest molecules and, for example, the influence of the delivery system can be a method to improve/change the photochemical behavior of the guest. In particular, very recent studies have shown the protective role of CDs preventing the degradation of the encapsulated guest. Starting from this consideration, in this work, only the structure and complexation mode of the inclusion complexes involving 4-thiothymidine (S4TdR, a known photosensitizer) and five CDs, namely 2-hydroxypropyl-α-cyclodextrin (2-HP-α-CD), 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD), 2-hydroxypropyl-γ-cyclodextrin (2-HP-γ-CD), heptakis-(2,6-di-O-methyl)-β-cyclodextrin (DIMEB CD) and heptakis-(2,3,6-tri-O-methyl)-β-cyclodextrin (TRIMEB CD) were investigated by different spectroscopic techniques (UV–vis, FTIR–ATR, 1H NMR) and cyclic voltammetry analysis (CV). This work is necessary for a prospective research on the photoreactivity of S4TdR in aqueous environment and in the presence of CDs to prevent its degradation under irradiation. UV–vis, FTIR–ATR and CV measurements suggested the formation of supramolecular structures involving the employed CDs and mainly the pyrimidine ring of S4TdR. 1H NMR analyses confirmed such indication, unveiling the presence of inclusion complexes. The strongest and deepest interactions were suggested when TRIMEB and DIMEB CDs were studied. The S4TdR affinity towards CDs was also evaluated by using the Benesi–Hildebrand (B–H) equation at 25 °C employing CV and 1H NMR methods. The stoichiometry of the interaction was also inferred and it appears to be 1:1 for all examined CDs.

scholarly journals Bioassay-guided isolation and identification of Aedes aegypti larvicidal and biting deterrent compounds from Veratrum lobelianum

2018 ◽  
Vol 16 (1) ◽  
pp. 324-332 ◽  
Author(s):  
Nurhayat Tabanca ◽  
Zulfiqar Ali ◽  
Ulrich R. Bernier ◽  
Nancy Epsky ◽  
Ayse Nalbantsoy ◽  
...  
Keyword(s):  
Larvicidal Activity ◽  
Ethanol Extract ◽  
Ethyl Linoleate ◽  
Significant Activity ◽  
Isolation And Identification ◽  
Human Carcinoma ◽  
Ethyl Palmitate ◽  
H Nmr ◽  
Bioassay Guided Fractionation ◽  
Nmr Techniques

AbstractAn ethanol extract fromVeratrum lobelianumBernh. rhizomes showed larvicidal activity with LC50values of 11.79 ppm and 89.9 ppm against 1stand 4thinstar larvae, respectively, at 24 h post-treatment. The extract also showed proportion not biting (PNB) value of 0.76 at 100 μg/cm2against females ofAe.aegypti. Systematic bioassay-guided fractionation ofV.lobelianumextract resulted in the isolation of five compounds that were identified as ethyl palmitate (1), ethyl linoleate (2), β-sitosterol (3), resveratrol (4) and oxyresveratrol (5) by GC-MS,1H-NMR, and13C-NMR techniques, comparison with literature data, and confirmation with authentic compounds. Compound2exhibited larvicidal activity with an LC50value of 24.1 (22.0-26.2) ppm whereas1was inactive. β-Sitosterol (3) displayed the highest larvicidal activity with LC50= 1.7 (1.3-12.3) ppm and LC90= 5.1 (3.4-13.8) ppm. Compounds4and5had larvicidal activity with LC50values of 18.5 (15.3-23.3) and 22.6 (19.0-26.8) ppm, respectively, and had an equivalent PNB values of 0.75 at 25 nmol/cm2. In addition,4and5were explored for their human-based repellency againstAe.aegypti, attractiveness against male medfliesCeratitis capitata, and also evaluated against series of human carcinoma cells (A549, HEK293, HeLa, SH-SY5Y); however, no significant activity was found.

scholarly journals New Sensitive Kinetic Spectrophotometric Methods for Determination of Omeprazole in Dosage Forms

2009 ◽  
Vol 2009 ◽  
pp. 1-11 ◽  
Author(s):  
Ashraf M. Mahmoud
Keyword(s):  
Reference Method ◽  
Fixed Time ◽  
Dosage Forms ◽  
Charge Transfer Complexes ◽  
Specific Rate ◽  
Spectrophotometric Methods ◽  
H Nmr ◽  
Nmr Techniques ◽  
Kinetic Spectrophotometric

New rapid, sensitive, and accurate kinetic spectrophotometric methods were developed, for the first time, to determine omeprazole (OMZ) in its dosage forms. The methods were based on the formation of charge-transfer complexes with both iodine and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The variables that affected the reactions were carefully studied and optimized. The formed complexes and the site of interaction were examined by UV/VIS, IR, and1H-NMR techniques, and computational molecular modeling. Under optimum conditions, the stoichiometry of the reactions between OMZ and the acceptors was found to be 1 : 1. The order of the reactions and the specific rate constants were determined. The thermodynamics of the complexes were computed and the mechanism of the reactions was postulated. The initial rate and fixed time methods were utilized for the determination of OMZ concentrations. The linear ranges for the proposed methods were 0.10–3.00 and 0.50–25.00   with the lowest LOD of 0.03 and 0.14   for iodine and DDQ, respectively. Analytical performance of the methods was statistically validated; RSD was <1.25% for the precision and <1.95% for the accuracy. The proposed methods were successfully applied to the analysis of OMZ in its dosage forms; the recovery was 98.91–100.32%  0.94–1.84, and was found to be comparable with that of reference method.

Adsorption behaviour of a CdII–triazole MOF for butan-2-one in a single-crystal-to-single-crystal (SCSC) fashion: the role of hydrogen bonding and C—H...π interactions

2019 ◽  
Vol 75 (6) ◽  
pp. 806-811
Author(s):  
Jia Wang ◽  
Tianchao You ◽  
Teng Wang ◽  
Qikui Liu ◽  
Jianping Ma ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Single Crystal ◽  
Specific Binding ◽  
Supramolecular Interactions ◽  
Adsorption Behaviour ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
X Ray ◽  
Π Interactions ◽  
H Nmr

The adsorption behaviour of the CdII–MOF {[Cd(L)2(ClO4)2]·H2O (1), where L is 4-amino-3,5-bis[3-(pyridin-4-yl)phenyl]-1,2,4-triazole, for butan-2-one was investigated in a single-crystal-to-single-crystal (SCSC) fashion. A new host–guest system that encapsulated butan-2-one molecules, namely poly[[bis{μ3-4-amino-3,5-bis[3-(pyridin-4-yl)phenyl]-1,2,4-triazole}cadmium(II)] bis(perchlorate) butanone sesquisolvate], {[Cd(C24H18N6)2](ClO4)2·1.5C4H8O} n , denoted C4H8O@Cd-MOF (2), was obtained via an SCSC transformation. MOF 2 crystallizes in the tetragonal space group P43212. The specific binding sites for butan-2-one in the host were determined by single-crystal X-ray diffraction studies. N—H...O and C—H...O hydrogen-bonding interactions and C—H...π interactions between the framework, ClO4 − anions and guest molecules co-operatively bind 1.5 butan-2-one molecules within the channels. The adsorption behaviour was further evidenced by 1H NMR, IR, TGA and powder X-ray diffraction experiments, which are consistent with the single-crystal X-ray analysis. A 1H NMR experiment demonstrates that the supramolecular interactions between the framework, ClO4 − anions and guest molecules in MOF 2 lead to a high butan-2-one uptake in the channel.

5,10,15-Triarylcorrole atropisomerism

2020 ◽  
Vol 24 (01n03) ◽  
pp. 153-160
Author(s):  
Martina Bischetti ◽  
Giuseppe Pomarico ◽  
Sara Nardis ◽  
Federica Mandoj ◽  
Daniel O. Cicero ◽  
...  
Keyword(s):  
Nmr Spectra ◽  
Aryl Ring ◽  
H Nmr ◽  
Ring Rotation ◽  
Complete Assignment ◽  
Nmr Techniques ◽  
Thermodynamic Factors

A series of 5,10,15-triarylcorroles has been prepared, with the meso-aryl rings functionalized with different substituents to investigate their influence on the aryl ring rotation with respect to the corrole plane. The study has been carried out by different NMR techniques, allowing the complete assignment of the 1H NMR spectra and giving insights on the kinetic and thermodynamic factors driving the atropisomerism in triarylcorrole derivatives.

Investigation of the disorder of dibromo- and dichloromethane in their tri-ortho-thymotide clathrates using X-ray diffraction and solid-state 2H NMR spectroscopy

2011 ◽  
Vol 89 (7) ◽  
pp. 854-862
Author(s):  
Glenn A. Facey ◽  
Ilia Korobkov
Keyword(s):  
Solid State ◽  
Nmr Spectroscopy ◽  
Guest Molecule ◽  
Type B ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
X Ray ◽  
Twofold Axis ◽  
H Nmr ◽  
Heavy Atoms

The tri-ortho-thymotide (TOT) clathrates of dibromo- and dichloromethane were characterized by single crystal X-ray diffraction at 200 K and solid-state 2H NMR spectroscopy as a function of temperature. The host structure was found to be typical of other cage-type TOT clathrates. The X-ray results showed a substantial amount of disorder among the guest molecules. In both clathrates, multiple guest molecule positions could be modeled. The heavy atoms of all the guest molecule positions lie approximately in the same plane, with some out-of-plane distortion. The guest molecules were of two different types in positions symmetric about the crystallographic twofold rotation axis: type A guests, with carbon atoms well removed from the crystallographic twofold axis, and type B guests, with carbon atoms very close to the twofold axis. The 2H NMR spectra for the guests confirmed that the disorder was dynamic. The experimental results could be accounted for by the presence of three simultaneous types of molecular motion, all fast with respect to the 2H quadrupolar interaction: (i) twofold molecular flips about the molecular C2 symmetry axis, (ii) exchange between the type A and type B sites in a single plane, and (iii) a two-site libration of the plane containing the heavy atoms of the A and B guest sites with a temperature-dependent amplitude.

scholarly journals Antifungal Activity and Isomerization of Octadecyl p-coumarates from Ipomoea carnea subsp. fistulosa

2011 ◽  
Vol 6 (12) ◽  
pp. 1934578X1100601 ◽  
Author(s):  
Eugene Sebastian J. Nidiry ◽  
Girija Ganeshan ◽  
Ankanahalli N. Lokesha
Keyword(s):  
2D Nmr ◽  
Conclusive Evidence ◽  
Isolation And Purification ◽  
H Nmr ◽  
Ipomoea Carnea ◽  
Dependent Inhibition ◽  
Test Organisms ◽  
Nmr Techniques ◽  
Dose Dependent Inhibition ◽  
Dose Dependent

Bioassay monitored HPLC assisted isolation and purification of the chief antifungal fraction of the leaves of Ipomoea carnea subsp. fistulosa (Convulvulaceae) were achieved using Colletotrichum gloeosporioides and Cladosporium cucumerinum as test organisms. The activity of the purified fraction was further confirmed by the dose dependent inhibition of the spore germination of Alternaria alternata and A. porri. The active fraction was identified as a mixture of ( E)-octadecyl p-coumarate and ( Z)-octadecyl p-coumarate. The two isomers were detected on an HPLC column with substantially different retention times, but once eluted from the column, one form was partly converted to the other in daylight. Conclusive evidence for the structures and their isomerization were obtained from the HPLC behavior, IR, UV, HRESIMS, CIMS and NMR spectral data. Important 1H NMR and 13C NMR signals could be separately assigned for the isomers using 2D NMR techniques.

Weiss's endo- and exo-tetracyclo[5.5.1.0.2,6 010,13]tridecane-4,8,12-trione: analysis of 1H NMR couplings in a system of fused 5-membered rings

1994 ◽  
Vol 72 (9) ◽  
pp. 1926-1932 ◽  
Author(s):  
Steven H. Bertz ◽  
Weijiang Zhang ◽  
James M. Cook ◽  
Martha D. Bruch ◽  
Lynn W. Jelinski
Keyword(s):  
Spin Systems ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Theoretical Treatment ◽  
H Nmr ◽  
Tightly Coupled ◽  
Nmr Techniques ◽  
Spin Coupling Constants ◽  
Stringent Test ◽  
Spin Spin Coupling

The configurational isomers of the title compounds consist of four fused five-membered rings. They contain tightly coupled 1H NMR spin systems, which provide excellent models for establishing the relationships between coupling constants and conformation. Complete chemical shift assignments and spin–spin coupling constants are reported for the title compounds by using high-field (500 MHz) 1H NMR techniques (e.g., 2D homonuclear and heteronuclear experiments, difference NOE enhancements, and computational spin simulations). In addition to the more familiar two- and three-bond couplings, the spectra of 1 and 2 also contain a number of long-range (four- and five- bond) couplings, which provide a stringent test of Barfield's theoretical treatment of four-bond couplings.

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