Search results for "Spectroscopy"
showing 10 items of 10293 documents
Investigations on organotin, organolead, lead(IV), and lead(II) dithiolates
1985
Abstract Bis(triorganometal) 1,2-dithiolates (R3M)2S2R′ [(HS)2R′ = C7H8S2 for toluene-dithiol-3,4 (H2TDT); M = Sn, Pb; R = Ph; or (HS)2R′ = C10H14S2 for 1,2-dimethyl-4,5-bis(mercaptomethyl)benzene (H2DBB); M = Sn, R = CH3, C6H5; M = Pb, R = C6H5], diorganometal 1,2-dithiolates R2MS2R′ [(HS)2R′ = C6H6S2 for 1,2-dimercaptobenzene (H2DMB); M = Pb, R = CH3, C2H5, C6H5; or (HS)2R′ = H2TDT; M = Sn, R = CH3, C6H5; M = Pb, R = C6H5; or (HS)2R′ = H2DBB; M = Sn, R = CH3, C6H5; M = Pb, R = CH3, C2H2, C6H5; or (HS)2R′ = C8H6N2S2 for 2,3-dimercaptoquinoxaline (H2QDT); M = Pb, R = C6H5] and some lead(IV) and lead(II) dithiolates Pb(S2R′)n [(HS)2R′ = H2DMB, n = 2; (HS)2R′ = H2TDT, n = 2; (HS)2R′ = H2DBB, …
Complexes hétéronucléaires Cp2MM′(Cp)(CO)3 (M Nb, Ta; M′ Mo, W) avec groupes carbonyles pontants et semi-pontants: synthèse et comportement dynam…
1991
Abstract Heteronuclear structures Cp 2 MM′(Cp)(CO) 3 (M Nb, Ta; M′ Mo, W) are obtained by heating Cp 2 MH 3 (M Nb, Ta) with Cp 2 M′ 2 (CO) 6 (M′ Mo, W) or starting from Cp 2 M(CO)H and Cp 2 M′ 2 (CO) 4 . These heterobimetallic complexes show three CO coordination modes: terminal, semi-bridging and bridging. The two cyclopentadienyl groups of the Cp 2 M moiety are anisochronous owing to molecular rigidity; rotation barriers around the MM′ bond have been estimated and are greatest with tantalum derivatives.
Rotational Isomerism in Acetic Acid: The First Experimental Observation of the High-Energy Conformer
2003
The high-energy conformer of acetic acid (cis-AA) is produced in an Ar matrix by vibrational excitation of the OH stretching overtone of the ground conformational state (trans-AA). IR-absorption spectroscopy provides a clear identification of the reaction product. cis-AA converts back to trans-AA in a time scale of minutes at 8 K by tunneling. http://dx.doi.org/10.1021/ja038341a
Clerodane diterpenoids from Salvia splendens.
2006
Four new clerodane diterpenoids, salvisplendins A-D (1-4), have been isolated from an acetone extract of the flowers of SalVia splendens, together with an artifact (5), arising from salvisplendin D (4) by addition of diazomethane, and the already known clerodane olearin (6). The structures of the new compounds (1-5) were established mainly by 1D and 2D NMR spectroscopic studies and, in the case of salvisplendin A (1), by chemical correlation with splenolide B (7). Complete 1H and 13C NMR assignments for olearin (6), not published hitherto, are also reported.
Trimeric Hemibastadin Congener from the Marine Sponge Ianthella basta
2012
The first naturally occurring trimeric hemibastadin congener, sesquibastadin 1 (1), and the previously reported bastadins 3, 6, 7, 11, and 16 (2-6) were isolated from the marine sponge Ianthella basta, collected in Indonesia. The structure of 1 was elucidated on the basis of 1D and 2D NMR measurements and by HRMS. Among all the isolated compounds, the linear sesquibastadin 1 (1) and bastadin 3 (2) showed the strongest inhibition rates for at least 22 protein kinases (IC(50) = 0.1-6.5 μM), while the macrocyclic bastadins (3-6) demonstrated a strong cytotoxic potential against the murine lymphoma cell line L5178Y (IC(50) = 1.5-5.3 μM).
Steroidal saponins from Chlorophytum deistelianum.
2016
Abstract Phytochemical investigation of the aerial parts of Chlorophytum deistelianum led to the isolation of four previously undescribed steroidal saponins called chlorodeistelianosides A–D with five known ones. Their structures were established mainly by extensive 1D and 2D NMR spectroscopic techniques and mass spectrometry as (25R)-3β-[(β- d -glucopyranosyl-(1 → 3)-[α- l -rhamnopyranosyl-(1 → 4)]-β- d -xylopyranosyl-(1 → 3)-[β- d -glucopyranosyl-(1 → 2)]-β- d -glucopyranosyl-(1 → 4)-β- d -galactopyranosyl)oxy]-5α-spirostan-12-one, (24S,25S)-24-[(β- d -glucopyranosyl)oxy]-3β-[(β- d -glucopyranosyl-(1 → 2)-[β- d -xylopyranosyl-(1 → 3)]-β- d -glucopyranosyl-(1 → 4)-β- d -galactopyranosyl)ox…
Triterpenoid saponins from Hydrocotyle bonariensis Lam
2011
Abstract Phytochemical investigation of the under-ground parts of Hydrocotyle bonariensis led to the isolation of five oleanane-type triterpenoid saponins, 3- O -{β- d -glucopyranosyl-(1 → 2)-[α- l -arabinopyranosyl-(1 → 3)]-β- d -glucuronopyranosyl}-21- O -(2-methylbutyroyl)-22- O -acetyl-R 1 -barrigenol, 3- O -{β- d -glucopyranosyl-(1 → 2)-[α- l -arabinopyranosyl-(1 → 3)]-β- d -glucuronopyranosyl}-21- O -(2-methylbutyroyl)-28- O -acetyl-R 1 -barrigenol, 3- O -{β- d -glucopyranosyl-(1 → 2)-[α- l -arabinopyranosyl-(1 → 3)]-β- d -glucuronopyranosyl}-21- O -acetyl-R 1 -barrigenol, 3- O -{β- d -glucopyranosyl-(1 → 2)-[α- l -arabinopyranosyl-(1 → 3)]-β- d -glucuronopyranosyl}-R 1 -barrigenol, a…
Triterpene saponins from Billia rosea.
2017
Five previously undescribed triterpene saponins, billiosides A-E, and a known analogue, were isolated from the seeds of Billia rosea (Planch. & Linden) C. Ulloa & P. Jorg. Their structures were elucidated on the basis of extensive 1D and 2D NMR experiments (1H, 13C, DEPT, COSY, TOCSY, NOESY, ROESY, HSQC, and HMBC) and mass spectrometry as (3β,21β,22α)-3-[(2-O-β-D-glucopyranosyl-O-[α-L-arabinopyranosyl-(1 → 4)]-β-D-glucopyranosyl)oxy]-21-[((2E,6S)-2,6-dimethyl-6-hydroxyocta-2,7-dienoyl)oxy]-22-(acetyloxy)-24-hydroxyolean-12-en-28-oic acid, (3β,21β,22α)-3-[(2-O-β-D-galactopyranosyl-β-D-glucopyranosyl)oxy]-21,22-dihydroxyolean-12-en-28-yl O-α-L-arabinopyranosyl-(1 → 4)-β-D-glucopyranoside, (3β…
Synthesis, structure, and nuclease properties of several binary and ternary complexes of copper(II) with norfloxacin and 1,10 phenantroline
2007
Three new binary Cu(II) complexes of norfloxacin have been synthesized and characterized. We also report the synthesis, characterization and X-ray crystallographic structures of a new binary compound, [Cu(HNor)(2)]Cl(2).2H(2)O (2) and two new ternary complexes norfloxacin-copper(II)-phen, [Cu(Nor)(phen)(H(2)O)](NO(3)).3H(2)O (4), and [Cu(HNor)(phen)(NO(3))](NO(3)).3H(2)O (5). The structure of 2 consists of two crystallographically independent cationic monomeric units of [Cu(HNor)(2)](2+), chloride anions, and uncoordinated water molecules. The Cu(II) ion is placed at a center of symmetry and is coordinated to two norfloxacin ligands which are related through the inversion center. The struct…
Formation of New η5-Rhodium(III) Complexes from η5-Rh(I) Rhodacarborane-Containing Charge-Compensated Ligands
2004
A series of new Rh(I) half-sandwich complexes of formula [3,3-(PPh 3 ) 2 -8-L-closo-3,1,2-RhC 2 B 9 H 1 0 )] (L = SMe 2 (2a), SEt 2 (2b), S(CH 2 ) 4 (2c), SEtPh (2d)) and [1-Me-3,3-(PPh 3 ) 2 -8-L-closo-3,1,2-RhC 2 B 9 H 9 )] (L = SMe 2 (2e), SEt 2 (2f)) have been prepared by reaction of the respective monoanionic charge-compensated ligands [10-L-nido-7,8-C 2 B 9 H 1 0 ] - and [7-Me-10-L-7,8-C 2 B 9 H 9 ] - with [RhCl(PPh 3 ) 3 ]. Complex [3,3-(cod)-8-SMe2-closo-3,1,2-RhC 2 B 9 H 1 0 ] (3) has also been prepared by reaction of K[10-SMe 2 -nido-7,8-C 2 B 9 H 1 0 ] with [RhCl(cod)] 2 . Rh(I) complexes 2a-d may be easily oxidized to the corresponding Rh(III) complexes 4a-d under N 2 atmosphere…