The photoelectron spectra of amides, thioamides, ureas and thioureas

Mines, G. W.; Thompson, H. W.

doi:10.1016/0584-8539(75)80225-x

Cited by 23 publications

(5 citation statements)

References 9 publications

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“…B. UPS and PIES of Thiourea. Assignment of the observed UPS bands in this study are consistent with previous studies. , Strong bands 1,2 are assigned to nonbonding sulfur orbitals extending in the out-of-plane and in-plane directions (n S ⊥ , n S ∥ ), which are originated from the 3p orbital of the S atom. Contrary to the case of urea, the intensity of bands 1−3 are larger than that of bands 4−5 ( I (1−3): I (4−5) = 1.7:1.0) because of the large intensity of bands 1,2.…”

Section: Discussionsupporting

confidence: 92%

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Penning Ionization of (NH₂)₂CX (X = O, S) with He*(2³S) Metastable Atoms. Difference of Anisotropic Interaction around N, O, and S Atoms

2000

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The anisotropic interaction potential energy surface around urea and thiourea ((NH2)2CX, X = O,S) with the He*(23S) metastable atom has been studied by two-dimensional (collision-energy/electron-energy-resolved) Penning ionization electron spectroscopy and by model potential energy calculation for the molecule−Li system based on a well-known resemblance between a metastable excited He*(23S) atom and a ground-state Li(22S) atom. A different trend was found in the interaction around the CX (X = O, S) group; an attractive interaction was found for the perpendicular direction around the CS axis where the 3p orbital of the S atom extends, while the collinear direction along the CO bond was found to be most attractive. A weak interaction was found around the “nitrogen lone pair” of the amino group in the conjugated systems (urea and thiourea), which is different from the general trend in previous studies that a strong attractive interaction was found around the “lone pair” of target molecules.

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Section: Discussionsupporting

confidence: 92%

“…A. UPS and PIES of Urea. He I UPS of urea and thiourea was observed by Debies et al and Mines et al In those studies, the observed bands were assigned on the basis of semiempirical MO calculation 40 or correlation of MO level with related compounds . Assignment of bands 1−3 and 4−6 of urea was, however, unresolved.…”

Section: Discussionmentioning

confidence: 91%

Penning Ionization of (NH₂)₂CX (X = O, S) with He*(2³S) Metastable Atoms. Difference of Anisotropic Interaction around N, O, and S Atoms

2000

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“…Here, we measured the IE values of urea and thioacetamide to be 9.81 Ϯ 0.02 and 8.3 Ϯ 0.1eV, respectively. These values are in good agreement with the adiabatic ionization energies via photoelectron spectroscopy [16,17].…”

Section: Solid Compoundssupporting

confidence: 83%

Electrospray/VUV single-photon ionization mass spectrometry for the analysis of organic compounds

Yang

Zhang

Pan

et al. 2009

J. Am. Soc. Mass Spectrom.

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For the comprehensive analysis of organic compounds, especially thermal labile and nonpolar compounds, an electrospray/vacuum ultraviolet (VUV) single-photon ionization (ES-SPI) method was developed. The fine droplets of the sample solution from the electrospray process were directed through a quartz capillary and two skimmers to form a molecular beam into a high vacuum ionization chamber. The neutral sample molecules were softly ionized with tunable VUV light and analyzed with a reflection time-of-flight mass spectrometer (RTOF-MS). The ionization energy (IE) and appearance onsets of fragments were obtained based on the photoionization efficiency (PIE) spectrum. The isomers can also be distinguished. With this new method, clean (fragment-free) mass spectra of nonpolar compounds, such as benzene, cyclohexane, and some thermal labile solid compounds (triphenylamine, thioacetamide, and urea) have been obtained without any tedious pretreatment. The components of complex mixtures (gasoline and kerosene) can be identified. Furthermore, quantitative analysis of the components can be obtained based on photoionization cross section data. This method may be used for quantitative analysis of small biomolecules and natural products. (J Am Soc Mass Spectrom 2009, 20, 430 -434)

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“…Geometry optimizations were first performed for free dmtu in C 2v −cis,cis and C s −cis,trans conformations; energies of the minimized structures differed by less than 0.05 eV in favor of the latter. Frontier orbitals for the free ligand are shown in Figure S4; these can be compared to a previous calculation, 84 reported UV absorption spectra, 85 and photoelectron spec- tra 86,87 of N,N′-dialkyl-substituted thioureas. A simplified [Ni(dmtu) 4 ]Cl + model was derived from the low-temperature X-ray structure, and the geometry optimizations were performed for diamagnetic and paramagnetic electron configurations (S = 0 and 1, respectively); for technical reasons, the calculations were carried out under applied C 2 point symmetry, but the models converged to nearly ideal C 4 symmetries (Figure 5).…”

Section: Resultsmentioning

confidence: 95%

Structural Characterization of Thermochromic and Spin Equilibria in Solid-State Ni(detu)₄Cl₂ (detu = N,N′-Diethylthiourea)

2016

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Consecutive thermochromic lattice distortional and spin crossover equilibria in solid-state Ni(detu)4Cl2 (detu = N,N'-diethylthiourea) are investigated by variable-temperature X-ray crystallography (173-333 K), DFT calculations, and differential scanning calorimetry. Thermochromism and anomalous magnetism were reported previously (S. L. Holt, Jr., et al. J. Am. Chem. Soc. 1964, 86, 519-520); the latter was attributed to equilibration of a singlet ground state and a thermally accessible triplet state, but structural data were not obtained. A crystal structure at 173(2) K revealed [Ni(detu)4](2+) centers with distorted planar ligation of nickel(II) to the four sulfur atoms, with an average Ni-S bond length of 2.226(3) Å. The nickel ion was displaced out-of-plane by 0.334 Å toward a proximal apical chloride at a nonbonding distance of 3.134(1) Å. Asymmetry in the trans S-Ni-S angles was coupled to a monoclinic ↔ tetragonal lattice distortion (T(1/2) = 254 ± 11 K), resulting in thermochromism. Spin crossover occurs by tetragonal modulation of nickel(II) with approach of the proximal chloride at higher temperatures (T(1/2) = 383 ± 18 K), which is consistent with a contraction of -0.096(4) Å in the Ni···Cl separation observed at 293 K. A high-spin (S = 1) square-pyramidal [Ni(dmtu)4Cl](+) model (dmtu = N,N'-dimethylthiourea) was optimized by DFT calculations, which estimated limiting equatorial Ni-S bond lengths of 2.45 Å and an apical Ni-Cl bond of 2.43 Å. Electronic spectra of the spin isomers were calculated by TD-DFT methods. Assignment of the FTIR spectrum was assisted by frequency calculations and isotope substitution.

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The photoelectron spectra of amides, thioamides, ureas and thioureas

Cited by 23 publications

References 9 publications

Penning Ionization of (NH₂)₂CX (X = O, S) with He*(2³S) Metastable Atoms. Difference of Anisotropic Interaction around N, O, and S Atoms

Penning Ionization of (NH₂)₂CX (X = O, S) with He*(2³S) Metastable Atoms. Difference of Anisotropic Interaction around N, O, and S Atoms

Electrospray/VUV single-photon ionization mass spectrometry for the analysis of organic compounds

Structural Characterization of Thermochromic and Spin Equilibria in Solid-State Ni(detu)₄Cl₂ (detu = N,N′-Diethylthiourea)

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The photoelectron spectra of amides, thioamides, ureas and thioureas

Cited by 23 publications

References 9 publications

Penning Ionization of (NH2)2CX (X = O, S) with He*(23S) Metastable Atoms. Difference of Anisotropic Interaction around N, O, and S Atoms

Penning Ionization of (NH2)2CX (X = O, S) with He*(23S) Metastable Atoms. Difference of Anisotropic Interaction around N, O, and S Atoms

Electrospray/VUV single-photon ionization mass spectrometry for the analysis of organic compounds

Structural Characterization of Thermochromic and Spin Equilibria in Solid-State Ni(detu)4Cl2 (detu = N,N′-Diethylthiourea)

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Penning Ionization of (NH₂)₂CX (X = O, S) with He*(2³S) Metastable Atoms. Difference of Anisotropic Interaction around N, O, and S Atoms

Penning Ionization of (NH₂)₂CX (X = O, S) with He*(2³S) Metastable Atoms. Difference of Anisotropic Interaction around N, O, and S Atoms

Structural Characterization of Thermochromic and Spin Equilibria in Solid-State Ni(detu)₄Cl₂ (detu = N,N′-Diethylthiourea)