Search results for "Spectroscopy"
showing 10 items of 10293 documents
Conformational polymorphism and amphiphilic properties of resorcinarene octapodands
2010
o-Nitroaniline functionalized resorcinarene octapodands 1-5 with pendant methyl, ethyl, pentyl, nonyl or 1-decenyl groups, respectively, were synthesized and their structural properties investigated using X-ray crystallography and NMR spectroscopy. The upper rim of each podand is identical containing flexible side arms, in which rotation around the -OCH(2)CH(2)N- linkers create excellent possibilities for polymorphism. Two conformational polymorphs of acetone solvate of 2 were identified containing different side arm orientation and crystal packing. Compound 1 crystallized from acetone and nitromethane yielding two pseudopolymorphs with different packing motifs. The longer alkyl chains of 3…
Configuration of Enolates of β-Ketocarboxylic Acid Esters — Carbocation-Carbanion Salts
1996
Deprotonation of (Z)- or (E)-3-hydroxy-2,3-dimesitylpropenoic acid methyl ester (1a) with tetrakis(dimethylamino)-methane (3) led to stable salt (E)-2a, which belongs to a very rare species of salts that consist of a heteroatom-stabilized carbocation and a heteroatom-stabilized carbanion. An analogous guanidinium salt (E)-2b was formed in the reaction of 3-oxo-2,3-diphenylpropanoic acid methyl ester (1b) and 3. The molecular structures of these enolates were studied by NMR spectroscopy and an X-ray analysis of (E)-2a {MC[N(CH3)2]3} and compared with those of the corresponding alkali enolates.
Noncovalent molecular imprinting: antibody-like molecular recognition in polymeric network materials
1997
Abstract Molecular imprinting techniques allow the preparation of polymeric receptors which bind small molecules with affinities and selectivities of the same order as those observed in the binding of antigens by antibodies. The molecular imprinting technology has now reached a stage where the commercial use of imprinted materials is being assessed, notably for separations requiring strong and selective binding of small molecules. This development is driven by the potential advantages of polymeric receptors over biological in terms of stability, capacity, cost and ease of preparation. In this short review the state of the art of noncovalent imprinting is summarised indicating a few areas in…
Radiosynthesis of (±)-(2-((4-(2-[18F]fluoro-ethoxy)phenyl)bis(4-methoxy-phenyl)methoxy)ethylpiperidine-3-carboxylic acid: a potential GAT-3 PET ligan…
2001
A dysfunction of GABAergic neurotransmission is related to diseases such as epilepsy, Huntington-disease and Parkinson-syndrome. A new 18F-fluorine labelled GABA transporter ligand for the GABA-transporter subtype GAT-3 was developed which may allow the in vivo visualisation of GABAergic neurotransmission. The precursors ethyl (2-(4-hydroxyphenyl)bis(4-methoxyphenyl)-methoxy)ethyl)-piperidine-3-carboxylate and ethyl(2-((4-(2-tosylethoxy)phenyl)-bis(4-methoxyphenyl)-methoxy) ethyl)-piperidine3-carboxylate were synthesised and labelled by the use of 2-[18F]fluoroethyltosylate or [18F]fluoride. Subsequent cleavage of the ester moiety gave the final product (±)-(2-((4-(2-[18F]fluoroethoxy)pheny…
Isolation of enantiomerically pure organometallic palladium compounds: synthesis of the triangles prepared from enantiopure [cis-Pd2(C6H4PPh2)2(NCCH3…
2009
Reaction of the racemic [Pd(C(6)H(4)PPh(2))Br](4) () with the silver salt of 1R-(1alpha,2beta,3alpha)]-3-methyl-2-(nitromethyl)-5-oxocyclopentaneacetate, (R)-AgO(2)CR*, results in the formation of a mixture of diastereoisomers (RRR)- and (SRR)- of the formula Pd(2)(C(6)H(4)PPh(2))(2)(O(2)CR*)(2) that were separated by standard chromatographic methods. Each diastereoisomer was readily converted into the tetrametallic stereoisomers (SS)- and (RR)-, of the formula [Pd(C(6)H(4)PPh(2))Br](4) that were isolated and characterized by X-ray crystallography. The R enantiomer of the solvated cationic species [cis-Pd(2)(C(6)H(4)PPh(2))(2)(NCCH(3))(4)](2+), obtained from (RR)-, was reacted with ammonium…
Synthesis, Spectroscopic, and Structural Investigation of the Cyclic [N(PR2E)2]+ Cations (E = Se, Te; R = iPr, Ph): the Effect of Anion and R-Group …
2006
Two-electron oxidation of the [N(PiPr2E)2]- anion with iodine produces the cyclic [N(PiPr2E)2]+ (E =Se, Te) cations, which exhibit long E-E bonds in the iodide salts [N(PiPr2Se)2]I (4) and [N(PiPr2Te)2]I (5). The iodide salts 4 and 5 are converted to the ion-separated salts [N(PiPr2Se)2]SbF6 (6) and [N(PiPr2Te)2]SbF6 (7) upon treatment with AgSbF6. Compounds 4-7 were characterized in solution by multinuclear NMR, vibrational, and UV-visible spectroscopy supported by DFT calculations. A structural comparison of salts 4-7 and [N(PiPr2Te)2]Cl (8) confirms that the long E-E bonds in 4, 5, and 8 can be attributed primarily to the donation of electron density from a lone pair of the halide counte…
Synthesis of C1-[18F]fluoroethylamnino asparagine for imaging cancer
2001
C1-[18F]fluoroethylamino asparagine was synthesised from N1-t-boc C1-p-nitrophenol asparagine and the radiolabelled precursor [18F]flouroethylamine in a one-pot-synthesis. The yield of this synthesis was 22% referring to [18F]fluoride, including the removal of the protection groups. The in vivo tests are in progress.
Bis(triorganometal) and diorganometal 1,3-dithiolates (R3M)2(C6H3XS2) and R2M(C6H3XS2) (M = Sn, Pb; X= H, Cl)
1984
Abstract Bis(triorganometal) and diorganometal 1,3-dithiolates (R3M)2(C6H3XS2) (C6H5XS2 1,3-dithiobenzene (for X = H) or 1,3-dithio-4-chlorobenzene (for X = Cl); M = Sn, X = Cl, R = CH3, C6H5; M = Pb, X = H, Cl, R = CH3, C2H5) and R2M(C6H3XS2) (R = CH3, C2H5, C6H5; M = Sn, X = Cl; M = Pb, X = H, Cl) have been prepared as the first organometal IVB derivatives of 1,3-dithiols, and investigated by vibrational, 1H NMR, and (in the case of organotin compounds) Mossbauer spectroscopy. The triorganometal derivatives are monomeric and the diorganometal derivatives dimeric in solution (37° C). For the latter a twelve-membered ring structure is proposed for both solution and the solid state.
Complexes of organometallic compounds XXXIII. The coordination chemistry of dimethyl and diphenylthallium(III) ith tridentate ligands
1973
Summary Several novel complexes Na[Me 2 TIL] and Na[Ph 2 TIL] (L 2− =dianion tridentate ligands with S, N, and O donor atoms) were synthesized, and investigated by infrared spectroscopy in the solid state, and by electronic and PMR spectroscopy in solution. Suggestions for the configuration of the complex anions are advanced and the nature of species present in solution is discussed.
Über polystannane
1987
Abstract The three compounds Ph4Sn2(X3CCO2)2 were synthesized from Ph2SnH2 and X3CCOOH (X = H, Cl) or by cleavage of two phenyl groups in Ph6Sn2 with Stoichiometric amounts of X3CCOOH (X = Cl, F). The crystal structures (R = 0.041, 0.030, 0.058) show that the Ph4Sn2 units are bridged by two isobidentate acetates resulting in five-coordinated tin atoms. Five crystallographically independent centrosymmetric molecules form three distinct conformers. Bonding parameters (compared with Ph6Sn2): distances d(SnSn) 269, 271, 272, 277 pm; NMR couplings (CDCl3 solution) 1J(SnSn) 16870, 9443, 12915, 4480 Hz; stretching vibrations ν(SnSn) 152, 155, 157, 159 cm−. The ion pairs [Ph4Sn2]2+ [(X3CCO2)2]2−…