Search results for "Spectroscopy"
showing 10 items of 10293 documents
Tin( II ) and Lead( II ) 4‐Acyl‐5‐pyrazolonates: Synthesis, Spectroscopic and X‐ray Structural Characterization
2004
Novel tin(II) β-diketonate Sn(Q)2 complexes [HQ = 1-R1-3-R3-4-R4(C=O)-pyrazol-5-one; HQC: R1 = Ph, R3 = Me, R4 = Cy; HQS: R1 = Ph, R3 = Me, R4 = CHPh2; HQL: R1 = Ph, R3 = Me, R4 = CH2Ph; HQT: R1 = Ph, R3 = Me, R4 = CH2tBu; HQE: R1 = Ph, R3 = Me, R4 = Et; HQB: R1 = Ph, R3 = Me, R4 = tBu; HQW: R1 = Ph, R3 = Me, R4 = p-(tBu)Ph; HQR: R1 = Ph, R3 = Me, R4 = p-[(CH2)5CH3]Ph; HQN: R1 = p-NO2Ph, R3 = Me, R4 = Ph; HQM: R1 = Me, R3 = Me, R4 = Ph; HQD: R1 = Me, R3 = Me, R4 = Me; HQP: R1 = Ph, R3 = Ph, R4 = Ph; HQG: R1 = Ph, R3 = Ph, R4 = Me; HQF: R1 = p-CF3Ph, R3 = Me, R4 = Ph; HQH: R1 = p-CF3Ph, R3 = Me, R4 = Me] have been isolated and characterized by single-crystal X-ray diffraction analyses, IR, 1…
Synthesis, crystal and molecular-electronic structure, and kinetic investigation of two new sterically hindered isomeric forms of the dimethyl[methyl…
2017
Two new structural isomers – 2,4-dimethyl-5-[methyl(phenylsulfonyl)amino]benzenesulfonyl chloride (1) and 2,4-dimethyl-3-[methyl(phenylsulfonyl)amino]benzenesulfonyl chloride (2) were synthesized by interaction of N-(2,4-dimethylphenyl)-N-methyl-benzenesulfonamide or N-(2,6-dimethylphenyl)-N-methylbenzenesulfonamide with chlorosulfonic acid. Both compounds have been structurally characterized by X-ray single crystal diffraction at 100 K. The crystals of 1 are triclinic: space group View the MathML source, a = 8.1542(2), b = 11.0728(3), c = 11.2680(3) Å, α = 116.557(3), β = 95.155(2), γ = 108.258(2)°, V = 831.97(4) Å3, Z = 2, R = 0.0251 for 2429 reflections; the crystals of 2 are monoclinic:…
Study of Confined 5-Aza[5]helicene in Ytterbium(III) Bis(2-ethylhexyl) Sulfosuccinate Reversed Micelles
2007
Some relevant physicochemical properties of 5-aza[5]helicene (H5) in solutions of ytterbium bis(2-ethylhexyl) sulfosuccinate (Yb(DEHSS)3) reversed micelles have been investigated by UV-vis-NIR, photoluminescence, and FT-IR techniques with the aim of emphasizing the role played by specific Yb(III)/H5 interactions and confinement effects as driving forces of its binding to reversed micelles, preferential solubilization site, and local photophysical properties. It has been found that the binding strength of 5-aza[5]helicene to reversed micelles, triggered by steric and orientational constrains as well as the water content, is mainly regulated by its interaction with the Yb(III) counterion. Mor…
Association of 2-acylaminopyridines and benzoic acids. Steric and electronic substituent effect studied by XRD, solution and solid-state NMR and calc…
2013
Abstract Eight single crystal X-ray structures, solid-state NMR spectroscopic, and theoretical studies utilizing QTAIM methodology were used to characterize the 2-acyl (alkyl in acyl = methyl, ethyl, t-butyl, and 1-adamantyl) amino-6-R-pyridine/4-R′-benzoic acid (R,R′ = H or Me) cocrystals. As expected among alkyl groups 1-adamantyl due to its bulkiness has the most significant effect on the relative positions of molecules in cocrystals. In addition, the subtle electronic and steric effects by the methyl substituents were observed. The theoretical calculations with full geometry optimizations are in agreement with the experimental findings (geometry, energy of hydrogen bonds). Based on the …
Macromolecules in ordered media: 4. Poly(2-vinyl pyridine)-liposome association induced by electrostatic interactions
1997
Abstract We have investigated the interaction between vesicles based on dimyristoyl phosphatidic acid (DMPA) and a polymer, such as poly(2-vinyl pyridine) (P2VPy), on the basis of both partition and binding models. The resulting association curves are non monotonous being three regions clearly evidenced. The electrostatic and steric origin of the attractive or repulsive interactions are analyzed as a function of pH, ionic strength and temperature using the fluorescence spectroscopy technique. We emphasize the importance of differentiating the ideal definition of the binding constant from the theoretically evaluated including the activity coefficient, γ, to take into account shifts from the …
Molecular Recognition via Hydrogen Bonding at the Air−Water Interface: An Isotherm and Fourier Transform Infrared Reflection Spectroscopy Study
1997
Molecular recognition in Langmuir monolayers at the air−water interface as a function of headgroup orientation and substrate using isotherms and in-situ Fourier transform infrared (FT-IR) reflection spectroscopy has been investigated. Isotherm measurements show that urea and 2,4,6-triaminopyrimidine (TAP) are specifically bound to barbituric acid lipid monolayers. As expected, TAP causes a larger shift in the limiting area of the isotherms than urea due to steric requirements. The peak positions of the CH stretching vibrations of the barbituric acid lipids indicate that the alkyl chains of barbituric acid lipids 1−3 are in a close-packed all-trans conformation both before and after the reco…
In-Situ DRIFT Spectroscopic Investigation on the Chemical Evolution of Zinc Phosphate Acid−Base Cement
2000
Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy has been used to follow the chemical evolution of zinc phosphate acid−base cement (ZPC), which has been prepared from unmodified, as well as from aluminum- and zinc-modified orthophosphoric acid. For the first time, amorphous dizinc cyclotetraphosphate octahydrate, Zn2P4O12·8H2O, although hydrolytically instable, has been observed as precursor phase prior to crystallization of α-hopeite, α-Zn3(PO4)2·4H2O, in both systems. Within minutes from onset of mixing the infrared spectrum of unmodified ZPC is dominated by the characteristic vibrations of α-hopeite, due to matrix crystallization. Setting of modified ZPC is strongly af…
Spectral and structural studies on Ni(II) dithiocarbamates: Nickel sulfide nanoparticles from a dithiocarbamate precursor
2015
Abstract Three new planar Ni(II) dithiocarbamate complexes; [Ni(4-dpmpzdtc)2] (1), [Ni(4-dpmpzdtc)(PPh3)(NCS)] (2) and [Ni(bupcbzdtc)(PPh3)(NCS)] (3) (where, 4-dpmpzdtc = 4-(diphenylmethyl)piperazinecarbodithioato anion, bupcbzdtc = N-butyl-N-(4-chlorobenzyl))dithiocarbamato anion and PPh3 = triphenylphosphine) with “NiS4” and “NiS2PN” chromophore units were synthesized and characterized by single crystal X-ray structural analysis as well as UV–Vis, IR and NMR (1H, 13C and 31P) spectroscopy. For 2, 1H–1H COSY spectrum was also recorded. Single crystal X-ray structural analysis of 1–3, reveals a slightly distorted square planar geometry in all three complexes wherein the steric and electroni…
Stereoselektive Glycosylierung von Steroidalkoholen mit 2,3,4,6-Tetra-O-privaloyl-α-D-glucopyranosylbromid (Pivalobromglucose) und 2,3,4,6-Tetra-O-(o…
1986
Steroidalkohole verschiedener Struktur, deren Hydroxyfunktionen aus elektronischen und sterischen Grunden in ihrer Reaktivitat differieren und die daruber hinaus empfindliche Gruppierungen enthalten, werden mit 2,3,4,6-Tetra-O-pivaloyl-α-D-glucopyranosylbromid (1) selektiv und effektiv in β-Glucoside ubergefuhrt. Dank des lenkenden Einflusses des 2-O-Pivaloyl-Substituenten wird eine Orthoesterbildung bei den Koenigs-Knorr-Reaktionen stark unterdruckt. Mit dem o-Toluoylrest als Hydroxyschutzgruppe wird diese Lenkung nur in geringem Mas erreicht. Stereoselective Glycosylation of Steroid Alcohols Using 2,3,4,6-Tetra-O-pivaloyl-α-D-glucopyranosyl Bromide (Pivalobromoglucose) and 2,3,4,6-Tetra-O…
13C NMR of carbonyl compounds -4. Solution conformation of β-ionone and related dienones
1986
Abstract The steric factors relevant for the conformations of β-ionone and structurally related compounds were studied by dynamic n.m.r. and 1 H, 1 H-NOE measurements.