Search results for "NMR"

Sesquiterpene lactones, flavonoids and coumarins from Centaurea collina

1989

Abstract The isolation and characterization of two coumarins, five flavonoids and four sesquiterpene lactones from the aerial parts of Centaurea collina are reported. The 13 C NMR data are included.

Ultrafast energy transfer in dansylated POPAM–eosin complexes

2006

Abstract Excitation energy transfer (EET) in dendritic host–guest complexes has been studied. Three generations G2, G3 and G4 of dansyl substituted poly(propyleneamine) dendrimers (POPAM) were complexed with a fluorescent dye eosin in chloroform solution. Arrival of excitation from dansyls to eosin was monitored by femtosecond transient absorption spectroscopy. EET rates from the dansyls to eosin(s) are characterised by two time constants 1 ps and 6 ps independent of dendrimer generation. Relaxation processes in eosin were clearly faster when complexed with dendrimer than in solution. As several eosins are bound to G3 and G4 dendrimers, besides host–guest interaction, also eosin–eosin inter…

Stufenweise darstellung eines cycloheptamers aus p-kresol, 4-tert-butylphenol und formaldehyd. Vergleich mit einem phenolischen, heptanuklearen kette…

1980

A phenolic cycloheptamer (11) and an analogous chain oligomer (10) with nearly the same structure were gained by stepwise syntheses. The cycloheptamer has a higher melting point and a better solubility in chloroform. In contrast to the chain oligomer his infrared spectrum indicates a stronger association of the hydroxyl groups which is not influenced by the solvent. The mass spectra announce a preferred statistical cleavage along the chain of compound 10 and a great stability of the ring of 11 which preferentially loses his substituents. The 1H NMR spectra confirm the constitutions of the chain (10) and ring compound (11). The cycloheptamer is distinguished by a ring inversion or a pseudoro…

Multivariate correlation between13C and31P NMR spectral data on dissolved lignin and the combustion properties of kraft black liquor

1999

Slow Relaxation of the Magnetization in a {Co <sup>III</sup>Mn <sup>III</sup>} Heterometallic Brick-Wall Network

2021

The use of the cyanide-bearing dicobalt(III) complex (PPh 4 ) 2 [Co 2 III (m-2,5-dpp)(CN) 8 ] as a metalloligand towards [Mn(salen)(H 2 O)]ClO 4 afforded the heterobimetallic two-dimensional compound of formula [{Mn III (salen)} 2 {(m-NC) 4 Co 2 III (m-2,5-dpp)(CN) 4 }] n (1) [PPh 4 + = teraphenylphosphonium cation, 2,5-dpp = 2,5-bis(2-pyridyl)pyrazine and H 2 salen = N,N’ -ethylenebis(salicylideneimine)] whose structure has been determined by single crystal X-ray diffraction. Compound 1 exhibits a neutral brick-wall structure, where each [Co 2 III (m-2,5-dpp)(CN) 8 ] 2- unit adopts a tetrakis-monodentate bridging mode towards four {Mn III (salen)} + fragments through four of its eight cyan…

Synthesis and characterization of a new spirooxindole grafted pyrrolidino/piperidine moiety

2021

In this text, we synthesized and characterized a new spirooxindole grafted pyrrolidino/piperidine moieties. The new hit obtained via one-pot reaction of the chalcone based cyclohexanone with the isatin and (R)-piperidine-2-carboxylic acid in MeOH under reflux for 48 h. The compound exclusively obtained in regio-selective and diastereo-selective manner. The chemical feature of the target compound is confirmed by 1H NMR and 13C NMR spectroscopy. In addition, we reported for the first time the X-ray single crystal structure of isatin. Its molecular packing  depends mainly on strong O…H hydrogen bonds and π-π stacking interactions as well as weak H…H and H…C contacts. Using DFT calculations, is…

A resorcinol derived calix[5]arene with C5-symmetry

1994

Abstract Condensation of 2,4-dihydroxy-3-hydroxymethyl benzophenone (4) in dioxane/H2SO4 gave the cyclic pentamer 5, a calix[5]arene with regular incorporation of the resorcinol units via their 2- and 6-positions. The structure follows from the 1H NMR and mass spectra and was further confirmed by single crystal X-ray analysis. Dynamic NMR in C2D2Cl4 gave a surprisingly high barrier of ΔG‡ = 17.3 kcal/mol for the cone-to-cone ring inversion.

Synthesis, characterization and crystal structure of 2-dicyanomethylene-1,3-bis(ferrocenylmethyl)-1,3-diazolidine

1993

By reaction of N,N′-ethylenebis(ferrocenylmethylamine)1 with tetracyanoethylene in dichloromethane the yellow compound 2-dicyanomethylene-1,3-bis(ferrocenylmethyl)-1,3-diazolidine 2 can be isolated. The single-crystal structure of 2 has been determined. It crystallizes in the non-centrosymmetric trigonal space group P3221, a= 12.255(2), c= 13.831(7)A, Z= 3. Refinement of the atomic parameters by least-squares techniques gave a final R factor of 0.038 (R′= 0.034) for 1782 observed reflections having I > 2.5δ(I). Anomalous values of the bond distances and the vinyl carbon chemical shift in the 13C NMR spectrum of 2 are explained on the basis of a polarization due to a combination of the elect…

BODIPY Dyes Functionalized with Pendant Cyclic and Acyclic Polyamines

2013

The synthesis and characterization of a series of BODIPY derivatives substituted with acyclic and cyclic polyamines, in particular, cyclen and homocyclen, are reported. The 19F NMR, UV/Vis, and fluorescence spectroscopic data of these compounds are discussed. One compound was found to be very selective for CuII ions, which makes it a very promising system for CuII detection.

Substituent and temperature controlled tautomerism: Multinuclear magnetic resonance, X-ray, and theoretical studies on 2-phenacylquinolines

2000

Proton-transfer equilibria in chloroform solution of twelve 2-phenacylquinolines were studied by 1H, 13C and 15N NMR spectroscopies. The (Z)-enaminone form stabilized by an intramolecular hydrogen bond was found to prevail in all cases. Electron-donating substituents in the phenacyl part of the molecule lead to an increase of the ketimine form (to 33% for p-NMe2). Variable temperature 1H NMR measurements show that higher temperatures have the same effect. The negative logarithm values of the equilibrium constant, pKT, were found to be linearly dependent on Hammett σ substituent constants. The pKTvs. temperature correlation also has a linear character. In general, strong electron-withdrawing…