Search results for " Spectra"
showing 10 items of 709 documents
Coordination properties of imino(2-pyridyl)methylpalladium(II) compounds. Reactions with the chloride-bridged allyl dimers [MCl(η3-2-MeC3H4)]2 (MPd,…
1990
Abstract The imino(2-pyridyl)methylpalladium(II) compounds py-2-CR 1 NR [R 1 = trans -PdCl(PPh 3 ) 2 , R = C 6 H 4 OMe- p ( Ia ), Me ( Ib ), CMe 3 ( Ic ); R 1 = Pd(dmtc)(PPh 3 ), R = C 6 H 4 OMe- p ( Id )] react with [MCl(η 3 - 2-MeC 3 H 4 )] 2 (M = Pd, Pt) in a molar ratio 1/0.5 and in the presence of NaClO 4 to yield the binuclear cationic complexes II , [M(η 3 -2-MeC 3 H 4 )(py-2-CR 1 NR)]ClO 4 , where the α-diimino group acts as σ,σ N , N ′ chelating ligand. In the absence of NaClO 4 and with a molar ratio 1/1, the reaction leads initially to formation of a ionic intermediate A , [M(η 3 - 2-MeC 3 H 4 )(py-2-CR 1 NR)] [MCl 2 (η 3 -2-MeC 3 H 4 )], which subsequently undergoes exchange …
Design, synthesis and spectral studies of novel bile acid-arene conjugates: Trans to cis isomerization of azobenzene core controlled by bile acid hyd…
2008
Abstract Four bile acid-arene conjugates, 1,4-bis[dimethyl(3α,7α,12α-trihydroxy-5β-cholan-24-amidoethyl)ammoniomethyl]benzene dibromide ( 1 ), 1,3,5-tris[dimethyl(3α,7α,12α-trihydroxy-5β-cholan-24-amidoethyl)ammoniomethyl]benzene tribromide ( 2 ), bis{4-[dimethyl(3α,7α,12α-trihydroxy-5β-cholan-24-amidoethyl)ammoniomethyl]phenyl}diazene dibromide ( 3 ), and bis{4-[dimethyl(3α-hydroxy-5β-cholan-24-amidoethyl)ammoniomethyl]phenyl}diazene dibromide ( 4 ), have been synthesized in good yields, and their structures have been characterized by 1 H, 13 C, 13 C DEPT-135, PFG 1 H, 13 C HMQC, PFG 1 H, 13 C HMBC, and PFG 1 H, 15 N HMBC NMR spectra. Their molecular weights and elemental compositions have…
1H NMR spectra of Ph2SbX, PhSbX2, and Ph3SbX2 (XCl, Br, I); 121Sb Mössbauer spectra of PhSbX2 and crystal structure of Ph2SbI1
1996
1H NMR spectroscopic data of Ph2SbX, PhSbX2, and Ph3SbX2 (XCl, Br, I) have been determined by iterative simulation. 121Sb Mossbauer spectra of PhSbX2 (XCl, Br, I) have been measured. The synthesis of Ph2SbI is achieved by reaction of Ph2SbCl with NaI in ethanol. The crystal structure of Ph2SbI consists of molecules with pyramidal C2SbI units.
"Through-space" 31P spin-spin couplings in ferrocenyl tetraphosphine coordination complexes: improvement in the determination of the distance depende…
2008
Abstract From the analysis of several nickel and palladium halide complexes of a constrained ferrocenyl tetraphosphine, the existence in solution phase of unique 31P–31P “through-space” nuclear spin–spin coupling constants (JPP) had been previously evidenced. Due to the blocked conformation of the species in solution, and based on the NMR spectra obtained for the complexes and their corresponding solid state X-ray structures, these JPP constants had been shown to clearly depend on the mutual spatial position of the corresponding phosphorus atoms. Herein, the quantitative correlation disclosed at that time (P⋯P distance dependence of coupling constants) is remarkably confirmed, and mathemati…
Substituent effects of1H NMR parameters of chlorinated diphenyl ethers. A statistical approach
1994
The 1H NMR spectra of 64 polychlorinated diphenyl ethers (PCDEs) were measured and assigned. Multiple linear regression analysis was used to estimate the effects of chlorine atoms on the 1H NMR chemical shifts and coupling constants. The ‘simple sum rules’ were found to be inadequate for the prediction of 1H NMR chemical shifts of PCDEs. Therefore, corrective terms of two chlorine atoms were taken into account. The most important effects on chemical shifts were shown to be the steric interactions of two adjacent chlorine atoms and the intramolecular ring current effect observed in the ortho-proton of tri-ortho-substituted PCDEs. The substituent effects on J(HH) coupling constants were found…
Untersuchungen zur Konformerenvielfalt von mono- und 2,5-dialkoxysubstituierten Poly(1,4-phenylenethenylen)en
1994
Investigations on the Conformational Variety of Mono- and 2,5-Dialkoxy Substituted Poly(1,4-phenyleneethenylene)s The alkoxy substituted poly(1,4-phenyleneethenylene)s 1 and 2 can principally exist in an enormous variety of conformers (table 1). However, force field calculations (MMX) reveal a far-reaching restriction to a relatively small number of non planar conformers with minimized steric energy. The decisive criterion is due to the interaction between the oxygen atoms and the olefinic hydrogens. An increasing steric hindrance should lead to higher twist angles θ in the main chain and hence to a shorter effective conjugation length. Such an effect could play a minor role between the uns…
Spectroscopic and conformational properties of size-fractions separated from a lignite humic acid
2007
Abstract A lignite humic acid (HA) was fractionated by preparative high performance size-exclusion chromatography (HPSEC) in seven different size-fractions. The size-fractions were characterized by cross polarization (CP) magic angle spinning (MAS) 13 C NMR spectroscopy and a further analytical HPSEC elution under UV and fluorescence detection. The alkyl hydrophobic components mainly distributed in the largest molecular-size-fraction, whereas the amount of oxidized carbons increased with decreasing size of fractions. Cross polarization time ( T CH ) and proton spin-lattice relaxation time in the rotating frame ( T 1 ρ (H)) were measured from variable contact time (VCT) experiments. The bulk…
2-Methyl-4-phenyl-3,4-dihydroquinazoline
2011
The title compound, C15H14N2, was formed during the lithiation of 2-methylquinazoline with phenyllithium followed by hydrolysis of the intermediate lithium 2-methyl-4-phenyl-4H-quinazolin-3-ide. NMR spectra as well as single-crystal X-ray structural data indicate that the reaction product to have the same structure in chloroform solution as in the crystalline state. The phenyl substituent is twisted out of the plane of the 3,4-dihydroquinazoline ring system by 86.47 (7)°. In the crystal, intermolecular N—H...N interactions connect the molecules into infinite chains.
Synthesis and Magnetic Properties of a Copper Cube: [Cu 4 (OH) 4 (C 16 H 18 N 2 ) 4 ] 4+ (ClO 4 ) 4 C 3 H 6 O [C 16 H 18 N 2 =( E )‐1,6‐[Di(pyridin‐4…
2019
We are grateful to the National Mass Spectrometry Service Center for mass spectra and to the UK National Crystallography Service for data sets. Supplementary Figure S1-S4: IR and UV/Vis spectra of compound 1
Properties of Swift's intermediate bursts
2011
Based on their prompt, high-energy emission, gamma-ray bursts are usually classified into short-duration and long-duration classes. A third intermediate group has been identified on statistical grounds but its individual properties have not yet been studied in detail. Using the large sample of follow-up observations of GRBs produced during the Swift era we analyze the individual characteristics of this group. We find that intermediate bursts are significantly different from short GRBs but share many properties with long bursts, probably pointing to a common progenitor type. However, we find that intermediate bursts are significantly dimmer and have on average lower redshifts. Based on their…